Need a bit of help here. Any opinions,suggestions,solutions are valued.
I have two FL350 and one with an Engine issue that I can't figure out.
The Engine starts fine and it idles fine. After it warms up and you rev it a bit it will take off at high rpm. This is a clear sign of an air leak. It will hold positive pressure for a week and it holds vaccum of 6-7 in/Hg for half hour plus. WTF???? Running out of ideas here. Pics enclosed.

Check your carb
Make sure the gasket is still in the cap

Yes rubber gasket is still in cap. Just checked to make sure and it's there. Cap was screwed down tight too when we ran it. I was the one that put it on so I know for sure.

Hmmm...


Got to be something in that carb...sticky float, needle, etc or a sticky cable maybe? Without it running and with the airbox/tube off, can you see your carb slide move up and back down freely and completely when you pull the throttle lever?

Got clear fuel lines you can use? When you rev it can you see steady fuel draw or does the flow tail-off anywhere? At least you can confirm the plumbing and pump this way.

you might as well be a fuel delivery or I see that you take your exhaust flange off it could be a leaky exhaust flange?

or somethings really finicky with your carburetor check for cracks

I would also check your chamber pipe maybe have a hole in it somewhere ?

I would also start with a fresh fuel filter just to rule that out

If the Engine will hold pressure and vacuum for an extended period of time, I would say you don't have an air leak.

As D Money mentioned I would look at carburetor problems.

1.) Check to see that your throttle cable is in good working order and is not kinked or binding anywhere.

2.) Check to make sure all of the jets in the carburetor are tight.

3.) Check to make sure your needle in the carburetor is not bent and doesn't have any burrs on it.

4.) Check to make sure that the slide in the carburetor will slide freely with the cable connected. Even the slightest amount of throttle with the Engine in neutral will rev out pretty high.

5.) Check to make sure that the slide in the carburetor is not worn or have any gouging in it that would cause it to bind.

Rand

The carb is brand new. Has less than one hour on it, that's when Engine poof kaboom last time.
Our return line from "T" is a clear tube to tank on both machines so we can see fuel returning.
Fuel filters are also clear and new and have fuel in them. We tried another fuel pump from a quad that a friend let me strip off his machine just to check but Engine did the same thing, after warm up if you blip throttle Engine runs away like it has an air leak.

No exhaust leaks because we red siliconed every joint on both machines.

When i took my topset off my stock carb once i had put it back in 180 deg wrong and when i started it up it ran away because the slide was in the up position. Could this be it?

Nope slide is in the right way.

Did you allow the silicone to dry 24 hrs before trying to start the Odyssey, if not recheck the joints 99% of the time just cranking the Engine over with wet silicone the pulse from the Engine is enough to upset the seal of the wet silicone.

Check the intake rubber to make sure there's not a small crack in it olny when u put the carb on it

I have seen that happen on an rubber intake for an pingal mount before
To where it will olny leak when a carb is on it

Now I feel stupid and I cant even lie about it because of the pictures. I just figured it out. Just needed a coffee and lunch break. If you look at the pics you will notice my canuck hillbilly rigging. The vaccum gauge is on the intake and the siphon tube with check valve is on the exhaust. When I pulled vaccum and got 8 in/hg on guage the reeds closed after I stopped pulling vaccum. They held the pressure on the gauge because reeds closed. I just put a small tie wrap in one reed to hold it open and I did test again. I lost 5 in/hg in 3 min. It's all over but the crying now. Rebuild.
Conclusion: The positive pressure test is no good to test your crank seals because this test sets the lip seals tight on crank. It is a good test with soap and water to check for leaks on head gasket,cyl and case gaskets. The vaccum test is good for testing the crank seals. It seems clear to me now that a motor (( Internal Combustion Engine ? )) MUST pass BOTH tests and you must complete BOTH tests.

This motor (( Internal Combustion Engine ? )) actually held some positive pressure for a week.