Changing That Gearbox Gasket

[neo]

Hi All,

I've noticed a seepage of oil coming from the central gearbox gasket and I want to replace it.

I've done just about everything on a bike before except split a gearbox, so I want to make sure I get it right and I'd like to do this as efficiently as possible. I've read the "Sherco Engine Teardown and Assembly Manual" but I'd also like advice from those who know....

So for those who have done this on a Sherco before can you please give me you opinion on the following:-

1. Do have any tips that will make the splitting easier?

2. After removing the head, is it possible to just work from one side of the engine (removing the cover from that side). while leaving every thing still bottled on, on the other side ?....e.g. Can I remove the clutch side case while leaving the generator flywheel and drive sprocket still on, on the other side?...or would it be simpler the other way around?

3. When fitting the new gasket is it better to use some form of gasket seal (if so, which one)?....or better to do without a replacement gasket and use one of those "Instant Gasket" products?

4. What other seals, springs, shims and bearing should I replace while the case is open?

5. Am I wasting my time...is it this far too hard for a mere mortal and should I pass it onto a someone that's done it before?

As much detail as you can spare the time for would be appreciate.

Many thanks for your help.

Best of balance.

Neo

[copemech]

Hi All,

I've noticed a seepage of oil coming from the central gearbox gasket and I want to replace it.

I've done just about everything on a bike before except split a gearbox, so I want to make sure I get it right and I'd like to do this as efficiently as possible. I've read the "Sherco Engine Teardown and Assembly Manual" but I'd also like advice from those who know....

So for those who have done this on a Sherco before can you please give me you opinion on the following:-

1. Do have any tips that will make the splitting easier?

2. After removing the head, is it possible to just work from one side of the engine (removing the cover from that side). while leaving every thing still bottled on, on the other side ?....e.g. Can I remove the clutch side case while leaving the generator flywheel and drive sprocket still on, on the other side?...or would it be simpler the other way around?

3. When fitting the new gasket is it better to use some form of gasket seal (if so, which one)?....or better to do without a replacement gasket and use one of those "Instant Gasket" products?

4. What other seals, springs, shims and bearing should I replace while the case is open?

5. Am I wasting my time...is it this far too hard for a mere mortal and should I pass it onto a someone that's done it before?

As much detail as you can spare the time for would be appreciate.

Many thanks for your help.

Best of balance.

Neo

A number of things come to mind here, firstly they seldom leak!

Second, I presume you are referring to gearbox oil?

Third, have you checked all the bolts for torque? As I seem to recall bolts from the mag side under the flywheel, this may be necc.

To pinpoint a leak, we often use a floroescent dye added to the oil to reveal casting pinholes and such which could be sealed externally! Takes a black light to spot them! This is a process, yet you must understand that a gasket may not fix it! You must KNOW for sure what you are fixing! Even a small crack can be near invisable to the eye! Tread lightly and do not jump to conclusions! You could perform a lot of work for nothing, my experience!

[neo]

Awsome reply Cope.

But where do I buy that floroescent dye from?...does it have a specific name I can search the net for?

Best of balance.

Neo

[alan bechard]

To answer last question first, good autmotive supply house should be able to provide you with dye, glasses etc.

I usually use Brake cleaner, talcum powder and patience. (Patience is always in short supply at my house)

I would look real close at what cope said first, are the bolts tight.

I would also look to see if the bolts did not come loose, and you hit the pan hard enough to shift the two cases relative to each other. I have not seen this yet on the sherco, but I have seen it on other older bikes, and I am guessing that your bike has hit the pan a time or two.

Have you read the instructions on the web on how to do it? I would have them printed out beside me when I was doing it.

It sounded as I read it like you were saying you were going to do it in frame, maybe I am reading wrong, but anyway I do not think it can "PRACTICLY" be done in the frame. Not impossible, just not at all the way I would do it.

You will need a 1/2" impact gun or clutch holder. A deadblow rubber mallet / brass mallet is very nice at times.

Take your time, watch for shims, washers etc. Touch things and make sure you are not looking at a shim, stuck on a case with oil, that when you later wash the case falls off in the Parts washer and gets lost.

