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Cometic .020 base gasket question

Started by Adam76, August 11, 2020, 05:07:00 PM

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Adam76

Hi guys, I bought a full top end Cometic gasket kit with the .030" MLS had gasket.

I've gone to install the cylinder base gaskets, and it seems like they don't have enough of the smaller holes?

Also, they have a small raised lip stamped around the middle of the gasket -- is this raised lip supposed to face up or down?? The only way I can see it working is facing down?

Thanks for any help.

Sorry, bike is an evo 1340 1996 softail


JW113

Besides the four holes for the studs, you only need two more. One for the dowel, and one for the oil drain hole. With those stamped steel crush gaskets, you can put them on in either direction.

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

Adam76

Quote from: JW113 on August 11, 2020, 05:51:49 PM
Besides the four holes for the studs, you only need two more. One for the dowel, and one for the oil drain hole. With those stamped steel crush gaskets, you can put them on in either direction.

-JW
Thanks JW.
Ive obviously got the dowel pin identified, but how do I know which of the other two holes is the oil drain hole?
Thanks again.

JW113

Just flip them around until you have the dowel in one hole and the oil drain centered in another hole. If I am not mistaken, they make those to be ambidextrous, meaning both gaskets are the exact same with enough holes to use on either cylinder.

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

Adam76

Quote from: JW113 on August 11, 2020, 06:35:34 PM
Just flip them around until you have the dowel in one hole and the oil drain centered in another hole. If I am not mistaken, they make those to be ambidextrous, meaning both gaskets are the exact same with enough holes to use on either cylinder.

-JW
Thanks, yes they appear to be"  "ambidextrous"  😂   so I'm right in assuming the oil drain hole is the one located just next to the dowel pin that I have marked with blue arrow?
There is one other hole, but it gets covered by the gasket entirely?

Cheers

JW113

2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

Adam76


98fxstc

Adam
will be too late by the time you read this I guess
Hayden oil fix is the ducks guts for Evos
two short brass tubes, slightly tapered at the ends, that sleeve the join at the oil drain hole between the crankcase and the cylinders and 100% prevent any oil leaks

Adam76

Quote from: 98fxstc on August 11, 2020, 08:46:27 PM
Adam
will be too late by the time you read this I guess
Hayden oil fix is the ducks guts for Evos
two short brass tubes, slightly tapered at the ends, that sleeve the join at the oil drain hole between the crankcase and the cylinders and 100% prevent any oil leaks

Not to late, haven't put it together yet.
Can you please elaborate on what it is exactly and where I can buy them if I need to? Cheers

98fxstc

this is them
https://www.haydensm6.com/tof_single.htm
plenty of literature about for them but work basically as I have mentioned
the problem will be whether or not anyone local stocks them
there are also pigtails which I have not used which tap and screw into the crank case but I like the brass jets/tubes
I will do an Oz search and get back to you

98fxstc


Deye76

Follow Cometic torque procedure, Cometic gaskets require more torque.
East Tenn.<br /> 2020 Lowrider S Touring, 2014 CVO RK,  1992 FXRP

JW113

They Hayden oil fix is probably not a bad idea, but with the Cometic gasket, probably not needed. The stock paper base gaskets get soft and blow out, no way the Cometic will do that. Are these base gaskets that you have the rubberized kind?

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

Dan89flstc

While the cylinders are off, have your machinist true the bottoms of the cylinders, this will solve the base gasket leak issue.
US Navy Veteran
A&P Mechanic

jsachs1

I like and use "Pig Tails". A little more work installing them in the cylinders, but they work great re: drainback oil leaks.

