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BIG NEWS.

It runs, but very reluctantly. I had to bring out the 500A portable jump-starter from the car and connect that to the battery before the starter could kick the thing fast enough to start, but it started. The thing is, it won't idle. I took some videos, maybe they can make things clearer:




And a second start:



What do you think? How can I make it idle?

Well, a few things have happened. I tried wiggling the boot, nothing. I tried measuring how far into the cylinder the plug was projecting--it seems that the threads in the head are the same length as the threads on the plug, and the end of the plug is projecting into the cylinder.

I was about to pull off the cylinder and start installing the old one when I decided I'd try shooting starter fluid or gas straight into the intake port. I removed the intake manifold and shot some starter fluid straight in, and although I didn't hear a "bang" or anything of that sort, the engine sped up to probably 1.5x the speed the starter motor can spin it. I was able to get this to happen with gasoline from a squirt bottle, too.

I also noticed something else--I'd lean on the starter and squirt a bunch of gasoline into the intake port, and the engine would go slow-fast-slow as (I guess) it went from flooded to ok to lean. so that might have been some weak firing, but at no point was it strong enough to keep the engine going without the starter.

Might it be fuel then, after all? Maybe the compression is low despite the rough test I've tried? SHould I get a compression gauge?

Well, that's very interesting. How could that happen, and what was your solution?

In other news, I was sent some literature by the guy who sold me the BBK that quoted a 0.01" valve gap. Tried that this morning, no help.


Here's a picture of the engine bay and the hoses, as Alleyoop requested:

Well, I've already drilled out the plug and tried the screw at 2, 1.5 and 1 rotations out from all the way in. Nothing there, even with lots of cranking from a freshly charged battery, probably half again as fast as it was in the video. I'll give the lots-of-air tack a shot tomorrow.

I double-checked the spark plug yet again, and I can definitely say there isn't a problem. Held against the cover it gives good blue (almost white) sparks, and held a couple inches from the cover, it actually arcs all the way to it. That's a good spark.

oh, I've tried it every which way. Gas on the vacuum port, plugged vacuum port, throttle open a little, open a lot, everything.

You know, I'm thinking of just reinstalling the old cylinder and trying to cut my losses. Maybe 50cc to 100cc is a bit much, anyway....

Sounds like a plan. I'll be giving it a try tomorrow after work, but in the meantime a question--wouldn't it be ok if the sprocket were 180 degrees off? I'd think (based on limited knowledge) that it would still run, it would just be one revolution off from where it would have been otherwise--running a bit later in the cycle, so to speak. I say this because I actually had it with the sprocket 180 off from where it is now, and reversing it didn't help. After I reversed it I spun the motor a few times with my hand and found that the sprocket was back to right-side up with the flywheel at TDC due to a 2:1 gearing between the cam sprocket and the crankshaft. If I reverse it again, wouldn't it be equivalent to spinning the crankshaft once?