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Buddy 50 hesitating/stalling

 
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tenders
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Joined: 03 Dec 2018
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Buddy International 50 Italia

PostPosted: Tue Mar 19, 2019 2:12 pm    Post subject: Buddy 50 hesitating/stalling Reply with quote

My 09 Buddy 50 starts beautifully and seems to idle and run fine with the autochoke on, and at full tilt, but once warmed up is hesitating when the throttle is opened about 20%. It has a distinct range of inactivity during which the engine idle gradually slows while the throttle is twisted in that 20% band, and will stall. This is a real stinker during slow-speed maneuvers! It catches if I goose the throttle to full, and will sometimes catch if I repeatedly blip the throttle from 0-20%. Top speed is fine, about 38 by GPS/41 BMPH.

This seems like a textbook slow-speed jet clog, right?

I’ve had the carb apart three times from the float bowl cover side. It, and the jets, are clean as a whistle throughout. I replaced the float bowl gasket; no change. Thinking maybe the throttle somehow wasn’t activating, I took that apart from the top of the carb and the spring, needle, and linkage to the cable seem perfect, and the throttle action in the carb body is smooth (gave it all a little shot of Teflon lube just to make sure). I replaced the inline fuel filter; the supply line didn’t leak while I was doing this, and I gave a little suck on the vacuum line to see what would happen. I got no feedback while I was doing this but there was gas in the new filter when I checked it a minute or so later so the vacuum petcock seems to be working. The vacuum and fuel lines look perfect, though they are likely original.

I was about to order a new vacuum petcock, thinking there should perhaps have been more feedback when I sucked on the hose, but it really doesn’t feel like the problem. There seems to be too much reserve fuel in the float bowl for a bad petcock to affect the engine so quickly.

My sense is that an air leak someplace would affect top speed, not slow speed. But the gaskets seem properly installed.

What am I missing? Should I just replace the two jets?
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BuddyRaton
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PostPosted: Wed Mar 20, 2019 2:07 pm    Post subject: Reply with quote

I would check the stator and pickup. Sometimes electrical problems don't start occurring until things are warmed up.
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tenders
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Joined: 03 Dec 2018
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Buddy International 50 Italia

PostPosted: Thu Mar 21, 2019 2:37 pm    Post subject: Reply with quote

I do think it’s fuel, and I may be getting closer to a solution. I took out the pilot jet again last night, compared it to a different type of jet I had upgraded from my Vespa, and realized that I couldn’t see clearly through it. My trusty jetcleaning tool, a length of baling wire I have used and kept carefully in these situations with larger carbs for twenty years, turns out to be too large to fit through a #40 pilot jet. I had only been poking it into the ends and hadn’t realized the hole is supposed to be larger than it appears.

A single strand of copper wire from some 14 gauge insulated wire I had lying around was eventually persuaded to go through the jet smoothly, so it saws back and forth in the jet like floss and the jet spins around it when flicked. Now the hole is much more visible and round. Although it looks like they should fit, I could not get two strands to go through for love nor money. If I can get two strands to pass through a brand new jet I ordered, I will be replacing it this weekend.

Nevertheless this, and an adjustment of the idle speed thumbscrew, helped a bit but not entirely. It is still pretty easy to get the engine to stop responding in the first 20% of throttle, but now at least it doesn’t stall.

Are there narrow passageways in the pilot circuit of the carb itself that need to be reamed out similarly? This link about a different model of carburetor makes me think there may be:
https://www.hondaatvforums.net/forums/repair-maintenance/16961-pilot-jet-plugged-how-do-i-clean-3.html

I’m not sure where this pilot jet hole schmutz came from, and I never saw any particulate matter actually fall out of the jet when I reamed it with the single strand. Maybe it’s brass corrosion? The carb itself and all visible ports are clean as a whistle. I dismantled the original fuel filter, too, thinking a clot of fuel gunk might be apparent from years past, but no, it was perfectly clean.

I used to think I knew enough about carbs to be self-sufficient on this kind of stuff. Now every time I take this one apart I feel like I know less than I did before!

