Stella 2T highway/performance upgrades
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Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Fri Mar 19, 2021 2:03 pm quote
qascooter wrote:
I still don't like that attached filter to the carb box. .
I'm not sold on it yet either, but I want to run with it to see how it does. I've been running no filter in carb box and through frame... which means still no filter all the way through so junk can get sucked in. This is breathable filter through cowl, so supposedly more airflow than regular filter, but now its sucking hot air from cowl. Both have their own negatives. I'll probably end up going back to the no filter through bellows/frame. Although I've read people put filters inside the bellows. I'd like to try that some day if i can find a filter that fits well with the bellows.
Ossessionato
79 P200E, 62 Allstate, 2008 Stella
Joined: 11 Jan 2006
Posts: 2098
Location: Florence, OR
Fri Mar 19, 2021 2:20 pm quote
I hear you. Maybe some filter media fixed over the frame hole under the seat? It's gotta breathe easy though. A cut up Uni filter perhaps?

I'll be interested in what you come up with cause I might do the same
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Fri Mar 19, 2021 7:51 pm quote
qascooter wrote:
I hear you. Maybe some filter media fixed over the frame hole under the seat? It's gotta breathe easy though. A cut up Uni filter perhaps?

I'll be interested in what you come up with cause I might do the same
Here is an option
https://www.vividracing.com/-p-153640154.html?gclid=Cj0KCQjwl9GCBhDvARIsAFunhsmd5xTYF1HhtKMDc7zbzhUXMoUVNVVdqcI4xp2cpuKwMXKWQRICaJ8aAqyZEALw_wcB

Cut that to fit either the under seat hole or the bellows frame hole.

I'm thinking this is more effort for not a lot of gain. Gonna just go back to bellows with no filter and call it a day!
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Sat Mar 20, 2021 1:56 pm quote
Boyesen reeds back on and they fit perfectly as expected. Malossi reed catastrophe did a little damage to the rubber seating pad of the reed block, but I was able to get a perfect seal with the boyesen reeds. QA, you'll be happy to see the bellow is back!

Engine runs no worse for the wear after eating a reed petal. Guess it passed the kidney stone at some point.

But, as usual.. next problem! When it runs, it runs great. But, it still dies every quarter mile or so. It dies under throttle and on idle still. Starts right back up after sitting for a few seconds, maybe a bit sluggish at first start but after running a few seconds its back to normal.

I discovered the issue causing this constant stalling. I believe the engine is flooding, because when I take the carb lid off, there is a sizeable pool of gas at the back of the carb box which is the lowest point. The liquid level is above the air mix screw which I am guessing is constantly drowning the carb and flooding the engine as that pool splashes into the carb.

I'm guessing Jack's theory the float needle is sticking is correct and is the root cause of this? I'll remove clean and replace that next chance I get. The only other option i can think of is the float passage hole is too large now and is dumping fuel into the carb when under throttle. But why would it just start to do this recently and not all along?

It's amazing the constant barrage of problems this scooter is presenting me with lately. I'm starting to hear this song every time I look at or think about the stella!

https://www.youtube.com/watch?v=Ag1o3koTLWM

Comedy, tragedy? At this point I can't tell anymore. I'll just keep moving forward and hope for an end!


gas puddle above the air mix screw. Approx quarter to half a cup of gas just sitting in the box.





Ossessionato
79 P200E, 62 Allstate, 2008 Stella
Joined: 11 Jan 2006
Posts: 2098
Location: Florence, OR
Sat Mar 20, 2021 3:24 pm quote
Oh man, bummer.

Could the fuel be coming from the Banjo gasket, or the top hat gasket, or the float bowl gasket?, or the carb to carb box gasket?

I cannot see how that much fuel can be in the box without leaking out of one of the above areas. Hmmmm....
Ossessionato
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 2241
Location: california
Sat Mar 20, 2021 4:36 pm quote
What Jack would say: ďRight. Float issue. Like I said.Ē

What I say:
Float issue. Float needle seat clean up in order.
Take a qtip, soak in mineral spirits or the like, and put it in ur drill.
Polish the tapered seat where the needle sits.

Get a new needle.
Check exact length of yours and diameter. There are two sizes. Red rubber said to be higher quality by some.

