Gearcase Gasket Replacement
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Gearcase Gasket Replacement
I need to replacethe gearcase gasket on my "new" '76 xlh project bike. It looks a little different than my Evo big twin, so I'm looking for someironhead wrench knowlege.
First, the manual says to remove the pushrods...is this necessary, or is there a work-around for this? Gears stay in the case, or do they come out with the cover? Anything thatwill fall out when the case is being removed?
Any problem areasI should specifically look for as long as I'm in here, or just a general look-over and clearance check.
Any tips on getting a good seal, other than using a good quality new gasket?
Thanks in advance.
First, the manual says to remove the pushrods...is this necessary, or is there a work-around for this? Gears stay in the case, or do they come out with the cover? Anything thatwill fall out when the case is being removed?
Any problem areasI should specifically look for as long as I'm in here, or just a general look-over and clearance check.
Any tips on getting a good seal, other than using a good quality new gasket?
Thanks in advance.
Stellar HDF Member
Joined: Feb 2006
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From: Houston Texas
RE: Gearcase Gasket Replacement
You need to follow the manual and take no shortcuts, because there aren't any.
There are 4 separate cams in there, one under each pushrod. Each cam has an unknown number of shims, and they are different thickness as well.
The purpose of the shims (.005 and .007 thick) are to mix and match to obtain the proper cam end clearance when everything is bolted up tight (timing cover). This also includes the thickness of the gasket. Let's assume you have an original gasket for a moment. Then you buy a new gasket (it's going to be aftermarket for sure) and it could be a greater or lesser thickness. If it is, there goes your cam clearance!
My point is to just make you aware that putting a timing cover gasket on a Sportie is a little more involved than it may seem. Added to that is the fact that 2 or more of the 4 cams are going to fall out when you remove the timing cover. The shims are on the inside of the gear(s) and between the bearings and the shims are 2 cam plates. The rear intake and exhaust share a cam plate, as do the front cams. All this stuff wants to fall off the shafts and you can have shims everywhere, unless you are careful.
If you manage to get the cover off without loosing shims and washers, then provided the new gasket is the same thickness, it can go back together without checking the cam end clearances, but I do not advise doing that because if just 1 cam jumps up and get a tooth off of the proper timing, serious engine damage will result..
If it were me though (and it has been many times) I always clean the oil off the cams and inside the gearcase. Then install the cam plates and the cams.........but with no shims. The cam plates have one side with a bevel on the hole. This bevel faces outward toward the cam. Tighten down the timing cover with the new gasket in place dry, using no gasket sealer.You have to remove the lifter blocks and then use feeler gages to see how much end play each cam has with no shims. Write the info down.
Go back with the proper number of shims (they come only in .005 and .007) and mix and match to obtain the proper end play which is minimum of .001 and a maximum of .005 clear. Do this for each cam. After the shims have been installed, remove the cover a final time and be sure the cam gear timing is set properly. This involves lining up the camgear witness marks.
Yeah, it's a pain, but this is the correct way to do it.
Stepping back to the beginning and the subject of removing the pushrods......If you were to get the cover off with the pushrods in place, you would never get it back on because the valve spring pressure will push the camshaft(s) so far out of line the cover will never line up. Inside that cover you have to have 4 cams, a piniongear, an idler pulley, the ignition end drive, the generator end and 2 dowell pins of the case face all lined up to get the cover in place. Good luck, it will go well, just follow what the manual tells you. Every step it tells you to do is very important that you follow it......pg
There are 4 separate cams in there, one under each pushrod. Each cam has an unknown number of shims, and they are different thickness as well.
The purpose of the shims (.005 and .007 thick) are to mix and match to obtain the proper cam end clearance when everything is bolted up tight (timing cover). This also includes the thickness of the gasket. Let's assume you have an original gasket for a moment. Then you buy a new gasket (it's going to be aftermarket for sure) and it could be a greater or lesser thickness. If it is, there goes your cam clearance!
My point is to just make you aware that putting a timing cover gasket on a Sportie is a little more involved than it may seem. Added to that is the fact that 2 or more of the 4 cams are going to fall out when you remove the timing cover. The shims are on the inside of the gear(s) and between the bearings and the shims are 2 cam plates. The rear intake and exhaust share a cam plate, as do the front cams. All this stuff wants to fall off the shafts and you can have shims everywhere, unless you are careful.
If you manage to get the cover off without loosing shims and washers, then provided the new gasket is the same thickness, it can go back together without checking the cam end clearances, but I do not advise doing that because if just 1 cam jumps up and get a tooth off of the proper timing, serious engine damage will result..
If it were me though (and it has been many times) I always clean the oil off the cams and inside the gearcase. Then install the cam plates and the cams.........but with no shims. The cam plates have one side with a bevel on the hole. This bevel faces outward toward the cam. Tighten down the timing cover with the new gasket in place dry, using no gasket sealer.You have to remove the lifter blocks and then use feeler gages to see how much end play each cam has with no shims. Write the info down.
