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The dreded Rear Cylinder Leak - Evo

28K views 23 replies 9 participants last post by  Scrapper 
#1 ·
Have a 97 FLH TPI, bagger, which developed a rear cylinder leak last year. Paid a local guy to do the repair then - which lasted until one long hard ride this year. Developed the same leak and decided to fix it myself, with the desire to do a better job. Checked a popular local shop for the best gaskets, went with James double sealed base gaskets and all James new rubbers, head and steel gaskets. Got it back together started it up and within 4 minutes saw a wet oil line at the rear and a clear oil/air pop on the left side of the cylinder base. Made some calls to the shop where I bought the gaskets and got varying advise from what one guy told me to another. The first guy said the studs were fine, at 40k miles, not to worry, just use them. Another guy said it was time, they're stretched. Also suggested to check the base and case for straight.

Got it apart and removed the old studs. When checking the case, it tested reasonably flat. Put a level gage across it and a small pen light behind. Very little light breaks the line all the way around. Not so on the cylinder base. Had a gap of about 2 or 3 thousands showing a lot of light coming through at precisely the point of leakage. Seems to me that the cylinder has developed the gapage over time and would require machining to correct it. Took it to a local machine shop for only the necessry shaving to flatten it.

Between the new James double sealing base gasket, new studs, and machine work I think I'll have it fixed to last.

I'd be interested to know if others had similar leaks and problems in getting their leaks fixed, or need my information to fix their leak. Seems to me that Harley would have developed a recommended fix complete with a great sealing gasket instead of the stock one offered since this is a well known problem for the Evo. Cause: (According to my first repairman) failing to warm up the motor sufficiently before putting the bike into a ride.
 
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#2 ·
i got a 90 with both cylinders leaking ever so slighty. just some wetness, no runs or such but i plan on redoing mine this winter, wanna upgrade the stock form ever so slightly but build for reliability. and at 40,000 i would have had the studs swapped anyway. those base gasket are much like a head gasket on cars, the do tend to leak, hell ford 3.8 liters have been horrible bout that until i think 99 or 2000 when they figured that 20 years a of the same setup and same common failures that they oughta change it, much like hd when they went to the tc. i have heard numerous complaints bout your problem on the evo. by the way i only got 36000 miles on mine.
 
#3 ·
I picked up a '85 FXST last year with God only knows how many miles on it. Both base gaskets were leaking. I read about the Hayden Oil Fix and for the price, figured I had nothing to lose. It comes with a set of base gaskets that look puny, but work. Almost 3k miles and no leaks!! I don't even bother to warm the bike up before riding off.
Here's a link

http://www.parts123.com/PartFrame.asp?ZTM=cadegfea&GHOME=www.jirehcycles.com&TITLE=JIREH_CYCLES

Not affiliated with any of these companies. I just wanted to pass on a tip that worked for me.

George
 
#5 · (Edited)
mudphish said:
Anyone ever tried the "PigTail" kit to stop this problem? I think I am going to give it a try this winter.

http://psndemohd3.com/eshopprod_cat_1114-9042-9043_product_100059.CYLINDER_PIGTAIL174_KIT.htm

This was a bandaid on the problem....this PigTail when installed restricts the return oil flow from the top end which causes oil carry over and several other problems. Most of the oil that leaks around the base gasket is from an untrue mating surface and the windage of oil being slung up in that area from the flywheels. The Factory say to lap the cylinder base area before installing it. This will insure the surface is true and it will seal. You can get the cylinder base lap tool at any aftermarket Co.
Correct torque proceedures are a must also.
 
#8 ·
mudphish said:
What about the Hayden Oil Fix ? it uses restrictor jets to control the flow of oil down the jug, is this recommended?

I also read you can O-ring the cases, this seems like it would be expensive as well...
Any thing used to slow the oil return I wouldn't use in my bike.
The vacuum in the lower end is used to pull the oil out of the top end....if you restrict that flow you are going to fill the rocker boxes up with oil and that will cause oil carry over into the air cleaner and posibably down the valve guides if there is a bad seal, that will give you a smoker.
 
