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Jet Eye Master
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Although there is a healthy increase in power, I was expecting more. Could be the exhaust. You have another one you could try? With all the running cool and 4 stroking, it could be a bit blocked.

The holding it out in gear on a two stroke is funny. Doesn't do any damage, on a four stroke is terrible, on a two stroke, nothing. 10,000 rpm is lots but in 3rd only 9,000rpm? 3rd is all that really matters. We'll go with 9,000rpm.

Once the jetting is better all round, the bottom end will come up a bit. The below 3,000rpm will never be as good but the rest should be as good or way better.

Go with the WOT plug colour. Keep the lean experiments to a minimum, you see they damage the cylinder.
Ignition timing is not changed. Porting and packers don't change the ignition degrees. The requirement may now be different but the amount of degrees is unchanged. Where you leave the timing set?

Focus on getting the temperature up, without going lean. Aim for 280F cruise and 325F when WOT for a long time.
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Nedminder
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Some surprises here - but that's what I signed up for.
I'll wait to pass final judgement when I have the bottom jetted more cleanly.
Quote:
Focus on getting the temperature up, without going lean. Aim for 280F cruise and 325F when WOT for a long time.
I have pretty good data from heavy use prior to tuning.
Targets you threw out would be under plug in my case - direct head sensor will be hotter
Assume you mean use ignition timing advance to lift temps in to the target range.
Quote:
Although there is a healthy increase in power, I was expecting more. Could be the exhaust. You have another one you could try? With all the running cool and 4 stroking, it could be a bit blocked.
Dont think there is any issue there - other than the extra weight I carry and what ever limitations exist in the Road II exhaust design.
Can't answer why there isn't more increase - tho not bad at 1.5-2HP jump.
The most interesting thing about the cool running was that it was the exact same cylinder - just lifted with larger ex. port - same ignition timing - and suddenly ran cooler.
That said rich to me.

How do you guys like the ring showing in the plug chop pic.
Max power but edge of rich enough?
Plan to take it through the canyons tomorrow.
Will tell the story on temps and torque - and have some hwy in the ride as well.
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Jet Eye Master
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charlieman22 wrote:
Some surprises here - but that's what I signed up for.
I'll wait to pass final judgement when I have the bottom jetted more cleanly.
Quote:
Focus on getting the temperature up, without going lean. Aim for 280F cruise and 325F when WOT for a long time.
I have pretty good data from heavy use prior to tuning.
Targets you threw out would be under plug in my case - direct head sensor will be hotter
Assume you mean use ignition timing advance to lift temps in to the target range.
The carb set up should get the temps as near to these limits as they will go with the current timing (was it 18@6000?). Without being lean. Unlikely it will be lean and below these values. Your head sensor maybe read more than the plug but assume it is the same for now.
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Nedminder
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Trigger warning - boring bit about jetting below:
Promise to find something to cut or weld as soon as I can.

Got in 50 miles today - included Hwy, sunset blvd (4 lane), Mountain passes, surface streets.
Dont have EK metering rods for my fancy carb - so utilizing the EQ range - which are less steep.

Dyno runs and plug chop were on EQ30.
Decided to take this ride using same to see how it felt.
Answer: Dull.
Just felt rich all through the throttle.

Came back - and put in the leanest rod I have in reaction (moving from EQ30 to EQ32).
(So much for not doing any of my lean experimentations...)
wow what a difference - at least it feels that way.
Tried to record some speed runs by struggled to get app to work so will have to wait.

Wont be surprised tho if it doesn't show on the Dyno tests.
Been here before - and until I moved to the EK rods - couldn't make the "what I feel" match the data from the dyno.

Then again - maybe its real - meaning the ride exposed the weekends of mid throttle vs the full throttle of the speed runs. IDK.
But my Butt and my ears say it is much happier at this leaner setting.

Meanwhile - I took it for a mile run in 4th with the EQ32 (leanest) rod.
275° ish. no drama - and no sense that I am running it too lean.
If going on temps to determine jetting - I am well safe with this rod.

Unfortunately have to wait until late next week I suspect to get my hands on some EK jets. Plan to re-run a bit of todays mountain climb with this leaner rod and see if it holds up to my expectations.

Jack - how can it be that this thing is demanding so much leaner - a feed?
With temps so tame - even when pinned or lugged - hard to believe that I am starving it.
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Jet Eye Master
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If it feels better, it usually is. This probably has something to do with the smartcarb but that is not the whole story.

