90hp vacuum leak

[Goneflyin]

I managed to get my motor (92/90hp) together this week and started it up yesterday, took my little squirt bottle of premix and a shot in the carbs, hit the key and it started right up. Then after a few seconds it started to die, I shot a little fuel in the carbs and it picked right up. Okay I have an air leak so I checked all the hardware and sprayed around reed plate and carbs to check for a leak, nothing, so I pinched off the hose that goes to the air box to scavenge blow back and spilled fuel from the carbs and the idle settled down and would restart without any coaxing.

I blew on the hose that goes into the reed plate and air moves through the hose barb very easily ( to easily I think), I pulled the barb and there's a brass restrictor in it with maybe a 1/32 hole in it.

After following this forum for the past few months and reading that even a maladjusted idle mixture can trash a motor I think I'll block that line. I got the motor partially disassembled, is there anything else that controls the vacuum that may not have been in the box?

Thanks Bill

 

[Frank Acampora]

Re: 90hp vacuum leak

It's not an air leak: It is not getting enough fuel. This is proved by you squirting fuel into the carbs and the engine picking up. Next time try squeezing the primer bulb. If that keeps the engine running, then for sure the fuel system or carbs are not functioning correctly.

You need to check the carbs, the fuel pump, and the fuel lines to be sure that the system can deliver enough fuel. Could be low float level, clogged low speed orifices, stuck inlet needles, or fuel pump not delivering.

The return hose and barb on the manifold is a metered orifice and should not affect idle.

 

[Goneflyin]

Re: 90hp vacuum leak

Turns out it was a stuck float valve in the center carb, I had gone through the carbs this winter but laying in the box possibly upside down the needle was stuck in the seat. I've just played with the engine a little using muffs and a 1qt test tank gravity fed to the pump, but it was hitting on all 3 at idle, I could put my palm over each carb and rpm woud drop and could hear the cylinder quit in the exhaust note. I guess it was getting gas through the passage that ties the intakes together.

Also I got the engine with a broken ring and piece out of the top piston, turns out the rings were broke in all 3 cylinders, previous owner said it ran fine till the top cylinder failed.

Thanks for the nudge to look further.

Bill