If this approach (one more carb disassembly) doesn’t pan out this weekend, I’ll start looking to electrical causes.
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sc00ter
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19 Piaggio Liberty S, 98 Zuma

PostPosted: Thu Mar 21, 2019 2:47 pm    Post subject: Reply with quote

My 09 Pinky Buddy had a dirty carb. I just pulled it off, removed the float bowl and tossed it in the ultra-sonic cleaner with a few drops of dish soap and the heat cracked to high. I even left the float on. Left it in for around a hour or two, moving it to a different position every half hour. Scoot ran so good after that. Harbor Freight has fair priced ultra-sonic cleaners.
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tenders
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Buddy International 50 Italia

PostPosted: Sat Mar 23, 2019 3:06 pm    Post subject: Reply with quote

sc00ter wrote:
My 09 Pinky Buddy had a dirty carb. I just pulled it off, removed the float bowl and tossed it in the ultra-sonic cleaner with a few drops of dish soap and the heat cracked to high. I even left the float on. Left it in for around a hour or two, moving it to a different position every half hour. Scoot ran so good after that. Harbor Freight has fair priced ultra-sonic cleaners.


Well, we’ll see what happens. You just sold me a Harbor Freight ultrasonic cleaner for about $60 with a coupon.
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tenders
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Buddy International 50 Italia

PostPosted: Sun Mar 24, 2019 11:06 pm    Post subject: Reply with quote

Well, after a weekend messing around with this, here's what happened:

* I cleaned the carb very thoroughly yesterday in the ultrasonic cleaner, every part removed, then blew it out with compressed air
* Last night, with great difficulty, I got it to start, and it stumbled for about 20 seconds, gushing white smoke, then died
* I've had the carb apart six or seven times to see what's going on, it all looks great
* Now the engine practically never starts, and when it does, it revs up once, then dies
* Fuel is leaking out the airbox; the needle valve and float look fine and I didn't change the float valve configuration
* I've fiddled with the idle mixture screw and the air/fuel screw ad nauseum, no difference

After a prolonged no-start period this afternoon, I checked the spark plug; it was wet and the engine did do one of its one-rev tricks afterwards. I replaced the CDI, no difference.

I don't know what I did wrong here but I'm replacing the carb. This poor little scooter went from slightly out-of-tune to completely inoperable!
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sc00ter
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19 Piaggio Liberty S, 98 Zuma

PostPosted: Mon Mar 25, 2019 12:42 am    Post subject: Reply with quote

I cant tell you how many times my clumsy hand has caught the float while pulling off the float bowl. Check the float height per the service manual. I gave the service manual back that I used for Pinky, or I would have posted the correct setting. It sounds like its flooding-bad. If the float height is 100% correct (make sure or you will chase your tail) then put in a new needle valve. Last thing, is the float "floating"? Is there a chance its warped or taking on fuel?
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tenders
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Buddy International 50 Italia

PostPosted: Mon Mar 25, 2019 10:43 am    Post subject: Reply with quote

Dang it, now you’re giving me some hope, and i had just gotten used to hopelessness. Thank you for your encouragement.

I don’t know why but these Keihin PB carbs are practically invisible online. I believe this one on the Buddy 50 is a PB16, 16 referring to the size of the venturi in mm. There is a Keihin logo but no model is stamped on my carb except for the numbers 086 ZHZ, with some kind of a graphic resembling an A inside a rectangle between the numbers and the letters. The jets are not standard and not compatible with the more widely-used Keihin models, and the only place I could find the slow speed jets is jetsrs.com. (Which i didn’t bother to install yet as the ultrasonic cleaner really worked magic on the old jets in a 10% citric acid solution. I used dishwasher treatment from the grocery store that is 25% citric acid, and diluted it with water about 1:1 in the ultrasonic cleaner.)

There is no carb calibration information in the Buddy 50 service manual, the PB series is not mentioned on Keihin’s website, and no PB carb manual exists on the internet. The best I was able to find was a 1986 manual for a little Honda CT110 motorbike, which mentions the float level as 10.7mm (0.43”) for a slightly larger Kehin PB carb with an 18mm venturi, and slightly smaller pilot and main jets (38 and 72, vs the Buddy’s 40 and 75). That will have to be good enough, at least to see if the current setting is far out of whack.

I dropped a few more bucks on a replacement needle valve under the assumption that either it or a misaligned controlling tab on the float is the culprit, but I’m not sure how much appetite I will have for more puttering with the carb next weekend when the box containing a drop-in replacement will be staring me in the face.

PS: the float is pristine, square in every dimension I can think to look at it, and very buoyant. I don’t think that’s the problem.