Technical theory coming up: As said before when going over 180 the exhaust pipe works considerably better. What flow goes through a jet is determined by density, temperature and differential pressure. If it's making more power with a smaller jet one of these has significantly changed. Exhaust pipe actually doing something considerable is now likely.

Now revving much higher the EK rod is going to be needed even more than before. Whatever you do with the EQ is unlikely to help. Save damaging anything the sensible option would be to park it until next week. Or.....get the SI carb back on!

Only a couple of bhp more and a spluttering bottom end is going to make this feel slower than pre tune.
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Nedminder
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What flow goes through a jet is determined by density, temperature and differential pressure.
Interesting. So my best guess is - pressure differential has changed with the enlarging of my exhaust port combined with my exhaust. Perhaps it is "sucking" more fuel in to the chamber - or as you suggest - the exhaust pipe is doing so more efficiently now.
Quote:
If it feels better, it usually is. This probably has something to do with the smartcarb but that is not the whole story.
I agree - but it's nuanced.
Riding is different than speed runs which are run at WOT from a 15MPH to ~60MPH in the same gear. I spend most of my time in the mid throttle range when riding - rolling on and off the power to full throttle from mid. Its in these areas of the throttle that I am probably perceiving more power.

So it is clearly more lively/more powerful currently in the middle of the throttle - but at WOT - it probably has less peak as seen in the Dyno's.

At the end of the day - a carb is a carb - mixing air and fuel - but there are subtitles that matter.
Smart carb has some advantages - and some compromises of course.
In ,my view - I get more net benefit from it.
- You can re-jet everything with a swap of a single component - rather than toying with a pilot, a needle, and a main. Smart carb comes with those relationships already set - by the amount of taper in the needle. I get how that could be a plus or a minus - but I have found it to be a plus.
- Smart Carb atomizes the fuel more like fuel injection. It gives it a super responsive feel. You can see the difference on the piston and plug. They don't look as "wet". But gray is still bad and chocolate milk is still good. I've never used another side draft - so I cant compare to anything but SI - but its meaningful compared to SI.
- I suspect Smart Carb protects against pilot jet seize. I have had it set to way to lean - but it still allows the pull of fuel and doesn't drop percipitously from one circuit to the other (it is single circuit).
- Smart Carb adjusts for altitude change. I've come to appreciate that with some rides - once tuned in - I feel no need at all to tweak for damp, hills, beach, etc. Just runs the same.
Forum member supplied image with no explanatory text
Piston after hill lugs and speed runs with EQ32.  No damage.  But Not that much time at absolute WOT.  Probably shows the EQ32 is right on for mid throttle position,
Piston after hill lugs and speed runs with EQ32. No damage. But Not that much time at absolute WOT. Probably shows the EQ32 is right on for mid throttle position,
Plug at same point
Plug at same point
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Jet Eye Master
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32 looks rich and seems better with the 30 but these EQ ones are not really helping. With the EK it will all change. I would put money on the 24 SI being quicker than the 25 smartcarb now it's tuned a bit.
Did you get splutter when it was on the rich rod?
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Nedminder
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32 is probably rich - somewhere in the throttle range.
That's the trouble with plug reads like this - you are getting an average.

My temps are still a bit on the low side compared to where they were pre -cylinder tune. Hard Hwy lug at 70 (did I mention I hit the hwy?) produced 300 degrees on a known run that I normally would have managed to get as much as 320-330° on. Vid below was shot today - when I come to a stop at the end - I am at 300°. Car moving too slowly in front of me cut off the point I usually hit top speed - would have gotten 2-4 more out of it I suspect.
You can hear it here if you want.
https://youtu.be/LLIUd1XRvzU

Short of JB welding a rod to the needed thicknesses - I am on hold until I get the EK's. Hmmm... Shhh emoticon
24SI - would probably create more peak. Agreed.
Then I would be at it trying to beat the 4 stroking out of the bottom end.
Unfortunately - Ebeth has most of my jets! 🙂

Didn't work from splutter on the rods.
Smart Carb tends to just refuse to rev out when too rich - I can literally just take 1000's of RPM off.
And when too lean - feels like it is starving and makes an oscillating sound when dumping off the throttle.
This guy was moving too slow.
This guy was moving too slow.
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Would a lapel microphone moved down by the exhaust tip work any better for recording a run and getting rpm data?
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Nedminder
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Christopher - am using a remote mic. have put it everywhere - including next to the exhaust mounted to the sidecar subframe - and at all volumes of input - but hasn't worked any better. Am successfully getting the sound above 5000 RPM - but the lower registers are just not well picked up (2K-5K RPM).

