Compression question

[David.Seth]

so I finally did a compression test on my 81 450L. The right cylinder got about 145-150 psi, while the left cylinder got about 135-140. Is the psi difference between the two ok or does it mean the left cylinder is going out? Also, are the levels I'm getting from them high enough, or should the compression be higher than 150?

[Octain]

How does the bike run?
If it runs good then ride the hellout of it!

[tkent02]

That's good enough. Well within limits.
Have you adjusted the valves lately?
Have you ridden it much or has it been sitting?

[David.Seth]

How does the bike run?
If it runs good then ride the hellout of it!

The bike runs "good" but I don't really know how a bike this age should run. I can tell you though it does run better than the 96 ninja I had

That's good enough. Well within limits.
Have you adjusted the valves lately?
Have you ridden it much or has it been sitting?

the bike had been sitting at a salvage yard for years. I bought it, cleaned the carbs, and ran the hell out of it for a year or so. I sold it, and the guy let it sit for two years. I just re-bought it, re-cleaned the carbs, and it actually runs better than before (thanks to basscliff's carb tutorial). I haven't gotten the o-ring kit yet, nor have I replaced the the intake boots (but I plan too as soon as i get the funds). I never even knew about valve adjustment until my ninja blew a cylinder (after 3 weeks of owning it). But thankfully I found these forums, so I should be good to go when i get the money and time to really wrench on it. But would the compression test give me different numbers if the bike has been sitting for a while vs if Ive been running it a lot?

edit: I did do the test after letting it warm up and riding it for 20 minutes

[tkent02]

Yes, the compression will likely test higher when it's been run a lot.
Also if the valves have never been adjusted that will effect the test, and if they are far enough out it will burn valves.
It's very easy to check.

[David.Seth]

if the valves have never been adjusted that will effect the test, and if they are far enough out it will burn valves.
It's very easy to check.

so should I just follow Basscliffs guide on valve adjusting ( http://members.dslextreme.com/users/...lve_adjust.pdf ) even though his is an 850? Would it still be the same concept?

[tkent02]

Download a free service manual, it will show you how.

http://www.mtsac.edu/~cliff/storage/gs/GS_GSX_250-400-450_Haynes.pdf

It is basically the same check, with slight differences in procedure on the two cylinder engines.

[Octain]

Sounds to me you have a good running bike.
Check the valves to insure it stays that way.

[David.Seth]

Download a free service manual, it will show you how.
http://www.mtsac.edu/~cliff/storage/gs/GS_GSX_250-400-450_Haynes.pdf
It is basically the same check, with slight differences in procedure on the two cylinder engines.

Sounds to me you have a good running bike.
Check the valves to insure it stays that way.

well i really appreciate all the advice you guys have given me. I do have a Clymer manual for my bike, and i assume that it has a guide for checking the valves. would I be safe to just follow that?

[tkent02]

Yes, probably.
I haven't checked that manual.

There are some errors in some of the after market manuals for other models.

[David.Seth]

Thanks, I will keep that in mind. The only thing I don't like about my Clymer manual is that its just very hard for me to follow. Its worded in such a way that its hard for a novice like me to understand. And yes, it does have a section for checking the valves, but it tells me I need special tools and dye (Prussian Blue) to check the valves... It just seems more technical than what basscliff posted. But I will check out the Haynes link you posted and compare it to my Clymer book

[tkent02]

You are just checking valve clearance, with a feeler gauge, not taking the valves out and checking the seats and everything. Easy stuff.

[David.Seth]

ah, ok. that would make sense to why the clymer instructions were so technical. Thanks! If you couldn't tell, I am a newbie to motorcycle repair/maintenance. But I am willing to learn! Plus the knowledge I learn here might help me when me and my dad finally get around to fixing up his 79 Triumph.

edit: ah, the valve clearance guide in the clymer manual was under the "periodic maintenance" section, not the "valve" section. Why do they have to make these books so complicated?