pw50 power issues

[MPSRT]

Been having power issues with my 05 pw50. Ive replaced the top end, cleaned the carb, new reeds, and blocked off the oil pump so I just use premix gas now. I can hold the bike still and give it gas and it still will barley move, seems like even with me holding the bike back it should atleast have enough power to pullt the front tire up but doesn't. Also when the airfilter is on it bogs down the bike like its not getting enough air, the airfilter is new and clean. When the airfilter is off and the bike is on the stand it seems to rip pretty good and will even put my kids around. The moment it goes up a incline it struggles and barley will move them. Also it will only idle if the choke is on, if I turn the choke off it dies out after a few seconds. Not sure if I should clean the carb again? and if the clutch is bad? and why the airfilter is restricting it? Any help would be great. Also the CDI box or rev limiter, whatever you wanna call it is unplugged so it has a little more power, and the exhaust restrictor washer is off too and still having power issues.

[delawhere]

When did this start? Was it happening before u replaced top end? How did u clean the carb? Did u remove all the jets and blow compressed air thru them and the passageways in the carb? Jets often have holes in the sides of them also that have to be completely clean

A choke restricts air flow (just like choking someone would be restricitng air flow) so if it only runs correctly (idles) when the air flow is restricted (choke on) that would imply that with the choke off it is getting too much air. That could mean u have an air leak somewhere (letting in excess air) like at a crank seal or it means that your fuel flow is insufficient for the normal amount of air... this usually means a clogged jet. Since it effects idle then I would suspect the idle jet to be the issue if there is no air leak. The idle jet is responsible for idle til about 1/4 throttle by itself (no main jet in circuit during this range) but is also active during the remainder throttle range. The main jet, jet needle n throttle slide handle 1/4 - full throttle in different degrees.

Anyway always start with the cheapest components when troubleshooting, I suspect your carb is not clean enough. I've had a few PW50's and PW80's and they're all super reliable. I don't know why folks feel compelled to disconnect the oil pump, I've never had an issue they're equally reliable but you've already done it so don't ever forget you'll need to use premix. And yes it should have much more power, I'm 6'1' 195 lbs and the PW50 would pull me around with no problem.

Let us know how your progressing with resolving the problem.

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[MPSRT]

Quote

 

Before I replaced the top end, all the existing problems were still there except for the idling issue. Before I replaced the top end it would idle. My son would ride it about 10 to 15 minutes and it would stop running, kinda like it got to hot or something. I cleaned the carb by taking it apart and spraying carb cleaner in all the holes. left the jets in because I tried to unscrew the main jet and it started to strip it with the screw driver so I left it alone, can try again though. I'm pretty sure theres no air leak but ill double check by starting it and spraying water around the seals and look for any air bubbles. I also disconnected the oil pump because it seemed like it made it to rich and didn't run right. the oil pump is still on the bike, I just disconnected all the hoses and drained the oil. I might hook it back up if I can get it running right and see if it still runs to rich with it. I'm hoping its just the carb needing cleaned. but if its the carb would it run bad as well with the rear tire off the ground? I can take the airfilter off and life the back tire off the ground and it will scream but as soon as I put it on the ground and try riding it, it barely goes with me on it.

[delawhere]

Jets must be cleaned with compressed air to guarantee cleaning. The main key should have a hex head to get a good grip on. Of its tough getting it out place the carb in water close to boiling temp for a little while (do not put gasket in water). U have to remove the jets n blow compressed air thru them n all the orifices n passageways in the carb... I've seen this before an issue for many bikes whose owners thought they had cleaned the carb thoroughly.

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[MPSRT]

ok. Ill try taking it apart and blowing it with my aircompressor and spraying it again with carb cleaner. The main jet, the biggest copper piece sticking out towards the bowl is a flat head screw driver not a hex. Don't remember seeing any hexes, just flat heads.

