How Much Pitting on a Cam Lobe is Okay?

[Lenny750]

I bought a set of 1989 GSX-R750 cams and one of the lobes has some pitting on it. Is it too much?

https://drive.google.com/file/d/0B5FMbLLYp5qgbDN1M09kdGxZbzQ/view?usp=sharing

[92xjunker]

I'm gonna say none, pitting causes excellerated wear on the valve trane.

[Lenny750]

Guess I'm gonna have to try and get a return on them. The guy on eBay said nothing about pitting. The GSXR1100 cams I got will have to do then.

[92xjunker]

1100 cams work well on a kat.

[Lenny750]

From the research I've been doing, they might actually be the same. I posted a thread on it, but didn't get any responses one way or the other. http://katriders.com/vb/showthread.php?t=136966

[Molochnik]

If memory serves, the 88-89 750 cams and the first couple generations of 1100s are indeed the same...at least comparing the lift numbers and duration graphics in the factory manuals.
They backed off on the exhaust cam for 90 750s. After that, I haven't paid attention. I do remember some kind of minor difference between the intakes of the '90 750s and the 88-89 750 and 1100 cams.
I'll see if I can find and post the duration graphics.

[Molochnik]

The shop I used to work in had a very extensive collection of Suzuki and Honda manuals. I used the earlier 1100 manuals to compare the 88-89 cams, and I have a hazy memory that the tech data showed they are "the same". I do remember using a degree wheel on the crank to confirm that I understood the tech data accurately when selecting cams for a hot rod 750 motor.

There is a very comprehensive thread listing the lift of GSXR cams on this site, so I'll let that thread speak to those numbers, however, I went through my manuals last night and since I can't seem to paste pic in a reply, I'll provide the info as follows...

The 88-89 750 GSXRs had the most radical 4-lobe cams of the earlier models (85-90)
Intake opens @42deg. before TDC and closes @70 deg. after BDC
Total duration of 292 degrees

Exhaust opens @65 deg. before BDC and closes @39 deg. after TDC
Total duration of 284 degrees

The 90 750 had a slightly milder intake and it appears that they went back to the exhaust cam of the old Humpbacks (85-87)
Intake opens @42 deg. before TDC and closes @63 deg. after BDC
Total duration of 285 degrees

Exhaust opens @55 deg. before BDC and closes @25 deg. after TDC
Total duration of 260 degrees

I'll include the old Humpies (85-87) just for fun...
Intake opens @32 deg. before TDC and closes @64 deg. after BDC
Total duration of 276 degrees

Exhaust opens @55 deg. before BDC and closes @25 deg. after TDC
Total duration of 260 degrees

I cannot speak to any cam specs on the Tunas since they do not seem to be included in the tech data, at least not in the 98+ factory manual I have, nor in the Haynes manual I have either.

Some anecdotal info...
As I mentioned in another thread, I dropped a set of 88-89 cams into my 90 750 motor, but was unsatisfied with the nature of the power. The big exhaust cam seemed to kill the bottom end although it did seem to run very strong on top. I pulled the exhaust out and replaced it with the stock 90 cam, leaving the big intake cam in place, and it seemed to run much better as far as I was concerned; much better bottom end and no noticeable loss on top. Your tastes may vary.
I replaced the stock intake cam in my 87 with the intake from the 90, since it was just sitting around bigger than the Humpy cam, and it seemed to wake it up nicely. No huge changes anywhere, just - more.

Hope this helps out.

[buffalobill]

I'm gonna say none, pitting causes excellerated wear on the valve trane.

I found some on a cam I had to replace already because a lobe and lifter were ruined. Really shocked me they were made of such shty steel.

[arsenic]

The GSXR 1100 cams and the GSXR 750 are not, I repeat, not the same. The GSXF 1100 cams and GSXR 750 cams are the same.

[Molochnik]

What's the difference between them? Just curious; it has been 20 years.

[arsenic]

lobe height for sure, probably duration also.

[Molochnik]

Cool; thanks.

Disregard what I said about GSXR 1100 cams Katriders.

[Lenny750]

Wow, thanks for all the information guys. Sorry I wasn't paying closer attention to the thread.

As for weather the 1990 GSX-R1100 cams are the same as the 1989 GSX-R750 cams, I am going to have to say that based on what I have seen, they are actually the same. The part numbers seem to be the same on the OEM websites like Bike Bandit and I briefly had a set of 1989 GSX-R750 cams that I returned due to pitting on one of the lobes. Both the GSX-R750 and GSX-R1100 cams had a "G" stamped on the Exhaust and a "B" stamped on the intake.