Ive been building engines for a while. But suddenly i came across a prob. I rebuilt my new 400ex to the book. What would burn up brand new rings. JE high comp. piston.

 

low oil, extremly high rpms, long run times, sand or small grit in the engine. it could be a number of differnt things but you dont know unless you look at it good or have a professional look at it.

 

everythings new in the engine. it had plenty of oil. i washed everthing with soapy water. and wasnt greedy when putting assem. lube on everthing. i jus dont know!!!!

 

did you put the oil ring on upside down?

 

Did you use a ridge reamer to remove the ridge at the top of the cylinder that is left when the ring doesn't go all the way to the top of the cylinder? The cylinder will be worn a few thousandths from the friction and it leaves the original cylinder diameter at the top causing what feels like a "ridge" at the top of the jug. If you don't remove this and install a hicompression piston the new piston rings will ride up on the ridge with every stroke causing them to wear quickly or even break. Rings on a stock piston will only go to the same place as the originals so they never make it up to the ridge and don't wear out quicker from it.
Did you use a cylinder hone to make a new cross hatch pattern on the cylinder? The cross hatch pattern helps the new rings seat quicker with less wear than a perfectly smooth cylinder wall.

Kev

 

How was the end gap, on the new rings? Could have been too tight.

 

<div class="FTQUOTE"><begin quote>What would burn up brand new rings. JE high comp. piston. </end quote></div>
What do you mean by "burn up?"
Low compression? If so, how low?
If so, did they ever seat? Was the jug ever bored, or just honed? What were the clearences? What kind of machine shop did the work? How long did it take to "burn up" the rings? What did everything look like when you took it apart? Heat signs? Score marks?

 

Ok lets see... I had the sleeve done at a pro work shop. They do good work. Next the rings on that piston can only go in a certain spot. All the letters went up. They were scattered like the book told me to do. I know nothing of a ridge, and might have to check in to that. Also ring gap was good. I put so much assem. lube on pin, rings, rod, piston, and so forth, i just dont know. It is getting oil. I broke it in, then let it cool. When i say broke it in i mean rode it for like 20 min. let cool completely. The next day it started fine ran for 5-10min and it cut off?

 

clean clean clean... Thats what the inside looked like. No heat marks, score marks. You still can see the cross hatchings!!! Just really low compression. I forgot to add this to the add above this one.

 

I would not personally suspect rings then. I've seen bores and pistons so screwed up you would think no way could it hold even a pound of compression. It did and then some.

The next step is to do a leak down. If you don't own a leakdown gauge, beg borrow or steal one. (Just kidding on the last one.) If you can't do that you can bust up an old spark plug and make a getto leak down gauge. At least this will tell you where the big leak is. I'm betting it's going to be a valve.

Either that or the shop screwed up the clearances but you seem to know your stuff and I would think you would see the piston is slopping around the bore and not install it.

The more I think of it the more I think it's going to be a valve. If it's as clean as you say it is, there is no way the rings can leak that much. I've pulled pistons out and all the rings drop out on the ground they are in so many pieces and it still had fair compression.

Do the leak down and get back to us. Or at least check the valves.