Hi Guys,
i have a small issue with my sons predator 90. Its a 2004, with the oil injector removed. I also replaced the stock reeds with boyesen power reeds.

It runs ok but at idle to 1/4 throttle, it smokes alot. It doesnt have any low end power and seams to be using a lot of gas. Running rich is more like it. The problem is if i turn the air screw out it doesnt change. Also if i put the choke on closed, it still runs and actually runs better. I assume this means i have a air leak.

What is the best way to attack this problem?

I would appreciate any input from you guys.

 

Make sure you have fresh fuel, replace the fuel filter, take your intake off and check it for cracks, check your reeds, clean your carb, then move to a compression test.

1/4 throttle is the needle jet. Has nothing to do with the idle screws.

 

If it runs better with the choke on, then you are to lean.

Both the air screw and pilot jet affects carburetion from idle to around 1/4 throttle (with a little help from the throttle slide valve as pass 1/8 throttle). The needle jet and jet needle kick in just before 1/4 and deliver most of the fuel until you reach 3/4 throttle.

Did you change any of the jetting when you removed the oil injection? Before I went chasing an air leak, I'd break down the carb and give it a good cleaning. Pay special attention to the pilot jet. They are so small that any dirt in them will stiffle these little motors. Drop the clip on the needle one notch(raising the needle) and see if it runs any better.

How did you block off the oil injection intake nipple on the carb and what oil ratio are you running?

 

No i didnt change the jetting. Im going to look at it in a minute. Thanks Ill let you know what happens.

SHould i remove the reed stops? The little metal pieces. I didnt remove them yet.

 

Man, I'm dyslexic or something. I read it runs alright at idle but....gotta quit skimming.

Yes, Fishez is right. Check the pilot.

 

Fishez,

To block off the oil line to the carb I cut the oil line put red locktite on a screw and i screwed t in. I then sealed up the end with more locktite making it air proof.

I moved the clip up one notch. Im mixing 32:1. Should i have to worry about running too lean? This wont mess anything will it? I did a plug check and at first it had carbon built up on. I heated it up, changed the plug warmed it up again and ran it. Did a plug check and it was light brown. Almost perfect.

The reeds have the stock metal stopper on them. I put it back on when i changed the reeds. Should i take the metal parts off?

Im going to have my son ride it tomorrow and see what happens on a ride. Before it was smoking alot and now it seems to be better. There is still a little bit of smoke.

THanks,
Bob

 

The problem with this is you can be fat at partial throttle and lean up top and still get this reading. Warm the quad up, then switch plugs, then nail it for a distance, hit the kill switch and check the plug.

I mix about 38:1 too.

 

Thats how i checked it. That was at top end as fast as it would move me and then i killed it and checked the plug. Should i do the same for the low end? Go 1/4 throttle and check the plug?

I dont want to blow this thing up. I just want it to run good.

 

I'd go 1/2, but yes.

I'd really recommend getting a handful of main jets before trying chop tests. Always work from the pilot (idle), to needle (1/2), to main (full). If you are lean, you can tell pretty easy by cover a portion of you air filter or snorkle (does it run better?). To see if you're rich, a good trick on the main is to turn the gas off and see if the engine runs better as the carb runs out of fuel. If you're very far off either way, the engine will fall on it's face. Use your ears and the seat of your pants and you can tune them pretty good without spending $2-3 per test on plugs.

 

Raising the clip one notch will make it leaner.You need to lower the clip to make it richer(raises needle higher).If you need to choke it to make it idle it sounds like crud in the carb or a fuel flow problem.Have you checked fuel filter,lines for dirt and make sure no kinks or blocked air vent to the tank.