#9 ·
mudphish said:
What about the Hayden Oil Fix ? it uses restrictor jets to control the flow of oil down the jug, is this recommended?

I also read you can O-ring the cases, this seems like it would be expensive as well...
The small dowel they use is not to restrict the flow of oil, but to make a seamless passageway between surfaces. Lots of other manufacturers use this method to mate oiling routes. In a perfect world, on finding this to be a problem with their top ends, the MoCo would've added one more step to the machining and countersunk a hole for a captured o-ring in the mating area.
Of course, that would've cost them a few extra dollars for each bike, as opposed to the millions it must've cost them in warranty work.

George
 
#11 · (Edited)
mudphish said:
I am going to give the pigtails a try this winter, I will document the process with photo's and a brief summary, I will then report my findings to this group....
I guess you don't understand the restriction those give.....Every one I ever saw had to be taken out because of it but if you got to have it go for it. Just don't ride too hard for too long.....:dunno:
Some times I wonder why I sit here giving advice on the things I experienced....I see its a waste of time. Well after you drill out the cylinders for that fitting and make a bigger spot for a leak how do you fix that.....let us know when you figure that out, I did it already but I'll keep it to my self for now.
 
#12 ·
I hear ya, I would probably change my mind once I had seen how restrictive the tubes are, the problem is I have not ever seen one and I was under the impression that the inner diameter of the tube would be the same as the channel in the jug.

Thanks for your advise I would not install them if they cut off the life blood of the engine thats for sure.
Thanks again...
 
#13 ·
mudphish said:
I hear ya, I would probably change my mind once I had seen how restrictive the tubes are, the problem is I have not ever seen one and I was under the impression that the inner diameter of the tube would be the same as the channel in the jug.

Thanks for your advise I would not install them if they cut off the life blood of the engine thats for sure.
Thanks again...
Sorry Mudphish...some times an old man gets grumpy! Don't want people to make the same mistakes I did thats why I get a little pushy at times.
Again sorry for being a bit rude.
 
#14 ·
No problem I get a bit grumpy as well... Check this out it is a good read, I have drawn the conclustion that lapping the cases or swapping them out for a set of delkrons would be the best thing to do...

Read on!


Weeping Base Gaskets
This has driven at least a hundred thousand Harley riders ballistic!
Harley tried the succession of 6 different material base gaskets to correct the problem over 16 years.

This was a Band-Aid approach to a symptom…the oil leakage….not the cause of the problem.

Aftermarket Base Gaskets

They didn’t even do this well as the aftermarket came out with silicone base gaskets, as well as copper and aluminum ones that all worked far better than Harley’s feeble attempts.

Harley has never addressed the actual engineering design problem itself.

The oil comes from the return oil passage from the top end, which must transfer from the cylinder into the engine block via a hole in the base gasket.

It is easy to correct but the Factory never got around to it in 16 years of production.

O-Ring Solution

O-ringing the oil passage where the cylinder meets the engine case works well.

This requires machining an o-ring groove into the engine case around the oil return hole. Enough but not too much rubber must protrude out to but up against the cylinder base.

There are many variations of performing the above fix but it requires skill, time and energy.

O-ringing the whole surface between the cylinder and engine case would also solve the problem.

Merch Performance did this first with production run engines.

This is what HD also did with the TC88.

Pigtails

Putting an insert up into the cylinder oil passage that would also fit into the engine case passage is another solution.

There is a unit called a "Pigtail" that is a screw in hollow insert with a tube attached.

The engine case oil return hole is tapped out to accept the screw in insert. The tube protrudes upwards. The cylinder is installed over the tube. The tube is a snug fit within the cylinder so that the oil now runs through this tube down into the engine casing with no contact with the cylinder base gasket.

Machining the Gasket Surfaces

Trock makes a double-sided machining plate called an Evo Lapping Ring, (Chrome Specialties #400304), that works extremely well.