Look closely and you can see the copper "Pigtail".
[attach=0,msg1357971]

Adam76

Quote from: 98fxstc on August 11, 2020, 11:57:04 PM
ok
cometic gaskets are the best and will likely be ok
will be 2 to 4 weeks from US
don't appear to be any stockists in Australia

https://www.ebay.com.au/itm/Hayden-Enterprises-TOF-The-Oil-Fix-Gasket/224056865139?epid=171138894&hash=item342ad47173:g:cNEAAOSwsxNe89cd&frcectupt=true
Thanks 98, they are $$$ and probably take too long to get here. I'll stick with just the Cometic gasket I have .
Cheers

Adam76

Quote from: Deye76 on August 12, 2020, 05:13:23 AM
Follow Cometic torque procedure, Cometic gaskets require more torque.
Thanks  for the info,  would the tq specs be on their website? I'll check the box they came in for recommendations of tq settings. 

Adam76

Quote from: JW113 on August 12, 2020, 06:59:43 AM
They Hayden oil fix is probably not a bad idea, but with the Cometic gasket, probably not needed. The stock paper base gaskets get soft and blow out, no way the Cometic will do that. Are these base gaskets that you have the rubberized kind?

-JW
Nope, the ones that came with the MLS .030 HG kit are also steel material base gaskets.

Adam76

Quote from: jsachs1 on August 12, 2020, 02:06:37 PM
I like and use "Pig Tails". A little more work installing them in the cylinders, but they work great re: drainback oil leaks. [attach=0,msg1357971] Look closely and you can see the copper "Pigtail".
Thanks John, where do I get those, and does it need machining to install? Thanks Adam

Adam76

Quote from: Dan89flstc on August 12, 2020, 07:18:47 AM
While the cylinders are off, have your machinist true the bottoms of the cylinders, this will solve the base gasket leak issue.
Thanks Dan, I don't actually have an oil leak issue, it was more a question of installation of the Cometic base gaskets and their orientation etc before putting my top end back on.
If my pistons are too far down the hole on mock up, then I will probably get the bottom of the cylinders  machined a little. Not a bad idea.
  Cheers.

FSG

QuoteIf my pistons are too far down the hole on mock up, then I will probably get the bottom of the cylinders  machined a little.

I'd true them regardless

kd

Quote from: JW113 on August 12, 2020, 06:59:43 AM
They Hayden oil fix is probably not a bad idea, but with the Cometic gasket, probably not needed. The stock paper base gaskets get soft and blow out, no way the Cometic will do that. Are these base gaskets that you have the rubberized kind?

-JW

I believe all of the Cometic steel base gaskets are micro rubber coated to promote sealing.  It is so thin it does not add to the thickness.
KD

Adam76

Thanks guys, all great advice.

One question about checking the deck height -- big boyz site shows a technique where the cylinder is bolted down using spacers and cyl studs to then check the piston height at tdc. But they say to use an old crushed base gasket (which I  don't have) and they don't say how much they torque down the cylinder to check deck height?. See below.

Deye76


[/quote]
Thanks  for the info,  would the tq specs be on their website? I'll check the box they came in for recommendations of tq settings.
It's been several years, but there were instructions that came with the gasket kit. If it's not on the web site and no instructions with your kit, then I'm betting things have changed and factory specs are good.
East Tenn.<br /> 2020 Lowrider S Touring, 2014 CVO RK,  1992 FXRP

kd

August 13, 2020, 05:48:42 AM #24 Last Edit: August 13, 2020, 07:47:23 AM by kd
Quote from: Adam76 on August 13, 2020, 02:06:35 AM
Thanks guys, all great advice.

One question about checking the deck height -- big boyz site shows a technique where the cylinder is bolted down using spacers and cyl studs to then check the piston height at tdc. But they say to use an old crushed base gasket (which I  don't have) and they don't say how much they torque down the cylinder to check deck height?. See below.

Adam, clean the deck and do it without a base gasket.  You can then do the math and calculate what the deck height would be with a gasket. If you can come up with a used base gasket, simply measure it with a micrometer and if not .020 do the calc. based on what you have. You can torque the barrel with a gasket but IMO on a bare fit simply good and snug approaching the torque value is fine.  Always use a torque wrench so you don't go over the spec and pull a stud. Be sure to use something under the head bolt as a spacer to prevent scarring the aluminum cylinder gasket surface.  I use a sleeve / spacer made from PVC pipe and that works well. 

