No spark? Checked CDI, plug and magneto.

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Thanks for all the suggestions guys! The engine is no longer on the bike, as I used it's working magneto to get my other dead engine running (water ingress killed it) and installed that instead.

I had previously looked for a spark like you suggested and didn't see one, but maybe I wasn't turning it over fast enough. I'm not sure how I can check it again without putting it back on a bike (which I don't have the patience for), so I'll open it up and have a look at the piston rings.

It's my oldest engine and noticably more powerful than the others, so I'd love to get it going again.


remove the plug and wack the good old electric drill on the crankshaft ;)
 
yeah yeah, my keyboard tends to miss the odd letter here and there...i meant "No loss of compression, due to anything, will cause a loss of spark..."

sheesh, one letter...cant you figure out what i meant? twerp.
I know what you meant. Your still WRONG! compression or lack of, has nothing to do with spark or lack of. And the square root symbol is as close to "check" as this phones keyboard allowed.
And you don't need to call people names.
That's being a "Richard".
 
compression or lack of, has nothing to do with spark or lack of.
um...maybe someone else can confirm this...


thats exactly what i said, wasnt it?

"no loss of compression will cause a loss of spark"


i didnt know there WAS a symbol meaning "check"? so why not just spell it?

ha ha...richard... ot me there...


oops.

GOT

:D
 
Well, I broke down the engine using Al.Fisherman's handy guide and found the culprit:
 

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Looks like a piece of piston ring broke off and scored a line down the piston, causing a loss of compression. I'm going to order a new piston and rings. There's also this thing, that looks like it's been damaged. Maybe it was a piece of this that caused the damage?
 

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that is the upper rod bearing and that means getting metal pieces in the bottom end even if the rod is still good

fixing and checking that is more work than most folks want to do, with a chance that it will blow out pretty quickly once put together again
 
Now that I have a working bike with my other engine, I'm prepared to fully tear this apart and replace whatever I need to to get it fixed. I'm guessing I should disassemble the bottom of the engine and check for any pieces of the upper rod bearing?

Why is there a chance of it blowing out again? Is there anything else I can replace or modify to stop that happening?
 
metal of cases can be warped a bit by a hard stop, crank can be knocked out of true during the process of opening/closing cases if the bearings get tight - not to say it isn't an interesting project for the hobbyist, but can be hard to get right

new mains might help in case some small bit of debris is hiding behind the bearing cage
 
It didn't have a hard stop, more like a fizzling-out, but I'm a bit wary of doing it now. I appreciate the warning, I might just replace the piston, rings and bearing, then wait until the next thing goes wrong :)

What do you mean by 'mains'?
 
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