PA50I Gutless

My '78 PA50I has no power. I got it ip to 14 mph. At that speed the RPM's were still very low. When I put it up on its stand it seems to accellerate like it should. The engine RPM's sound higher than it does when you are riding it at 14 mph. The carb is clean, the timing is right on, compression is good. What do you guys think?

Re: PA50I Gutless

Sounds like a plugged up main jet to me.

Litely loaded, like on the stand, it does not need much fuel but under load on the road it takes much more.

Have you checked your throttle cable linkage to make sure the throttle is opening all the way?

Re: PA50I Gutless

You weren't exactly clear about what's happening but i'll take a guess.

Engine RPM is not determined by road speed if your variator is working properly.. The variator automatically adjusts engine RPM when you start to climb a hill or hit a head wind or for other reasons..

Both the front and rear variator units must be free to widen and narrow so "gears" are able to change from lowest to top gear ratios. If either one is rusted stuck or has other mechanical difficulties, road speed will be limited and/or engine RPM will be affected.

Aside from that, there's a big bolt on the side of the muffler. Remove that and right inside there is a small baffle tube. All your exhaust must flow through that tube. The reason for the bolt is so you can stick something in there and clear that exhaust baffle tube (which, being so small, is the first thing to get clogged up). Also check the cylinder exhaust port for carbon build-up.

Re: PA50I Gutless

The PA50I is only rated for 20mph top-speed, so it is naturally gutless.

The PA50II is the one you really want, rated for 30mph.

Re: PA50I Gutless

Ken Manning /

Thank you everyone for the advise. I have cleaned the carb thoroughly and actually replaced the main jet. So I am doubting that the carb is the problem. It was good to hear that it could be the variators. This bikes variators do not fluctuate like my PA50II. I thought that could of been because it is the 20 mph version. I have heard the variators are different. They look identical but the one on the crankshaft of the PA50I does not put any more tension on the belt.

Re: PA50I Gutless

The variators are different.. if you look closely at the front ramp plate of the PA50I, you'll see that it's curves do not curve inward as severely as the plate on the PA50II. and there are other differences you will notice if you take them off and compare..

If that front pulley is unable to close completely becaue of rust on the shaft or something, top speed will be lower.

Another thing on old units is the internal parts can get really messed up and worn down. The weights inside and the plate-ramps they slide on need to be perfect. If the rollers are prevented from traveling all the way out , the pulley will not close all the way. When those weights are thrown outwards they actually push on the inner plate and move it inward.

I have a variator that's worn badly inside.. the little ramps that the weights roll on are practically gone. Although the weights are thrown outward by centrifugal force the plate hardly moves.

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account