Camshaft Markings

[Guest]

Hi all,
This is my first post as I've recently purchased a 1982 Suzuki GS750, as a very cheap project bike. The first thing I tested was the compression on all cylinders and it didn't look good (80psi, 120, 60, 60). I popped the head off, and noticed that there are some pitting on the camshaft lobes. It's consistent on ALL of the lobes, and in the same spot. Measuring the lobes they are 1.3724" which is considerably larger than what the service manual suggests (upgraded cams?):

20170615_095008.jpg

I am on a bit of a budget, should I let it be? Let me know your thoughts - any input would be fantastic. Thanks guys

[hjfisk]

Is there any other markings on cams?

[Burque73]

If it will work I've got some 850 cams you can have. Shipping might be pricey though.

[Steve]

If it will work I've got some 850 cams you can have. Shipping might be pricey though.

He has a 16-valve 750, the 850 cams will not work.

Hopefully you only removed the valve cover, not the head, after reading those compression numbers. First thing to do is to check valve clearances. Get those in spec, then you can worry about compression numbers.

Ideally, compression check should be done on a warm engine, but if you can't warm it up, you can still get a decent idea of balance and overall condition. Just be sure to have all spark plugs OUT and hold the throttle wide OPEN while cranking the engine.

Do you know anything about the history of the bike? Has it been used regularly until recently? If the compression numbers are somewhat even and the engine has not been run for a while (several months?), and you can get it to run, just give it an Italian Tune-up (google that) and run it several hundred miles and check the compression numbers again.

I don't have a manual available at work to compare your cam dimensions, someone else will have to let you know if it's an aftermarket cam.
.

[chuck hahn]

Yes..check valves and go beat the scitznit out ofit a while..then recheck compression on a warm engine and hold the throttle wide open when you crank it.

[Rijko]

i talked to an engine rebuilder, my cams looked worse than yours.
Expected him to laugh and declare my cams ready to scrap.

All he said was sand the sharp edges down on the pitted lobes, the pitting holes
will carry oil and do not pose any problem at all.

[Burque73]

He has a 16-valve 750, the 850 cams will not
.

Oh, so did all 750's have 16 valves? Some have mentioned using a head from an 850 on a 750. I'm not familiar with all the models yet but I'm picking up quite a bit.

It just doesn't make sense that a head with 16 could be swapped for one with only 8.

Sorry to sidetrack the thread here.

[chuck hahn]

8 valvers prior to 1980

[Burque73]

Thank you. I Learnt sumthin!

[Mechanically Geeky]

Wow, you guys are fantastic. Especially you Burque, very generous to offer your cams!!

Hopefully you only removed the valve cover, not the head, after reading those compression numbers. First thing to do is to check valve clearances. Get those in spec, then you can worry about compression numbers.

Do you know anything about the history of the bike? Has it been used regularly until recently? If the compression numbers are somewhat even and the engine has not been run for a while (several months?), and you can get it to run, just give it an Italian Tune-up (google that) and run it several hundred miles and check the compression numbers again.
.

Yes the first thing I did after checking the compression was to check the valve clearances. Unfortunately they were all within spec, so I popped off the head I did make sure that the throttle was wide open and all spark plugs are out.

I know very little about the history of the bike. But I know that it hasn't been running for a while, as the wiring is completely apart.

Here some pictures of the piston and valves:
20170614_225745.jpg
I can only post 1 picture?! Give this a shot:

https://drive.google.com/file/d/0BwdUxbT9ce7vRThxOEI4VjlyODA/view?usp=sharinghttps://drive.google.com/file/d/0BwdUxbT9ce7vNXRDT2hyQk1sdW8/view?usp=sharing

https://drive.google.com/file/d/0BwdUxbT9ce7vaWVzeV9PN1JrQkk/view?usp=sharing

https://drive.google.com/file/d/0BwdUxbT9ce7vVTJiZENTVWdWdk0/view?usp=sharing

[Burque73]

Hey, you're welcome M. G. Not a big deal though as I stripped the cams and all other internals from a head with stripped spark plug threads and a botched repair job that made it useless.

[Big Jay]

When it has low numbers, always do a leak down test before pulling it apart. This will tell you where it is leaking from and how much.