Do I have a leaky head gasket?

[jonrick]

Nope. Walbro only has the idle jet and the main. No accelerator pump or power valve.

I think you were on the money with idle. When I brought the idle speed up a bit the tractor seemed a lot happier (no more stumble). I still need to tinker with it a bit but I think that's the main issue. I've noticed as well that the stumbling doesn't happen when the engine is under a load.

 

[HKCooper44]

Use it a bit more and see how it operates. Sounds like you're OK.

 

[mgonitzke]

It should not stumble at all, so it still is probably a bit lean. Make sure the timing is set correctly, too. After you've done that, start it, warm it up, set the throttle at wide open, then enrich the main jet slowly until you notice an RPM drop, which may be accompanied by rough running and black smoke. Then, slowly lean it back out. The RPMs will increase, then decrease again until the engine stumbles. Next, enrich it again until you find the spot where the RPMs peak, then enrich it ~1/8 turn more. Then, set the throttle to idle, set the idle speed screw at the desired RPM (1000 RPM for most K-series, but I think the QLs like your 1450 are set to 1800 per the manual so they shake less), then set the mixture similarly to what I described above for the main so it will idle smoothly at that speed.

After doing this, quickly advance the throttle from idle to wide open. The engine should quickly respond without stumbling. If it hesitates and pops, the main is still too lean. If it runs rough and blows a bunch of black smoke, it is too rich.

 

[jonrick]

It should not stumble at all, so it still is probably a bit lean. Make sure the timing is set correctly, too. After you've done that, start it, warm it up, set the throttle at wide open, then enrich the main jet slowly until you notice an RPM drop, which may be accompanied by rough running and black smoke. Then, slowly lean it back out. The RPMs will increase, then decrease again until the engine stumbles. Next, enrich it again until you find the spot where the RPMs peak, then enrich it ~1/8 turn more. Then, set the throttle to idle, set the idle speed screw at the desired RPM (1000 RPM for most K-series, but I think the QLs like your 1450 are set to 1800 per the manual so they shake less), then set the mixture similarly to what I described above for the main so it will idle smoothly at that speed.

After doing this, quickly advance the throttle from idle to wide open. The engine should quickly respond without stumbling. If it hesitates and pops, the main is still too lean. If it runs rough and blows a bunch of black smoke, it is too rich.

Regarding timing: When I go to start it up, the starter often engages and starts turning but then hestiates like it's fighting compression. If I let of the key and try again it'll usually spins right over no problem. My gut feeling is that it's timing. Any thoughts? The key did just burnout yesterday so I'm going to replace it and see if that makes a difference first.

 

[HKCooper44]

I doubt it's the timing. If you set your point gap (I think it's .020"), then that sets the timing. There is no other timing adjustment other than the point gap.

 

[mgonitzke]

The 0.020" gap in the service manual is only a starting point that should get the engine to run. Depending on manufacturing tolerances, wear, etc. this may not correspond to the spark plug firing at 20° before top dead center. I have had engines with the point gap in the 0.015" range or less once the points were adjusted for proper timing.

If you have a multimeter you can static time the points to get the adjustment correct. I have found this easier than using a timing light:

http://mgonitzke.net/cubcadet/tools/static_timing.pdf
Other possibilities for hard starting like that include the compression release not working, or the commutator and brushes on the starter needing attention.

 

[abthomas]

I flattened the head with the tile and sandpaper trick suggested by you gentlemen, got the new gasket and head torqued down to spec today and fired her up. It appears to have fixed the head leak. Thank you to everyone who helped me by providing your input. I'm grateful for the new knowledge! The engine is still running a bit "off." But I think that discussion is likely a candidate for a new thread.

I normally re-torque the head 2-3 times after a rebuild, run it long enough to heat up, let it cool down completely and torque it , you'll find it's loosened up from the original torquing ! call me anal but iv'e never had to revisit a leaking head gasket !

 

[dsarow]

I normally re-torque the head 2-3 times after a rebuild, run it long enough to heat up, let it cool down completely and torque it , you'll find it's loosened up from the original torquing ! call me anal but iv'e never had to revisit a leaking head gasket !

Head torque maintenance is a big part of keeping these old girls running well,and its not hard to do and time consuming

 

[jonrick]

I normally re-torque the head 2-3 times after a rebuild, run it long enough to heat up, let it cool down completely and torque it , you'll find it's loosened up from the original torquing ! call me anal but iv'e never had to revisit a leaking head gasket !

I'll definetely be sure to re-tighten before I fire it up tomorrow! Thanks for the pointer.