Superjet issue

[Wade Auckland]

Asking for a friend. His motor recently blew up, he rebuilt it and now the ski will idle just fine but when you go to give it throttle it will rev a little then start sputtering like its getting to much fuel. also a lot more amount of oil than normal is coming out of the exhaust. He didn't change anything with the carbs in any way and he only when a few mm up, just enough for the cylinder wall to be perfect for the new pistons. don't know why so much gas is getting in. Cracked Reed? we checked them and they looked ok. Any help of advice would be great!

 

[Mike W]

A needle and seat is probably stuck open.

 

[john zigler]

Could be many different things....

Did he determine what caused his engine failure originally?

What is compression after the rebuild?

Did he use assembly oil during the engine build? (could explain excessive amounts out of exhaust)

Are you sure it is not the overheat sensor, or CDI cutting the ignition out? (kinda common on Yamaha's)

Could be a fuel related issue, and maybe it is time to go through the carbs. I go through the fuel system completely regardless after a re-build.

 

[Wade Auckland]

The engine failed because the o-ring on his ada head blew and some water got inside the motor. the compression is 185 in both cylinders, we did use oil in the re assembly but the amount of oil is still way to much its easy to tell that. The heat sensor has been removed because it is a aftermarket head. we also rebuilt the carbs fresh before we put them back on, they are set to exactly the same as before, we triple checked. and i havnt personally seen his reeds but he said they where intact. we know its a fuel issue as we already replaced the entire electrical system.

 

[Kaylee.S]

Make sure the pistons aren't installed backwards...

 

[Wade Auckland]

They are not, ive rebuilt multiple motors, i double and triple checked everything, our buddy that is a certified mechanic for skagit powersports even took a look at everything and he doesnt know whats wrong either.

 

[Ducky]

Even though you rebuilt the carbs, I would still tear them apart and blow out the passages with compressed air. You could have something super tiny blocking the return on the carb(s)

 

[Kaylee.S]

Even though you rebuilt the carbs, I would still tear them apart and blow out the passages with compressed air. You could have something super tiny blocking the return on the carb(s)

What hillary said ^^^

 

[Wade Auckland]

Even though you rebuilt the carbs, I would still tear them apart and blow out the passages with compressed air. You could have something super tiny blocking the return on the carb(s)

we have done this multiple times, at this point im going to remove the carbs from my superjet and put them on his just to see what happens

 

[john zigler]

When you rebuilt the carbs, did you use Genuine Mikuni brand kits? Did you replace needle and seats? Again Genuine Mikuni ones?

 

[smoofers]

Was the motor pressure tested? Were the carbs pressure tested? Was pop-off verified on each carb? I agree with the other members, this is definitely a carb issue.

 

[Wade Auckland]

motor and carbs have been pressure tested and check out almost perfect, not sure whos rebuild kit he used i will ask him

 

[Vortex]

I had a reed break once. It wouldn't run at all. I doubt that's your problem. Id check the needle/seat. Or your cdi/coil/stator/flywheel

You said the motor got water in it, was there an attempt to purge that water out by cranking it over a bunch with the plugs removed? If the plugs were not reinstalled into the wires and grounded to the engine manually then it's very possible your cdi is fried. Possibly the coil as well. The capacitors in the cdi swell up and fail when the plugs aren't grounded and the ignition attempts to fire.

 

[Blaine Mac]

Flywheel key fell out when reassembling?