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GS 1000 cylinder pressure compression test values

  • Thread starter Thread starter Anonymous
  • Start date Start date
A

Anonymous

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Seeking the advice of all you GS1000 "motor gurus" out there...

In referencing my Clymer's manual on the GS1000's recommended cylinder compression spec of 128-187 psi,

Does anyone recall if their bike's have compression above 160 psi?

Also, a bike I am interested in had a recent test result of 122, 115, 117 and 120 respectively in cylinders 1 to 4. This seems very low to me. The owner did not mention if the tech did a "wet test" afterwords.

He did say the values should be adjusted by 10-15% to account for the Sea Level factor as the test was done at a location of 5,200 feet above seal level. I have never heard of this factor before.

Can anyone shed some light on this?

Lastly the bike is a sub 10k mileage version, the valves have never been adjusted though. Should this low cylinder pressure be a "red flag" to a possible impending required Top End service or worse?

Been badly burned before in this manner, not looking for a "repeat performance"...

Thanks in advance guys!
 
sea level and valves?????? he might have ment to adjust the carb mixture
 
Why not just ask the owner if you can pull the plugs and do your own test?

(Offer to buy the plugs if any break, before doing anything)

It takes only a few minutes to do the check, and then you will be sure.

Remember to take out ALL plugs before testing, and keep the throttle OPEN
while doing it.
 
I doubt if any GS1000 ever had anywhere near 188 psi even when new, my engine with a fairly fresh Yoshimura high comp 1085 Kit is only good for 160-170 and the new battery and reconditioned starter motor struggles with that.

The stock engine I fitted is averaging about 135-140 which is probably closer to the mark. The main criteria is that all cylinders should be pretty close to each other, I think the factory manual says they should be within about 10% of each other.

The factory limit is 100 psi, but if the bike is so low mileage, the lower compression figures could be due to stuck rings, due to it sitting idle for so long. (I can't get over how low mileage the bikes are in the US, here in Australia we ride them until the wheels fall off, then stick 'em back on and ride some more, ha ha!) :twisted:
 
I would expect the compression to be better than around 120psi for the age of the bike. Currently my 1085 GS1000 has around 150psi after 70,000kms (total mileage 145,000kms).

Where do all these low mileage bikes hide? I consider 10,000km not even run in!!
 
Hey Terry,

With a stuck ring(s), will the bike still run? It has been ridden, but not long distances in this present condition.

It was described as sounding and running good. I have not seen it yet, so I can't confirm or deny this.

Does the whole motor have to come out to do a top-end job?
 
G'Day Iron-Man,

Yeah, the bike should still run ok, and more than likely a long enough ride will help unstick the rings, if that is the case. There are some oil additives that might help as well, but even though I am an advocate of such products as "Pro-Ma", (no I don't sell it, I just think it's great and it unstuck the rings in an old Ford I bought cheap because the compression was real low in #6 cylinder) you'll need to be real careful because they work so well in reducing friction they can also make your clutch slip like a bastard.

Regardless, the first thing you should do is change the oil and filter, as if the bike is such low mileage and it's been sitting for a long time, there will be a fair bit of contamination present in the oil which won't do it much good. It's been my experience that when bikes sit for such long periods, the owners have pretty much lost interest, so regular maintenance generally doesn't get done, and considering the extremes of weather you guys have there, the oil will break down fairly quickly whether the bike is rgularly ridden or not. :twisted:
 
Sorry mate, I forgot your last question, no, the engine doesn't have to come out to do a top end rebuild, it's only a couple of hours to strip everything, plus the labour time to clean up the pistons and un-stick the rings, run a "de-glazing" hone through the cylinders, use new base/head/cam cover gaskets (don't forget to clean all the old gasket crap off the mating surfaces) torque the head back down, retime the cams, and refit everything. Not expensive, just time consuming, but it'll give you a good idea of what sort of condition the bike is in. :twisted:
 
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