Hey all!
Suzi is an '86, and has been my favorite possession since I got her. When I first bought it, I fully rebuilt my carb, and it ran great. I've done routine oil changes every 20 hours and a new spark plug every 100 hours.
I rode it hard for a few years, and the old engine finally started burning oil and losing power. As that started, it got harder and harder to start. We finally just got used to pulling it with another quad or a truck to start it whenever we went out. Once it started and warmed up, it would run great.
Kept riding it, and it got to the point that it wouldn't hold an idle.
Kept riding it anyway.
I finally decided to rebuild the engine. I tore it apart, and had my auto mechanics teacher (who did motorcycle rebuilds on the side) take a look at it, and he assured me that the wrist pin and the piston were in good enough condition to keep. So I replaced the rings and gaskets, and honed the cylinder. While it was taken apart, I took my carb apart and rebuilt it again.
It doesn't burn any oil now, and it has all the power back. However, it still doesn't start without pulling it, and won't hold an idle. I have tuned the carb a million times, but nothing helps unless I turn the idle up so high that it mimics moderate throttle, which makes it idle WAYYY too high. When tuned correctly, it'll idle for maybe 10 seconds or so, slowly choking out until it dies out.

That was a little long-winded, but I wanted to get in all the info, just in case someone can turn me in the right direction. Any ideas?
Thanks in advance!
Quinn

 

I think your valves need adjusting.

 

I think you need to adjust your needle jet in your carb take the clip on the needle n drop it down a notch see if that works n did you buy a rebuild kit for the carb? Sounds like your your small jet is somewhat clogged take a wire out of a WIRE BRUSH straighten it out n use it to clean the small holes in your jets this has worked perfect for me if the wire doesn't fit through the jet they r still clogged.let us know how u make out

 

Yep the carb is spotless, when cleaning a carb I take a bread tie or twistie tie, bend it in half so it has a good kink in it, straighten it, and run it through all the holes. I then inspect every hole to make sure that it's clear. I havent, however, looked at the needle.
I will take a look at the valves today


I forgot to mention something. The mixture screw does absolutely nothing for how the bike runs. I can have it turned in all the way, or I can have it just about falling out and it makes no difference to the idle. The only time I've ever seen that was a time when my buddy put the float in upside-down, but I checked that and everything's normal in there. Bizarre, eh?

 

According to the internet, the black plastic floats can absorb gas over time, and become heavier than they were initially. You either have to replace them, or modify your float adjustment accordingly.

 

So I just ripped my carb apart again, cleaned everything out, and adjusted the float to close a little earlier. It seemed to help, but it still doesn't want to idle. It will idle at around 1500 RPM for a couple minutes, but eventually starts to cut out.
The mixture screw actually does something, now
I'm going up to the store right now to get some feeler gauges.
Thanks so much for your help guys

 

So just got to the valves, the exhaust was dead on. The intake was WAY too tight. So I adjusted it to 0.0025, now it runs amazingly!! It'll idle down at like 200 rpm thank you so much for your help!

 

Now that I have Suzi running good again, I've been riding it around a little. However, the chain keeps popping off; something that's never happened before. I adjusted the chain, but it was already as tight as possible.
I'm obviously gonna get a new chain, but out of curiosity, can these chains stretch? I am just trying to understand why this is going on.
Thanks!
Quinn

 

If you're adjusting it as tight as possible, you're forcing either the chain to stretch or for it to loosen the adjustment mechanism.

There should be about 1" of slack in the upper part of the chain with you sitting on the quad. You should confirm that number though.

The issue could also be your swing arm bearing, the swing arm itself (where the swing arm bearings are installed), or the axle bearings. You have to make sure none of those are worn out, and that there is no play in either joint. If that chain pops off and wraps around your front sprocket it will take out your engine. Personally, I wouldn't ride it anymore until you figure this out, it doesn't take a lot of speed to break the engine cases.

 

Shoot...I had my heart set on riding this Monday.
So, I loosened the two bolts and started to move the carrier with a pipe wrench. As I approached the apex of the cam, it would tighten slowly. If I kept turning the carrier, it would then start to loosen. I just found the tightest position and left it there. It still has maybe 3" of play without me sitting on it.

How should I check the bearings?