First time rebuilding an engine... Now what's wrong?

[emolatur]

... well, the bottom end anyway. My '94 KX80 seized its lower rod bearing, silly me thought I'd save a lot of money by doing as much of the work myself as possible. I had to get a local machine shop to split the crank and put the new rod on it, everything else I thought I could handle. I printed out all the diagrams and asked a lot of questions of a couple friends who have done this before (but have moved away, so this was done online)... All went pretty well, it even started first try after reassembly...

... then promptly stalled and wouldn't restart.



Backing up a tiny bit, I called a local Kawasaki place expecting to order a new gasket to go between the case halves. I was informed that there wasn't one, but that they used, and I quote, "gasket maker". No further detail was given. I could see that the last guy who did this engine ALSO used a chemical compound, which was red and could be seen where it overlapped the seam. So I went to the hardware store for 'gasket maker'. The last guy used red stuff, but there was a warning on that saying it wasn't gas/oil-resistant, so I wound up with the black stuff. Another call to another Kawasaki place (after the whole thing was put back together) revealed there's a SPECIFIC chemical they use, 3-bond #1194, which is neither red nor black (it's gray), so I used the wrong stuff. I am now pretty well convinced that's my problem, but I wanted to run this by the folks on here before I tear the whole thing apart again.

Any time I drain the oil and let it sit for a while, then partially refill, kick it over a few times with the plug wire disconnected and just barely enough oil in there to keep it lubricated, then fill it back up, hook up the plug wire, and try again, it'll run for a short while. Pretty much long enough to go up and down the driveway a couple times, then it stalls. Trying repeatedly to start it results in a single fire every 5-6 kicks, but no actual running.

I have verified that there is spark. I also blew air through the carburetor, getting a spray mist of fuel out the other side, so that appears to be working as well.

I do have compression, although not as much as I would expect.

The oil visible through the window in the clutch cover turns white. Shortly thereafter it disappears altogether.



My THEORY is that I have a leak (due to having used the wrong compound) between the bottom crank area and the transmission. Oil gets sucked into the crank area gradually and effectively alters the oil/gas mix ratio, eventually to the point where ignition fails.

Valid theory? Or is something else more likely?

 

[ellandoh]

if it doesnt smoke excessively your not burning oil. after rebuilding a motor it may be necessary to rejet. check the plug next time it dies. see if its wet, dry, charred etc.

sounds like youre flooding it, next time it dies, dont drain the oil and just pull the plug, kick, replace and start. or after the stall hold it wide open and kick it over. that is my routine for a flooded 2stroke. last guy i seen trying to kick over a flooded bike that took my advice LITERALLY spewed approximately a gallon of fuel apparently out of his crankcase when it fired

the white you see in the glass is bubbles and you should put the right amount of oil in it next time

 

[emolatur]

It did smoke excessively when I very first started it, now when I get it to run it doesn't.

I've discovered that it sheared the key where the generator rotor attaches to the end of the crank, so the timing is off. I gotta wait for a hardware store to be open tomorrow to pick up a new key...

One of my "question targets" believes the key may have just been weakened from the sudden stop when the bearing originally seized. I guess I believe him since I can't find any other explanation, but other than loose/foreign objects in the generator area, is there anything else specific I should be looking for?

 

[ellandoh]

It did smoke excessively when I very first started it, now when I get it to run it doesn't.

sounds normal. looks like you got it handled, so far.

i would guess bad timing could cause flooding also

 

[IndyMX]

All of the two strokes I have rebuilt have used a black silicone sealant between the case halves.. It's a Suzuki branded sealant.. It works..

I'm with Ellandoh.. Get that woodruff key replaced and your timing dialed in and you should notice a marked improvement in the performance...

 

[emolatur]

The stuff I used is black silicone sealant, branded "form-a-gasket".

Thanks for the input and advice, I'm now feeling fairly confident that timing is the issue. There's no place to buy a key right now, but I cut one out of a spare washer with a dremel and the bike started first kick.

I'm obviously not going to leave the homemade "key" in there, I'll get a real one tomorrow, but I just had to know if that was the only problem - the suspense was killing me. :)

 

[csdwarf]

I know what you mean, i have filed down plenty of keys because i couldnt wait for the right one, They end up working and i never take it out

 

[gary2010]

i made a washer in to a woodruff key on an old kx80 and it broke the crankshaft where the key sits in. i must of used a weak washer it worked for about 20 mins

 

[whenfoxforks-ruled]

If the oil is turning grey/white? You have coolant getting into the tranny somewhere. Not really an issue with the black sealer. Oil disappearing is another story, it has to be going somewhere? Make sure the rotor nut is properly torqued, the biggest reason for broken/sheared keys. A service manual is a really big help. A leak into the combustion chamber is very likely, and will cause some of the issues you are having. Vintage Bob

 

[emolatur]

Fixed. No idea where that oil went to, I was so dead from several days on two hours of sleep that I probably forgot to put more in. I bought a real key today, ran it all day, no loss of oil.

I did have a coolant leak, but into the dirt, not the oil: I broke a hose clamp. Fixed that, refilled, good to go.

Thanks a lot for the input.