Jack - that pic was misleading.
Here it is in fresh sunlight.
Pics can be tough...
Un-doctored - just different light.  Closer to what I am seeing with my eyes.
Un-doctored - just different light. Closer to what I am seeing with my eyes.
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Jet Eye Master
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Sounds rich to me. Even at the top. Plug says 10 points over on an SI carb. Carb is running open mouth again? Is there any bellows or filter? If your old bodge casings are running open mouth it's going to really confuse the jetting.

So it is quite a bit quicker than before even with not so good jetting. There is hope. If it hits 75mph it is as expected. The tuned Malossi will be quicker.
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Nedminder
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Carb is running open mouth again? Is there any bellows or filter? If your old bodge casings are running open mouth it's going to really confuse the jetting.
When you say "bodge casings" - are you referring to my scoot or the driver?
As for carb - its got the same air filter on that I ran with the un-modified BGM.
I know you want to see what an SI would do on there - would be kinda interesting if I didn't blow it up - but as you have noted - what we are really missing are the proper rods with the steeper taper on them (EK).
Will lean on SC guys to cut some new rods for me ASAP so we can find out what this thing will do using those.

Also need to order new disc and new brake pads. Have absolutely worn mine thin. 🙂
Nicely tucked away
Nicely tucked away
One of these
One of these
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Jet Eye Master
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Would have thought the bellows to frame gave the most bhp. Sounded like it was open, maybe you had the panel off.
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Nedminder
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Jack - good ear.
Yes - side panel was off as attempting to improve recording quality - particularly down low.
Ran this filter for all other tests - going back to the Polini -with side panel off - so sticking with for consistency.
Lower temps/plug/feel/sound say I am too rich for at least significant portions of the throttle.
Doing what I can to get them to supply me some EK rods this week so we can play.
Insert jeopardy theme here:
Forum member supplied image with no explanatory text
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Molto Verboso
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Could be more the The Chase. You vs Jack221?

"
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"https://youtu.be/jl1Zfz-Widc"
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Nedminder
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hahahaha. that's pretty infectious!
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bodgemaster
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Is the carb Fanny Chmelar?
Or the exhaust?
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Nedminder
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Depends what country you are in I suppose.
Some might also question if the rails match the floorboard - but some secrets remain un-knowable.
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Is there a smaller needle jet available, or whatever they call the jet for the needle on that carburetor?
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Jet Eye Master
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SoCalGuy wrote:
Is the carb Fanny Chmelar?
Or the exhaust?
carb is definately fishy
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Nedminder
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Is there a smaller needle jet available, or whatever they call the jet for the needle on that carburetor?
Christopher - stepping in to save us from this downward spiral!
Yes - there are. They're called metering rods - and they do the job of a side draft needle - only they also do the job of a pilot and main.

I have them on order - but it will likely be a week.
It's high ridable right now - but lacks the oomph it should have - so there is always the chance I will get impatient and rig something else up.
🙂
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Nedminder
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Jack - this one's for you.
Since work has been sorta a heavy load this week - and I am waiting for the metering rods for the Smart Carb - I found myself putting the 24/24 SI on this evening and bombing down the test road to see how it goes.
¯\_(ツ)_/¯

Qualifier: I sent all my jets between 122 and 126 to Ebeth - so I had to choose from 120 or 128 as first run. So I made the choice you might expect... right. 120 it is then.

Smart Carb's heroin silky smoothness is gone. Sigh.
But power is there - and its not optimized yet.
I'll see if I can get it all the way to the sound of chopping wood this weekend.
My guess after first quick runs - I will be walking it down, not up.

Already had to walk my pilot jet up richer and richer from the crazy lean the Polini was demanding - to get it to run on 1/4 throttle or less. Un-drivable even with a 40,42, & 45/160 in it - at least as jetted now - so settled on a 50/160 as was in a hurry to get a quick run in.
There is still a significant pause - a choking like effect - at hand off - then it takes off as it gets on the main. I can see it when looking down the throat of the carb (which should answer your next question about any sort of carb box top)

My sense is - as I lean out the main - it won't want to flood at hand off - but just a guess.