If u canít get a needle, just clean tip of float needle ya got. Plus above.
Molto Verboso
Vespa
Joined: 19 Jun 2007
Posts: 1291
Location: California
Sat Mar 20, 2021 6:43 pm quote
Hey Swiss are you still running a float top spacer? Had trouble with mine and removed. Others seem to work with no issues.
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Sat Mar 20, 2021 6:52 pm quote
No I got rid of that a while ago. Just running with normal 1 gasket stock float height.
Molto Verboso
Vespa
Joined: 19 Jun 2007
Posts: 1291
Location: California
Sat Mar 20, 2021 8:29 pm quote
There are some nuances with the LML reed induction Iím sure but wondering if the absence of a filter above the carb is contributing to the excess fuel in the air box.

I like / love the T5 air filter the new SIP one is not restrictive. Itís wet around the carb opening but clean forward. Get that with a Pinasco cover and you will be pleased.



Ossessionato
76 Sprint V, 63 GL, 62 VBB, 05 Stella
Joined: 16 Jun 2011
Posts: 3201
Location: Nashville
Sun Mar 21, 2021 5:18 am quote
If fuel is leaking into the airbox, it has to be coming from the fuel line, banjo, or float cover.

I'll vote for the float cover.

When it dies, what's the stall like? Have you confirmed it's not a blocked fuel tank breather, which can cause fuel starvation and stalling like that?

Have you tried pulling the plug after a stall to confirm it's a wet plug (flooding) and not a dry plug (fuel starvation)?

Have you confirmed it's not your autolube failing and causing a soft seize? This is pretty rare, but it can happen and produces similar symptoms.
Ossessionato
62 VBB1T Round Tail W/ leaner sidecar
Joined: 26 Jan 2019
Posts: 2241
Location: california
Sun Mar 21, 2021 7:01 am quote
My $.02
If you run with no filter like you did the prior videos - do you see a lotta blowback? If yes - that is likely the source of the fuel in the box.
If no - its an old fashioned leak.

Kind sounds like blow back?
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Sun Mar 21, 2021 7:08 am quote
I got out in the garage early today to diagnose. Have not run it yet to confirm problem solved, cause I couldn't break the peaceful Sunday morning quiet for everyone around my garage, but the problem is probably from an extremely stupid user error.

Float upper body casing that holds the float and needle was loose. Started unscrewing the banjo to take carb out and immediately saw the whole upper casing wobbling around loosely as the two screws either came loose or I just didn't tighten them enough after carb clean. So that whole upper casing was probably just bouncing around allowing fuel to come gushing out the float area into the carb. Idled fine cause it wasn't enough to vibrate and splash out, but once running it was a good ole fashioned zoolander gasoline fight in the carb!

I'll wait till noon before I go for a run.

the reference never gets old for me.

https://www.youtube.com/watch?v=OTrxEQnPtAg
Ossessionato
79 P200E, 62 Allstate, 2008 Stella
Joined: 11 Jan 2006
Posts: 2098
Location: Florence, OR
Sun Mar 21, 2021 7:34 am quote
You're killin me... I'm glad you found the leak..
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Sun Mar 21, 2021 9:43 am quote
I figured it out.. this is a comedy!

Everything fixed.. still dying under throttle. Lift up the seat and notice the new seat has an impression of the gas cap on it, and the gas cap has clearly worn edges to the protruding top where the vent is. So literally everyone was right in every suggested solution.

Summarize all the things i did at the same time last week:

1.) Clean carb and gas tank.. caused float leak.
2.)Tried malossi reed petal instead of boyesen.. destroyed reed petal.
3.)Put a new seat on it... Caused fuel vacuum issue from the seat contacting the vent hole.

Every one of those things was causing problems all at the same time.

Old seat going back on this bike as the gas caps for lml are too high and the seat even if i raised the bottom plate up would cause issues cause the rubber feet aren't high enough to raise above the gas cap.

Also unrelated but still funny. Brand new seat already falling apart. Nisa not cool. The seat itself has a metal base that holds a magnet in it. This metal base slides into a metal sheath on a mounting plate attached to the frame. The glue holding the magnet inside the metal base on the seat came off already and the magnet was left in the mounting base plate. Requires more heavy duty glue.


Wear around the raised edges belies the problem.


Accompanied wear spot on bottom of seat. Fuel tank can't get airflow needed


Nisa fail. This magnet..


