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Pw50

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Hi, I recantly bought my son a second hand pw50. I did all the usual on receiving the bike (cleaned carb, changed oil and replaced plug) but the bike won't start with the exception of a few splutters. I have double checked carb. I have got good spark so I figure it must be the exhaust. I removed the exhaust and while that was off I removed the head and barrell as well. I cleaned the piston and rings. There was no scarring in the cylinder and the piston and rings are still good. I bolted everything back together with the exception of the exhaust. I kicked it a few times and it roared to life so I figured the exhaust was blocked. I have cleaned and gutted the expansion pipe, but nothing. It will not start. I took the exhaust off, it runs but as soon as I put the exhaust on it runs for a few seconds and then dies. Please help!

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did you open the muffler? if not take it apart and clean, re-pack, and try again.

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take out the spark arester and clean it out. they get pretty nasty pretty fast. and if that doesnt work im not sure wat its called but theres a round washer sorta thing that goes between the engine and exhaust that restricts it pretty bad. take it out.

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Hi, thanks for the assist. but I have already done that, I even went as far as to cut open the expansion box and gut it. But still nothing?

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Two things that come to mind that occurred on my son’s PW50 is the carb slide isn’t fully seated in the proper groove (it can look like it’s in the proper spot however still doesn’t go as far down as it should) and the on/off/start switches will not work properly when wet or dirty. Triple check that the carb slide is in properly and take the switch apart and spray with some contact cleaner.

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Did you check the air filter and air box? The airbox and filter can fill with oil (if you over fill the engine) and make it run like crap.

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Thanks Fast Forward and LGCDEVIL, I have just bought a brand new air filter but did not fit it as I wanted to get the bike running first, when it was fitted it kept on filling with fuel?(which is why I removed it), Ive cleaned the carb several times and the bike only seems to start with the exhaust off?

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Dude, it's too rich which is why it chokes out when you put the pipe back on. Removing the pipe makes it run leaner and while you gutted it, that still wasn't enough. We have a pw80 which is basically the same and we gutted the silencer and then it broke so we just welded a steel pipe on there and you can't tell the difference.

You also checked a buncha stuff, but didn't check the reeds and if they are sealing right, as soon as you change the pressure by putting the pipe back on the reeds 'fail'.

To test that, fat as you may be, you might have to ride it without the pipe to put it under load to test the reeds. If it carries you without horribly gagging they are fine, if it dies, you need new reeds.]

I also learned this the hard way in that your piston and cylinder my look good, but the rings may not be in tolerance and have too much clearance at the end which will also allow it to run with no load, but as soon as you put load on the engine you get so much blowby it won't run. I learned that cause some 'a$T' sold me the wrong size rings and I didn't know better and put it together without measuring clearance and it started but couldn't carry a load so i then had to take it to a mechanic who told me I got screwed by the other guy.......

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Hey Wrencher2s, no I havent checked the reeds (thanks for that)will check them and get back to you. As for me testing them when the bike is running with out the exhaust I cant rev it, the chock must be on and the idle screw all the way in befor it will start, then when I switch it to run the revs go up but I cant twist the throttle it seems to bog and die?

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That's more good info!

Even on the choke which is a different circuit you should be able to rev it and since you can't, it's too rich! The air screw really shouldn't affect the choke and by turning the idle screw all the way in that's as rich as it can be!

The puzzling part is that when you switch from choke to main the revs go up even though the air screw is all the way in (rich as possible), that shouldn't happen and revs should immediately go down. (too lean is high revs which is why it revs wild on the choke at first, turning air screw in makes it richer and kills the engine)

Can you run/ride it and rev it on the choke? It won't hurt if you do it for a short time.

The bog and die is rich which you twist the throttle, but revs going up when you switch over is lean and maybe your main jet is too small?

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Hi, its not the air screw turned in all the way its the idle screw, the air screw is one and a half out.

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