I was given a project ATV. It had several issue, most of which have been resolved (including welding the broken aluminum gearcase, welding broken shift linkage, patching the gas tank, etc). It also had low compression. I had it professionally rebuilt by the best machine shop in the area, who also sized and ordered the piston and rings.

I had it running, but it was running rough. I should have started by scrapping the ATV. ANYWAY... other projects got in the way, and I parked it for awhile and thought about it occasionally.

Recently, I obtained a service manual, and went into the carb for a cleaning and inspection. The clip on the jet needle was NOT set to the standard (set too lean). I did not confirm that the jets were stock. When I had it running, the pilot air screw was out about 2 1/2 turns (lean) to have it running, but the choke was also off (dumping fuel making it rich). How it was running, I do not know. I should really have checked the settings instead of just putting them back in the way they were. Sigh.

With the pilot air screw at it's stock position (1 turn) and the choke at the stock position (lever at 3/16 freeplay) and the idle screw at stock (1 1/2 turns), it is not quite starting. I played with the pilot a little and could not get it to run (will start, but cannot run more than 10 seconds). I am starting with ether into the airbox.

Oil pump is disconnected and I am running mix (just to eliminate any problems) of 40:1. Fuel lines are unobstructed, new fuel filter in-line, and I have new fuel. Air is unobstructed. carb vent lines are all loose, but not not plugged.

I am getting good consistent spark. I bought a new plug (BR8ES). But I figure I should look at timing, with everything else being off. The problem is, I do not know how to give it a base setting. I have a timing light, I DO NOT have a tach, and it is not running. I have micrometers and a 1" machinist travel meter that can be used on the cylinder.

I understand it is supposed to be 25 degrees at 3000 RPM. I can place the cylinder at a specified height, but how can I tell where the stator is in its spark cycle in relation to the crank position? Is there another way? Just guess and put it in the middle of the range?

Thank you!!

 

How about the needle and seat? Did you change it out? Check the float level,plus check the pilot and main jet to make sure their not stopped up since you let it sit for awhile? The timing is set automatically by the cdi plus,should be a mark on the stator plate and also on the engine case where the stator plate lines up for correct timing advance. You shouldn't have to touch this unless someone has been monkeying with it! 1 - 2 turns is normal setting on the air/fuel (idle mixture) screw. Think you're working around the problem! Check the carb out on the inside. OPT

 

Thanks for the reply.

I did not charge the needle and seat, but I looked at them. I expected everything in the carb needed to be replaced, but when I got into it, it was really clean, and nothing seemed gummed up. I adjusted the float using a micrometer and manual specs. Pilot and main jet were cleaned with carb cleaner and it flowed easily. At one point, I did use the air compressor to blow it out too. The floats have nothing in them. In fact, I went through this carb TWICE; once after the rebuild and once now. Since I received the bike (before the rebuild), it has NEVER run right. That is why I am suspecting the timing.

Mark on the stator plate and engine casing? Where? I suspect the prior owner monkeyed with it completely, given the needle setting on the carb was off, yet it was running.

In my mind, a 2-cycle should just start. Even if stuff is off by a bunch, it should start. But it does not. I doubt it is the stator, but is there a test for it? The spark looks good, and a timing light used with the started shows the timing in a constant location and it is not jumping around.

 

We used the timing light method too to see if spark was consistent and not breaking down also. But that's really the only time we used one as much of the ignition is already set! The stator plate is behind the flywheel. Another thing that could cause problems is the crank seals especially the one behind the drive clutch! If the seal is leaking,distorted,or simply popped out,it wont crank or run right! You have to have good compression on the top end along with bottom end compression with seals holding about 7psi if a leak down test is performed. OPT

 

I have the flywheel off and have access to the stator plate. I just did not see any marking like you mentioned.
Update: After you mentioned this, I did find in the book where it says "Reinstall stator plate and align timing marks." Where would I be hunting for the marks? Wait, nevermind. I found the reference that says, "Center the mark with stator plate attaching screw hole." That tells me it must be right next to one (or more) of the holes. NICE!
Aaak! I do not have the tools for a leak down test. The crank seals were never considered. That would truly stink, as I bet I have to fully tear down the motor again in order to do that.

 

If a crank seal is the problem it's usually the one behind the front drive clutch,just need a cheap clutch puller to check the seal out out(or best just to replace it since you're there!). OPT

 

Thanks for the tip! I know I have pulled the clutch on this. I don't have a "clutch puller," but I think I used a larger gear puller, a smaller version of what I used to pull the flywheel.

For the seal, is it just a standard "rip it out however you can" and then "press it in with a large socket and rubber mallet?"

 

For the seal it's just a "rip it out" as you say! Easier if you have a seal puller. Put a little Lock Tite around the outside of the new seal,will help to secure it. DON'T try to use a gear puller on the clutch! You must use a threaded bolt puller OR I believe others have used a 3/4" fine thread bolt from hardware stores(research this IF you don't want to purchase a drive clutch puller!) OPT

 

Thanks for the advice.

Hmm. I do not recall now if I used a gear puller or a homemade contraption. Thanks for the warning.

BTW, I was able to get out and check the timing mark. It was off by a very minute amount, so it probably was not contributing. I am hoping to find 30 minutes tomorrow to try to get it to start with the adjustments before checking out those seals.