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Old 01-01-2013, 09:57 PM   #1
SamH OP
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Location: Tasmania, Australia
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How to identify airhead cams?

I've got two cams that came with my R90 project and I've no idea which one to use when I put it back together. The lobes measure up differently between the two but I haven't been able to find much in the way of information on airhead cams.

Here's a pic of the two.

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Old 01-02-2013, 06:06 PM   #2
supershaft
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It looks like it might be a 336 on the our left. I don't know what the marking are on those earlier cams. It could be other cams as well. You might have to time it to find out. If it's a 336 it could be a very early one timed straight up. That I would want to know for sure.
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Old 01-02-2013, 06:37 PM   #3
Kai Ju
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Except the left cam looks to be in rough shape, especially the oil pump drive area.
I would try and clean it up before I'd even consider using it.

Kai Ju screwed with this post 01-02-2013 at 08:24 PM
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Old 01-02-2013, 09:27 PM   #4
supershaft
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Except the left cam looks to be in rough shape, especially the oil pump drive area.
I would try and clean it up before I'd even consider using it.

It might just be stains. I hate stains but the FAA says that stained metal doesn't warrant rejection. It looks ruff but it might be usable.
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Old 01-02-2013, 10:24 PM   #5
SamH OP
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Yes, the cam on the left certainly looks a bit rough but it's really not that bad, the picture looks much worse than reality. It's mostly staining.
How do I go about figuring out the numbers on these two, do I have to have the top end together?
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Old 01-03-2013, 03:08 AM   #6
SamH OP
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Ok, I measured up the cams tonight as best I could. Put them both in the lathe and setup the dial gauge. I could only measure lift.

The cam marked 921 measured 6.75mm lift on all four lobes, x1.39 = 9.3825mm or 0.3693"

The cam marked 630 measured 7.64 lift or near enough on all the lobes, x1.39 = 10.6196mm or 0.4180"

Is lift alone enough to identify these two? Is there a list of specs somewhere?
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Old 01-04-2013, 04:47 PM   #7
mattcfish
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Quote:
Originally Posted by SamH View Post
Ok, I measured up the cams tonight as best I could. Put them both in the lathe and setup the dial gauge. I could only measure lift.

The cam marked 921 measured 6.75mm lift on all four lobes, x1.39 = 9.3825mm or 0.3693"

The cam marked 630 measured 7.64 lift or near enough on all the lobes, x1.39 = 10.6196mm or 0.4180"

Is lift alone enough to identify these two? Is there a list of specs somewhere?
BMW specs.
308 has a lift of 9.4mm
336 has a lift of 10.68mm
284 has a lift of 8.62mm

Lucky you. #630 has the lift of a 336. An early one with a key drive on the OP is a rare thing......#921 is a 308.
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Old 01-03-2013, 11:27 AM   #8
supershaft
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You could probably get a good idea from lift alone but there are a lot of cams out there now and a lot of them have just about the same lift.

There are usable specs out there for a 336, 308, Andrews, Megacycle, Crane? Chances are it's a 336 but . . . . Either way you will need to time it in order to see how it is timed. Chances are if it's a 336 it is timed 3* advanced but it might be timed straight up since it has the old style oil pump drive. I suggest reading a few books on timing cams. Other inmates know how to post the specs. There is two more recent cam threads that have most of the specs I referred to. Some inmates don't like cam discussions. It gives them a headache. It is a bit more complicated than removing grips!
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Old 01-03-2013, 04:45 PM   #9
disston
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Yeah. But removing grips is were the real money is.
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Pay your debt, piratejohn.http://www.advrider.com/forums/showthread.php?t=949341
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Old 01-03-2013, 05:38 PM   #10
supershaft
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It's been cracking me up.
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Old 01-03-2013, 06:47 PM   #11
motu
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I removed and replaced my left hand grip yesterday just to see if I could do it - thank God for ADVRider!
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Old 01-03-2013, 09:57 PM   #12
SamH OP
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I know, it's a good thing this bike's in bits. I only have to worry about installing a new set of grips. Phew.

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