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Mechanics 101 Can't get it to run right? Find a trick to add HP?
From the first oil change to completely rebuilding the engine,
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Old 03-11-2018, 07:55 PM   #1
Dhawk12
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Default Too much cam lobe wear?

I was doing a valve adjustment on my 89 Kat 750 with 70,000 km on it and noticed some wear on several of the cam lobes. Is this enough wear to replace immediately or is there still some life left? The attached photos are 3 of the worst lobes, the rest have minimal signs of wear and the rocker arms under these lobes don't look like they have any significant wear.

https://imgur.com/a/W9B1a
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Old 03-11-2018, 11:08 PM   #2
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If it were mine, Iíd replace them. Wear is one thing, pitting would not be acceptable to me.
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Old 03-12-2018, 03:07 PM   #3
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If you're going to replace them, might want to consider upgrading to gsxr cams. There's a write up in the wiki on which bikes to pull from, but I want to say it's 89 750.
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Old 03-12-2018, 10:10 PM   #4
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Ya I was looking at that yesterday. What are the benefits of the upgrade?

Also, if I buy used cams online, is there something I should do regarding the cam caps? I can't remember what that area is called, but I thought you weren't supposed to use worn things with new, or differently worn if that makes sense.
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Old 03-12-2018, 10:16 PM   #5
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Weeeeeeeeeeeeeeeeeeeeeeee!!!!!! at the upper RPM range. Makes a Kat respectable.... your supposed to match them, but hey, itís just a katana. Just make sure the cam bearing/cap area is clean and show no wear. Then take it easy for a few miles to set them in. Havenít had a problem with them.

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Old 03-12-2018, 10:22 PM   #6
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The other problem I have is trying to find cams from an 89 gsxr at a reasonable price. Kat 750 Cams are a dime a dozen for pre-kats on ebay. Well, not quite a dime a dozen, but at $25 per cam its pretty close.
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Old 03-13-2018, 02:02 AM   #7
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Even if you could find a set they might be worn out like the journals on these ones

https://www.ebay.co.uk/itm/352248843...torefresh=true

I had a set welded and reground to 89 spec last year cost a bomb

Frankensteinís guide to oil cooled engines
"Cam shafts from the 1127F, 750F, 90-750R, B6, B12, 88/89 750R are theoretically all swappable,
but of course the profiles are different."

maybe you could look further afield some OLDSKOOL guys seem to prefer 1100F cams they're only marginally shorter on the exhaust lift compared to 89 gsxr

Last edited by Lachie; 03-13-2018 at 02:54 AM..
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Old 03-13-2018, 01:42 PM   #8
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Ya, I guess same story with the 86-87 GSXR cams, just less lift. There is this set on ebay, but I am guessing its safe to say the journals have seen better days on the first:

https://www.ebay.com/itm/1986-Suzuki...EAAOSwlXhZZ5l3

https://www.ebay.com/itm/1987-suzuki....c100005.m1851

What about these cams? They look pretty good from the photos, but I am a not an experienced mechanic. Just don't buy them out from under me if they are good lol.

https://www.ebay.ca/itm/1990-SUZUKI-...p=mtr#shpCntId

Last edited by Dhawk12; 03-13-2018 at 01:42 PM.. Reason: Automerged Doublepost
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Old 03-14-2018, 02:26 AM   #9
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Yeah I'm no mechanic either so you can take my advice for just an observation but the 90's do look pretty clean def less journal wear than the set off a 99 I've got which had done @ 70K and spent the last 5 years been ridden on the track (not me) but I didn't have any problems with them in that regard and would easily put them back on if I needed to.

If I had to get a set (which I don't) and they were available I would, as always it's buyer beware
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Old 03-14-2018, 02:36 PM   #10
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Just wanting to double check what would make replacing the rocker arms necessary. There is no pitting or score marks on them, just places where the surface is not completely flat (ie a low spot where it appears the rocker arm is not touching the surface of the cam lobe) These low spots only take up at most a strip about 1/8" on the worst one.

Also, I know the camshafts from a 90 GSXR 750 would fit, does that mean that the head is the same? Or at the very least are the rocker arms the same?

Last edited by Dhawk12; 03-14-2018 at 03:14 PM..
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