Is glued inside this mounting spot. Glue failed in a couple minutes riding


Magnet and metal mounting spot sit inside this metal ring and lock the seat into place.. when the magnet doesn't get pulled off the seat.

Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1683
Location: Rochester, Minnesota
Sun Mar 21, 2021 10:03 am quote
I don't think that those two surfaces are going to make an airtight fit. If your really worried dent it in the area with a ballpeen hammer.

If you want to sell it instead let me know.
Ossessionato
1979 P150X, 1983 P200E, 1988 T5, 1995 PX200E, 2011 Yamaha Fazer 600 S2
Joined: 02 Aug 2015
Posts: 2261
Location: Veria, Greece
Sun Mar 21, 2021 10:29 am quote
Haha, same sh!t happened to me in the summer, returning with the T5 from our annual Vespa gathering. At first, I thought I seized and sh!t my pants. Then I thought that it was probably fuel related. Saw the capís impression on the seat and realized what had happened. Made a dent with a hammer and that was it...
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Sun Mar 21, 2021 11:44 am quote
Christopher_55934 wrote:
I don't think that those two surfaces are going to make an airtight fit. If your really worried dent it in the area with a ballpeen hammer.

If you want to sell it instead let me know.
It was the seat. Swapped old seat on and all my problems evaporated. I will be keeping the seat and shaping it like Safis. I'll hit it with the heat gun slightly to soften it up and then ball peen it into shape. Thats for another time though.

New plug after fouling the last one. Only about 5 miles on it.

45/120 idle 2 turns out, 120/be4/128mj




this dark and light line on the bend of the electrode is what Jack was talking about on cm22's thread I believe.

Molto Verboso
Vespa
Joined: 19 Jun 2007
Posts: 1291
Location: California
Sun Mar 21, 2021 12:15 pm quote
Great news Swiss by the way recently I swapped out my Super Corsa for a new sprung PX seat after 25 mile freeway ride my back ached for a month.
Molto Verboso
2007 Stella 225
Joined: 02 Nov 2019
Posts: 1683
Location: Rochester, Minnesota
Sun Mar 21, 2021 12:48 pm quote
swiss1939 wrote:
Christopher_55934 wrote:
I don't think that those two surfaces are going to make an airtight fit. If your really worried dent it in the area with a ballpeen hammer.

If you want to sell it instead let me know.
It was the seat. Swapped old seat on and all my problems evaporated. I will be keeping the seat and shaping it like Safis. I'll hit it with the heat gun slightly to soften it up and then ball peen it into shape. Thats for another time though.

New plug after fouling the last one. Only about 5 miles on it.

45/120 idle 2 turns out, 120/be4/128mj
Seat pan is a urethane then? I was thinking it was a metal pan. Do you have a link to the seat that you purchased. Still looking for a seat that sits lower, if your rubbing the gas cap it sits lower than mine.

I was looking at the Nice site and there are a few.
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Sun Mar 21, 2021 12:58 pm quote
Hibbert, good to year you still riding and enjoying!

Christopher, my new seat sits lower and is also narrower/thinner padding.. although it is comfortable despite not being as thick as the standard seat pad. When I put it back on, I will have to remove the rear rack which wraps around the front helmet hook area because the bar that goes around the front of the seat sticks out now and your legs rub up against it with this smaller seat. It was fine with the big thick original seat, but isn't comfortable with this narrower seat. I do love the new seat though! Rack that now is uncomfortable with narrow seat pictured here:


And the seat bottom is molded plastic. Only the magnet holder on the seat bottom is metal. pictured here:


As mentioned, two mods required. Mold the seat bottom around the gas cap to not interfere with vent, and apply stronger metal to metal glue on the magnet which sits on the seat bottom.

https://www.sip-scootershop.com/en/product/sport-seat-2020-sport_75903SBL
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2755
Location: London UK
Sun Mar 21, 2021 3:43 pm quote
Sorted at last. Looks slightly hot. If that plug is an 8 put a 9 in. How's the jetting feel? Any spluttering or coughing?