[bradcutter]

Yeah pw jets are just flathead. Also check the silencer. Make sure its not chocked full of oil. I think they hardly use any oil at all. Wonder if premix caused too much oil because I have had a pw for years now and kids ride it all the time. My son even races it, i just finished my first quart of oil on god knows how many tanks of fuel. Everyone i know with a pw says the same thing. Part of a proper breakin for new topend is lots of idling which would add a lot of buildup to exhaust. So all that to say: check your exhaust system, especially silencer.

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[MPSRT]

Ok so I took the carb apart including the jets sprayed everything with carb cleaner and took the air compressor to it and it still doesn't have enough power. It will idle now though. I do notice even before I cleaned the carb it spits out a little fuel from the back of the carb opening where the air filter is, not sure why it does that. Also when I put the bike on the kick stand and rev it up, it sounds like it wants to hit a power band but it can't quit reach it. I have got it a couple times to hit it for a few seconds but slightly bogs and won't reach it. On flat ground such as the road it has good speed but no power still. Could the clutch be slipping and cause it to not have the power it should have? I also sprayed a bunch of break and carb cleaner in both exhaust pieces and ran gas through the expansion chamber to clean it out, just swisher it around and drained it. Also let it dry before I started the bike up, so exhaust system is clean too. I'll try and post a video of it tommorow when I get off work.

[MPSRT]

Yes the piston arrow is facing up and the rings are in the correct position aswell, notched opening are seated with the notches on the piston.

[MPSRT]

well damn....hope that didn't ruin anything? ill turn it around today, but I highly doubt that is the problem considering it still did this before I replaced the top end. The rings are on right though lol.

[MPSRT]

Do you think the main jet is putting to much fuel in? which might be why its spitting fuel out of the carb by the air filter?? might need a smaller main jet? if so what is a good size that should work? I live in Oklahoma, and I'm about 1100 FT above sea level.

Edited August 15, 2017 by MPSRT

[MPSRT]

Here's a video of the pw50. Sorry for the poor quality. I was holding it full throttle and backed it off a little to show that when not full throttle it sounds like it wants to hit it's power band but can't reach it. Did everything I was told so far, might be thinking the 70 main jet is putting to much fuel.

[MPSRT]

The piston and plug were black but not to extreme. It will move on flat ground but any incline will slow it down and barley move if I'm on it. If my son is on it it will do the same but but obvously is easier on the bike cuz he weighs less. I know they naturally don't have much power but it should be able to move me around no problem, I only weigh about  170. Guys weighing 200 tell me thiers put's them around fine.

[MPSRT]

so why is it not idling now? before I cleaned it, it was idling ok. I have read other guys weighing 200 pounds ride these things around fine, and I only weigh 170 lol.

[MPSRT]

which one is the pilot jet, unless that's the same as the main jet? not sure what you mean by on, if you mean the on switch then, I unplugged the rev limiter so the start and run switch works but doesn't need to be on start to start the bike, it can be on start or run, it wont stay idling on either. sometimes it does small backfires too now after I took it apart and cleaned it. not sure why that would make it do that?

Edited August 16, 2017 by MPSRT

[kurbe397]

The pilot jet is #5 in the diagram. If you only removed one jet and cleaned it then it was most likely the main jet which is #3 in the diagram and the most accessible. Once you get the carb figured out if you're still having issues with the power delivery then I would look to service the clutch. I don't have any experience with PW50s but regular service on the KTM 50sx clutch makes all the difference.

[MPSRT]

I think it will idle with the choke on. Sometimes it will and sometimes it wont

[MPSRT]

ok, ill take it apart again and make sure everythings correct. ill let you guys know how it works out later this evening.

[MPSRT]

Can anyone else do the same with their pw50s? hold it open at full throttle and stop it from moving just by holding the handle bars back?

[MPSRT]

damn I just bought a new top end lol...was only about 45 bucks but I guess I can buy the 60cc kit. which is the best affordable one to get?

[MPSRT]

will I need to adjust the carb at all?