was 130 DR loss of power - now CP21 jetting
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Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sat May 05, 2018 7:16 pm quote
OK had a go with air brakes today.

1mm air brake felt great but even moderately long cruising at 1/4 throttle was pushing CHT's of 350 and I decided to go to the 0.6mm.

Installed 0.6mm and went for a ride where I knew I could hold 1/4 throttle for a few miles in a row. CHT's up to near 400 when I pulled off and let it cool down. it was a long slow steady climb in CHT, but there is clearly not enough fuel at 1/4 throttle with the 0.6mm.

I'm going back to no air brake and the 98 main instead of the 100. This is the setup I was riding before trying all the air brake stuff. To be honest, I probably need to take this setup over to the same stretch of road and have a go to see if the 2.6 needle bushing is too lean. I'm pretty confident it's OK, as I've never seen temps climbing too high at these throttles (I've seen 320's) but it is worth checking off.

I'm glad I found that stretch of road as a 1/4 throttle test. I can assure you it will come into play as a testing ground on my P200 jetting.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Sat May 05, 2018 8:02 pm quote
Well that wasn't what I was expecting. You should really have a very big main jet in at this stage (or none) while you are doing this. I'm sure I mentioned that.

Try the same with the 2.6 and closed air brake and see how it goes I expect it might not be enough. Should really be holding 300F at the spark plug on 1/4 throttle runs. Leaves somewhere cool to wind down after a 20 mile full throttle thrash.

Seems like you might get onto the 2.7 bushing yet, up to the big league.

Doing the 200 should be easier but this is good practice.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sat May 05, 2018 8:16 pm quote
This was the biggest main I have, more on the way. I did it with 100. You mentioned the no main for the rev out test but I didnít think it was fair to do this test with no main.

Yes I was surprised too. Iím hoping I can stay with the 2.6 bushing.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sat May 05, 2018 8:17 pm quote
The temps are at a stud, not the plug, so they are hotter at the plug by a bit.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Posts: 1032
Location: London UK
Sat May 05, 2018 8:34 pm quote
The main jet has very little affect on the 1/4 throttle unless it is too small, then it can be a very big effect (needle carb only, SI carb is the exact opposite).

400F on the stud on the P200 and you'll be waiting for the recovery truck.
I know smallies can be hotter but wouldn't have thought that much. Check the 1/4 throttle plug colour next time, that will give a good idea of the real story.

Edit: Could just pick a main jet you don't like and put a 1.5mm drill through it, just a thought.

On my jetting routes I have a few secluded stopping places to make quick adjustments by the side of the road. As the years go by and I make less mistakes, I'm sure its easier but with being older and more critical, it still seems to take many goes to get just right.
Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4395
Location: So Cal
Sun May 06, 2018 7:33 am quote
Jack, I have the identical carb as John on my mid-tuned smallie (Polini 130, cut crank, 178/124 timings, PM40 pipe). Nice carb but Iím convinced the 21 is just too small. Itís quick but just canít deliver what the engine needs WOT in 4th.

Iím running the stock needle, custom drilled 1.5mm air brake hole, 48 pilot/115 main.

And yes, it runs hot. I top 400* regularly with the sensor on the plug.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sun May 06, 2018 10:00 am quote
No air brake with same settings except 98 main in place of 100 (it was a known setup) gives 367 on the same stretch of road. Nice improvement, but is it good enough? I can go 2.7 needle bushing and if it cools off enough can add an air brake. But the idle starts over again then. I had to run a 36 idle with the 2.7 bushing in place of the 40 Iím running now.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sun May 06, 2018 10:06 am quote
Main jets 100-122 should arrive tomorrow.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Sun May 06, 2018 7:17 pm quote
Temperature is going in the right direction.

First I would try the run with 2.6, closed air brake and no main jet (or 150).

Then try the same run with 2.7 bushing and 1.0mm air brake and still no main jet (or 150).

For this carb I think it will run better with some open air brake, so I am hoping the 2.7 with adjust into temperature.

