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1991 Evo base gaskets supply list

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falconbrother

Member
As is common on these engines, I have a weeping rear base gasket. I'm hoping to wait till fall to fix it. I have a 1991 FLSTC that is mostly stock. It does have a mild cam, S&S Super E, Vance and Hines pipes and the Screaming Eagle ignition. I don't ride it very hard very often. I bought this bike recently and have put about 3,000 miles on it. A couple of weeks ago I noticed that the rear cylinder base is weeping some oil. I talked with my local off brand Harley repair shop. He says that all evo's will eventually weep oil from the rear cylinder and that he will fix it for $300. I am a decent wrench and figure I'll do it myself for the cost of parts. And, while I'm in there I'm gonna do both cylinders. With 23,000 miles on the bike I don't plan to replace the piston rings or any of that. Just the base gaskets.

What parts do I need to order?

My thinking is, Cometic base gaskets (what thickness .10 or .20?), HD Head gaskets and rocker cover gaskets.

Any thing else?
 
falconbrother said:
As is common on these engines, I have a weeping rear base gasket. I'm hoping to wait till fall to fix it. I have a 1991 FLSTC that is mostly stock. It does have a mild cam, S&S Super E, Vance and Hines pipes and the Screaming Eagle ignition. I don't ride it very hard very often. I bought this bike recently and have put about 3,000 miles on it. A couple of weeks ago I noticed that the rear cylinder base is weeping some oil. I talked with my local off brand Harley repair shop. He says that all evo's will eventually weep oil from the rear cylinder and that he will fix it for $300. I am a decent wrench and figure I'll do it myself for the cost of parts. And, while I'm in there I'm gonna do both cylinders. With 23,000 miles on the bike I don't plan to replace the piston rings or any of that. Just the base gaskets.

What parts do I need to order?

My thinking is, Cometic base gaskets (what thickness .10 or .20?), HD Head gaskets and rocker cover gaskets.

Any thing else?
Click to expand...

Welcome to The Forum, Cosmetic gaskets are a good choice, I would stay with stock thickness
 
You may find that the head gasket has changed from the original design and the o rings need to be removed from the cylinder dowels prior to fitting the head gasket

Brian
 
I would suggest some serious thought on this project. To replace the base gaskets, you have to strip the top end of the engine. My thoughts are that if you are disturbing the engine to this degree, you should put it back in "like new" condition. That would mean valve jobs on both heads, rings, and honing the jugs. Obviously all new orings, gaskets and seals.

Of course this is your decision. You may not intend to keep the bike long, or you may like pulling the engine apart, so the need to do this again in the future may not trouble you. All factors that go into your decision. Just recognize that the added effort to complete the top end project is not much more than what you will be doing anyway especially if someone else will actually do the valve jobs and hone the jugs (I have those done by the shop since I don't have the tools).

TQ
 
TQuentin1 said:
I would suggest some serious thought on this project. To replace the base gaskets, you have to strip the top end of the engine. My thoughts are that if you are disturbing the engine to this degree, you should put it back in "like new" condition. That would mean valve jobs on both heads, rings, and honing the jugs. Obviously all new orings, gaskets and seals.

Of course this is your decision. You may not intend to keep the bike long, or you may like pulling the engine apart, so the need to do this again in the future may not trouble you. All factors that go into your decision. Just recognize that the added effort to complete the top end project is not much more than what you will be doing anyway especially if someone else will actually do the valve jobs and hone the jugs (I have those done by the shop since I don't have the tools).

TQ
Click to expand...

Very good point TQ, I sold my valve grinder and valve guide tools, might I suggest Chopper at Chops Garage:s
 
I used Cometic gaskets on my evo stroker chopper motor, I recommmend them highly. You can purchase a top end kit and it will have everything you need including base, head, orings , rocker box, etc.

Also agree with TQ to freshen things up once you are in there. I think I wrote down the Cometic Kit # somewhere, I will post the part # when I find it.:D
 
What is the stock thickness of the base gaskets? Thanks for the suggestions. When I get it apart I'll let my guy evaluate the heads etc.. he said he would do the whole job for me but, I used to be an aircraft mechanic so pulling cylinders is no big deal. The finer machine shop work I'll let an expert do.

There are some new Cometics on ebay right now cheap but, I dont know which thickness to get.
 
I'm going to suggest as others have you go just a bit deeper than you mention in the original post. At a minimum I would lightly hone the cylinders (you can get a ball type hone, the ones with multiple small balls on it, pretty cheap), just enough to remove any glaze that might be in them, and then replace the rings. That should be the minumu you do. I recently had to re gasket an old Triumph with low miles on it everything looked just fine, there was even some cross hatching visable in the cylinder bores, so I made the decision to only replace gaskets. Well long story short when it was all reassembled the piston rings just did not want to re-seat, so apart it comes again, right down to the engine cases to replace a $40 set of rings. At best you have a 50/50 shotof being in the same situation.
 
10-4, thanks.

My bike is a 1991 with 24,000 original miles. 4,000 of those are mine. My independent Harley repair guy didn't say much about what all he thought needed to be done. But, he thought it would be a simple job to do. I'm not going to do it till this winter. Right now I'm just buying parts. Which brings me to a question.

I bought Cometic base gaskets, .020. Can I just get a top end gasket kit for the other gaskets? And, what's the best head gasket, teflon or carbon?

About the cylinders, at this point my plan is to have a good look at the head and valve seats. I haven't honed a cylinder before but, know the procedure for it. Plenty of light oil and hone. Your suggesting that I need to replace the piston rings? That would require checking those end gaps also, correct?
 
falconbrother said:
10-4, thanks.

My bike is a 1991 with 24,000 original miles. 4,000 of those are mine. My independent Harley repair guy didn't say much about what all he thought needed to be done. But, he thought it would be a simple job to do. I'm not going to do it till this winter. Right now I'm just buying parts. Which brings me to a question.

I bought Cometic base gaskets, .020. Can I just get a top end gasket kit for the other gaskets? And, what's the best head gasket, teflon or carbon?

About the cylinders, at this point my plan is to have a good look at the head and valve seats. I haven't honed a cylinder before but, know the procedure for it. Plenty of light oil and hone. Your suggesting that I need to replace the piston rings? That would require checking those end gaps also, correct?
Click to expand...

I have a 1992 police special. I had to replace my bottom jug gaskets because of the weeping. When I took my jugs off. I took them to the machine shop to hone them out. When I picked them up the machinist didnt even touch them. The cross thatched honing from when the bike was assembled in the factory were still there. He said he didnt need to touch them. My bike had 100,000 miles on it at that time. All I did was change the piston rings. Your engine only has 24000 miles. You dont need to do anything but the gaskets. You wouldnt even need to do the rings. Not with mileage that low. I know I wouldnt bother.
 
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