Spitting and popping

B

bobmcmillen11

New Member
Hi. This is my first post. I've had a BGF 66cc for a few years with no problems. I used it on a box store urban bike with direct drive, and then put on a SBP shifter. The engine hasn't had much use, probably 5 to 19 hours. Then I saw the skyhawk gt frame and had to have one. It was more trouble than I expected, wrong wheels,brakes, seatpost, etc. Everything is together now but I can't start the engine. Spark is good and timing is acceptable (around TDC). I've tried two carburetors and even tried some starting fluid. All I get is an occasional pop. Compression feels normal but I didn't use a gauge. I did take head and cyl off to check the rod (LEV) so it's a PK80. Any suggestions? I guess it has to be the rings.
 
due usual checks for air leaks & checks for head, case, and seal leaks

if you search on this forum for timing marks, you'll find a way to get a pretty good idea of just when your spark is happening
 
I don't recommend using starter fluid on it. It washes ALL the lube from the cylinder. A BGF, huh? When I first started that's where I got all my kits, best price at the time. While yer standing around doin nothing but scratchin yer head, check for a bad or weak coil. A weak one will pop once in a while. And yeah, they go out "Just like that" Quick and for no apparent reason.
fatdaddy.usflg
 
Thanks for the replies. Head gasket and base gasket were both bad. Replaced them and it's back to normal.

Crassius, I found TDC with a dial indicator and then used a timing light. Best I could tell, spark was 0 - 3 degrees BTDC, and I couldn't see any advance. Now that it's running, I'll try it again at higher rpms. Not expecting much.

Fat Daddy, I knew better than to use ether, but I was getting frutrated, and besides, it's a $100 engine.

I did discover a new problem. My head studs aren't particularly parallel. PITA to get gaskets, cyl, and head back on. Can't think of a cure for this but new cases.

Anyway, thanks a lot, all of you.
 
bobmcmillen11 said:
Thanks for the replies. Head gasket and base gasket were both bad. Replaced them and it's back to normal.

Crassius, I found TDC with a dial indicator and then used a timing light. Best I could tell, spark was 0 - 3 degrees BTDC, and I couldn't see any advance. Now that it's running, I'll try it again at higher rpms. Not expecting much.

Fat Daddy, I knew better than to use ether, but I was getting frutrated, and besides, it's a $100 engine.

I did discover a new problem. My head studs aren't particularly parallel. PITA to get gaskets, cyl, and head back on. Can't think of a cure for this but new cases.

Anyway, thanks a lot, all of you.
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Yeah bro,I got one of those engines on my bike now. Whats up with those studs? makes it hard to get it together. I think I've got a bottom end from one guy and the top from another and they just don't line up right. I'm glad ya got it up and running brother.
fatdaddy.
 
Once you get the cylinder down on the studs you can 'tap' it the rest of the way using just a little force and maybe a wooden block or a plastic head hammer. I've seen many studs that weren't aligned perfectly but with just a little wiggling and prodding you can usually get them started into the cylinder. After the cylinder is seated the head 'should' go on reasonably easy but I've also had them give a little trouble.

If things are 'way off' you could taper the top ends of the studs on a bench sander or grinder to bring it to a rounded point. That will help get them started into the holes in the cylinder and the cylinder head.

Tom
 
Yeah Tom, I used a 2x4 block. it still aint right though. Ya shouldn't have to do crap like that. Got it running and NOW it surges.I think it might STILL be a bad case seal. It will go to the top, then goes to the bottom without letting up on the throttle, Then catches again, ACTS like its gonna run, REVS up, then revs down. It's gotta be sucking air through a seal. I've tried 3 carbs so it aint that. I have another bottom end I'm gonna try. I'm tired of messing with this one. I replaced a bad seal that was throwing oil on the clutch. Maybe I F'd it up putting it in. It don't throw oil anymore, just wont run right. I GIVE UP. ANOTHER bottom end that came off a running bike should do the trick.
fatdaddy.
 
those studs are rarely straight - just squeeze one or two to get things on since they bend easily by hand

did you look at the timing mark thread, I'm not in the shop right now to check, but I think they time somewhere more than 20degrees BTDC
 
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