You can hear it here:
https://youtu.be/Z24PFgj6Pdg
First two passes.  My guess - will get a bit more out of it possibly with a 118 or 116.  Terrible bog between idle and main currently.
First two passes. My guess - will get a bit more out of it possibly with a 118 or 116. Terrible bog between idle and main currently.
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Jet Eye Master
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Well that was unexpected changing carb but still, SI carb on dodgy jetting already produced slightly more max power than the Smartcarb did at its best. Appreciating the science.

Un-surprising you started at 120 main. Assume AC120/BE3 still in there. Revs like it's still rich in the video. 116 probably. Where did the Polini end up (don't mean Indo customs)?

You won't be able to set the pilot until the lid and bellows are fitted, as they matter. Even the main will be confusing without the lid. Will save more time and less cylinder damage, if you start fitting the carb lid between jet changes. Fit the 55/160 until the main jet is done. Don't want to be running lean, as that cylinder doesn't need any more nicasil coming off.

While the Smartcarb is off is there any opportunity to change it for a 30mm?
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Nedminder
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Tks for input.
55/160 on the bench and ready.
The larger Smart Carb first articles just delivered in 28mm with other sizes on their way - but I am staying on my best behavoir by eschewing the temptation for time being.
Used a fancy word there to help me feel better.
editors note: that could always change...
Quote:
Where did the Polini end up (don't mean Indo customs)?
Good chuckle on that one.
Polini with top and bellows was 120MJ, 40/160 idle, with a bit of 4 stroking I just couldn't knock out of the 1/8th throttle area no matter how lean I made the idle jets.
Here's the Polini on SI for reference.
This was the Cosa/Rally older carb with 2mm hole drilled.
Matched performance pretty closely with the DRT version with 2.3mm hole (though that one used a 116MJ to achieve same peak HP).
https://youtu.be/HawZP1wURU0
AC120/BE3 Jackstack in play of course then and now.

Funny - feel much more at risk jetting an SI than the SC.
Don't think its only perception.
Will try not to burn this thing up.
Polini was heavy and rough around the edges - but I was never more than a hone and some new rings from fresh...
Interesting look at the Polini - SC vs SI.  Bit more pull down in lower RPM with SC, more in higher RPM SI.  May be subtitles of how I had both jetted.
Interesting look at the Polini - SC vs SI. Bit more pull down in lower RPM with SC, more in higher RPM SI. May be subtitles of how I had both jetted.
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Jet Eye Master
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Is funny how the tuned Polini and the tuned BGM have worked out at almost the same peak power with very similar curves. All differences are quite subtle and like you say could be jetting and/or a slight difference in port timing.

Before doing any more jetting it might be worth doing a packer change. I think the BGM has the transfer angles too low. To compensate raising it up will help it get ahead of the Polini.
While the lockdown time is plenty, change the 0.2mm packer for a 0.5mm packer. This will give 126/182.5/28 and should increase mid torque and max power.

The Smartcarb really needs to be bigger. What's next after 28mm? Were you just borrowing this 25mm?
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Nedminder
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Quote:
While the lockdown time is plenty, change the 0.2mm packer for a 0.5mm packer. This will give 126/182.5/28
Last week when I carved 2mm out of the ex port roof - I also put a .5mm packer in to replace the .2. By my calcs, it gave me 124.5/181.5/28.5
See below comparing bolt on numbers with new numbers after I lifted by .3 and ground 2mm out of the ex. port.

So I am basically there.
There is always the possibility that I have more wind resistance, or more weight, then I am calculating for - but I think I am reasonably close - and I have kept those numbers consistent since the start (inputs on the GSF software.)

Larger Smart Carb is in the plans. Im not sure if they offer the 30 - or if it jumps even higher after 28. I might even be able to mix bodies - using a 28 and what ever the larger size up is in a half and half mix (output 28 - input thirty something). They will swap out what I have for what ever size I wanna do when time comes.

I'll re-jet today and put the box top on.
Saw nothing with temps that would suggest I was too lean with the 120 - though it would have been nice to make it slower with a 122 or 124 so I knew I was moving in the right direction with a move down to a 118.
I suspect we will get over 18HP with the SI 24/24 as our max - which will be fun.
I will have to put up with the nasty vibration through the handlebars compared to the smart carbs refinement (have Klauss Studio engine bushings in so I really feel the change from Smart Carb to SI).

