[bsavard]

NO ONE can figure this out yet. My son and I purchased a 2000 Yamaha 1200 SUV. We had a new rebuilt engine put in it and had an experienced independent mechanic do the work. He rebuilt the carbs and tried everything he could to figure this out. He said he talked to everyone he could. He ended giving us back the SUV as is.

The problem;
1/ When outside on hose, starts and runs fine but with a little smoke.
2/ It starts fine on the water. When reaching about 25 mph RPM boogs down quickly, backfires a couple of times and starts idleing fine again and goes through the same cycle again.
3/ The mechanic closed off the oil pump, mixed the oil manually but it did the same thing.
4/ The smoke is white

It feels like the engine is flooding. The mechanic rebuilt the carbs, adjusted them and can't figure it out. Can anyone help us??

 

[glockm22]

Compression test first thing. Then look for any vacuum leaks or bad hoses, when in dought replace them their cheep. Just because the carbs were just rebuilt doesn't mean something still couldn't be wrong with them, a stuck float or improper jetting can happen to the best of us. After all of that go to electrical may be a bad cdi?? Just some idea's

 

[Kelly_A]

white "smoke" = steam, unless your ski just elected a new pope.

I'd be looking at the head gasket as the suspect. May hold fine under no-load (trailered) but put some stress on the the components and cooling water is allowed to enter one or more cylinders via the gasket. May be improperly torqued head bolts, warped head or a bad gasket. Gasket will most likely need replacing now, even if problem is related to improper bolt torque.

water doesn't burn well, hence the "bog".

Alternatives are: a cracked block, broken or stripped head bolt(s) or cracked head.

 

[glockm22]

Very possible Kelly_A . Could be a bad head gasket. If assembled wrong this is where your problem could be. As rev's and and torque increase the head gasket could be failing on you. A Gasket kit wouldn't hurt to own and you can replace the head gasket just to be sure and make sure you deck the head and check the top of the block with a straight edge to be sure their is no warpage.

 

[6atenza220]

I agree with glockm22 and Kelly_A. My uncles 2000 gp1200 had the same problem along with an extreme loss of power. It ended up being hose/exhaust leaks and things not tightened/torqued properly. The head gasket is a likely suspect as well.