SoCalGuy, I think this carb is a little bit small too but I think it will deliver ok in the end. Let's see how John gets on with the set up. What's your compression and ignition timing?
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Mon May 07, 2018 5:48 am quote
I will try as above, but probably with the 122 main that arrives today. The area has some traffic and the bike isnít safe with no main jet at those speeds.

I also have jets starting in the high 130s that I forgot I bought for the P .
Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4395
Location: So Cal
Mon May 07, 2018 6:49 am quote
Compressionís ~130 psi. Timingís set at 18į, electronic non-variable ignition. Short 4th. Engine probably has less than 500 mi since it was built. Donít mean to hijack... just passing along info since itís the same carb as Johnís.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Mon May 07, 2018 7:01 pm quote
sdjohn wrote:
I will try as above, but probably with the 122 main that arrives today. The area has some traffic and the bike isnít safe with no main jet at those speeds.

I also have jets starting in the high 130s that I forgot I bought for the P .
Just be sure the Main jet is way over for the 1/4 test to work. This is only the first go round the bases but the closer to correct the quicker it will be.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Mon May 07, 2018 7:06 pm quote
SoCalGuy wrote:
Compressionís ~130 psi. Timingís set at 18į, electronic non-variable ignition. Short 4th. Engine probably has less than 500 mi since it was built. Donít mean to hijack... just passing along info since itís the same carb as Johnís.
Nothing wrong with compression or timing to cause high temperature, so must just be that oversize air brake. A smaller air brake (1.0), the needle down a clip and re do the main jet, should help.
John seems to think his will end up with a 42 pilot. Your 48 might be bleeding all over your 1/4 making you think you need a weaker air brake.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Mon May 07, 2018 7:19 pm quote
Iím sending Socal a 2.6 bushing to try as well. I had a spare.

Installed 118 main, will test again soon. If it drops the temp at 1/4 a lot I may spend the time to figure out the main before trying the other bushing. Iím just not sure how much interplay will be there between the main and 1/4 throttle.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Mon May 07, 2018 8:30 pm quote
Socal is on the 2.7. Now it makes even more sense.

As said, the more air at 1/4 is way more air at WOT. With the emulsified atomiser type carbs of the Kehin type, some air is good but too much is a real problem.

There is only interplay if the main jet is too small.
Ossessionato
1976 Super (x 2), 1974 Primavera (x 2), 2006 Fly 150
Joined: 26 Sep 2013
Posts: 4395
Location: So Cal
Wed May 09, 2018 6:12 am quote
Jack221 wrote:
SoCalGuy wrote:
Compressionís ~130 psi. Timingís set at 18į, electronic non-variable ignition. Short 4th. Engine probably has less than 500 mi since it was built. Donít mean to hijack... just passing along info since itís the same carb as Johnís.
Nothing wrong with compression or timing to cause high temperature, so must just be that oversize air brake. A smaller air brake (1.0), the needle down a clip and re do the main jet, should help.
John seems to think his will end up with a 42 pilot. Your 48 might be bleeding all over your 1/4 making you think you need a weaker air brake.
Thx Jack. Iíll give a slightly smaller (1mm) air brake a try, but I have my doubts.

Iíve run it with a closed air brake and a 110 main. It would not get on the pipe in 4th and still pushed 400įF.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Wed May 09, 2018 7:33 pm quote
Try the 2.6 bushing that John is sending you. This with a smaller air brake should work out better at WOT.

Running a weaker main jet is more powerful but there is always that risk of surprise seize up when held open too long in the wrong weather

The two easiest checks for a slightly weak main jet are,
1. The last 1/4 of the throttle doesn't seem to do much. If its 3/4 open or wide open is about the same road speed.
2. After initial warm up you can do say 100km/h in 3rd gear, after thrashing around for an hour you can now only do 97km/h in 3rd gear.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Thu May 10, 2018 6:40 pm quote
Main jet 118, 2.6 bushing, no air brake, 1/4 throttle run gives 310F CHT. Clearly the main does bleed into the 1/4 throttle temp reading.

