Compression test, GS1000G

[Jon]

Did compression tests on each cylinder today. Each one was more or less bang on 150psi (engine practically cold).

The fact that all 4 came out the same was good, but is 150psi to be expected? It seems low to me.

 

[Guest]

It all depends on what it is supposed to be from the factory. For instance, mine are supposed to be 180, but all my reads were in the 170 or so range. They say that you shouldn't worry too much unless it is around 120 or less.

 

[Datsa Noydb]

Engine was "cold", so that's not too bad.

How long since the engine last ran? If it was just a few weeks (months?) ago, that is not bad.

If it was more than a year ago, it's pretty darn good. :encouragement:

 

[tkent02]

Depends on too many factors for a number to mean anything, Cranking RPM, elevation, the gauge you used, did you open the throttle, how long you cranked it, engine and air temperature, are the valves adjusted correctly, cam timing, etc, etc, etc.

These are low compression engines anyway. 150 is very good, all cylinders the same is great, the big question is how does it run?

 

[Nessism]

150 psi is excellent. Make sure to adjust the valves and keep it that way.

 

[Jon]

Thanks all - this looks like good news. The engine last ran (prior to the test) about 20 minutes prior, when I started and ran it until I could let it tick over with the choke off. Then let it cool down enough to do the comp. tests. Before that, last time it was run was about 3 months ago.

I held the throttle wide open, of course. I cranked it over until the needle stopped rising on each cylinder.

The gauge is fairly new (2 years old), a Draper, so decent make. We tried another much older one which gave similar results.

I'd say it runs well. My friend, who brought his old gauges and is a professional bike mechanic who really knows Japanese fours (I don't!), said he though it sounded really good. He put his vacuum gauges on the carbs and with a tiny bit of tweaking got them all dead-level with each other.

I should mention that we changed the petrol before we started in earnest. Our first attempt gave hesitant running, but the petrol was 6 months old. New gas transformed how it ran.

I should add that I have had the vlave clearances checked and adjusted - all are nicely within the range. The bike has done about 45000 kilometres, which is under 30000 miles, and it looks to have been very well looked after.

The two remaining problems I need to solve are (a) I need to fit slightly higher and wider handlebars, as the originals cause my knackered wrists to ache very quickly.

(b) the rear shock upper mounts have almost stripped threads (right hand one is worse, left side isn't too bad). The previous two owners kept chopping & changing rear carriers etc, I think this is how the thread came to be damaged. I need to figure out the cleverest fix possible, ie: minimal expensive work, but maximum effectiveness.

Any ideas welcome!

 

[jdvorchak]

Extreme fix is to cut off the studs and drill a hole where the stud was. Insert new high grade bolt and nut.