Low compression test result. Interpretation correct?

[Anonymous]

I just did a compression test on my GS1000G motor. Here they are - hope the column alignment works OK for you. The wet reading is with a squirt of engine oil.

Cyl: 1 2 3 4
Dry: 125 60 90 90
Wet: 150 90 150 140

It looks like all rings need replacing (Cyl 1 is just in spec) and Cyl 2 valves need work. If it wasn't for Cyl 2 I would probably just keep riding it, but I don't want to do any more damage.

Is my interpretation correct, Oh GS gurus?

Kim

PS. My column alignment doesn't show up on the forum, the thing doesn't like multiple spaces between text, but you can figure it out.

[saaz]

Don't need GS gurus for those numbers...any piston engine gives the same results.

From my thinking,

1 is ok but a little worn
2 has a valve problem (burnt, bent, just not sealing)
3 ring problem (worn), valves ok
4 see 3

When I rebuilt mine it had the same compression readings as for your 3 and 4 for all cylinders. The exhaust clearances can close up and be too tight on standard bikes, so perhaps could lead to a burnt out exhaust valve.

On the bright side, a big bore kit with little other work gives a very nice grunty machine....and they last...

[Anonymous]

On the bright side, a big bore kit with little other work gives a very nice grunty machine....and they last...

Everyone is keen to spend my money for me these days. :-)

Tell me how much, where from, exactly what.... and anything else I need to know before I just go and get the bare necessities. :?

Kim

[saaz]

Hmm, I have not priced such things in years.

You will need to price up something like a wiseco kit, what a bore job and head job (for the bike) cost these days, and the gasket kit.

Zpower advertise in Australian Motorcycle Trader...they deal in older stuff for Zds etc. Wiseco kits (incl gaskets) from $700

[SqDancerLynn1]

Rings are a definated likely hood with the increased reading with oil. to determine exactly what is happening would require you to do a leakdown test to see if it is bad rings, bad valves, head gasket. I assume that you have checked the valve clearences. Has the bike sat for long time?? If it has I would maybe run it for 1-2 hours and then recheck comp readings
If not take it apart and have the head rebuilt by competent machine shop that has exp with MC. Then mic the cylinders to see if they are out of specs. If they are in excellent cond have them honed and install new rings.
If there is any question about the condition of the cyls rebore it and install new pistons. Wisco seems to be the mfg of choice It will make your engine have a little more noise, due to the fact that the performance pistons are forged and run with slightly more clearance to allow for heat expansion. Don't go overboard on the compression ratio

[focus frenzy]

When I did my top end, I used suzuki 1mm oversized pistons and rings, and factory gaskets.
total including macheine work was about $500US

[Anonymous]

if you need these kind of parts a word of advice go to www.2canucks.com get the phone number the guys are excellent prices and quick shipping you won't find better anywhere

[saaz]

The trouble is that we are in Australia......double any of your prices for us!!

But somethimes things seem to be cheaper here if sourced directly from Europe of Japan...that I don't mind!