Derby Cover Leak

[Jim Bronson]

I recently replaced the diaphram spring on my 2013 Dyna with a lighter version. I re-installed my VPC and added a full bottle of Spectro primary fluid. I started it up in the garage, and everything looked fine. This morning I noticed a little oil under the derby cover. I replaced the bolts and made sure the torque was 100 in/lb (star pattern). Everything was fine today until I came out of the restaurant. More oil under the derby cover. How can oil leak from around a derby cover with a new gasket? The new bolts are hex and slightly shorter than the originals. Even if I added too much oil, how could it sneak past the new gasket?

I should add that it is impossible to see past the VPC and see the oil level relative to the bottom of the clutch. To deepen the mystery, it is leaking from the lowest point of the cover and nowhere near a bolt head. Looks like it will be going back on the lift today. Think a good thought for me.

[Hossamania]

Are you sure it's not the plug leaking?
Stand it up straight so you know the fluid is not against the cover, leave it sit overnight, if no leak, it may be the gasket, if it still leaks, it is not the derby cover gasket.

[Jim Bronson]

I did as you suggested Hoss. Stand by for more news tomorrow. I forgot to mention there's a narrow stream of oil from the bottom of the cover down to the bottom of the outer primary cover. It seems that it is conclusive to be a derby leak.

[Fugawee]

If and when You should take the Derby Cover off, You may want to place it on a known good flat surface to see if it is bowed or warped from maybe previous over tightening.
Another thought is to maybe try and reduce the amount of Primary Fluid by 2 oz's or so and see if the problem goes away.  I know some that only use approx. 26 oz's in there with no performance problems.
I also have known those that use both the large Orange "O" Ring style gasket with the large Full Round gasket over that.

[Rockout Rocker Products]

You're playing derby roulette using a torque wrench on the screws.   

 

[FLDavetrain]

Did you check if it's the inner primary seal? That leak can travel to bottom derby in a narrow stream as you say

[Jim Bronson]

You're playing derby roulette using a torque wrench on the screws.   

 

I've been doing it per the SM for 15 years and 4 bikes, and I've never seen this problem.

[Jim Bronson]

Did you check if it's the inner primary seal? That leak can travel to bottom derby in a narrow stream as you say

I don't think oil flows uphill even in CA. When I installed the cover, the level was way down near where it should be, and there were no leaks. I couldn't see the exact level due to the VPC. Tomorrow I'll try to find my bore scope and take a look. Also, I didn't notice any clutch slipping going through the gears.

[Ohio HD]

Jim, your running a flat derby gasket, and not the OEM seal?

[kd]

It has to be a gasket surface issue such as dimpled at the stud holes from squeezed gaskets.  The hot oil will sit on the inner primary lip where the bottom of the derby cover matches up.  It can seep out from there with the right conditions.  I would check the cover on a glass plate with a piece of fine grit paper.  If it only dresses the area around the derby screw holes you have the culprit.  Your choices will be dress it down all across and true or replace it. 

[Jim Bronson]

Jim, your running a flat derby gasket, and not the OEM seal?

It's the flat type minus the center portion and with beads of sealant along the outer edges.

[Jim Bronson]

It has to be a gasket surface issue such as dimpled at the stud holes from squeezed gaskets.  The hot oil will sit on the inner primary lip where the bottom of the derby cover matches up.  It can seep out from there with the right conditions.  I would check the cover on a glass plate with a piece of fine grit paper.  If it only dresses the area around the derby screw holes you have the culprit.  Your choices will be dress it down all across and true or replace it. 

Very good idea KD. I never had this problem  before with the same cover, so I'm leaning toward the gasket. I can see how it would leak for a while and then stop per your description. I'll pull it apart tomorrow morning and hopefully find the problem. Thanks.

[Ohio HD]

Jim, your running a flat derby gasket, and not the OEM seal?

It's the flat type minus the center portion and with beads of sealant along the outer edges.

I'd put the bead in the inside towards the inner primary. Also make sure you don't let the outside edge between the cover and primary opening.