Will see!
Here were the numbers for the BGM out of the box with .2 base and 1.5 head gaskets - I measured, then subtracted .2 (base) & 4.0 (head insert to cylinder) and added 1.5.  Assumed my squish = PBT.
Here were the numbers for the BGM out of the box with .2 base and 1.5 head gaskets - I measured, then subtracted .2 (base) & 4.0 (head insert to cylinder) and added 1.5. Assumed my squish = PBT.
Same calcs as above, with change to .5mm base
Same calcs as above, with change to .5mm base
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Jet Eye Master
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UTC quote
If you have a 0.5mm packer now, then you need a 0.8mm. The idea is to get up to 126/182.5/28, is struggling where it is.

Vibration means your jetting is wrong. btw. Where does it vibrate the most? And that is where it is the most wrong.
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@charlieman22 avatar
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Nedminder
62 VBB1T Round Tail W/ leaner sidecar
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Timing - gotcha.
I woulda stopped short of using "struggling" for an adjective - but hey - everyone has their own style.
🙂

I don't plan to make any port timing changes until I have the SC back on and tuned in. With all due respect to the SI - which can absolutely deliver raw power - in its best moment - with the sun at the exact right angle (not like the last time you rode) - and the humidity just right - it cant match the smart carb's fuel injection like feel - which once tasted - is pure heroin.

Which is to say: this week I am stuck smoking crack.

But - I am all about making this the best crack I can!
I posted on Hebert's thread today as he is suffering from what I will term a "pause" at hand off between the idle and the main circuits on the SI.
Coincidentally - I am suffering the same symptom- and it is occurring at handoff between idle jet and main.

What's interesting is - I can see exactly what is causing the hand off issue when on the stand - looking down in to the carb - with top off.
The first 1/4 throttle is ok - but as I approach 1/3 - the first large drops of fuel start to come out of the main jet feed tube - which pokes into the carb throat - and as those drops hit - it bogs. Not enough air!

Basically - to run better - it would need to either deliver that drop later - meaning when the slide is more open and more air is rushing in to the cases - OR - it would need to deliver a smaller drop. It just looks like it is getting too much fuel for the amount of slide that is open.

Thus my next move is to experiment with the atomizer to see if I can delay or limit the fuel delivery from the main. Endless thread with experts chiming in - and all disagreeing with each other is here: Lets talk atomizers

Below is a chart which I am going to use as my guide.
Looks like I would need to find a BE2.

Jack?
Others?
My German is not so good - but this pretty much says - the BE3 is in between the BE1 & BE2, the BE2 being leaner or handing off later?
My German is not so good - but this pretty much says - the BE3 is in between the BE1 & BE2, the BE2 being leaner or handing off later?
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Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
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Jet Eye Master
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UTC quote
charlieman22 wrote:
Timing - gotcha.
I woulda stopped short of using "struggling" for an adjective - but hey - everyone has their own style.
🙂
Is a good word for the situation. In original English it works. Angles too low. Torque lost. Not doing it easily.
Quote:
I don't plan to make any port timing changes until I have the SC back on and tuned in.
If it's not done now it means jetting in the SI, then jetting the SC, then jetting it again. And you will really like it when it goes. Until the tuned Malossi that is.
Quote:
It just looks like it is getting too much fuel for the amount of slide that is open.
Slide. This is where changing the slide comes in. The SI carb already gets an increase in virtual size over side draught because it is very close to the crank. Now, the slide draws in air from the front tube bypassing the venturi, this is another virtual increase in carb size during mid throttle.
When revving on the stand the throttle opens less. Under load it is open much more for the same rpm.
If the main jet ends up at 116 I think this issue might go away. If not there is another way. But for really smooth transition when higher tuned you have to drill your own pilot jets (like I do Razz emoticon )
Quote:
Thus my next move is to experiment with the atomizer to see if I can delay or limit the fuel delivery from the main. Endless thread with experts chiming in - and all disagreeing with each other is here: Lets talk atomizers
Never joined this thread. They seemed to be having such a nice time.
Quote:
Looks like I would need to find a BE2.
I'm going to say no don't. Seems like a good idea but it isn't. The AC120 doesn't have enough air for it.
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Nedminder
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UTC quote
More about Atomizers
Quote:
Slide. This is where changing the slide comes in. The SI carb already gets an increase in virtual size over side draught because it is very close to the crank. Now, the slide draws in air from the front tube bypassing the venturi, this is another virtual increase in carb size during mid throttle.
Good explanation.
Quote:
I'm going to say no don't. Seems like a good idea but it isn't. The AC120 doesn't have enough air for it.
well - by now - you must have known my first move would be to see for myself.
So I did.
Much worse - Couldn't get out of the driveway.
Pause changed to canyon.
Found a solution afterward.
Will get to that in a minute.
First - let's talk atomizers.