What about using a hole saw to cut above the gas cap?
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Sun Mar 21, 2021 3:53 pm quote
It is an 8. No dead spots feels solid throughout, but if anything the first quarter throttle off the line is slightly slow but not enough to bog. Trying to figure out if the idle is slightly lean or slightly rich, but I'll do a more detailed plug chop when i get a chance. Hoping i can do an idle plug chop by just putting a new one in letting it idle for 10 min then cutting the sheath off to see what the ring looks like.

Holding at quarter to half throttle stays rock steady no racing and no hiccups.
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2755
Location: London UK
Mon Mar 22, 2021 12:18 am quote
The issue is at a bit under 1/4, like 3/16. Focus on that area. If you ride steady at 3/16, accelerate up to it, decelerate to it, then you might work it out. CHT might help. If slow cruising for a while and it gets hot, it's lean. And it probably is lean.
You tried a few miles holding WOT yet?
Hooked
Vespa PX200
Joined: 27 Jun 2010
Posts: 430
Location: Belgrade
Mon Mar 22, 2021 6:17 am quote
Dang, came late to this conversation -- glad you got the problem sorted.

I was going to weigh in that that a weird, inconsistent engine problem is almost always something with fuel. If it's consistent (but no less baffling), probably electric.

Re. the leaking fuel, here's a 5 minute hack you can do to an SI carb that at least lets you rule out leaks from the top hat:

https://youtu.be/0jwM65sP06s?t=561
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Mon Mar 22, 2021 9:34 am quote
Jack221 wrote:
The issue is at a bit under 1/4, like 3/16. Focus on that area. If you ride steady at 3/16, accelerate up to it, decelerate to it, then you might work it out. CHT might help. If slow cruising for a while and it gets hot, it's lean. And it probably is lean.
You tried a few miles holding WOT yet?
Not yet on the few miles wot.. still a bit nervous to give that a shot again after the last time. I want to do a true plug chop of a short wot run and also confirm the idle isn't lean first before I give that long WOT run a go.

JVM, thanks for the link. I have seen that video when first posted, and went looking for it this week but couldn't find it.
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Mon Mar 22, 2021 4:25 pm quote
BR9ES plug in now. Took it for a good 30 miles or so and did both a wot run on fresh plug pulled immediately after engine cut off, and also took it on my highway test run for first time since last seize.

Engine runs great, I think it is very close on jetting, but again still think possibly slightest rich on idle because it just seems the slightest slow off the line until it gets onto the mj.

Plug chop photos below. These plugs are strange in that the ceramic center doesn't go all the way down to the bottom of the sheath, instead its only about halfway down. Any thoughts on the ring? It looks good to me but maybe slightest lean? I forgot to actually measure the ring thickness. I'll do it tomorrow.

Also the ring gets wavy on one side of the ceramic. Guessing its a turbulent airflow thing?

Photos of the piston top after those 30-40 miles also attached.

WOT Run temp gauge shot (egt on left, CHT right, CHT markings go from yellow to red at 300F)
https://youtu.be/xP4dWjrXzvo


As far as highway run.. about 3 miles, held mostly 3/4 throttle with some wot but not pegged at wot, just kinda 3/4 with a little wot pulsing. Temps seemed to stay rock steady at around 300F, maybe slightly more?? If more it wasn't more than 315F. Forgot to use gps, but the speedo was at around 67mph for the 3 miles at 3/4 throttle. This highway run was somewhat confidence building finally after the last attempt took all the confidence out!

Balanced front hub and tire, not balanced rear hub and tire.. and the bike felt so smooth at 67mph! Like i could go another 15 mph before it felt sketchy. Granted, I think the top speed for this engine is maybe 73-75mph given what I just ran on 3/4 throttle.

The first 3 min or so of this video starts off with my 3 mile highway run cruising around 65-67mph... then a few minutes of various parts of riding back to my garage so you guys can see how crappy Staten Island streets are. Audio on this camera sucks so its not great to judge minutiae of jetting at lower throttle. I'll get a better audio recording this week.
https://youtu.be/grhOy5cwEuY

My thoughts based on that plug chop at wot and the other plug at low throttle right before photo is that i could go up two main sizes to 130 to get that ring slightly thicker from richer main, and one size leaner on idle jet.




wavy line section


same but without flash. natural light.


WOT Plug chop before cutting sheath off. This plug is brand new.. only used for that quarter mile wot run.


same brand new plug only run quarter mile WOT run.


