PW50 engine swap?

[buds302]

hello. i have a 1990 yamaha PW50. we have owned it for almost 15 years now.

the bike itself has been good to us.the only thing in 15 years that i know we have replaced it the kill switch which was replaced last year adn the spark plug that was replaced last week. i took the carb off yesterday and cleaned it real good. im 25 years old and wiegh 250 pounds. this bike pulls me around quite well. have to give it a running start but once its moving it keeps going. mine experiences all the common problems that i have read in the 30+ pages of threads i just went through. it takes 4-5 min to warm up. once you do that. its good to ride for a while. if you shut it off after about a 20 min ride... you have to let it sit for 10-15 min. it has always had starting problems. takes me i know 20 min to get it running. my leg is tired after all that kicking.

i was reading around and looking and pondering. i looked into maybe rejetting it. and i read a few posts where you guys say move the clip up a notch on the needle. << i have no knowledge of this clip ? a picture would help me greatly. i also want to know if this bike is oil injected? i have always premixxed the gas. but i took the seat off yesterday to get to the carb. and noticed the throttle cable runs into this whitebox. and a hose comes out of that box and to the carb right next to the idle screw.

im pretty sure the exhaust washer is gone. and the airbox is MIA. im in the process of ordering a new one from yamaha but was wondering about the notiol air filter. do i need the factory box? or does it just slip on.


but my biggest question is.

can i put the motor and trans from a PW80 into the bike? my freind had one when i was a kid and it had a 3 speed trans. this would be a great upgrade to this bike. but. has anyone done it?

im also wondering about the suspension. my ass hurts from riding this thing. anything i can do to make it sit up higher? or give me more travel? im gonna prolly buy the handlebar kit from peeweecycle to give my knees more clearance. i read in a random google search about an extended swingarm. clicked on it and i found myself searching through a forum. never did find it.

any help would be nice. if not im not really worried about it. my 7 month old son will enjoy it either way in a few years.

one more question! does all the parts from newer PW50s go on this thing? like a kickstand? and a set of training wheels? man a kickstand would be nice.

 

[IndyMX]

250lbs on a PW50??? Oh My!

Man, give that little kids bike a break and ride something you actually fit on..

 

[buds302]

250lbs on a PW50??? Oh My!

Man, give that little kids bike a break and ride something you actually fit on..

hey man.....i dont have a liscense. i have to do something to occupy myself. ive only ridden it maybe 4 times since i was a kid. it sat for 10 years i know of and wasnt started. this past week or 2 it has seen new life. still fun. my bro busted it out last year and ran it 3 or 4 times. hes 100 pounds lighter than me

 

[IndyMX]

You don't need a license to ride a bike that fits you.

 

[buds302]

i dont have money to buy a bike that fits me. this bike was free to me.

 

[buds302]

if i could find a bike for under 200 bux that might fit me... id buy it.

 

[FruDaddy]

I don't think the 80 engine will fit, it is chain drive and the 50 is shaft. Also factor in the fact that the 50s shaft also serves as the left swingarm, and you have a big problem. The cost of making it work would likely be greater that the cost of a new KLX110.

Has that PW ever had a new piston and/or rings installed? It might help but that bike isn't intended, or designed, to pull your weight around. The frame isn't strong enough either.

 

[IndyMX]

It might help but that bike isn't intended, or designed, to pull your weight around. The frame isn't strong enough either.

I don't think I'd be able to get my fat a$$ down on that thing, and I'm only 220..

 

[buds302]

well so far the frame has held up.i dont fit on the seat really. i kind of have to sit on the fender. and we have bent that part of the frame and broke it off. welded it back on... still bent. but much stronger now. so really all my wieght is on the back of the bike.

and no. no rebuild done on this bike ever. that i know of anyway. we havent even changed the oil in it. and like i said. i just changed the plug in it in damn near 15 years. and frankly. id like to know how to get the old oil out? there doesnt seem to be a drain. so what? i gotta pump it out? or tip it over. also anyone know about the oil injection?

 

[Jasle]

I go 260 and the pw50 pulls me fine. especially with the qt50 rearend.

but no you will not be able to get the pw80 motor to work. you can buy a YT60 piston. then have your cylinder offset bored and you can get a pretty nasty 60. find the QT50 rearend and press the ring gear off the shaft and press the pw50 shaft in. drop the new ring gear and pinion in and you have 5.7:1 instead of 4.9:1 rearend. this thing will wheelie very easy. also buy the aftermarket clutch springs. makes a HUGE difference in takeoff beause the clutch has a higher stall.

but first you must address your problem on the motor. sounds like an air leak. get the bike nice and warm to where it starts having the problems. then spray carb cleaner around the case and cylinder base. if the bike rpm's get better or instantly die you found your leak.

 

[IndyMX]

I go 260 and the pw50 pulls me fine. especially with the qt50 rearend.

but no you will not be able to get the pw80 motor to work. you can buy a YT60 piston. then have your cylinder offset bored and you can get a pretty nasty 60. find the QT50 rearend and press the ring gear off the shaft and press the pw50 shaft in. drop the new ring gear and pinion in and you have 5.7:1 instead of 4.9:1 rearend. this thing will wheelie very easy. also buy the aftermarket clutch springs. makes a HUGE difference in takeoff beause the clutch has a higher stall.

but first you must address your problem on the motor. sounds like an air leak. get the bike nice and warm to where it starts having the problems. then spray carb cleaner around the case and cylinder base. if the bike rpm's get better or instantly die you found your leak.

The dude can only afford $200 for a real bike, and you have him off modding the crap outta this turd.. Wow..

No offense, but damn dude.. You really think he can manage all of this? I doubt it.

 

[Jasle]

hey he asked, I answered. If he does it is up to him. Just letting him know whats avail and also squelch the guys thinking these things cannot carry his weight. There is a reason this motor design has not changed since 1981 and is still in production. Its solid. With a little knowledge these bikes haul ass. They just don't handle worth a crap.

Besides a new cylinder is $127. parts for these are incredibly cheap realativley. give up a few soda's and ciggy's and one could afford the parts needed to mod them out.

 

[buds302]

im a hell of a mechanic. i can fix literally anything. but this bike does stump me in its problems. it could just simply be a carb issue. i havent sat down to mess with it really. i just know what ive seen now and in the past. the same issue coming up. a rebuild is prolly what it needs.

noone answered my one question if the bike was oil injected or not? ive never used the oil injection on it...but i didnt know it had onE?

 

[FruDaddy]

noone answered my one question if the bike was oil injected or not? ive never used the oil injection on it...but i didnt know it had onE?

Didn't know that you asked unless this

also anyone know about the oil injection?

is what you are referring to. It's a little vague, but

The oil tank is behind the number plate, the pump is on the engine, yes, the PW50 is oil injected.

 

[buds302]

but is the 1990 PW50 oil injected? i have no tank behind the number plate.

 

[FruDaddy]

I have a manual that covers the 81-98 PW50. It was good for my son's 2001. There is no exception for any years in the oil injection system. If you do not have an oil tank, then somebody has removed it. Yamaha has not (significantly) changed this machine since it's debut, with the exception of aesthetics.