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Old 03-03-2005, 10:03 PM   #1 (permalink)
IronButt
 
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cam cover changes

Anyone know the difference in the pre 92 cam covers and the later ones? Can I install a 92+ on a 87 evo.
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Old 03-04-2005, 12:15 AM   #2 (permalink)
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Quote:
Originally Posted by lectraglidedad
Anyone know the difference in the pre 92 cam covers and the later ones? Can I install a 92+ on a 87 evo.
Just look in a parts book for the year cam cover you want to use. That is, if you have a Gear Cover from a 95, then check the part number for when that part was first put into use.

For example, the 1991 parts book shows the evo chrome gear cover was first used in 1984 (part # 25268-84A).

The regular gear cover has the part number of 25258-80B, indicating the gear cover from some of the pre evo bikes would work in 1991.

You need a later parts book to determine how long the part was in use.

Just a guess but I expect those gear covers didn't change for the entire evo run.
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Old 03-04-2005, 01:41 AM   #3 (permalink)
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Ok, your going to make think again. My first impression is no, not because it wont fit, but because of how the oil flows in the engine. You see the EVO, at least the early ones had 3 distinct pressure zones that help oil move around the engine. Yea I know it has a pump and it applies pressure and so forth. But, the motor also scavenges that oil too. And how the motor breathed its crankcase pressure plays a role also. Your 87 vented through that closed off chamber, if you notice, there should be a tube in your older cam cover. Some have a plastic oil seperator stuck in it. Thats that funny shaped black thing. If you put on a newer style, that chamber doesn't get sealed, and the crank case pressure, although some will still exit, some will escape back into the cam cover and into the push rod tubes and back into the center of the cases and on, this will upset those 3 zones I have spoken about. Additional crankcase pressure will not only upset the oil feed and scavenging system but will cause you to lose horspower. Any pressure under that piston takes away from all that push on the piston you paid so much money for. I really would have to sit down and think about all the differences in the pressure zones (so to speak) in the 92(late) and later models (head breather) verses the pre 92 case breather, but pretty sure you need to stay with the old style.
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Last edited by Jeff S.; 03-04-2005 at 01:47 AM. Reason: remembered some more
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Old 03-04-2005, 09:49 AM   #4 (permalink)
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That tube has been the only physical difference I can see and I didn't know what it was used for. I was thinking some kind of alignment that wasn't needed in the newer models. I wan't thinking about oil..I've been looking for a chrome one without paying HD $150 and my machinist says the aftermarket (not Jims, S&S..ect) are junk causing engine problems. Thanks for clearing that up.
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Old 03-04-2005, 11:06 PM   #5 (permalink)
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Lots of the offshore ones are junk. The only alignment issues are when you are line reaming for cam and pinion bushings. If you look at an 87 cam gear gasket and a 93 + gasket you will see a difference. If you took the 2 looked at the back you would also see the difference. And knowing things like that and how the system works is what makes the difference between these so called "master bike ASSEMBLERS" you see on TV and a bike mechanic, which I never wanted to be in the first place, but, if your going to do something, do it the best you can. Anyway, I'll stop rambling now, get yourself an older style one, new, used or whatever.
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Old 03-06-2005, 03:35 PM   #6 (permalink)
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Quote:
Originally Posted by Jeff S.
Lots of the offshore ones are junk. The only alignment issues are when you are line reaming for cam and pinion bushings. If you look at an 87 cam gear gasket and a 93 + gasket you will see a difference. If you took the 2 looked at the back you would also see the difference. And knowing things like that and how the system works is what makes the difference between these so called "master bike ASSEMBLERS" you see on TV and a bike mechanic, which I never wanted to be in the first place, but, if your going to do something, do it the best you can. Anyway, I'll stop rambling now, get yourself an older style one, new, used or whatever.
==========================
What you say about the breather system is correct. I've noticed differences in covers. The only other big change was back in the 1970's when HD went from a side-oiler to an end-oiler timing shaft but those are really old.
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