30-40 miles on this jetting and 9 plug.






BR9ES Plug with 30-40 miles on it. 45/120 idle, 120be4128mj. This was the plug used for highway run shown in video.


BR9ES Plug with 30-40 miles on it. 45/120 idle, 120be4128mj

Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2755
Location: London UK
Mon Mar 22, 2021 11:24 pm quote
Plug is now looking good. Piston colour confirms it. Main jet is probably good. Might be worth checking the 130. When at 67mph, did the pulsing from 3/4 to wot feel like it did something? Or it went better at 3/4?

Sound recording too bad to help with the pilot jet. 48/140 would be my next try. I don't like the feel when the small number is too small.
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Tue Mar 23, 2021 10:24 am quote
48/140 idle. 120/be4/130 main jet.

Runs better! Still possibly slightest rich on idle.

https://youtu.be/qAVq-kWluaI

extended ride video so you can hear all the glory of low and high throttle and possibly deduct where to improve. Audio is from my cell married to the video for better sound quality.

Added some notes on scenics for you guys to see the location.
Quote:
When at 67mph, did the pulsing from 3/4 to wot feel like it did something? Or it went better at 3/4?
Just felt like it wanted to go faster, but not out of control faster. Felt same at both 3/4 and full.. I just didn't have the confidence to take it full throttle for a long time, not due to speed but out of fear of temps. But now that I've ridden it quite a bit with this jetting and see the temps stay 300 and less, I have more confidence in trying a long wot run now to make sure temps don't keep climbing.





Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2755
Location: London UK
Wed Mar 24, 2021 1:50 am quote
Running heavy on the transition. The 130 main jet is a bit too big. Go back to 128 confirming it is 128 in relation to the 130. Then check again.

Confirm that you can feel acceleration when going from steady 3/4 to WOT. And check the 1/4+ position has improved.
Mixture screw is slightly too far in.
Front brake hose is hanging too low. Not clamped in correctly somewhere.

Otherwise running pretty solid. Nice tour round the island.
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Wed Mar 24, 2021 4:46 am quote
Jack221 wrote:
Mixture screw is slightly too far in.
I agree with the mj suggestion that the transition is heavy and was thinking the same, but i am wondering what you hear or see that tips you off the mixture screw is slightly too far in? Would love to know that little hint because i can't tell. Is it the slight sluggishness accelerating from stop or a hiccup that I'm just not hearing? Or is it the idle at stop is just a bit fast and staccato?

It's currently 2.5 turns out.
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2755
Location: London UK
Wed Mar 24, 2021 5:37 am quote
Just the sound. Is too rich as it throttles up. Check the main jet on the first lap. Then if better on transition but still not good on pick up change the pilot to a 45/140 for the next lap.
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Wed Mar 24, 2021 6:19 am quote
Ok then we are 100% in agreement. My initial thought was 130 was slightly rich cause the crossover had just a bit richness to it, and the idle was still slightly rich cause of slow takeoff from stop.

I was confused by you saying the mixture screw was too far in.. thinking you meant the idle was too lean and screw needed to be opened more, cause mixture screw leans out inward and richens outward.

Not far off now, and what a difference a week makes.. going from 99 problems... to almost dialed in!

This stella:
https://www.youtube.com/watch?v=wzUCoIGsFdA
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2755
Location: London UK
Wed Mar 24, 2021 6:44 am quote
swiss1939 wrote:
cause mixture screw leans out inward and richens outward.
All good just the other way around. Screw is a mixture screw and richens as its undone/outwards/anticlockwise
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Wed Mar 24, 2021 6:59 am quote
Jack221 wrote:
swiss1939 wrote:
cause mixture screw leans out inward and richens outward.
All good just the other way around. Screw is a mixture screw and richens as its undone/outwards/anticlockwise
Slight confusion cause we are talking across each other but saying the same thing! All good. Inward screwed into carb clockwise.. lean.. less fuel more air through idle is what i was saying.

End result is the same. I'll drop to 128mj first then drop to 45/140 if idle still a bit rich.

EDIT: I see where the confusion came in.. I was saying "lean out inward" what I meant was "lean the mixture out, by screwing inward".
Jet Eye Master
PX221 MHR, O tuned PX200, PX125 and some motorbikes
Joined: 14 Jun 2017
Posts: 2755
Location: London UK
Wed Mar 24, 2021 9:33 am quote
My mistake, no language confusion, I just wrote the wrong word. Always going in when I should be staying out.

