I've rebuilt this engine with all new internals, including crankshaft, new. I reused the heads and bought aftermarket carb. The PO had hacked the old Nikki carb. It fired up initially and for 4 hours breaking in rings, it ran perfect. I noticed oil leaking around drain plug and replaced O ring there and the dip stick tube. When draining oil, I noticed it was black metallic. Filled with fresh oil, warmed up engine, checked stick, it was foamy. ?? I started up after topping off oil and ran at different RPMs for about 3 or 4 min. with clutch engaged and it just died. I got it to start again on full choke. It would stall off choke. I checked oil again and there was a lot of pressure released unscrewing the dip stick. I assume that pressure may have caused the O ring problems. Do you have any suggestions on the black and foamy oil ? And the crankcase pressure ?
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Export threadPressure release from the crankcase when the engine is stopped? If so, the crankcase may not be venting through the breather system. The reed valve might be stuck. This would prevent fuel pump operation resulting in not being able to keep the engine running. Black oil is caused by blow-by of hydrocarbons. This could be from not venting the crankcase as well.
Thanks for that, txmowman. that makes sense. I also noticed it was slow to pour oil down dip stick chute. It would fill tube and sort of burp back. Is the breather filter necessary? I saw that new kit has none.
I pulled the breather, discarded the oily filter, and found port to the carb tube to be stopped up. ?? I used a good spare crankcase during rebuild that was sitting around. I'm assuming a dirtdobber nested in that port.? All seems normal with vent now. Thanks txmowman !The breather filter is not necessary and should be discarded if you get in there.
txmowman, you seem to be knowledgable,I have one other question. Once i cleared vent tube, I started it up and still have a throttle problem, not related to crankcase pressure (I hope). When I try to Rev it up, it stalls around mid-throttle. If I ease it up, it seems OK but will surge at mid-throttle only. ? Aftermarket carburetor. I tried pilot screws and static governor setting. Any suggestions ?I pulled the breather, discarded the oily filter, and found port to the carb tube to be stopped up. ?? I used a good spare crankcase during rebuild that was sitting around. I'm assuming a dirtdobber nested in that port.? All seems normal with vent now. Thanks txmowman !
I'll check that out tomorrow. It doesn't seem as bad under a load. It sounds smooth a WOT.When it is surging, if you slowly apply the choke, does it tend to want to smooth out? How does it run at full throttle?
So at high idle under load is sounds good? WOT on a governed engine is when the engine is under heavy load and losing RPM. If the engine runs fine with the PTO engaged, then the idle jet likely is incorrect for this engine or debris in the idle circuit. The engine has no purpose at mid-throttle anyway. If it doesn't surge and runs fine while mowing, that is what you want.