It's pretty entertaining trying to drive a bike that bogs out at 1/2 throttle. Accelerate at 1/8 throttle until high revs, don't shift until you know you will have some revs in the next gear, and don't forget not to grab a handful of throttle .

I've dropped the main to 108 and will test again for splutter. I want to find one jet under the last one that splutters and then test the 1/4 throttle temps again. Assuming I might have been on the lean side, I think the 2.6 bushing and no air jet will be OK. We will see....
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Thu May 10, 2018 7:19 pm quote
sdjohn wrote:
Main jet 118, 2.6 bushing, no air brake, 1/4 throttle run gives 310F CHT. Clearly the main does bleed into the 1/4 throttle temp reading.
Seems closer now if the 1/4 temperature goes up again with to 108 main jet, try the 2.7 and 1.0mm air brake.

Last edited by Jack221 on Thu May 10, 2018 7:25 pm; edited 1 time in total
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Thu May 10, 2018 7:25 pm quote
As you are running the weakest needle, there is not much room to move.

Set the main jet by getting wide open throttle splutter then reduce 2 whole jets. I think you will need to do this every time you touch the bushing or air brake.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Thu May 10, 2018 7:41 pm quote
108 splutters and reduces top speed, have gone to 104 for next test.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Thu May 10, 2018 8:16 pm quote
Jack221 wrote:
As you are running the weakest needle, there is not much room to move.

Set the main jet by getting wide open throttle splutter then reduce 2 whole jets. I think you will need to do this every time you touch the bushing or air brake.
yes I agree the main has to be set to check the 1/4 on this carb.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Fri May 11, 2018 1:14 am quote
This carb would seem to be like an SI carb where just one part at a time can be adjusted.
If you treat this adjusting like the second or third go round and just make smaller movements it should be ok.

I would much prefer you running on the 2.7 with 1.0mm air brake, as that should lean out the 3/4 better than the 2.6 with closed air brake.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Fri May 11, 2018 3:57 am quote
You are thinking I wonít have any room for clip adjustment, I assume? Makes sense.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
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Posts: 1032
Location: London UK
Fri May 11, 2018 6:51 pm quote
Just concerned it will end up be ok at 1/4 and WOT but rich at 1/2. Clip down from there and will just make the 1/4 too weak.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Fri May 11, 2018 7:07 pm quote
As I thought. Weíll see. There are only a couple paths forward and seeing the main involvement actually makes each one go faster as setting the main is pretty easy.

I would try the 0.6 air brake with 2.7 first, I have a gut feeling the 1.0 will cause trouble.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sat May 12, 2018 10:35 am quote
104 main doesnít splutter at WOT but feels a bit rich. I will go 102 and check 1/4 throttle temps. It is rich at 1/2-3/4. Maybe it all works out at 102 and 1/2 clip leaner....
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sat May 12, 2018 1:37 pm quote
102 main guves 330 at 1/4 throttle. Feels a bit rich 1/2-3/4.

Lowered 1/2 clip, same temps, middle is cleaner but might still want leaner. Going to ride it like this for a bit.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Sat May 12, 2018 7:36 pm quote
Good you're starting to like how it goes. Although going better, you can see it's not correct. Weak at the bottom and rich at the middle. As the clip goes down the 1/4 will get even hotter. After a seriously long thrashing 1/4 may be doing some piston damage.

Needs more air brake and more fuel. 2.7 with 1.0mm

With an emulsified atomiser the air element becomes more significant as the pressure increases. This should work better than the 2.6.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sat May 12, 2018 8:32 pm quote
You think the air brake will move the idle? I had a 36 idle in with that needle bushing before.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sat May 12, 2018 8:48 pm quote
Thinking back it didnít move it much on this bushing, probably need to start at 36 idle.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Sat May 12, 2018 9:04 pm quote
There will be a certain amount of bleed over from the atomiser/needle diameter to the idle. Everything affects every thing to some degree.

Try not to get hung up on the numbers. Non emulsified pilot jets will be smaller for the same fuel flow.