There are several ways to get the measurement and a dial indicator seems to be the best.  You are more likely to find the piston "in the hole" rather than the way your pic shows unless you are not using a base gasket.  With no base gasket the piston is more likely to be out of the hole as the pic shows.  Searches on this site will bring up many discussions and ideas for you to consider.
KD

JW113

Quote from: kd on August 12, 2020, 08:14:26 PM
I believe all of the Cometic steel base gaskets are micro rubber coated to promote sealing.  It is so thin it does not add to the thickness.

Yeah, that's what I recall. I have them in my '92, nary a hint of oil weep and did not do any machining to the cylinders either.

-JW
2004 FLHRS   1977 FLH Shovelhead  1992 FLSTC
1945 Indian Chief   1978 XL Bobber

Adam76

Quote from: kd on August 13, 2020, 05:48:42 AM
Quote from: Adam76 on August 13, 2020, 02:06:35 AM
Thanks guys, all great advice.

One question about checking the deck height -- big boyz site shows a technique where the cylinder is bolted down using spacers and cyl studs to then check the piston height at tdc. But they say to use an old crushed base gasket (which I  don't have) and they don't say how much they torque down the cylinder to check deck height?. See below.

Adam, clean the deck and do it without a base gasket.  You can then do the math and calculate what the deck height would be with a gasket. If you can come up with a used base gasket, simply measure it with a micrometer and if not .020 do the calc. based on what you have. You can torque the barrel with a gasket but IMO on a bare fit simply good and snug approaching the torque value is fine.  Always use a torque wrench so you don't go over the spec and pull a stud. Be sure to use something under the head bolt as a spacer to prevent scarring the aluminum cylinder gasket surface.  I use a sleeve / spacer made from PVC pipe and that works well. 

There are several ways to get the measurement and a dial indicator seems to be the best.  You are more likely to find the piston "in the hole" rather than the way your pic shows unless you are not using a base gasket.  With no base gasket the piston is more likely to be out of the hole as the pic shows.  Searches on this site will bring up many discussions and ideas for you to consider.
Thanks kd, that's exactly the info I needed.  I'll check them with no gasket at all, then add .018" to the cylinder height (for a .020" gasket) when doing the math to factor in the base gasket thickness crushed?
Does that sound right? 

Cheers  :up:

kd

If you're using the MLS Cometic gaskets, when they say .020, it's .020 installed and torqued height.  They will tell you the same and it has been my experience when setting mine up.
KD

Adam76

Quote from: kd on August 13, 2020, 05:34:02 PM
If you're using the MLS Cometic gaskets, when they say .020, it's .020 installed and torqued height.  They will tell you the same and it has been my experience when setting mine up.
👍👍

Adam76

Quote from: JW113 on August 13, 2020, 06:55:36 AM
Quote from: kd on August 12, 2020, 08:14:26 PM
I believe all of the Cometic steel base gaskets are micro rubber coated to promote sealing.  It is so thin it does not add to the thickness.

Yeah, that's what I recall. I have them in my '92, nary a hint of oil weep and did not do any machining to the cylinders either.

-JW

Yeah,  viton micro rubber coating. 001" thick - I just found out the hard way 😂 
I stupidly used a cloth with a little brake cleaner on it to wipe the gasket surface to get some oil off and this is what happened....

Is it good for the trash now?


rigidthumper

Should be fine- I clean all gaskets with a lint free cloth and non-chlorinated brake cleaner before installing.
Ignorance is bliss, and accuracy expensive. How much of either can you afford?

Adam76

Quote from: rigidthumper on August 14, 2020, 06:13:45 AM
Should be fine- I clean all gaskets with a lint free cloth and non-chlorinated brake cleaner before installing.
Ok, cool.   I got all worried about the special .001" viton rubber coating  😅

Adam76

Quote from: kd on August 13, 2020, 05:34:02 PM
If you're using the MLS Cometic gaskets, when they say .020, it's .020 installed and torqued height.  They will tell you the same and it has been my experience when setting mine up.
I checked the piston height on the front cylinder installed with no base gasket at all, and it came out at .010" above deck height.  So my guess is with the .020" of the base gasket I just need to remove .010" material from the base of the cylinder and I'll be at zero deck.

