Running motor or unknown motor you pick...

[Fearthepack]

Dilemma...... would you use a known running engine that has 35,000 miles with badly worn transmission and suspect abuse. Or an unknown engine with pristine
trans almost no wear on any dogs and the inside of the engine is a pretty golden oil color no signs of excessive heat or abuse don't know mileage???? Gut says use unknown motor.. but head says go with what you know works anyone want to express their opinion???

[DiverRay]

Go with the unknown! The oil tells the story. With care, this engine will go well over 100K miles without any problems. A beat engine can be hiding all kinds of problems. I've replaced the engine in my '79 because it had about 115K, AND the trans locked up on me. I would have needed to split the cases to repair the trans, and pay for the new bearings, pistons, overbore, etc.
With 35K of abuse, what else may go wrong?!?!

[tcoop]

if the unknown engine has good compression... swap it with out hesitation.

[Fearthepack]

Compression..... when I rotated both engines with a wrench with plugs in the unknown motor was much harder to rotate because of compression, not very scientific.

[DiverRay]

Put a battery/jumper cables close to the engine. Pull all 4 plugs, make sure you have oil in the engine! Connect the ground to a bolt near the starter, and then tap the positive cable with the positive clamp.
Check compression by seeing how much it jumps the first hit, and how high it gets after about three to five hits. You are looking to see that all 4 are close to the same. If the "newer" engine has not been run for a while, understand it can show low until it has been running for a few hundred miles. ( you DO have a gauge, correct? if not, most auto parts stores will "loan them")

[IanDMacDonald]

Umm, sorry for the confusion Ray, but do you mean having all the plugs out while doing the compression test? I always leave all plugs in except for the cylinder I test.

[Gmac]

Pull them all

You're not going to be running the motor and it just makes it faster to test each cylinder. Plus it's less stress on the battery and starter motor.

[DiverRay]

Pull them all because:

Plus it's less stress on the battery and starter motor.

. Motor on a bench, keep the stress DOWN on it. And, you pull a little less current, and less heat for the starter.

[Fearthepack]

Because I was just going to steal the tranny out of the motor the current condition is... clutch and cover removed, shift cover and components removed tranny pan removed and no fluids....cylinder head removed so can't test anything at this point. If you could look at both engines side by side and didn't know any history everyone picks the non-runner.... I think.....
I was totally surprised by the internal external condition of the non-runner... great problem.

[IanDMacDonald]

I bought an engine for my 750 that was unknown to me. Only thing I did was check compression and oil level, painted it, and installed it, and it still runs to this day.

[BA80]

I bought 6 parts bikes from Karla Jones several years ago. My SG had a knock that had manifested itself when I grossly over revved the engine. (being stoopid). Old enough to know better but too young to resist.

I had a rally to go to in a week.

Out of those 6 only 1 turned over and had compression......... That 2H7 engine is STILL in there today and I've put (guessing) 60K+ on the thing. Finally had to fix 2nd gear a couple years ago.

[IanDMacDonald]

When u say "over-rev", I take it that u don't mean accidentally downshifting . . .

[BA80]

When u say "over-rev", I take it that u don't mean accidentally downshifting . . .

Ha ha no, missed a gear (more than once) upshifting out hammering on it on a lonesome stretch of highway. Tach needle spun down past 10K.

[Fearthepack]

Lets have some fun then and go with the unknown motor.... Makes first start-up much more special... You know like teeing off on #1 hole in front of a bunch of strangers.

[Fearthepack]

And thanks for your feedback