Need 1200 SUV suggestions

[mdavidthomas]

Bought a 2003 SUV from a guy last week. Had a premium SBT engine in it ~20 hours. Checked it out and took it for a spin before the purchase. Has a bad vibration on throttle tip in and shakes pretty bad. After a 15 min spin today, it has water and oil/gas in the bilge. The unit has been changed to premix and I mixed the gas at 45:1. I may have overfilled the tank but it did not back up to the gas fill cap. I rode it last week and the vibration would go away as more throttle was applied and then it seemed smooth I higher rpms. The full open throttle rpms seem to be at ~6750 and it ran around 43 mph which is obviously a little low. This was using the waverunner's display so it may be off. I found a bunch of aluminum pieces in the bilge but I assumed that was from the original engine destruction. I plan to do a compression test in the morning. Unit cranks easily. Spark plugs looked ok. Thinking carbs may be leaking??? Any suggestions would be greatly appreciated.

My thoughts on vibration:

1. Engine to coupling alignment
2. Engine issue

My thoughts on oil in bilge

1. carbs/fuel line leaking
2. overfilled tank
3. Hole in block

BTW, I have a 2000 SUV and it does not vibrate like this.

Thanks,

mdavidthomas

[dolson]

Was the engine aligned when the sbt engine was put in? Both carbs clean? Could be one partly clogged carb that is robbing the one cylinder of gas cause it not to fire properly and shake and there's enough pressure at higher rpm that it fires to get rid of the shaking but still slows it down. Or could be a leaky carb causing both issues. Not enough fuel to the cylinder due to leak it's causing these symptoms

Focus on and Look for issue #2 and see if it solves issue #1 .You don't want to be running it if you suspect a fuel leak.

[mdavidthomas]

I agree totally on not running with a fuel leak which I found the number two carb seemed to be leaking between the carb body and fuel pump plate. The previous owner supposedly had the carbs rebuilt. The bolts for all three carbs fuel pumps were not very tight. I am concerned that they might have used non-mikuni carb rebuild kits. Also, the intake manifold gasket was torn when I removed the carb baseplate. Looks like a cheap aftermarket intake gasket with no metal in it.

Thanks for your suggestions. Keep them coming.

mdavidthomas

[birdgod]

you can do the carb test while the carbs still on jet ski. just not the pop off test.

[mdavidthomas]

What is the carb test?

Thanks,

Mdavidthomas

[birdgod]

the pump should hole 4 psi for 10 sec
the carb body should hold 10psi for 30sec.
get a mikuni carb service menu it is all inside.

your top RPM seem right, but if you get low speed at that RPM you should check the jet pump.

[mdavidthomas]

I have the Mikuni SBN manual. I don't see it there but the test makes sense to me.

Regards,

mdavidthomas

[mdavidthomas]

All three carbs leaking on the pump side of the carbs. Carb #1 leaks the least but leaks between the check valve plate and pulse plate. Carb #2 leaks really bad between the check valve plate and carb body, straight below where the pulse line connects. Carb #3 leaks slightly between the check valve plate and the carb body. Needle and seat has groove on the viton tip, and Carbs #1 and #3 where missing the round o-ring between the check valve plate and the clear pump diaphragm. I thought maybe the person used the extra flat seal from the Mikuni kit but it is not there either. Carb #2 had the o-ring installed.

Not sure about the SBT engine. Compression was off between the cylinders as follows:

Cylinder #1 113 psi
Cylinder #2 118 psi
Cylinder #3 123 psi

This was a fire waiting to happen. I really hope it helps the vibration.

mdavidthomas

[birdgod]

Rebuild them using oem kits...

[macGruber]

All of the missing parts is absolutely ridiculous! If a person uses non Mikuni rebuild kits the carburetor is very likely to leak at the base of the fuel pump. WSM, SBT and ALL of the non-mikuni kits I have ever seen or tried have ALWAYS....100% of the time leaked air from the base of the carb where the square block mounts to the carb body. The reason is that the big round Oring with the square legs on it ( sorry, that's the best way I can describe it lol) is fractionally not tall enough so it doesn't make a seal. The ONLY one I have ever gotten to seal is the OEM Mikuni oring. Aside from that, the needle sounds trashed if the Vito tip has any groove in it. Replace it. If it leaks, pop off will probably hiss more than pop. Pretty sure this is why my SUV leaked fuel into the motor while at rest. Doesn't matter now because I fried cylinder 2 last week. Good luck man.