MH30 fuel flow

[Anonymous-0]

...seems to be too high.

Background: The carb has always leaked, and the tractor has been running too hot lately (mostly due to the oil and cedar-clogged radiator) so I decided to do some cleanup. Part of this was to rebuild the carb...new gasket, needle valve and seat, etc. Tightened up the accessory belt, all is good. Tractor starts right up, must have done something right...

Problem is this...the throttle is set to the lowest notch and the tractor runs like its full throttle. There is still lots of travel in the butterfly valve in the carb so I do not believe it is throttle-rod setting (not to mention I didn't change it). Changing the main jet & pilot jet settings does not change the speed of the tractor.

Basically, I've made no changes to the system and it doesn't run the same. I know this is NOT true (something must have changed). Any ideas on what the problem is? I was careful to set the jets back to their original settings.

Anyone seen this before?

Thanks, Steve.

 

[Anonymous-0]

I would first suspect the throttle valve is not as originally installed on the shaft.You can install them upside down or inside out.So turn the butterfly loose LOL What was wrong with the jets which I assume were made of brass and never rust?If you cannot get a too lean or too richness on both the low speed throttle stop position (idle)and the high speed circuit then put back the old jets which were right.Today kits are often not as original in many cases.Adjust both jets till you get the too rich or too lean position.Do not be afraid to turn them in and out.Get the maxuum RPMs out of both positions.

 

[Anonymous-0]

Did you happen to replace the throttle shaft? A lot of the rebuild kits must be designed for different tractors with this same continental engine. I put a kit in my old carb and the linkage arm was shorter on the new shaft. Meaning, the distance from the center of throttle shaft to the center of linkage hole was about 1/4" too short. This would have pulled the carb open enough in the original idle position to make it rev up. I compared the two and brazed on an extension and drilled it to match.

 

[Anonymous-0]

More info...

Took the carb off last night (getting lots of experience with that) just to make sure I didn't miss anything. The main jet is still stock; I changed the idle jet back to the original. Only difference is the main gasket & the needle valve...which is about 1/8 inch shorter than the original. So...this will change the float height and *apparently* affect the carb operation.

So, I bent the float to change the location that the float stops fuel flow and reinstalled (did I mention I'm getting good at that?) Tractor still behaves the same but changing the idle jet setting changed the idle of the engine, so I think the float height change had some effect. Still not there but getting closer - repeat the whole process tonight.

Incidentally I noticed that the governor is doing its job. At one or two notches on the throttle opening the engine is running wide open. Pulling the throttle wide open does not change the carb setting...the governor is preventing any more fuel being introduced to the engine.

No Ian I did not replace the throttle shaft. Those setting have remained constant. Currently only the gasket & needle valve have been replaced.

I changed the needle valve because I found on my motorcycle that they get old & don't seal...all that fuel running by them. I *thought* this is why the carb leaked after I shut things off...still leaks. There is an in-line fuel shutoff, I just use that.