I put about 3/4 tank through it before it blew. I oiled the crank and pistons prior to start up- a few drops here and there. I had primed and confirmed operational oil lines. I did 5-6 heat up and cool down cycles of about 5 minutes running around idle or maybe 1/4 throttle- each cycle with oil lines stuck wide open- smoke fun. I retorqued head, coolant manifold (under exhaust) and exhaust manifold. I looked for obvious leaks all around.
After that process, then I let the oil line operate normal with the throttle and ran throttle 1/4 to 1/2 up to short bursts of 6000rpm with track and tunnel suspended (no load). Did this maybe 3-4 times to warm it up and cool down. All the time checking plugs for too lean- they were always rich.
After that, I ran it for half dozen 5 minute rides up to maybe 40mph (1/2 throttle) for short bursts. During this process I started to be more critical (intolerant) of the rich plugs and mismatched plugs. In fact, several times I could not get it started for fouled plugs. But I never saw a "lean" plug, just a good plug with a rich plug. With this process I made a couple bursts to 3/4 throttle, still not full throttle.
The best plug signature I got was without the air box. This is probably when I got too bold and impatient. (I know- dangerous territory). This got me a lightly gray plug with a brown plug. And, with a short burst of full throttle, it got me 85mph. But still the worst plug was light gray and the other was brown. At this point I had gone through about 1/2 tank and I did not feel like I did anything wrong. And, I figured maybe I should give it a short ride (15-20 minutes).
I puled into the gas with good power and it shut itself down as I pulled to a stop. @#!$ I had the same mismatch plug problem on the other rebuid. Motivated by a fresh rebuild blown up, and frustrated by thinking I had done nothing wrong, I began to investigate the 2nd rebuild closer.
CARB BOOTS: original boots, insulators, and new gaskets. Torque proper, maybe one click tighter... No sign of leak on any of it.
DID I PRESSURE TEST THE ENGINE: No- not on either motor. Frankly, I never have. In my opinion, and lack of experience, after all the "plugs" and closures you need to make on the motor, if it did show a leak I wouldn't know where to look for the leak. I'm always afraid I would get a false reading. So, instead, I did the poor mans tests on the 2nd Invader (not on the blown one). I did a ether spray test at idle around all intakes and engine case. And I did a warm engine half throttle test of the same spaces. Passed all tests. I know- this is not a great test: that is why I call it a poor man's test. Me and my buddy were nearly beside ourselves with why one cylinder on both engines would be lean.
I joked (ok threatened) that I would simply "correct the rich cylinder problem by running one carb lean"...then we both looked at each other and simultaneously said "...what if someone else tried that?"
BINGO- my 2nd motor had mismatched needles. Then I looked at the blown motor and ...yep- mismatched.
That is when I started to feel better that my rebuild was "tight" and "proper"; albeit imbalanced by an oversight and ASS-umption...
Moments like this push an otherwise capable person to the brink of throwing in the towel. But- I'm fine now. I've got some carb rebuilding to do along with the motor. Then, at some point, I'll give that 85mph a try again.
Topic: Rings to fit Invader Piston (Read 7814 times)