Go back with the proper number of shims (they come only in .005 and .007) and mix and match to obtain the proper end play which is minimum of .001 and a maximum of .005 clear. Do this for each cam. After the shims have been installed, remove the cover a final time and be sure the cam gear timing is set properly. This involves lining up the camgear witness marks.
Yeah, it's a pain, but this is the correct way to do it.
Stepping back to the beginning and the subject of removing the pushrods......If you were to get the cover off with the pushrods in place, you would never get it back on because the valve spring pressure will push the camshaft(s) so far out of line the cover will never line up. Inside that cover you have to have 4 cams, a piniongear, an idler pulley, the ignition end drive, the generator end and 2 dowell pins of the case face all lined up to get the cover in place. Good luck, it will go well, just follow what the manual tells you. Every step it tells you to do is very important that you follow it......pg
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RE: Gearcase Gasket Replacement
Thanks for the advice PinionGear.
Because the engine is out of the frame and is easy to move around, will the shims & gears have a better chance of staying in place if I tip the motor "gearcase up" when I pull the case cover off? I'd like to use their current shimming as a starting point if possible.
Do you suggest any gasket cement or sealant on the newgasket? The manual doesn't seem to call out any. Do you recommend a certain brand of gasket to use (or stay away from) ?
Because the engine is out of the frame and is easy to move around, will the shims & gears have a better chance of staying in place if I tip the motor "gearcase up" when I pull the case cover off? I'd like to use their current shimming as a starting point if possible.
Do you suggest any gasket cement or sealant on the newgasket? The manual doesn't seem to call out any. Do you recommend a certain brand of gasket to use (or stay away from) ?
Stellar HDF Member
Joined: Feb 2006
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From: Houston Texas
RE: Gearcase Gasket Replacement
OK, if the engine is out on a bench, yes, you can turn it on it's left side and then remove the cover. See what happens. The engine side has needle bearings (caged) that are pressed into the case.
The timing cover has bronze bushings pushed into the cover. What happens is when you remove the cover, the bushing holds onto the cam shaft tighter than does the needle bearings. That's my grand theory anyway. So, maybe you can try tapping the cover to loosen the bushings grip as you remove the cover? Worth a try.
Anyway, if some of the cams do slip out, the oil usually holds those thin shims close together. Just make sure to replace the correct stack back on the correct cam. This is not as bad as it sounds.
Then, as long as you trust that the shimming was correct (if the bike has been running OK, then all is probably well) go ahead and bolt it back up with out checking the end play on the cams. Be sure to check the cam timing marks though.
I use Permatex #3 gasket sealer. This is the non hardening type. I have used it for years and not found anything better. Tighten the timing cover screws in a cross pattern until they are tight. This helps get it seated flatly against the case.
Be sure to adjust the pushrod clearance correctly. You do know the procedure for that I guess.
If not, let me know and I can explain it.
One final thought....When you replace the pushrod tubes I recommend you replace the cork washers as well. There are 3 of them in each tube, so you will need 12. The rocker boxes have a deep recess in them where the flat flange of the tube will push up against the top cork washer. Be sure the cork and the flat flange are located in this recess. Otherwise, if you crank the engine and oil runs everywhere, the top corks are not seated on the tubes that leak and you need to go back and reseat them again.........pg
The timing cover has bronze bushings pushed into the cover. What happens is when you remove the cover, the bushing holds onto the cam shaft tighter than does the needle bearings. That's my grand theory anyway. So, maybe you can try tapping the cover to loosen the bushings grip as you remove the cover? Worth a try.
Anyway, if some of the cams do slip out, the oil usually holds those thin shims close together. Just make sure to replace the correct stack back on the correct cam. This is not as bad as it sounds.
Then, as long as you trust that the shimming was correct (if the bike has been running OK, then all is probably well) go ahead and bolt it back up with out checking the end play on the cams. Be sure to check the cam timing marks though.
I use Permatex #3 gasket sealer. This is the non hardening type. I have used it for years and not found anything better. Tighten the timing cover screws in a cross pattern until they are tight. This helps get it seated flatly against the case.
Be sure to adjust the pushrod clearance correctly. You do know the procedure for that I guess.
If not, let me know and I can explain it.
One final thought....When you replace the pushrod tubes I recommend you replace the cork washers as well. There are 3 of them in each tube, so you will need 12. The rocker boxes have a deep recess in them where the flat flange of the tube will push up against the top cork washer. Be sure the cork and the flat flange are located in this recess. Otherwise, if you crank the engine and oil runs everywhere, the top corks are not seated on the tubes that leak and you need to go back and reseat them again.........pg
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RE: Gearcase Gasket Replacement
Thanks,
I'll update the progress of this project as I go.
It always amazes me what you find after you get 20 or 30 years of "character" on a bike. Unfortunately, I have already found a coupleareas where the previousmechanic got his "inch pounds" and "foot pounds" of torque mixed up.... Broken and stripped fastners suck.