Quite often a cylinder base will leak because of a machining deficiency or abnormality. Maybe one of the three surfaces consisting of two case halves and the cylinder base has warped.

Sometimes the engine case halves do not mate correctly with one side being a little higher than the other.

Maybe there is gasket residue or a bump on one of the mating surfaces that prevent and a leak-free union.

The lapping ring is used with a lapping compound. It works fast and with minimum effort once everything is ready to be worked on.

If ever rebuilding your Evo get one of these fixes done as a preventative measure even if you have never had a problem.

It is very little effort and expense while rebuilding but if the engine must be taken apart for this purpose only it becomes expensive.

There are over 1,000,000 Evos still on the road.

Harley never corrected this problem.

Compare this inaction with how vigorously Harley attacks Twin Cam problems.
 
#15 ·
As a note:

Cylinder-head clamping pressure created by the different expansion rates of the steel studs and alloy cylinder is lowest when the engine is cold. The base gasket relies on this clamping pressure to prevent leakage. The cylinders grow faster than the studs and distortion occasionally pulls it out of shape. A warpage depression of as much as 6 to 8 thousandths of an inch can develop along the mating surface of the cylinder where it bolts to the case. That much gap just makes the 0.020 inch base gasket’s job that much harder. The base gasket has to survive constant shape shifting when hot and high oil pressure when cold.

One of the simplest ways to avoid a blown base gasket in Evo engines is to warm your bike up thoroughly before running hard.

Keep
 
#16 ·
Keepmvng said:
As a note:

Cylinder-head clamping pressure created by the different expansion rates of the steel studs and alloy cylinder is lowest when the engine is cold. The base gasket relies on this clamping pressure to prevent leakage. The cylinders grow faster than the studs and distortion occasionally pulls it out of shape. A warpage depression of as much as 6 to 8 thousandths of an inch can develop along the mating surface of the cylinder where it bolts to the case. That much gap just makes the 0.020 inch base gasket’s job that much harder. The base gasket has to survive constant shape shifting when hot and high oil pressure when cold.

One of the simplest ways to avoid a blown base gasket in Evo engines is to warm your bike up thoroughly before running hard.

Keep
Very Good and I agree 100% with that......
 
#17 ·
Keepmvng said:
As a note:

One of the simplest ways to avoid a blown base gasket in Evo engines is to warm your bike up thoroughly before running hard.

Keep
Could you all define, even roughly, a thorough warm up and running it hard please.

As an example, I used to lean over and feel the exhaust (not the pipes) for some heat. Then I put 2-1 White Bros. pipes on and started feeling the rear head for some heat. Then, when going to work, it's abou 1/2 mile of easy driving to expressway on-ramp and easy acceleration to 60 (3000 RPM). During the warmer months, I find myself warming up for a couple of minutes and then leaving w/o checking cyl head for heat.

Also, I have a cyl head temp gage but am unsure where it should read.

Joe
 
#18 ·
arjonaut said:
Could you all define, even roughly, a thorough warm up and running it hard please.

As an example, I used to lean over and feel the exhaust (not the pipes) for some heat. Then I put 2-1 White Bros. pipes on and started feeling the rear head for some heat. Then, when going to work, it's abou 1/2 mile of easy driving to expressway on-ramp and easy acceleration to 60 (3000 RPM). During the warmer months, I find myself warming up for a couple of minutes and then leaving w/o checking cyl head for heat.

Also, I have a cyl head temp gage but am unsure where it should read.

Joe
Cylinder head temp should be between 175 and 220 for best performance.
 
#19 ·
My Evo's base gaskets were changed at around 5k. I put in the James top end gasket kit, and borrowed a cylinder base honing device from my buddy called a Trock cylinder Lapping tool. I have 85k on the evo now and have not had even so much as a tiny weep since. I do warm up my bike before blazing down the road, but I don't go over board, and I also don't go over board on the throttle until she is fully warmed. Even then, I don't use her a a race bike.
 