Mixture screw too far out (not crazy far out, that's something else). But not the case, mixture screw is 2.5 turns and the 48 number is too big. 45 should do it but with 140 this time.
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Wed Mar 24, 2021 9:54 am quote
BTW, I haven't moved the brake line at all since I got it. I believe this is how LML fed the line stock. All photos I find online have same brake line layout and slack.

I guess maybe I could push the line up the fork slightly to remove some slack.. I've taken the caliper off a bunch so maybe when it was dangling it pulled down more than normal.



You've got me googling px disc brake photos now to see how everyone has the line fed!
Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Sat Mar 27, 2021 11:00 am quote
I've done a lot of experimenting with various jetting in the last 3 days and think I am close, but not quite there yet.

I tried various atomizers between super rich, be4 all the way to lean be3 (be4, be5, be1, be3). be3 felt the best but I was not happy with the plug color. be4 had the nicest brown color while be3 had a yellower tip and black base.

I tried both a 128 and a 130 on the highway in longer runs. 128 gets a little hot for my liking and 130 seems close and more stable on wot temps on highway runs.

I last left off yesterday with a 140/48 idle 2.5 turns out and a 120/be3/130 main jet. this felt really good through the full throttle range with only a slight hiccup at the upper limit of the crossover point which I believe was a lean hiccup. It also felt slightly rich on the low end. So I sat around last night and this morning contemplating it all. I know I did not want to go leaner to 128 cause the temps on WOT highway run yesterday were a little more than I would like.. 300-325F with potential to go higher very slowly over time.

What I decided was that I needed to solve for just the hiccup at the upper quarter crossover point by making it richer, but not make the full WOT any richer. I remembered a discussion somewhere on here about how the atomizer and jet circuits work on SI carbs.. low throttle fuel is only covering the bottom of the main stack so all the other holes are open to air, mid throttle, the middle to bottom holes are covered in the atomizer by gas, and high throttle, the top of the atomizer holes are covered with gas. So I figured I wanted to try to see if I could control this hiccup using this knowledge and experiment with atomizers to solve for it. I compared photos of the be3 to all the other atomizers and saw that going to an e3 is almost exactly the same as a be3, with one exception, the top large air holes at the top end of the atomizer is slightly richer on e3 vs be3. This is because there are 4 top holes at the four poles around the cylinder on the be3. The e3 has the same size holes up top, but only 2 holes vs 4. I figured this would richen just the top 3/4 crossover point and possibly get rid of any hiccup.

So this morning, I went in and left everything the same but swapped the be3 for e3. This definitely improved it, but there was still a slight stutter. So then I figured I am on such razor thin lines of rich vs lean that i now have made my 130 mj slightly too rich with change to e3 at the top third crossover. To solve for this I went down to a 128mj and instantly it felt amazing through the full throttle range at all rpms (with the exception of the standard bottom 1/8 barely opened throttle four stroking that no one seems to be able to get rid of). this simple change from 120/be3/130 to a 120/e3/128mj seemed to make a huge difference where it is nearly perfect running now.

So I took it back on the highway for another hard long wot run to see what temps do. To recap, my previous two days of WOT runs proved a 128mj was up around 300-325F when held on wot, but around 300F when held at 3/4 throttle. A 130mj was closer to 275-300F when held at 3/4 and 300 or just barely over 300F when held at WOT. It felt more in control of temps at WOT on a 130 mj. But I figured because I made the upper middle crossover slightly richer with e3, the 128 mj was now close to a 130 mj previously on the be3. I did about a 5 mile run in one direction got off and came back the same 5 miles in the other direction. I held WOT for a really long time to really push it to see what temps would do. Temps on this 128mj were 325-350F held long WOT. EGT temps were approx 1200F on same long WOT hold. Both the EGT and CHT were at the upper limit of my yellow to red warning markings on the gauges. EGT right on that line, while CHT slightly into the red line marking by about 25-50F. I tried to control temps by backing off throttle into 3/4 throttle. I was able to keep temps from going higher than 350F, kept around 325-350F after slowly backing off WOT while maintaining my speed at 3/4 throttle. I did not take any chances letting fully off throttle, but slowly crept off throttle to ease it down so the temps would not spike from lack of fuel. When I got off the highway and came to red light I went to idle, and temps definitely spiked up between 340-375F but came back down relatively fast. Being at the red light idling for about a minute, temps came back down to 290-300F. It did not seize at all the whole time which I was waiting for. So that is good news, but I still believe I was a bit on the line of too lean on main jet or too much timing due to that higher temps.

