|
|
Post by CrankingWithCG on Nov 2, 2020 23:50:57 GMT -5
Ive bought a new 28mm PWK for my 155 build. However, its doing this crap still. Its- -wandering at idle -missing at low throttle -chugs and dies if i crack the throttle hard (like an empty sucking sound. Similar to turning the scooter off while moving/running and trying to open the throttle) I had to helicoil the spark plug. The o ring on the intake isnt 100% perfectly sticking out evenly on the bottom. It could be pulling in air through these places, but i highly doubt it. The 32 pilot is the best it ran, yet still has the problems. It was 40 degrees yesterday, so im not sure why going so low on jet size made it better? My stock modified pipe could not be flowing enough for even a 35, but again, why the seemingly lean symptoms? The scooter would also start after a ride from cold on a 35 with no choke. It needed choke to start on a 32 from cold. The smell of hot gas also went away with the 32. I just need help here. Im so fed up youtu.be/q-uYelWmtxI |
|
|
|
Post by FrankenMech on Nov 5, 2020 7:44:53 GMT -5
First of all those tachometers are not very accurate or stable. The idle sounds a lot slower than indicated. Are you sure you have the right number of pulses per revolution set? For these engines it is one pulse per revolution. Do you have the impulse source wired correctly? Some wire to the coil and others wrap a wire around the spark plug wire. The pulse is sensitive to the number of turns and the wire routing.
The intake can be checked for leaks with an unlit propane torch. I use a hose on the torch to get into tight spots. The intake O-ring should be changed every time it is removed but you can sometimes get away with using an old one if it has not been squished very long or subjected to heat. Beware, the O-ring will swell and must be replaced if it has been exposed to ethanol in the fuel.
I installed an adjustable carb jet to add a little fuel in the winter. I don't even have an enricher or choke.
I understand the heli-coil. I hate those itty bitty spark plugs and butter soft aluminum heads suck. Mine is cross threaded at the moment but I have not had to remove or change it.
I also vent my carb bowl to the intake side of the carb with a pod filter. With that mod I was able to use a 'performance' carb right out of the box with no jet changes.
|
|
|
|
Post by Steve B on Nov 5, 2020 9:09:06 GMT -5
You should check you're valve clearance after you're done. The valve clearance specification is 0.004". I can hear a ticking when idling.
|
|
|
|
Post by fugaziiv on Nov 5, 2020 9:56:30 GMT -5
These are all pretty common issues on a 4t build with a low quality or poorly tuned PWK. You kind of get used to it, get a better quality PWK carb or do a lot of carb tuning to get rid of it... but if you are running a Nibbi or something off brand like that good luck. Genuine OKO is the point of entry for decent PWKs.
Personally, I run CVKs on all 4t builds. I find they work better.
Matt
|
|
|
|
Post by CrankingWithCG on Nov 6, 2020 12:02:36 GMT -5
These are all pretty common issues on a 4t build with a low quality or poorly tuned PWK. You kind of get used to it, get a better quality PWK carb or do a lot of carb tuning to get rid of it... but if you are running a Nibbi or something off brand like that good luck. Genuine OKO is the point of entry for decent PWKs. Personally, I run CVKs on all 4t builds. I find they work better. Matt It seems like a high quality carb. Its a real pwk as far as i can tell. Yeah, im kinda regretting just not getting a bigger cv carb. I love the throttle response on this though. And high end flow is huuuuge. This carb feels still 10x better than the old keihin knockoff i had on it |
|
|
|
Post by CrankingWithCG on Nov 6, 2020 12:03:28 GMT -5
You should check you're valve clearance after you're done. The valve clearance specification is 0.004". I can hear a ticking when idling. I set mine to .004 and .006. I could dedinuely double check. Would a loose valve cause that? |
|
|
|
Post by CrankingWithCG on Nov 6, 2020 12:07:09 GMT -5
First of all those tachometers are not very accurate or stable. The idle sounds a lot slower than indicated. Are you sure you have the right number of pulses per revolution set? For these engines it is one pulse per revolution. Do you have the impulse source wired correctly? Some wire to the coil and others wrap a wire around the spark plug wire. The pulse is sensitive to the number of turns and the wire routing. The intake can be checked for leaks with an unlit propane torch. I use a hose on the torch to get into tight spots. The intake O-ring should be changed every time it is removed but you can sometimes get away with using an old one if it has not been squished very long or subjected to heat. Beware, the O-ring will swell and must be replaced if it has been exposed to ethanol in the fuel. I installed an adjustable carb jet to add a little fuel in the winter. I don't even have an enricher or choke. I understand the heli-coil. I hate those itty bitty spark plugs and butter soft aluminum heads suck. Mine is cross threaded at the moment but I have not had to remove or change it. I also vent my carb bowl to the intake side of the carb with a pod filter. With that mod I was able to use a 'performance' carb right out of the box with no jet changes. I have it wrapped around 4 or 5 times i think. I set it for the right pulse too. From what ive figured out, the big bog i get is normal for slide carbs on 4 strokes. The idle actually got more stable with the exhaust drilling, and its worse with cold, with backfiring i think im lean now. It seems like its flowing what it needs to now. Still not sure though |