Last edited by tenders on Mon Mar 25, 2019 3:04 pm; edited 1 time in total
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sc00ter
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19 Piaggio Liberty S, 98 Zuma

PostPosted: Mon Mar 25, 2019 2:56 pm    Post subject: Reply with quote

I know its kinda a pain to put a "normal" aftermarket carb on the Buddy 50 because of the weird mounting base. They sell conversion kits but I understand you cannot reuse the OEM air box, and have to go with a pod style filter? No thanks, I didnt want to open a can of worms. I've never cared for pod filters anyways. To bad you dont know a go-cart or dirt bike enthusiast as most of them have a pretty good understanding of carbs, to be there in person. Even I have to reach out for help sometimes.
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tenders
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Buddy International 50 Italia

PostPosted: Mon Mar 25, 2019 5:43 pm    Post subject: Reply with quote

So the reason there isn't more information on PB-series carbs on the internet, according to Chad Thompson at Sudco, Kehin's subsidiary:

Quote:
Keihin cannot publish any information on them because they differ from model to model and the OEM that it was made for owns the rights. So if it’s off a Kawasaki, it’s up to Kawasaki to publish that information. Float height should be in the owner’s manual and/or service manual for the vehicle. A lot of the carburetors on the Taiwan bikes are counterfeit and will say Keihin even when they are not. Typically, the float arm will be parallel to the gasket surface when the float height is set correctly.


I have no reason to doubt the pedigree of my Kehin-branded carb, but it does seem to have been PGO/Genuine's oversight to not include the float level spec in the maintenance manual. The spec doesn't seem to be anywhere on ModernBuddy after all this time, either...has nobody had to adjust this before after all these years?

How badly will I want to take the float bowl cover off of a brand new carb just to check the float level so it might be applied to a messed-up carb? Not very badly...but I'll be replacing the JIS/pseudo-Phillips fasteners with Allen-heads on the new carb anyway.
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k1dude
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PostPosted: Mon Mar 25, 2019 9:04 pm    Post subject: Reply with quote

dupe

Last edited by k1dude on Mon Mar 25, 2019 9:06 pm; edited 1 time in total
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k1dude
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PostPosted: Mon Mar 25, 2019 9:05 pm    Post subject: Reply with quote

dupe

Last edited by k1dude on Mon Mar 25, 2019 9:06 pm; edited 1 time in total
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k1dude
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'08 Orange Buddy 125

PostPosted: Mon Mar 25, 2019 9:06 pm    Post subject: Reply with quote

I know it looks like a fuel problem, but it's sounding more and more like a stator problem.

When people start having stator problems, they always first think it's a fuel delivery problem.
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tenders
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Buddy International 50 Italia

PostPosted: Mon Mar 25, 2019 9:18 pm    Post subject: Reply with quote

I’m having a hard time understanding how a stator/electrical cause is more likely than a carb issue that got worse after the carb was messed with. Possible, yes, I guess. But more likely than prosecuting a carb cause? The scooter yesterday was plugged into a battery charger while I was fussing with it so the battery was as topped off as it’s ever going to be. I would think that would move the stator cause even further down the likely list.
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k1dude
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'08 Orange Buddy 125

PostPosted: Mon Mar 25, 2019 9:36 pm    Post subject: Reply with quote

tenders wrote:
I’m having a hard time understanding how a stator/electrical cause is more likely than a carb issue that got worse after the carb was messed with. Possible, yes, I guess. But more likely than prosecuting a carb cause? The scooter yesterday was plugged into a battery charger while I was fussing with it so the battery was as topped off as it’s ever going to be. I would think that would move the stator cause even further down the likely list.


Purely coincidental? Simply bad timing for the stator to crap out?
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tenders
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Buddy International 50 Italia

PostPosted: Tue Mar 26, 2019 12:00 am    Post subject: Reply with quote

I’m all ears on this but my thinking is simply Occam’s Razor: is it logical to pursue coincidence when carb cause is a simpler explanation that fits the symptoms? The simpler, more likely possibilities have to be ruled out first.

And how to pursue...by replacing a $100 stator before a $160 carb? (Or trying a $10 needle jet and giving that little float lever a bend?) Or is there an easier test?

