rebuilt motor still doesn't run....

[TxPowderCoater]

Originally Posted by andcon83

Sorry I am not at the mechanical aptitude that you are. I have rebuilt diesel engines, rear-ends, and other heavy equiptment related parts.

How do you check ring end gap? What is scrub pressure? Again, sorry I do not have the knowledge, but I am trying to learn. The cylinder was in great condition.

I said I wasnt bashing you or trying to be mean, but really, if you are going to learn and attempt stuff, even if its from making a burrito in the kitchen to rebuilding a small engine, there is always videos to watch and an internet full of "how to's" to learn from. Again, not being mean, just common sense, I applaud your willingness to do the work, now educate yourself properly and have reliable fun and pride knowing you built it.
as far as ring end gap, I dont know the specs on your engine, but I usually hone the cylinder (always should be done with new ring set to help "seat" them). then I take all the old rings off the piston paying attention to their orientation, up or down, beveled edge or not etc etc and without any rings on the piston, I can then take my new ring set, one ring at a time and slide it into the piston bore about a 1/4" inside the bore from the top, then I slide the piston top into the bore to push the ring evenly flat into the bore diameter. once this is done, I remove the piston and use feeler gage to measure the gap between the ring ends and then remove ring and if needed, file from both ends to get the gap to the specs. re-insert and re-measure and repeat until you get the right gap for each ring. then install rings on piston, and install piston into bore and on crankshaft etc etc etc

edit; forgot to address scrub,
the thing with ring end gap is that if its not set correctly, they (rings) swell/expand with heat and touch on the ends and then there is no give and they swell/expand some more and push against each other to tighten in the bore. usually it happens when your hauling *** down the back stretch, engine getting hot and your a wheel up on the other guy and thats when it locks up on you and you learn about ring end gap and piston seizing etc etc

[worqhors]

Based on my experience, if you buy a standard piston and ring set, the rings are already correctly sized. In like manner, if you buy an oversized piston and ring set (say .25mm o/s), the rings are properly sized already. I never found the need to file the end of the rings. The rings and the pistons are already matched.

[gray horse]

From my experience of building HD motors for years you always check ring end gap. It makes no difference whether the rings/piston are new or not. The rings that I put in my 104ci Sputhe motor last year all had to be filed before I could install them. It's just a good habit to get in to.

[TxPowderCoater]

Originally Posted by worqhors

Based on my experience, if you buy a standard piston and ring set, the rings are already correctly sized. In like manner, if you buy an oversized piston and ring set (say .25mm o/s), the rings are properly sized already. I never found the need to file the end of the rings. The rings and the pistons are already matched.

dizzamn! ok
Based on my experience of 40 + years, you've been damned lucky.....It does matter, just sayin'.
In fact, on the minibike (predator) race engines I build, I relieve the stress on the second (scrub) ring by filing to fit and then heating it with propane while still in the bore, it relieves the scrub pressure and makes for a looser set up, less friction, less resistance = more rpms... and on these motors not worried about longevity but I have one with billet interior and 14.1 compression and its still going strong 8 months later.

[andcon83]

Thank you for the information. It sounds like something that should always be checked. I ordered a ignitor module. I think that is the problem. With a timing light hooked to it, you can see the spark cut out when it starts to skip and flutter. Won't know untill it gets here next week.

Didn't mean to get defensive. I think I have a good mechanical background. I read alot of threads on this site about rebuilding engines, and never see anything about end gap. We all learn somehow. Thank you for expaining it.

[worqhors]

As I said, if you buy the piston and rings as a set, they are already matched. It does not hurt to check the gap after installation,. however. But I still have to encounter an unmatched piston and rings. But then, I have not been doing this for 40 years.

[andcon83]

I did buy them as a set. I am pretty sure that rings are ok. But I can see where it will be good practice to check the end gap. Like I said before, the engine idles perfect then when I try to rev it up it starts to mis fire. I am in hopes that the ignitor is the problem.

[TxPowderCoater]

Originally Posted by worqhors

As I said, if you buy the piston and rings as a set, they are already matched. It does not hurt to check the gap after installation,. however. But I still have to encounter an unmatched piston and rings. But then, I have not been doing this for 40 years.

This proves exactly that there are rebuilt motors and there are "rebuilt" motors out there. [wink wink nod nod know what I mean?]

[worqhors]

Originally Posted by andcon83

I did buy them as a set. I am pretty sure that rings are ok. But I can see where it will be good practice to check the end gap. Like I said before, the engine idles perfect then when I try to rev it up it starts to mis fire. I am in hopes that the ignitor is the problem.

As i said earlier, it could be an ignitor problem. Swap the one in your cart with a working one, if only to test it. I am saying this because I solved a similar problem that way.

[1989Marathon]

Originally Posted by TxPowderCoater

This proves exactly that there are rebuilt motors and there are "rebuilt" motors out there. [wink wink nod nod know what I mean?]

RANT
Lighten up Francis. We all like to try to give constructive advice on this forum. Your comment is a quick way to turn people away from asking for help. We aren't all engine builders here.
RANT OVER


If the starter is having a hard time turning the motor over since it was put back together, I would suspect cam timing, or valve adjustment.