But a question I was left with is what is too hot for EGT? In terms of dangerous seize territory? My EGT was in a safe 1000-1100F range with everything but the end of the long WOT at 65+mph. At that point it was encroaching around 1200F.

After those jetting changes I believe I am close in terms of jetting because the throttle response is excellent, but either my timing is slightly too much, causing the 128 to get a bit hot, or my idle is too rich and main too lean. I believe after that hard highway run watching the temps and trying to control them through throttle actions, that a 130 mj or possibly a safer 132 is the correct main I should be at. Only problem is going to a 130 introduces a bit of mid range dirtiness.

Plug looked real tan at 128mj after that really hard wot run. So i know it is close. But again the plug base looks too black, and the true plug chop of a 128 mj shows it is a bit lean.

In comparison I did 3 true plug chops, 2 on a 128 main, and 1 on a 130main. The photo below shows them and lists what the jet stack is for each. This I think proves a 130 or 132 main is the correct jet.

BTW, confirmed on the gps yesterday that I hit 70mph in 4th but not max rpm still slowly climbing. Today on this long hard wot run I did not have my gps going as I was focusing solely on temps and making sure I was ready for a seize, but I did glance at the speedo at one point and noticed the needle was pegged at the max 75mph, and knowing my speedo is about 5mph slow, I was definitely over 70mph and it felt comfortable aside from the 350F temps which were worrying me. This is about when I slowly eased off to 3/4 throttle to bring temps down slightly. I'm guessing based on how much it still felt like it had in it that I was probably going about 72-73mph and could reach 75-76mph max? Granted I don't necessarily want to do that other than to see the limit once. It was a very comfortable ride cruising at about 65mph not peak rpm.

Also linked here a separate run of 2nd gear WOT which is the true plug chop of the 120/e3/128 plug seen in the comparison photo. Too lean.
https://youtu.be/-ZIa_aieRIc


kinda messed up the 130 plug chop cause I sat idling for far too long before I went on the run. but you can see the line beneath the color cast.


2nd gear WOT run on a 120/e3/128mj. Definitely lean as proven by the highway temps.


140/48 120/e3/128mj after 10 miles highway WOT and slowly backing down to idle.




piston top at same time as plug photos right after highway run.





Ossessionato
VSX, Stella 177, VNX1T, V9B1T
Joined: 20 Jul 2018
Posts: 2990
Location: Staten Island, NY
Sat Mar 27, 2021 6:20 pm quote
Found the discussion on atomizers which clicked in my head last night. It was ginch!
http://modernvespa.com/forum/post1643545#1643545

Although this shows i had the concept reversed. Was thinking holes closest to ac affected high throttle not low throttle. So going from be3 to e3 enriched the lower third of the range. Which i guess if you think about it, spreads the rich idle (as seen from black plug base) out higher into the crossover range so it cleaned up the middle range by richening the middle not from the main, but from the idle.. and compensated for a slightly lean mj.

Now I'm thinking if i go to a 132 mj, the be3 might run better.

First step.. true clean plug chop of a 132 main to confirm the ring is right thickness. Then try to narrow down the idle so the plug base looks correct being brown instead of black. Then sort any middle throttle dirtiness by using this atomizer knowledge.



Ossessionato
79 P200E, 62 Allstate, 2008 Stella
Joined: 11 Jan 2006
Posts: 2098
Location: Florence, OR
Sat Mar 27, 2021 6:45 pm quote
I go away for a week and come back to this most excellent writeup of your experimentations. This is some good info Swiss - thank you for documenting it.

I'm going to use some of the knowledge you've shared to help get the two 177s dialed in.

Good job and thanks again!
Molto Verboso
Vespa
Joined: 19 Jun 2007
Posts: 1291
Location: California
Sat Mar 27, 2021 6:59 pm quote
my eyes are bad is that 20hp and 7,500RPM
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