'99 Mountain Max 600 running on one cylinder

[Yamaha_Ryder]

Can't get the old 1999 Mountain Max 600 to run on both cylinders. Top end was rebuilt about 1000 miles ago, just cleaned the carbs, replaced the reed petals, spark plugs etc... It's getting a spark, it's just simply wet fouling the plug on the clutch side cylinder. Never had any issues with her, what gives?

Thanks in advance!
Chris

Edit: It was having these issues before I replaced the reed petals and cleaned the carbs.

 

[Yamaha_Ryder]

Could this be caused by a crank seal failure?

 

[paulharris]

does the pipe/can have a rats nest in it? sounds funny, but i had a mountain max 700 that this happened....it sounded like it was running on one cylinder and it turns out the whole exhaust system was full of a nest that mice built. otherwise check plug wires, coils, etc. if it has old gas in the tank suck all that out right away too

 

[Yamaha_Ryder]

Checked plugs, they are both getting a spark. The spark on the cylinder that isn't firing does seems a little weak compared to the other. They are both running on the same coil though? Checked exhaust, it's clear. I'll get some fresh gas in there.

 

[Yamaha_Ryder]

Could the non firing side of the case be full of fuel/oil from possibly a stuck needle in the carbs? I pulled the carbs apart and cleaned them, but honestly didn't pay enough attention to weather or not one was stuck. Looks to me like the plug gets instantly soaked after just one pull.

 

[RXMax]

Bad needle valve. It would appear that its leaking. Take the carbs off and pressure check them. Pretty common on that vintage if they have never been replaced. Its due.

 

[Givemeaboost]

Do a compression test on it. Those engines were notorious for losing cyliners and pistons and cranks.

Ken......

 

[Yamaha_Ryder]

Thanks guys, sled is 100 miles away. Will check compression on Saturday. Keep the ideas coming!

 

[BBNytro]

also check the sparkplug boots they unscrew off the wire and check with an ohmmeter. I had a similar issue on my SRX. All three of mine were open circuited.

 

[Yamaha_Ryder]

It is getting spark, I may just replace the boots while i'm at it though. Same thing happend to my SRX but i was getting no spark at all.