Cleaned carbs, now it's worse! Help!

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blizzard78

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Jan 18, 2011
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Monroe, MI
VMAX was running real bad. Hesitating until half throttle or so.

So I cleaned the carbs. When I removed the 2 screws that hold the metal lid on top, the screw that holds the throttle slide to the shaft was really loose. I torqued it down real good and finished up cleaning them.

It ran great for 10 min. I went over a 2 ft drift and when I landed it stalled. It started right back up, BUT it is running real bad. Seems like an obstruction or only running on 1 cylinder. :o|

I tore it back down and inspected everything to no avail.

Any ideas? We were planning a trip next weekend. So I'm desparate.

Thanks in advance.
 
I made absolutely sure the jets were clear. I could see light thru them. And I cleaned everything twice with gumout and compressed air. I rechecked the screw for the throttle slide and it's still tight. I loosened throttle cable and disabled TORs and still won't run right.
 
You made sure jets were clear the 1st time or the 2nd time? I had to clean mine again after some gunk getting knocke loose after a few miles... but when I got into the carbs again it was obvious that something got knocked loosed and clogged a couple of the jets in 2 of the 3 carbs. I didn't stop at that though and I completely tore all 3 down again, compressed air, cleaner etc. Even that little screen got gunk in it again.

After the full 2nd cleaning, start and see if the idle is normal again.
 
Did you start with fresh gas in the tank after cleaning them the first time? When I clean the carbs for the first time each year if I didn't drain the tank at the end of the last season, I drain the tank and start with fresh gas.
 
I made absolutely sure the jets were clear twice so I am 100% sure that is not the issue.

It seems to be running on only 1 cylinder. If I remove the right spark plug boot while idling nothing changes. If I remove the left plug boot (clutch end) it stalls. I verified both plugs are getting spark. Nice blue spark. So, I think the right carb is not getting fuel.

So, is it possible the fuel pump has sucked in air when I hit the drift? The fuel tank was very close to empty when I did that. What is the best way to verify if the carb is getting fuel? Can I disconnect the fuel line and turn it over to see if it is pumping?

I have another guy looking at it right now but I would like to throw some ideas his way. Thanks!
 
sleddineinar said:
Did you start with fresh gas in the tank after cleaning them the first time? When I clean the carbs for the first time each year if I didn't drain the tank at the end of the last season, I drain the tank and start with fresh gas.
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Yes, it had fresh gas before and after the carb cleaning. I also filled the tank after it stalled thinking it was just low on fuel. But it is running bad even after filling up.
 
had the exact same problem as your having .it was the screw inside the top of the carb ,came loose and when i pressed the throttle only one carb was opening.recheck your work up top on the carb.
 
cougar1985 said:
had the exact same problem as your having .it was the screw inside the top of the carb ,came loose and when i pressed the throttle only one carb was opening.recheck your work up top on the carb.
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That was my first thought. But I checked and it is still tight. It is definitely fuel related; so it is carb, pump, fuel line, or something in that system.
 
how about setting the float height? I have had a lot of issues with the floats get out of adjustment. Just a thought.
 
700max said:
how about setting the float height? I have had a lot of issues with the floats get out of adjustment. Just a thought.
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Although I didn't set it with any special tool, it appeared parallel to the bowl mating surface which is what I read somewhere to be real close.

UPDATE: The guy called and said there is a hole in the piston. That would explain the issues we are having. But I don't understand why there appeared to be plenty of compression when I put my finger over the plug hole when turning it over. Is that possible? I wish now I would have checked it with a comp gauge.

Anyways, what's a reasonable price to swap a piston (including labor)? I assume we should do both pistons right?
 
blizzard78 said:
Although I didn't set it with any special tool, it appeared parallel to the bowl mating surface which is what I read somewhere to be real close.

UPDATE: The guy called and said there is a hole in the piston. That would explain the issues we are having. But I don't understand why there appeared to be plenty of compression when I put my finger over the plug hole when turning it over. Is that possible? I wish now I would have checked it with a comp gauge.

Anyways, what's a reasonable price to swap a piston (including labor)? I assume we should do both pistons right?
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Before I read this post I was going to ask you if there was a hole in the piston...

You can do just one piston as long as the other is fine. But I do all my own work, so I couldn't tell you what is a reasonable for labor. I will say that the general consensus is to stick with OEM parts. I buy from Port Yamaha, they are site sponsors and Kevin is very helpful. There are others on the site that can get OEM parts as well.
 
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Any problems with Wiseco? The mechanic is planning to use them. I know for my CR250 dirtbike I have used Wiseco. They are somewhat the standard for dirtbikes. I am sure whatever he puts in will outlast the rest of the sled. We are going to drive it till the track falls off now! Thanks to all for your help. This site is great.
 
I don't have any experience with Wisecos but I have heard you need to picky about your pre-ride warm ups, that they are more apt to a cold-seize if you are not careful about warming the engine up enough before you rip. My buddy had a set in his Polaris twin and you could hear them slap in the cylinders, when they were cold.
 
X2 on the hole,
My bet would be the slide dropped closed on that side when the screw came loose makeing it run on one cylinder and burned down the other side.

I too do my own work so labor cost is unknown but i have read it can run a couple hundred like 2-300 for topend rebuilds.

A lot of guys on here have said some bad things about the wisecos however i have a set in my XT and my dad has a set in his 94. I have about 1500-2k on the rebuild with no issues and it warms up and runs fine (this is just my experience i may be lucky).

If you have the extra cash or the other pistons is OEM then i would go OEM i like to keep both sides the same whenever possible just my preference.

Last time i checked it is about 90 for wiseco piston and rings, 50 for gasket set and you may need a cylinder depending on how bad it got.
 
Picked up the rebuilt sled on Sat. Took her for a spin and she runs great now. I bet you are right about the carb slide causing the piston failure. That makes sense to me.

My Dad has the sleds up in Curtis for the whole week. Hopefully no problems. I will be up there with him next weekend. Looking forward to it.

Thanks for everyones help. Hope you guys have a great winter.
 
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