TOPIC:

What a buzz kill, just got the engine running on a engine stand and did my first compression test..

#1 was 100 lbs , #2 was 90 lbs, #3 was 25lb and #4 was 78 lbs

So I added a little oil to the number 3 cyclinder and the it tested out at 90 lbs.

SO now I'm looking at new rings? Since I need to take apart the topend again, What would everybody do if it was you? At least this time I wont be fighting 15years of dirt/oil/grease....Thanks for all help!

If you added oil and the compression went up then it's rings, sorry. Oil will settle in and temorarilly seal the rings, does nothing for the valves. I'm a mechanic and we do this at work all the time. On the bright side, it's not a big deal to pull the head off and if the cylinders mike out ok go ahead and hone them and slide new rings on. Oh what the hell!, let's just throw that big bore kit in!!

Post edited by: Bluemeanie, at: 2006/12/23 18:35

Depends on how far you're tearing it down and what you did or did not do the first time around.


If you didn't do a full inspection and measure things up properly, then I'd start right back at the start. Go through the bottom end, check bearing clearances, check piston to cyl clearance...address any problems you may find.

Top end only....rings and a valve job...

When a motor is completely apart, check everything...

Big Bore Kit questions.... Is it just bigger pistons and rings? I would need something to make the cycliners larger? Would I need to change the jets in the carbs or anything? Thanks

saw this in another thread.....Great info!

Re:Compression - is there an easy answer? - 2006/08/08 08:29
Since compression popped up on the cylinder where it was down after checking with oil, this indicates the seal of the rings on that cylinder are not good. It wouldn't be prudent to just expect that a new set of rings will fix the problem. The obvious answer is to take the block off and MEASURE the diameter of the bores and MEASURE the diameter of the pistons. This is done in a very precise way so that the bores are measured in at least three different depths and in three different angles to check for out of round bores (called ovaling). The pistons are measured on the skirts below the piston pins in a precise location. GET A SERVICE MANUAL for the exact method. Anyway, once you know what the bore diameter is and the piston diameter, the difference is the CLEARANCE. This clearance figure is specified in the same SERVICE MANUAL. If it is within spec, hone and rering. If it is outside spec, bore and new pistons/rings OR buy another used block/pistons that is in spec and hone/re-ring. It is a waste of time to rebuild a top end and not do this measuring. You can use a digital caliper from Harbor Freight (under $20) and a set of TEE BORE GAUGES (eBay - under $20).

wiredgeorge Motorcycle Carburetors
www.wgcarbs.com
(too many bikes to list - Mico TX)

Can someone explain the numbers .040 on the ring set?

13024: RING SET,PISTON,0.040 from bikebandit.com

Thanks

.040" oversize (1mm) for .040 (1mm) oversize pistons.

Tim, I have accses to tee bore gauges at work. Be happy to help you mike out those cylinders. You have a manual?

1mm, huh? Hmmmmm... so does that mean it already has "little bore kit" installed? Sorry, I could'nt resist.

That sounds great. Thanks! Once I have the top-end apart, I'll schedule with you. I guess I can't buy new parts untill I know the measurments and all that goes with that. Oh yeah.... what kind of beer do you drink?

Thanks but not a drinker, will be stepping outside for a cig though. Sometimes wish I drank instead of smoking! Let me know, you have my e-mail in your guest book.