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Discussion Starter · #1 ·
Hey guys here is one of my first posts, so bear with me....... I have a both base gaskets leaking on my EVO, and the last few rides, I have noticed that my rocker boxs are leaking also. Anybody have any specific reccomendations on what type of base, head, and rocker box gaskets to use?? I am leaning toward ordering the James top end set out of J&P cycles.... Any help, and tips on changing all this would be appreciated. Thanks, Brian
 

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The stock newer HD gaskets are fine for all but the bases. I swear by Hanna's. About 20 bucks for 2. I will not even work on an EVO without them when doing base gaskets. Defineatley check the cylinder studs to make sure they are tight when the top end comes off. Loose studs are the main reason base gaskets start leaking.
 

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Discussion Starter · #3 ·
Can I just tighten the studs back up or do I need to put some lock-tite on them?? This is my first time into an evo, but I am sure I can handle it..... Thanks, Brian
 

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If the studs come out of the engine cases when you remove the heads, red loctite them when you put them back in. They need to be installed to a certain heighth also. Check the appropiate service manual. Also make sure the threads in the cases are clean and dry. James gaskets should work fine
 

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personally i like the cometics you didnot say what year and how mant miles if your takin things apart replace the plastic breather gear the #1 cause of base gasket leaks on a evo. they are usually shot at about 10k causing a reduction in crankcase vaccume just remember the engine was designed to keep air out not oil in
 

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Discussion Starter · #6 ·
I have heard about the breather gear....... My bike is a 94 model and has about 25,000 miles on it. I am leaning towards a new set of rings also, while I am in there. Thanks to all for the replies and keep them coming........
 

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In 1993 and 1994 the dealers were doing base gasket replacements on warranty. I took my 1993 FLHS in to have it done and they did the following:

1. Disassembled the top end and replaced base gaskets.
2. Bent the frame bracket that secures the rear exhaust pipe out of the way and left it that way with no bolt holding the rear exhaust pipe.
3. Charged me for new piston rings. You can argue about this but a warranty requiring removal of the cylinders to replace gaskets should include a set of pistons rings also. Cost me $38.00 which I paid under protest. They offered to use the old rings again with 11,000 miles. No thanks.
4. Scratched gas tank. They denied this.
5. Put small dent in outer primary. They denied this.

Gaskets leaked again in 5,000 miles. I did the job over myself with James gaskets and fixed it. Yes, I replaced the rings again because they should be changed when you remove cylnders.

Above are the reasons why I would not take my bike to a dealer anymore.


When you do the cylinder studs, if they are loose, I would check to see if you have the late model ones. They made a change. It's very cheap to replace all 8 studs and this will prevent blown head gaskets which is a well-documented problem on the Evolution engine.

Good luck
 

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The problem with base gaskets is, there is gaskets there. HD wisely eliminated them and replaced them with orings on current TC models. This was hardly inovative, I happened to look at a 1973 Yamaha 650 cylinder and it has orings" Wow".
All EVO engines can be reasonably converted if the cases are machined to accept them.
The main cause of Evo base gasket failure is not so much the gasket, it is distortion of the cylinder base.
This distortion can be easily detected with a finger nail skimming across the base surface. It can be felt that the cast iron sleeve will slightly extrude out and the aluminum surface. the aluminum will ever so slightly slope away. This creates a bad sealing convex flange. This distortion is caused by heating and cooling cycles, disimular metals and stress relief from the machining process. All cronic base gasket leaks are traced to this.
A company does make a lapping plate to reface the cylinder base surface, but they are better dusted off true by machining.
The plastic breather gears become brittle with age and tend to become abrasive and cause damage to the case.
A Jims steel breather gear is a good replacement as it will maintain the higher flow rate of the plastic breather gear vs the steel gears with the fine mesh screen.
I hope that is of some use.
 

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Discussion Starter · #9 ·
I would guess that my bike has the original studs.......The previous owner told me that it had never been apart. I had no leaks until about 3,500 miles ago, but they seem to be getting worse the more I ride it. I am taking it to Daytona in March and I am not going to have it leaking oil on a trip. My list so far is: James base and top-end gaskets, a new plastic breather gear, a new set of rings and probably some new studs just to be safe. Hopefully I can get it buttoned up and put a couple of hundred miles on it before we head to Florida. I do all my own work just because of all the things you listed. Nobody works on any of my stuff, I have enough connections that I can usually get to the stuff I need to do my own stuff. Thanks, Brian
 

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newultraclassic said:
In 1993 and 1994 the dealers were doing base gasket replacements on warranty. I took my 1993 FLHS in to have it done and they did the following:

1. Disassembled the top end and replaced base gaskets.
2. Bent the frame bracket that secures the rear exhaust pipe out of the way and left it that way with no bolt holding the rear exhaust pipe.
3. Charged me for new piston rings. You can argue about this but a warranty requiring removal of the cylinders to replace gaskets should include a set of pistons rings also. Cost me $38.00 which I paid under protest. They offered to use the old rings again with 11,000 miles. No thanks.
4. Scratched gas tank. They denied this.
5. Put small dent in outer primary. They denied this.

Gaskets leaked again in 5,000 miles. I did the job over myself with James gaskets and fixed it. Yes, I replaced the rings again because they should be changed when you remove cylnders.

Above are the reasons why I would not take my bike to a dealer anymore.


When you do the cylinder studs, if they are loose, I would check to see if you have the late model ones. They made a change. It's very cheap to replace all 8 studs and this will prevent blown head gaskets which is a well-documented problem on the Evolution engine.

Good luck
Your dealership sounds a lot like the one we have here.... That's why I would NEVER take my bike to them, I'd rather do my own work.

As for the gaskets, I've always used the stock HD gaskets except for the head gaskets... then I use Cometics. If all your sealing surfaces are smooth and the studs are tight, then you should not have any more leaks. Also, DO NOT use gasket sealer on them, except maybe a small amount of adhesive to hold them in place during assembly. If you are careful, you won't even need to do that. On an EVO, using gasket **** is just covering up the real problem, IMHO. :)
 
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