If tight is good......then.....super crazy monkey tightmust be better.
I'll update the progress of this project as I go.
It always amazes me what you find after you get 20 or 30 years of "character" on a bike. Unfortunately, I have already found a coupleareas where the previousmechanic got his "inch pounds" and "foot pounds" of torque mixed up.... Broken and stripped fastners suck.
If tight is good......then.....super crazy monkey tightmust be better.
Cruiser
Joined: Feb 2007
Posts: 102
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From:
RE: Gearcase Gasket Replacement
Be sure to adjust the pushrod clearance correctly. You do know the procedure for that I guess.
If not, let me know and I can explain it.
One final thought....When you replace the pushrod tubes I recommend you replace the cork washers as well. There are 3 of them in each tube, so you will need 12. The rocker boxes have a deep recess in them where the flat flange of the tube will push up against the top cork washer. Be sure the cork and the flat flange are located in this recess. Otherwise, if you crank the engine and oil runs everywhere, the top corks are not seated on the tubes that leak and you need to go back and reseat them again.........pg
I Have a Question along the lines you mentioned during this post, but the Main one is, do You use a different P/R Adjusting procedure for these than what might be in a Repair Manual? If so, Would You explain it Please? This is Trying to help a Friend of mine with a 1979, and he has lost/misplaced, the rear ex. cam, and gotten ahold of a set of Siftons, (NOS) from Somebody. No Paperwork what so ever. The Markings on the box say Sifton PB+. I Don't know If in fact this IS what they are, or not. They still have the Green Plastic screening around them, That's about All I know about them. I was at a shop Trying to look up the correct Seals for the P/R tubes, and the Cam Cover, and the Guy asked me, Early 79, or Late 79? I Guess it was for the Seals. I Would Not mind your explanation/Procedure for adjusting though. These (on my Buddies Bike) are a solid P/R, and adjustable Tappets/Lifters, sound right? any and ALL help on this Beast is Very Much Appreciated.
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Joined: Feb 2006
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From: Houston Texas
RE: Gearcase Gasket Replacement
Hogman55.....
I didn't mean to sound like I had some secrete way of adjusting the pushrods, because I do not.
The important thing is to just do it correctly.....like it says in the book.
Here are a couple of things that make it easier though.
The engine should be stone cold.
Raise the rear wheel off the ground and put the bike in 4th gear.
Remove both spark plugs.
Remove the keepers for all 4 pushrods and collapse the covers.
I use 4 rubber bands with a bent paper clip at each end to hold the pushrod tubes up.
Now you are ready to adjust.
Using the rear wheel, move it forward to rotate the engine. Watch the rear intake lifter come up to it's highest point. Stop. You can now adjust the front intake. Do the same for all of the pushrods. The pushrod you want to adjust is ready when the like pushrod in the opposite cylinder is at it's highest point.
The adjustment is made by backing off the lock nut and turning the adjuster down until noticable slack is detected.
Then put one single finger tip against the pushrod and roll it back and forth while raising the adjuster. The correct adjustment is when you can just barely rotate the pushrod 360 degrees with that one finger. Tighten the locknut.
After all four are done, heed my advice regarding the tubes and corks when you put the tubes back in place.................pg
I didn't mean to sound like I had some secrete way of adjusting the pushrods, because I do not.
The important thing is to just do it correctly.....like it says in the book.
Here are a couple of things that make it easier though.
The engine should be stone cold.
Raise the rear wheel off the ground and put the bike in 4th gear.
Remove both spark plugs.
Remove the keepers for all 4 pushrods and collapse the covers.
I use 4 rubber bands with a bent paper clip at each end to hold the pushrod tubes up.
Now you are ready to adjust.
Using the rear wheel, move it forward to rotate the engine. Watch the rear intake lifter come up to it's highest point. Stop. You can now adjust the front intake. Do the same for all of the pushrods. The pushrod you want to adjust is ready when the like pushrod in the opposite cylinder is at it's highest point.
The adjustment is made by backing off the lock nut and turning the adjuster down until noticable slack is detected.
Then put one single finger tip against the pushrod and roll it back and forth while raising the adjuster. The correct adjustment is when you can just barely rotate the pushrod 360 degrees with that one finger. Tighten the locknut.
After all four are done, heed my advice regarding the tubes and corks when you put the tubes back in place.................pg
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Cruiser
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RE: Gearcase Gasket Replacement
I didn't mean to sound like I had some secrete way of adjusting the pushrods, because I do not.
Oh, OK, That's Fine.
After all four are done, heed my advice regarding the tubes and corks when you put the tubes back in place.................pg
Will Do Sir, Thank You for The Reply, And The Help.
Thanks PG, Hogman
Oh, OK, That's Fine.
After all four are done, heed my advice regarding the tubes and corks when you put the tubes back in place.................pg
Will Do Sir, Thank You for The Reply, And The Help.
Thanks PG, Hogman
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