Unless I’m missing how this could more obviously be a stator problem when the scooter is flailing like this with full power to the electrics. That hasn’t been articulated.
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sc00ter
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PostPosted: Tue Mar 26, 2019 4:29 am    Post subject: Reply with quote

I dont recall the stator being a issue on the 50cc Buddy's and all the failing stators I've seen (125 Buddy) break-up on the top end first and work their way down to idle. Not saying that a stator issue could be the cause of stalling at idle, but I have personally never seen it without the top end suffering first. You Tube has stator test post but you need it running first......
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ucandoit
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2008 buddy 125

PostPosted: Tue Mar 26, 2019 12:46 pm    Post subject: Reply with quote

I don't have anywhere near the knowledge of most of the people on this site, but when you said fuel was coming out the airbox I could relate. I had that problem and also the stuttering/missing upon acceleration in a certain speed range, etc. and the problem was that the petcock was not holding back fuel properly BUT more importantly, the float height was too high. I lowered it--twice-- and that finally solved the problem.
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tenders
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Buddy International 50 Italia

PostPosted: Wed Mar 27, 2019 9:41 am    Post subject: Reply with quote

Do you recall to where you adjusted the height of the float? How did you know to try twice...did the situation improve a little after the first time?
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ucandoit
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PostPosted: Thu Mar 28, 2019 1:09 am    Post subject: Reply with quote

tenders: Soon after getting my used scooter (and I knew nothing about scooters) I had a major episode of gas pouring out my air box (with the engine off) all over my garage floor. The tank was literally emptying. For that to happen both the petcock and float had to fail. The petcock was faulty and there was debris in the float bowl of the carb. So, I cleaned the carb. and replaced the petcock. But the engine still stuttered and hesitated at lower speeds and there was gas in the oil. I took the carb. to a scooter mechanic who said the float looked "a little high" and he lowered it. I don't know if he measured it. There is a way to measure float height, but I never understood it.
Anyway, the scooter ran a little better, but I still felt gas was getting into the engine. So, I lowered the float myself--just a tad. I don't even recall how it's done, but I had studied it to death at the time. I didn't measure anything. The scooter then ran better. The new petcock is also faulty, (I found this out when I went to drain the carb. for winter storage) so I installed a little plastic lawnmower fuel shutoff valve in the fuel line between the fuel filter and the carb. I turn this valve off after riding is finished for the day. The scooter runs fine and I now feel I have some control over the fuel flow incase both the float and petcock fail.
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tenders
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Buddy International 50 Italia

PostPosted: Fri Mar 29, 2019 4:13 am    Post subject: Reply with quote

Problem: solved with new carburetor, but I compared the new to the old so I probably have a properly-functioning old carb to use as a spare.

Likely causes of my problems:

(1) initial clogged idle jet (high certainty), which was likely fixed with the copper wire reaming and then ultrasonic cleaning of the carb but then messed up by...

(2) ...a sagging carb float (moderately high certainty) - mine was dangling nearly 7/8" below the gasket surface whereas the new carb's float was at 5/8". LET ME SAY THIS AGAIN BECAUSE IT IS NOT DOCUMENTED ANYWHERE ELSE: THE BUDDY 50 KEIHIN PB CARBURETOR FLOAT LEVEL FROM THE FACTORY IS 5/8" BELOW THE PLANE OF THE FLOAT BOWL GASKET!! It doesn't sound like much difference but it is very noticeable. Not sure when this got bent. It is also possible that...

(3) the needle valve may have been worn (moderate certainty) and/or its valve seat could have used some dressing (pure guess) with a wooden dowel sharpened like a pencil.

I am reasonably confident that with a tiny bend of the float bowl level and a $7 replacement needle valve that my old carb is now completely functional. However, I've taken the darn thing out eight times over the past week and I'm not taking a perfectly-working new one out to confirm it.

The new carb was set quite rich from the factory, as in, stop-at-a-red-light-after-running-for-half-a-mile-and-wonder-if-you-are-going-to-be-asphyxiated-by-your-own-exhaust-before-the-light-turns-green rich. But this was readily solved by setting the air mixture screw to 1.25 turns out and the idle speed thumbwheel to a reasonable slow but smooth level. She now runs perfectly and I now own an ultrasonic cleaner, a backup Keihin PB 16 carb, extra size 40 and 42 idle jets for this rare carb, an extra vacuum petcock, and a bunch of gaskets for the next time the carb needs to be disassembled, which will hopefully be NEVER.

Thank you all for your advice. Sc00ter, you were right on the mark with your float valve/needle jet train of thought, and ucandoit, your confirmation was very helpful too.
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ucandoit
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PostPosted: Fri Mar 29, 2019 1:42 pm    Post subject: Reply with quote

Tenders. Nice job getting it all figured out and completed. It feels good to have a nicely running engine. I know what you mean about NEVER wanting to take out the carb. again. lol.
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