I actually will probably have to take .005 from the base and .005 of the top of the cylinder as the top surface doesn't look smooth enough for a good seal?

98fxstc

Quote from: rigidthumper on August 14, 2020, 06:13:45 AM
Should be fine- I clean all gaskets with a lint free cloth and non-chlorinated brake cleaner before installing.

Robin
Do brake cleaners usually indicate chlorinated or non-chlorinated ?
I haven't looked for this in the past.
Thanks

rigidthumper

The ones we use have to be notated due to EPA regulations. 
Ignorance is bliss, and accuracy expensive. How much of either can you afford?

Adam76

Quote from: rigidthumper on August 14, 2020, 07:00:05 PM
The ones we use have to be notated due to EPA regulations.

Hey rigidthumper, thanks for the  input.

If I'm .010" down the hole would you recommend getting the cyl bases milled or just use a .010" MLS base gasket instead of the  .020" one I have?
Thanks

kd

 :doh:  I completely forgot the .010 MLS base gasket was available from Cometic.  I actually have a couple for 4.060 barrels.
KD

Adam76

Quote from: kd on August 14, 2020, 09:27:36 PM
:doh:  I completely forgot the .010 MLS base gasket was available from Cometic.  I actually have a couple for 4.060 barrels.
Thanks, I think I'll go the gasket route instead of more machining if it's a safe enough option. It's only a mild build at 9.5 comp with zero deck and .030" HG.

wfolarry

I always true up the cylinder bases on the lathe. Those Evo cylinders are rarely flat & that Cometic gasket likes a smooth flat surface.

Adam76

August 15, 2020, 04:07:50 AM #39 Last Edit: August 15, 2020, 04:42:24 AM by Adam76
Quote from: wfolarry on August 15, 2020, 02:44:31 AM
I always true up the cylinder bases on the lathe. Those Evo cylinders are rarely flat & that Cometic gasket likes a smooth flat surface.
Thanks Larry, input much appreciated. I don't want to take any chances that may cause me grief later.....

While I'm truing the bases on the lathe,   I have the opportunity to properly set the quench / squish.... , What's your recommended squish setting?   30 ?  32 ?  35 ? 

EV27 with 9.5 comp pistons
.010" off the heads and basic valve job.
With Cometic. 020" gasket my pistons are .010" in the hole. 

Thanks for any advice.

rigidthumper

Quote from: Adam76 on August 14, 2020, 09:24:39 PM
Quote from: rigidthumper on August 14, 2020, 07:00:05 PM
The ones we use have to be notated due to EPA regulations.

Hey rigidthumper, thanks for the  input.

If I'm .010" down the hole would you recommend getting the cyl bases milled or just use a .010" MLS base gasket instead of the  .020" one I have?
Thanks

I'd take a little off the top, 3-5 thou, just to have a fresh, true-to-the-bore, head gasket surface, and the rest off of the base, partly to set deck height, partly to have a fresh, true-to-the-bore, gasket surface.  I like to set quench distance on street bikes .030"-.035".
Ignorance is bliss, and accuracy expensive. How much of either can you afford?

wfolarry


Adam76

Quote from: rigidthumper on August 15, 2020, 06:40:41 AM
Quote from: Adam76 on August 14, 2020, 09:24:39 PM
Quote from: rigidthumper on August 14, 2020, 07:00:05 PM
The ones we use have to be notated due to EPA regulations.

Hey rigidthumper, thanks for the  input.

If I'm .010" down the hole would you recommend getting the cyl bases milled or just use a .010" MLS base gasket instead of the  .020" one I have?
Thanks

I'd take a little off the top, 3-5 thou, just to have a fresh, true-to-the-bore, head gasket surface, and the rest off of the base, partly to set deck height, partly to have a fresh, true-to-the-bore, gasket surface.  I like to set quench distance on street bikes .030"-.035".
Thank you, that's a plan.