Issue with 89 Yamaha moto 4 250cc

[Gwbarm]

Definately, i see that a lot in machines that have been sitting for years. It usually is a by product of water getting into the carb mixing with bad gas already there. I usually scrape as much out as possible, get the rest that is visible with a dremmel tool with small wire brush. Then i put it in a Ultrasonic cleaner to try and vibrate the rest out with a lime and scale remover, and also be sure to take the emulsion tube out to make sure all the holes are open before the ultrasonic cleaner.

[Need-help-with-quads]

Ok yes I tried the ultrasonic cleaner and scraping as much out as I can but I couldn't get it to come off it was really stuck on there, but I just watched a video on carb tuning and I had the air/fuel mixture screw turned all the way in so that no fuel should be getting in there, and yet it still does it, would that mean I have the wrong size for one of the jets? Also the guy said something about the needle height, would that have anything to do with it?

[Mech]

Is the air filter clean ?

The end of the mixture adjusting screw may be damaged or wrong for the carb.

The float level does have some effect on the idle mixture but the mixture screw should be able to overcome that effect. I'd check the mixture screw first.

Most carbs these days it's pretty hard to muddle jets when you have them out. Jets do occasionally fall out though if people haven't tightened them enough.

Before pulling the carb off I'd make sure the throttle butterfly was closed off almost completely by backing out the speed screw, then I'd try adjusting the mixture again. I'm sure you will have read my going on about how important it is to have the butterfly closed off when we adjust mixture. If you haven't, do a search.. I've written screeds about getting the mixture settings right in here.

If the mixture really won't adjust properly after you've checked the tip of the mixture screw, and tried adjusting it with the butterfly closed way off, then I'd suggest pulling the carb off and checking the fuel and air jets are the right sizes and in the right places, I'd check the float level adjustment, and that the float needle was in fact cutting off the fuel by blowing into the fuel hose fitting while tilting the carb.

 

[Need-help-with-quads]

Ok so before I read this the carb was already off so I messed with the float and it was ok but no matter what I did for some reason when I tilted the carb, gas would leak out the drain plug. Even though the screw was fully screwed in. Also when I tilted it gas leaked out three holes in the intake side of the carb so if it tilted then it would leak into the airbox

Im just so frustrated with the carb because i already rebuilt it and i dont know what the issue is and cant figure it out

[Mech]

Well carbs with floats are meant to be kept fairly vertical. And depending which way you tilt it, the float may get jammed tighter shut, or drop away from the float needle and let fuel in. The drain hole at the bottom of the bowl serves as a drain when the screw is undone and an overflow if the fuel gets too high.

You really need to know the carb is clean and the float height is right as a step in a process of elimination.It's easier to strip , inspect, clean and assemble a carb with new rubber parts if needed, than it is, generally, to be certain some electronic unit isn't giving some intermittent problem/symptom.

You need to know the carb is right, then you can move on to other things. That's how mechanics do it if the diagnosis isn't proving conclusive.. We eliminate possibilities, but we have to be absolutely certain that the possibility has been ruled out or cured. Sometimes there can be two factors contributing to a problem, and then it becomes even more crucial that we know for certain that we have eliminated them one at a time.  When you strip and clean a carb you should always take out every brass bit possible, including the emulsion tube, you should blow gently through every drilling in the direction the fuel or air normally flows in to ascertain where the drilling comes out, then blow hard through the opposite direction to dislodge any bits of dirt stuck in a restriction. The idle discharge holes by the butterfly need to be blown backwards especially. They are tiny holes there that get blocked easily if you blow the wrong way. The emulsion tube also has tiny holes up it's side, the need careful cleaning. To clean jets get a slither of some hard wood and whittle it down to a fine three sided point that you can use to ream the jets with. That will clean out any crud without taking any metal off. Don't break the wood off in the holes, but if you do, burn the wood out, don't try forcing anything harder through.

[Need-help-with-quads]

Ok well in that case im pretty dang sure that the issue isnt the carb because the back off issue was still happening right after i cleaned and rebuilt the carb i was mostly just wondering about float height and jet sizes but i dont know what else it could be, because the jets are clean 

and if thats the case with the drain and all that then i think the float height is good

[Mech]

Well pull the idle mixture screw out and check the needle on the end. It should close the idle mixture right off when you wind it right in.

 

[Gwbarm]

I must have missed something, you cleaned the carb,  you tilted it to reinstall on the quad, there shouldnt be any gas in it at this point. So is it leaking at all these places after it is installed and in the correct position.

 

[Mech]

I'm wondering if there's an O ring in there somewhere that's leaking. Some have an O ring hidden away under the slide guide thingy..

Part #23 in this case !!!

https://www.babbittsonline.com/oemparts/a/yam/50038938f870021f60a09fe3/carburetor

[Gwbarm]

I was thinking there should be one under the drain screw #14, but none shown on the diagram.

[Need-help-with-quads]

Hey so if I have another issue with the same kind of quad except just a different one do I do that here or make a new thread?

Basically what happens is the thing smokes like no other, it idles and revs just fine in neutral but when I go in first and get about quarter to half throttle is sounds like it bogs but it still runs and there is massive loss of power

[Gwbarm]

A new thread would be easier to keep track of and maybe get more responses.

But it sounds like a tired engine with lots of blowby, do a compression check and then add some oil to the cylinder and see if it increases. It could also be flooding is the smoke blue or black and what does the plug look like shiney black or matt bllack.

[Need-help-with-quads]

Ok I’ll make a new thread but it’s white smoke and the plug is matte black, one of my buddies told me that it’s probably piston rings