#20 ·
arjonaut said:
Could you all define, even roughly, a thorough warm up and running it hard please.

As an example, I used to lean over and feel the exhaust (not the pipes) for some heat. Then I put 2-1 White Bros. pipes on and started feeling the rear head for some heat. Then, when going to work, it's abou 1/2 mile of easy driving to expressway on-ramp and easy acceleration to 60 (3000 RPM). During the warmer months, I find myself warming up for a couple of minutes and then leaving w/o checking cyl head for heat.

Also, I have a cyl head temp gage but am unsure where it should read.

Joe
The problem is the differential temp between the cylinder and the studs.

If the rocker arm cover is hot to the touch, than you can assume that there has been adequate heat transfer to the studs.

Keep
 
#21 ·
Made a run from Houston to Fredericksburg (220 miles one way) with Mrs. Keep for a day ride so when we got back I checked temperatures on both the cylinders and heads as soon as I stopped (laser thermometer).

Temp checked on the heads just above the sparkplug was 254 deg f on the rear and 227 deg f on the front.

Temp checked on the cylinders at the base was 214 deg f at both the front and rear.

Temp checked on the case was 180 deg.

Ambient (air) temp at the time was approx 67 deg.

Cylinder head temperatures run hotter due to more area exposed to the flame of combustion.

Cylinders get a cooling bath of oil with more so for the rear due to fly wheel rotation.

Rear cylinder temp readings are a product of oil temp. If I had been running in slow traffic with low air flow across the engine the rear cylinder would have run cooler (to a point).

Cylinder and head temps are two separate issues.

Some people would think that the cylinders would have higher temp than the heads (false).

Cylinders have more cooling area (both internal and external) than the heads.

Heads have more exposed surface area to combustion while the cylinder is exposed to spent combustion over a larger area. The exhaust port never gets a cool charge through it, so it is always hot.

Also carbon buildup on the piston acts as a insulator. H-D also has a oil jets to the underside of the piston on twin-cams to help cool.

The temp readings that I gave on the heads is directly on the combustion chamber. Rear heads don’t get as much air cooling which explains Buell’s additional cooling to the rear.

As a note: my bike is an Evo (RK) and the oil temp seldom gets over 210 f.

I have seen a reported reading on a twin-cam engine in which the rear cylinder had a higher temp than the front. But that may be due to the higher oil temps they run at and the bike only having 2500 mile on it.

TCs run much hotter oil temps than an Evo, which may be a product of the oil jets to the underside of the piston. It’s not uncommon to see oil tank readings in the 250f range on hot days.

I would really like to take some readings on a shovel.

Keep
 
#22 ·
Evo back cylinder

I don't know about the twin cam designs, still learning about those, and not sure about reduction in temps being equal front to rear due to cooling oil jets, but shovels and evos rear cylinders usually ran hotter due to it being behind the front blocked from a more direct breeze and bottlenecked in with more heat surrounding it. On my old shovels i used to spin the little gas venturi slightly more to the rear cylinder so it ran richer and hence cooler to compensate for the above mentioned extra heat.
 
#24 ·
base gasket leak

rickr01 said:
My Evo's base gaskets were changed at around 5k. I put in the James top end gasket kit, and borrowed a cylinder base honing device from my buddy called a Trock cylinder Lapping tool. I have 85k on the evo now and have not had even so much as a tiny weep since. I do warm up my bike before blazing down the road, but I don't go over board, and I also don't go over board on the throttle until she is fully warmed. Even then, I don't use her a a race bike.
Ok - I,ve got a '96 Heritage that just recently devolped a base gasket leak on the front cylinder ( front right hand side of cylinder on push rod side). My ? rickr01 is, Did u use the metal beaded gaskets or paper ones , I see James has both..... Now if you used the metal beaded ones I see they have a greater final crush,, would that not affec/reduce compression?? affecting power or not ?? Thanks!!
 
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