This one has me stumped/6.5 hp quantum

[dougand3]

Above is IPL. You'll see it's a flathead/L head. Valves are in the block under the breather assy. Sounds like you're burning oil - where is it coming from? Breather bad?
1st, check fuel delivery. See if you can keep it running with short bursts of carb cleaner or starting fluid. You could have a bad new Chinesium carb.

 

[louky1150]

Thanks. Do you have info on how to check the breather? I found a youtube about changing it but not troubleshooting.

 

[hlw49]

It could be the engine was turned with the spark plug pointing down or turned upside down and gotten oil in the cylinder or into the crankcase breather. Since it is an L head engine a blown head gasket won't cause it to get oil into the cylinder. It could cause it not to run if blown bad enough. 70 psi is probably enough compression since it has a compression release. Could be a leaking intake tube gasket or loose bolts like upupandaway said. If you had someone to help you and could start the thing while you spray carb cleaner in the carb might help. Think you still have a fuel delivery problem. I have not been into one of these things in years only work on the big stuff. Are the cams like the single OHV engine with the cam lobes and gears pressed onto the shaft. Had and OHV that would start and run but would not throttle up. Turned out both valves were opening at the same time. Lobes had slipped on the cam shaft.

 

[slomo]

This STILL looks like a fuel problem with the smoking as a secondary problem

Agree.

Most likely a dirty carb.

 

[louky1150]

Some progress! Some other questions. Acting on the forum advice I got into this again and had some good news. I took everything apart that I have had apart before. I took off the muffler and got down to the breather to examine but no visible problems. I took the governor plate and magneto off to get to the intake tube and removed it, no visible problems. I did NOT disassemble the carb again. I carefully reassembled everything; the engine started on fluid for a few seconds and smoked a bunch. I did it again and it actually stayed running, smoked for a minute then the smoke cleared. I took it off choke and it still ran. It starts first pull every time now, and runs good but with a surge.

1) I did replace the Oring behind the carb. It looked slightly flattened but I don't think that was it.
2) It's "possible" I had the carb slightly cocked when I installed it originally. I paid more attention this time with better lighting.
3) I had taken the pump off and reattached the engine to the frame while troubleshooting. It was a hassle to hook the hoses up everytime I did something and wanted to try the engine. I will replace the pump tomorrow but I was wondering if the "surging" would have anything to do with the engine having no load?
4) If the surging continues after reinstalling the pump, where should I look? I did see a Youtube where Taryl fixed some surging on a riding mower by increasing the size of the main jet. Since I have a "China" carb on it now I wonder if this could be an issue. They sell these carbs to cover many different applications and it seems like the main jet size wouldn't be the same for all uses.

Thanks again for everyone sharing their knowledge on this forum!

 

[slomo]

Surging is a lean condition. Look for vacuum leaks on both ends of the intake pipe and carb mount. The intake pipe has a flat gasket. Also look into the engine block where the pipe mounts for a part of the intake tube down inside the engine. I had one do this. There is an air smoothing plastic part where the gasket goes on the pipe. That plastic part broke off and fell inside the engine behind the intake valve face. Also don't over torque the two tiny bolts that hold on the intake pipe to the engine. A gentle snug is all you need. Thread locker would be a good idea too. And a new intake pipe gasket.

Next most likely is a dirty carb. Buy an OEM carb for it and call it a day. Chinese carbs are a gamble on if they will work or not. Make sure the carb linkages are installed proper. Springs go where supposed to.

 

[DaveTN]

I never could get an engine to run w/o 90 to 100 psi. They may hit a
lick or two but won't run. Even with pouring oil down the spark plug
hole it will only temporarily increase compression. But it sounds like
worn rings. With a shot of carb cleaner or starting fluid in the carb, it
should run if you keep spraying it a shot at a time. If that's the case
then look to fuel supply issues. Even a vacuum leak wouldn't cause
low compression. Good Luck!

 

[nbpt100]

I would pull the head and inspect the cylinder wall and valves. check the valve lash while you are at it. If they are too tight it will cause issues. If too loose you are looking at worn parts. A new valve may solve it but if it is a worn cam lobe, it won't. As long as the head gasket comes off clean you can reuse it. 18 Ft -lbs of torque on the bolts.