If anyone else has ever tried to understand wtf the deal with atomizers is - and just thrown their hands up in the air - join the club.
Since the SI is back on - figured it was time I sorted it out.
Here is CM's consolidated "7 facts about atomizers" (needless to say: )
Humore intended

1. Rule one - ignore the nomenclature: It's horeshit. Doesn't tell you anything about what the atomizer does - don't let the stupid numbers intimidate you. BE1, BE2, waddever - they don't fall in order.
2. Atomizer's create different rich or lean effects at different parts of the throttle - see diagram below
3. More holes adds air. Any portion you see holes is leaner when compared to one without holes or with small holes in same area.
4. Position on the atomizer high or low affects where in the throttle this rich or lean effect occurs (WOT, Mid, barely open). See diagram.
5. So - one atomizer is not "richer" or "leaner" than another - as it depends what part of the throttle you are in.
6. At WOT they are all the same (except BE6 - which is leaner with 6 holes there - just say no.)

Ok - there it is. Atomizers can bump you up or lean you out in any part of the throttle where you cant quite reach with the main and idle jets. Done.

So, about that solution.
I was suffering from the same issue Hibbert is.
A nasty pause at the handoff point between idle and main jets ('bout 1/3 throttle).
Quote:
If the main jet ends up at 116 I think this issue might go away.
Was hoping the same.
It didnt.
Nor at 114, or 113 or 112 - where it just got itself to chopping wood sound.
I have a 55-160 idle in - so as rich as they come for 160's.
After the can't get out of the driveway due to exacerbation of handoff "pause", I decided to go the other way.
Moved from BE2 (leaner in hand off area fo throttle) to BE4 (richer in same area).
Much better.
I had it wrong - I was not bogging - I was starving.
And the BE4 - which is richer in the lower throttle - improved.

I miss my smart carb - its simplicity - and its smoothness - but its fun to make an SI work well.
If you've jetted in your carb - but have a certain spot in the throttle that just isn't right - consider trying an atomizer that attacks that spot.
There is not only one recipe that works.
SI carbs are full of levers to pull.
They are a pain in the ass 'cause every lever overlaps another.
But refinement of a single throttle area can be done with atomizer change - based on my experience.
My $.02
-CM
Placement and size of holes adjust how much air is introduced in that part of the throttle.  Note: all of them are the same at WOT.
Placement and size of holes adjust how much air is introduced in that part of the throttle. Note: all of them are the same at WOT.
@ginch avatar
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Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
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@ginch avatar
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UTC quote
Like the diagram CM, it's helpful.

Not sure if you watched this video or skimmed... but please do, its quite explanatory I think. https://youtu.be/1pkFSA_rRFI
UTC

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
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Jet Eye Master
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UTC quote
Re: More about Atomizers
charlieman22 wrote:
I had it wrong - I was not bogging - I was starving.
And the BE4 - which is richer in the lower throttle - improved..
-CM
That's shocking. It is hard to tell though. Rich and lean both cough it's just in a different way. At least you never run the BE2 on the road. That can be like self destruct for the nicasil with normal sized main jet.

If it can take a BE4 and not actually 4 stroke at 1/3 or go rich (slow) at 1/2. It's going to need a vey low numbered pilot something like 45/120 hopefully much less. This is good news. Could even be why it sounds like it's struggling.
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Jet Eye Master
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Jet Eye Master
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Quote:
Like the diagram CM, it's helpful.
especially where the main jet goes Razz emoticon

One thing about the holes is that their area is accumulative once above the level.
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Ossessionato
2007 Stella 225
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UTC quote
I'm going to show my ignorance but I have to ask. I thought as the holes progressed towards the main jet, that is what they were affecting as far as rpm or throttle position. A lower rpm wouldn't have as much vacuum so only the holes by the air correction jet would allow air in. As the rpm increase there is more air or suction so the holes closer to the main jet start working.