|
|
|
Post by fugaziiv on Nov 6, 2020 12:59:08 GMT -5
These are all pretty common issues on a 4t build with a low quality or poorly tuned PWK. You kind of get used to it, get a better quality PWK carb or do a lot of carb tuning to get rid of it... but if you are running a Nibbi or something off brand like that good luck. Genuine OKO is the point of entry for decent PWKs. Personally, I run CVKs on all 4t builds. I find they work better. Matt It seems like a high quality carb. Its a real pwk as far as i can tell. Yeah, im kinda regretting just not getting a bigger cv carb. I love the throttle response on this though. And high end flow is huuuuge. This carb feels still 10x better than the old keihin knockoff i had on it Who made/where did you get the carb? Seems high quality but don't actually know is a tailor made recipe for a poor running bike. What you're suffering from is inconsistent airflow or a leak. Poorly made PWKs are notorious for this. Well, the idle and poor running is caused by that anyway. The bog as you crack the throttle WFO from idle is a characteristic of the PWK when used on a single cylinder 4t and is difficult to tune out fully even with a high quality PWK. Matt |
|
|
|
Post by CrankingWithCG on Nov 6, 2020 17:12:50 GMT -5
It seems like a high quality carb. Its a real pwk as far as i can tell. Yeah, im kinda regretting just not getting a bigger cv carb. I love the throttle response on this though. And high end flow is huuuuge. This carb feels still 10x better than the old keihin knockoff i had on it Who made/where did you get the carb? Seems high quality but don't actually know is a tailor made recipe for a poor running bike. What you're suffering from is inconsistent airflow or a leak. Poorly made PWKs are notorious for this. Well, the idle and poor running is caused by that anyway. The bog as you crack the throttle WFO from idle is a characteristic of the PWK when used on a single cylinder 4t and is difficult to tune out fully even with a high quality PWK. Matt So in 70° weather, a 32 pilot with two turns out still isnt perfect, but its way better. Still a bit of spitting and a bit of low idle/inconsistency after a rev after its sitting for a while. It gets worse the longer it sits and idles. Ill blip a very tiny amount, it stumbles and idles really low but recovers. |
|
|
|
Post by Steve B on Nov 7, 2020 1:37:29 GMT -5
You should check you're valve clearance after you're done. The valve clearance specification is 0.004". I can hear a ticking when idling. I set mine to .004 and .006. I could dedinuely double check. Would a loose valve cause that? The ticking noise will be the valves, Which can cause several running issues. I believe you're main issue is you're carb like fugaliv said get a better quality carb or keep on tuning it until you solve the idle and backfire issue. It would be much easier to buy a good quality carb and install it without all this adjusting the jetting and sensitive air fuel issue. |
|
|
|
Post by CrankingWithCG on Nov 7, 2020 15:55:24 GMT -5
It seems like a high quality carb. Its a real pwk as far as i can tell. Yeah, im kinda regretting just not getting a bigger cv carb. I love the throttle response on this though. And high end flow is huuuuge. This carb feels still 10x better than the old keihin knockoff i had on it Who made/where did you get the carb? Seems high quality but don't actually know is a tailor made recipe for a poor running bike. What you're suffering from is inconsistent airflow or a leak. Poorly made PWKs are notorious for this. Well, the idle and poor running is caused by that anyway. The bog as you crack the throttle WFO from idle is a characteristic of the PWK when used on a single cylinder 4t and is difficult to tune out fully even with a high quality PWK. Matt You think with a big valve head a 30mm cvk would be too much? |
|
|
|
Post by Steve B on Nov 7, 2020 19:24:49 GMT -5
The larger the carburetor the harder it will be to tune.
|
|
|
|
Post by CrankingWithCG on Nov 7, 2020 19:37:16 GMT -5
The larger the carburetor the harder it will be to tune. I just dont wanna go back to the 24. It hit 69mph, i think anything smaller than a 28mm would kill my top end. From what i can figure, its either a 24mm, or a 30mm for the cvk. No inbetween |
|
|
|
Post by fugaziiv on Nov 9, 2020 9:18:53 GMT -5
On a 58.5 mm kit (with or without a BV head), I'd take a hard look at tuning a good quality 26mm CVK... but that's just me and I'm not usually looking for the most extreme top end I can get out of a build, I'd rather it run great top to bottom. I don't think I'd look larger unless you had at least a 61mm bore with a matched high flow head. Here's the 26: www.partsforscooters.com/169-276-OKO-QMB139-Performance-CVK-CarburetorMatt |
|
|
|
Post by CrankingWithCG on Nov 10, 2020 10:29:39 GMT -5
On a 58.5 mm kit (with or without a BV head), I'd take a hard look at tuning a good quality 26mm CVK... but that's just me and I'm not usually looking for the most extreme top end I can get out of a build, I'd rather it run great top to bottom. I don't think I'd look larger unless you had at least a 61mm bore with a matched high flow head. Here's the 26: www.partsforscooters.com/169-276-OKO-QMB139-Performance-CVK-CarburetorMatt I may buy a 26 for now, but ill definitely keep the pwk for the turbo. She got t boned the other day and the frame is destroyed. Is it still the same bike if its a different frame? 😭😭😭 |
|
