OC 46 Backfire problem

[davidr]

We have completed repairs on an OC 46 dozer with the three cylinger Hercules engine that was stored in our shed for about 10 years. The repairs included new clutch and throwout bearing, new yokes on propeller shaft, repair kits in the carb and fuel pump, plugs and wires,points, condenser, and distributer cap. When we start the engine it backfires and dies. If we start the engine and leave the choke half way out it will run but with about half of its normal power and will still backfire occassionaly. We have checked the timing and it appears to be correct. Does anybody know what may be causing the problem.

[John Schwiebert]

If the choke needs to be out you are starved for fuel. A lean mixture tends to backfire. Do you have acess to a vacuum gauge? Tell us more about your carburetor rebuild and did you check for a leak between the carburetor and the head on the intake side?

[RAB]

You  may have a valve which is sticking open or not seating properly after 10 years?  Never had a 3 cylinder gas, but I would think a hanging valve would affect the running very considerably.
Regards, RAB

[mtncrawler]

Was this machine running well when parked years ago?

[John Schwiebert]

Have you checked compression on the engine? Do you have a vacuum gauge, have you taken a reading. Maybe lets start with the fundamentals.

[yellowcrawler]

I had a similar problem on an HG with an IXB3, eliminated the obvious, even took the carburetor apart several times after the rebuild.  Choke had to be halfway out, idled very poorly, very lean and with no power.  I had been working through this for about a month, after a total engine rebuild.

Then I noticed Saturday that the venturi fit loose in the upper half of the TSX Marvel-Schebler body.  I thought this could be a vacuum leak, bypassing the idling circuit.  So I sealed it up with aviation style Permatex, then let it set for a day.  Fired it up last night, ran real smooth, with no choke!

For what its worth, I hope it helps.

I still have a lot to do on my project, I literally inheirited a basket case, but it runs a lot better.  

yellowcrawler

[mleves]

If you have the 3 cyl gas engine, i've notice that the carb is adjusted
to compensate for the vacuum created by the oil bath filter.  ie no
filter will cause it to run lean.