Looper compression issue

[jommer]

Hey guys, still plugging along trying get my '89 200 Looper going.

I still have lower compression on top port cylinder. All others are 90, this one is 60. All six are bored .040 over with Wiseco KD pistons. Had a burnt ring on that cylinder, put new rings and honed cylinder. Absolutely, no scratches in the the cylinder wall. Still 60. Head is good. Why am I down 30 psi on that cylinder?

There are plugs on the side of the cylinders that have hoses running to check valves on the front half of the block on the under side of the intake. If the check valve is bad, will that cause me to lose 30 psi on that cylinder?

I'm trying to think of everything I can. Please help!

Thanks,
Jim

[ultrafast]

Have you run it yet. I have seen motors that were seriously hurt between rounds and they come back with new rings and a cleanup.

[whatsamerc??]

after you honed it did you check the cyl to see if it was still within spec?

[jommer]

Yes, I have run it and the compression stays between 55 and 60. Doesn't idle very good at all.

[jommer]

No I didn't check it. I didn't hone it very much at all. There was just a slight scuff where the ring burnt. It was 55 at first and it went up to 60 after I honed it and replaced the rings.

[Euroski]

That cylinder may be out-of-round... did you check it?

[jommer]

"That cylinder may be out-of-round... did you check it? "


See above.

[wrechin2]

It needs to be checked. If it is out of round, it needs to be ridgid honed and checked to see if still within limits. I have a 175 ficht tore down now that had 25 PSI lower compression on 1 and 5 and it is was due to egg shape. After a few seconds with the ridgid hone, you could see the high and low spots. After it was trued to within .0005, they are still within specs. Problem with a ball hone and a triangle hone, they will follow the contour of cylinder and not put it in true like a ridgid hone. Could be your honing is not correct or that the finish is too smoth to induce ring seat. JMO....

[Instigator]

I've had motors that were only honed and ringed (some bored too) that had intial compression all over the board. After breaking them in (3 hrs for honed, 10 for bored) and allowing the rings to seat they've come right up and evened out.

[ChrisCarsonMarine]

This shouldn't be such a mystery,pull the head and use a bore guage,or inside mic and you'll find your cyl. is out of round.It sounds like you "honed" it with a glaze breaker instead of a real trueing hone,all that is accomplished is a good looking out of round cyl,if you started out with an out of round cyl.A glaze breaker[spring loaded 3 stone,or ball hone]is to prepare a cyl. to break-in new rings by removing the slick carbon film called cyl. glaze that prevents new rings from wearing to a good seal,it will not correct abnormal wear,or other flaws such as taper and out of round.A proper trueing hone,[sunnen or lisle in my shop] will remove high spots only,untill the cyl. is round and straight again,then it must be measured to see if it is still within specs,or needa re-boring.weisco does make a 060 piston for your motor,if you need to re-bore,chris

[jommer]

Thanks Chris. That makes sense to me. I think I just have that cylinder resleeved and start from scratch.

[wrechin2]

Just check it. If it is a standard bore, it can be bored. Usually the limint is .003 and it doesn't sound like alot, but is it a good margin for cleaning up. You can run 1 .020 over and the rest standard. This is not a 4 stroke where the mentality is they all have to be bored.

[brussrude]

Use plenty of honing fluid for the honing process. Like stated earlier a flex hone or the triangle hone would make the cylinder even worse. You need a rigid hone (I use sunnen )
Take measurements before & while you hone.. with the Wiseco's you can run a bit more clearance so probably you have room for corrction.