So going to number 4 from 3 would cause you to run richer the higher the rpm and throttle position, since it has one less set of holes.


So from my understanding your 1/4 and WOT are reversed.
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@charlieman22 avatar
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Nedminder
62 VBB1T Round Tail W/ leaner sidecar
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Quote:
Not sure if you watched this video or skimmed
Well, I listened to it - and it was the core of my understanding.
There's nothing to watch tho - just a still image - but it really lays it out.
Quote:
That's shocking
you mean the part about me being wrong? IK! Crazy - but tru.
Quote:
especially where the main jet goes
Quote:
I thought as the holes progressed towards the main jet, that is what they were affecting as far as rpm or throttle position
Oops. See corrected below.
Ironic - I made that on where the main jet goes to help avoid confusion.
Ginch must have skimmed and not noticed.
🙂
Quote:
So from my understanding your 1/4 and WOT are reversed.
Had the wrong end identified for the main... good catch.

Edit:
Quote:
One thing about the holes is that their area is accumulative once above the level.
Jack - what did you mean with this?
Also - are you saying that at WOT - the additional holes at the middle of a BE3 - though not near the main - still lean it out vs BE4?
Forum member supplied image with no explanatory text
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Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
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Jet Eye Master
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UTC quote
Yes but it's all about area and differential pressure.

Diagram making much more sense now.

If you fancy sunday a ride, do a video of riding at half throttle and WOT, with the AC120/BE4/116
If holding half throttle in 3rd it should slowly rev out to near max rpm. If any good.
If the BE4 is actually too rich a lot of time will be wasted.
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@charlieman22 avatar
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Nedminder
62 VBB1T Round Tail W/ leaner sidecar
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Quote:
If the BE4 is too rich a lot of time will be wasted.
I was mostly interested to see what kind of peak HP I would get from putting the SI on - the smoothing of the entire range to factory perfect was not really my goal at outset.
I may keep toying with the jetting on the SI while I wait for the SC metering rods tho.
BTW - the answer to that question was about 17.5hp with SI. I've seen similar numbers with the SC - though there may be a small edge in peak with the SI.

The whole atomizer experiment was due to a single weird spot in the throttle at 1/3 (hand off between main and pilot).
Enriching middle helped.
Am running a 112 MJ already - so its possible it gets a little enriching with the BE4 up at the top based on what you are saying - though it feels the same to me with BE3.

Though perhaps not clear from prior posts - I've modified how I have the SC mounted - to make it as close to a down draft as possible. That manifold you see in the pic used to be a fancy MRP one with a 90° curve. I cut the base plate away - drilled holes for studs, got rid of the adapter, and hacked half the tube off it. Works a charm.
Quote:
If you fancy sunday a ride, do a video of riding at half throttle and WOT, with the AC120/BE4/116
If holding half throttle in 3rd it should slowly rev out to near max rpm. If any good.
Hot as hell here - but bike running nicely enough to cross the hills to the ocean - so perhaps. Did you mean 112MJ? Easy enough to test what you propose - good means to read of how rich the middle is. Like it.
(Dirty) Carb Porn.  ~ 40°
(Dirty) Carb Porn. ~ 40°
@hibbert avatar
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Molto Verboso
Vespa
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@hibbert avatar
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UTC quote
Wow so much going on lately.

One thing I noticed Charlieman22 how smooth the PHBH carb tune was on my P2 compared to the Bajaj Si this compelled me to work on the Si more.

I like your SmartCarb manifold.
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@charlieman22 avatar
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Nedminder
62 VBB1T Round Tail W/ leaner sidecar
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UTC quote
Thanks Hibbert.
The SI's are a challenge - but they do have many levers.
I like to think of it as a recipe - there is more than one way to get it done.
Cross over of effects from pulling any lever is the challenge...

I would be interested to see what happens if you put a BE4 in yours.
Might leave you too rich in the middle - but does it get rid of your hiccup at transition.
If yes - then you know its an issue of being too lean there - rather than too rich.
Not saying it is the best solution - just a means to clarifying what's going on with yours.
As noted - any change has overlap.

As I've watched your tune - it seams that as you have tried to nock out that pause - its driven you to an idle jet that reads very rich on the plug.
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