With a bigger air brake the higher rpm will be weaker. With more needle choice the carb would just be re jetted with a weaker one. As you are already on the 1.4 tip and weakest needle, there is nowhere to else to go.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sat May 12, 2018 9:12 pm quote
Yeah Iím not hung up on it being a small number, just need to know where to start again. Seems like as good a place as any.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sun May 13, 2018 10:24 am quote
2.7 needle bushing
0.6mm air brake
110 main, 36 idle, 3rd clip

WOT doesn't splutter, main will go up to 114 for next trial. Return to idle isn't fluffy, will go with 34 next trial. Middle seems a bit fat but we can work with the clip on that.

It really seems a little goes a long way with the air brake on high RPM. I'm guessing the 1.0mm air brake would take me into the 120's on main jet. I'm going to work with the 0.6 and I'm wondering if 0.3 might be better (too bad I drilled it out ).

No wonder it got hot as hell back in the beginning when I just slapped the 0.6 air brake in with 95 main and 2nd clip .
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sun May 13, 2018 2:00 pm quote
114 main splutters, 110 is the winner

34 idle is fine

1/4 throttle temps are next
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sun May 13, 2018 3:28 pm quote
1/4 throttle is rich, 250 max temps.

Dropping clip by 1/2. Lots of room to work with.
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Sun May 13, 2018 6:59 pm quote
Its gone in the right direction, as expected.

With the temperature on the stud, if it was PX I would put the 1/4 at 250F to give 300F at the plug. You seem to think your smallie needs another 50F. Should still be fine.

Looking more and more like 2.7 and 1.0mm is going to give the correct curve to me

Remember the clip affects the whole needle. All throttle positions change together. On this carb, use the clip to adjust 1/4 and the air brake to adjust 1/2.
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sun May 13, 2018 7:12 pm quote
Yeah I'm not really sure it needs 50 more, it just was a bit spluttery at 1/4 throttle, especially lower RPM. That's safe side, but probably overly conservative. That said, clip adjustment still hasn't been done. I'm pretty sure the whole throttle range can take 1/2 or even 1 whole clip down based on the temps I'm seeing.

At this point, I'm not sure what the advantage of going 1.0 air brake vs the current 0.6 would be. I'd need to buy the next jet set up because I only have out to 118 and I'm sure the change would take me beyond that for main jets. (going from 0 to 0.6 raised the main jet by 15). *edit* I see now that you are saying if I can't get 1/2 right I may need to go up on air brake, gotcha.

I will see how the 1/4 and 1/2 are with clip at 2.5 next.

Thanks for the help!
Molto Verboso
PX221 Malossi, O tuned PX200 and some motorbikes
Joined: 14 Jun 2017
Posts: 1032
Location: London UK
Sun May 13, 2018 7:58 pm quote
If there is a splutter at 1/4 then it might need a whole clip. Might all come in ok but moving the clip away from the middle would indicate an atomiser issue, in this case air brake.

Did you order the set of the bigger jets already?

Seems like really going well. You feel its any quicker or riding smoother?
Ossessionato
1980 P200E, 1974 Primavera, 04 Ninja 250
Joined: 04 Apr 2013
Posts: 3604
Location: San Diego, CA
Sun May 13, 2018 8:21 pm quote
I'm game to go a whole clip if need be. Before I started all this, I was on 2nd clip with no air brake. 3rd clip wasted about 10MPG vs 2nd clip, it was nuts. I won't be surprised or upset to end up there. The Polini recommended carb settings for a ET3 (close enough) are 40 idle, 96 main, 2.7 needle bushing, no air brake, 2nd clip.

I haven't ordered the next batch of jets up from 118. I will if the mid range needs more leaning, as it will make me use more air brake and thus more main jet. So far the 1/2+ range is not feeling nearly as rich as it was on the 2.6 needle bushing with no air brake. I think the 0.6 might cover it or maybe the 0.8 if need be.

I'd say overall that yes it is feeling smoother throughout the upper end of the range and based on past experience the clip should clean up the bottom end. At worst we're looking at some more main jets and a swap upward to 0.8 or 1.0. I'd try 0.8 first, I think we are already very close.
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