[Fugawee]

I believe that the Flat Beaded Type of Gasket states on it to have the Beaded Side towards Clutch.

[Ohio HD]

You're playing derby roulette using a torque wrench on the screws.   

 

I've been doing it per the SM for 15 years and 4 bikes, and I've never seen this problem.

I always use a torque wrench on the derby and primary fasteners.

[Ohio HD]

I believe that the Flat Beaded Type of Gasket states on it to have the Beaded Side towards Clutch.

I think most do say clutch side.

[Jim Bronson]

Mine has beading on both sides, and the center is cut out. I can't use the one pictured because it interferes with the VPC. So I either have to cut out the center or buy one with the center already cut out. I have a spare if I need it.

[Rockout Rocker Products]

You're playing derby roulette using a torque wrench on the screws.   

 

I've been doing it per the SM for 15 years and 4 bikes, and I've never seen this problem.

I always use a torque wrench on the derby and primary fasteners.

 Every post I read about broken derby cover screws invariably has..."I used a torque wrench..."

 You do you.

[Jim Bronson]

I never set the wrench to the top value in the range. I set it to max minus 10-20%. I don't know what setting all those other guys are using, but I'd bet they're setting them to max plus 10-20% "just to make sure." Also if they use replacement bolts made from a softer material, all bets are off.

[Ohio HD]

You're playing derby roulette using a torque wrench on the screws. 

 

I've been doing it per the SM for 15 years and 4 bikes, and I've never seen this problem.

I always use a torque wrench on the derby and primary fasteners.

 Every post I read about broken derby cover screws invariably has..."I used a torque wrench..."

 You do you.

   

[Hossamania]

Luckily broken (or rounded) derby cover screws are generally pretty easy to remove. Don't ask me how I know.

[millerm64]

I recently replaced the diaphram spring on my 2013 Dyna with a lighter version. I re-installed my VPC and added a full bottle of Spectro primary fluid. I started it up in the garage, and everything looked fine. This morning I noticed a little oil under the derby cover. I replaced the bolts and made sure the torque was 100 in/lb (star pattern). Everything was fine today until I came out of the restaurant. More oil under the derby cover. How can oil leak from around a derby cover with a new gasket? The new bolts are hex and slightly shorter than the originals. Even if I added too much oil, how could it sneak past the new gasket?

I should add that it is impossible to see past the VPC and see the oil level relative to the bottom of the clutch. To deepen the mystery, it is leaking from the lowest point of the cover and nowhere near a bolt head. Looks like it will be going back on the lift today. Think a good thought for me.

...........
If it did not leak before I would retrace my steps. First drain all of the fluid out into something you can measure the amount of oil.

Second there can be issues with the VPC where it will hit the derby cover. In a pinch I would reinstall the old spring you were using and check them for differences, thickness ect. Check the derby cover itself while it is off to be sure it is perfectly flat and not damaged.

Also check around the derby screw holes in the primary cover to make sure there isn't a crack (ouch).

It you haven't found the issue yet I would put it back together with the diaphragm that was in it before it leaked and add only 25 ounces of primary fluid. That is more than enough to take it for a good ride. If the leak stopped you could reinstall the lighter spring and try again. There does not seem to be a set amount of primary fluid from bike to bike. Anywhere from 26 to 28 ounces of fluid should be enough for a full fill.

Good Luck

[mrmike]

No more "O" rings for the cover? My bike is an 03 so that's what I've always used.

Mike

[Jim Bronson]

Thanks for the hints. After spending a relaxing afternoon in the ER, I'll get back to it tomorrow.

[smoserx1]

No more "O" rings for the cover? My bike is an 03 so that's what I've always used.

https://www.denniskirk.com/genuine-james/derby-cover-seal-25416-99.ph26241.prd/H26241.sku?cid=17923638713&gclid=EAIaIQobChMIi42p0Jud-gIVlIXICh1SpwIREAYYASABEgIrCfD_BwE

If you use this type seal you need to make sure your primary has a groove for it.  I have seen some pics of primaries that do not appear to have the groove, and I believe you need the disk gasket in that case.