Yamahe PW 80 Performance

[aggio]

I have a 1996 Pw 80 I purchased used last summer. I have allot of trouble with its performance once I hit 1/2 to 3/4 throttle and all the way through wot. When I get to that point in the throttle the bike just bogs out and smokes big time. I have tried putting in a 100 mj (stock is 125 mj) and get the same results. The bike performs great at ¼ to ½ throttle. The exhaust restricter has been removed and I have cleaned and checked all the carb components. I have checked the oil injector and have no problems there either. In fact I removed it at one point and ran premix with the same results.
Is the some sort of govenern? I am out of Ideas. Anyone have any Ideas?

 

[Gary B.]

My kids had two of these and neither had any top end. It's as though the motor can't pass any more air. I never messed with it because the kids never complained, and the bikes still went too fast for my wife to watch. :eek: But seriously, did the bike ever run great at the top end? If the bike has alot of miles, the exhaust may be getting clogged. :think: Just my two cents.

 

[Chili]

My son had one of these bikes last fall for a few months and I always felt like the bike was not running right at WOT, the dealer said it was running fine that it was just totally top end impaired ours however did not smoke like you stated yours is doing.

 

[Durt Cycler]

Does the pipe have alot of carbon buildup at the head of it? This could restrict exahust flow. My cousin had a '92 PW80 and the pipe had a ton of carbon buildup so I took a dremel tool to it and clean it perfect and it ran alot better. that thing would pull wheelies wide open.

 

[aggio]

I have cleaned everything from top to bottom trying to find more top end. It sounds like this is the way they run and I should get on with my life. Sometime at WOT the thing comes to life for a second or two. That's why I thought something was up. I have spent way to much time trying to fix something that can't be fixed. My wife rides it and she has never complained about it.

 

[ewbish]

My daughter was on a 2001 PW80 for about 6 months. There isn't a lot you can do with it. She raced in the mini-playbike class so here is what I found to work the best:

Don't mess with the oil injector-it works well. Remove the snorkle from the top of the airbox. Drill about 8 1/4 inch holes along the side on the back of the airbox-be carefull not to drill behind the filter. Get rid of the stock POS filter foam and cut your own out of a good quality sheet of foam. For the track, remove the spark arrestor. Another tip I received from a PW owner but never tried, replace the entire ignition system with a 94 or older. Apparently after 94 the ignition retards as the RPM goes up (just try and advance it-you'll see), this is what causes the completely flat top end. I had a buddy who had a 94 and it had way more top end than my daughter's so I suspect there might be something to this. Really though, other than the airbox work I wouldn't sweat it, the big limitation on the bike is suspension and there ain't a whole log you can do with that. When they start pounding it move up to a 60 and sale the PW for what you paid for it!
Eric

 

[aggio]

Thanks for the info. Sounds like My Pw is no different than any other(post 94). I'll do these mods and call it good.

 

[tri-mx'er]

This is a very common problem on the PW80s. Mine did it from the time it was new. Like yours, sometimes it would run properly for a few seconds at top RPM. I was told there is a rev limiter built into it, which is probably the ignition mentioned by the other poster. I kinda wonder though, since it occasionally ran well. I ended up boring the carb a couple of millimeters, and freeing up the intake, and it helped. Also mentioned, was the plugged exhaust. I think this may be the real culprit. The pipe is really restrictive. Someone told me to throw the thing in a fire every now and then and cook out the carbon buildup. I did it with a rosebud torch, and it worked well. Of course it needs a paint job afterwards. Another thing you may think about, is a top end job. These things have a reputation of running forever, like the PW 50s, but I found they went through rings a lot faster than I would have thought. If you go the track you will hear lots of the older ones making a funny sound which I found out was bad rings and worn pistons. Mine were really worn after 6 months on both bikes (PW50 and PW80), and I am really anal about oil and air filters. I ran Mobil 1 MX2T most of the time, but am not sure the Yamaha 2s isn't better for the air cooled bikes. And most PW dads don't do much maintenance, so I bet yours really needs a new top end. This should help with the power a bunch.
But don't sweat it, when you are ready to sell it, they go for top dollar on E-Bay all the time.
Hope this helps some.
Rich

 

[aggio]

I did the mod to the air box over the weekend and it made a big difference. I'm gonna leave it alone at this point. My wife rides it and she is not complaining. I'll keep the top end up my sleeve if I need to.

Thanks for all the good stuff......

 

[Jasle]

Not sure about the pw80's but the pw50's rev limiter could be over-ridden by disconnecting the start/retard switch. the lil bike rips with it disconnnected. Also helps when you can't start the bike after washing.