I have a square of 2 X 4 lumber about 12" on each side. It is probably my handiest tool to work with the engines. It allows you to set the engine down at about any angle, and have it be stable and firm.

A handy thing to do is to have a digital camera handy (and an agreeable kid to take pictures so You don't get the Missus camera oily) Take lots of pictures, especially anytime you say to yourself, oh, I will remember the purple widget goes on the right.............................. You wont.

They are very straight forward, and easy to work on. I would say go for it, but all the better if you have someone experienced and confident at your side who knows the difference between stuck, hit it harder, and you forgot and left a bolt in.

Oh, and when it comes to putting it back together

I like to grease the gaskets.

If it does not "slide" together, you have it wrong, when you find yourself saying I will just draw it down into place, you are wrong. Not quite sure how to explain the difference in writing, because you can use the bolts to draw it down, but it has to "feel" right. Again, that is where an experienced hand on your shoulder can really give you some confidence.

[schweizmeister]

Previous posts are good information. I changed the main bearings on a Sherco and it was very straight forward. Probably two hours to strip, four or five hours to rebuild, back in frame ready to go.

One point I would make is take this as an opportunity to strip and inspect condition of all bearings, seals, piston, rings etc. There is really no point in trying to save time on not disassembling the full motor.

Best of luck - next time will be easier!

[stork955]

Gday Neo, find the leak first! Wash it down well with degreaser and ride a little bit till you find the actual location of the leak. (Use Talcum if neccessary as Alan said above) Then have a good look at it to see what's going on. If you can avoid splitting the cases it will be better for you! "3 Bond" is the only sealant to use, available from a Bursons Auto Parts near you. Use they Grey Case Sealant. It will work even if you apply it to the outside of the case at the leak point.

Cheers,

Stork

[copemech]

To answer last question first, good autmotive supply house should be able to provide you with dye, glasses etc.

I usually use Brake cleaner, talcum powder and patience. (Patience is always in short supply at my house)

I would look real close at what cope said first, are the bolts tight.

I would also look to see if the bolts did not come loose, and you hit the pan hard enough to shift the two cases relative to each other. I have not seen this yet on the sherco, but I have seen it on other older bikes, and I am guessing that your bike has hit the pan a time or two.

Have you read the instructions on the web on how to do it? I would have them printed out beside me when I was doing it.

It sounded as I read it like you were saying you were going to do it in frame, maybe I am reading wrong, but anyway I do not think it can "PRACTICLY" be done in the frame. Not impossible, just not at all the way I would do it.

You will need a 1/2" impact gun or clutch holder. A deadblow rubber mallet / brass mallet is very nice at times.

Take your time, watch for shims, washers etc. Touch things and make sure you are not looking at a shim, stuck on a case with oil, that when you later wash the case falls off in the Parts washer and gets lost.

I have a square of 2 X 4 lumber about 12" on each side. It is probably my handiest tool to work with the engines. It allows you to set the engine down at about any angle, and have it be stable and firm.

A handy thing to do is to have a digital camera handy (and an agreeable kid to take pictures so You don't get the Missus camera oily) Take lots of pictures, especially anytime you say to yourself, oh, I will remember the purple widget goes on the right.............................. You wont.

They are very straight forward, and easy to work on. I would say go for it, but all the better if you have someone experienced and confident at your side who knows the difference between stuck, hit it harder, and you forgot and left a bolt in.

Oh, and when it comes to putting it back together

I like to grease the gaskets.

If it does not "slide" together, you have it wrong, when you find yourself saying I will just draw it down into place, you are wrong. Not quite sure how to explain the difference in writing, because you can use the bolts to draw it down, but it has to "feel" right. Again, that is where an experienced hand on your shoulder can really give you some confidence.

Again, Al makes good points from(he,he) Lots of experience screwing with things!

Back to pure basics:

Isolate the problem, insure things are tight, and fact is that a good sealer can work wonders on this type of thing!

[alan bechard]

Again, Al makes good points from(he,he) Lots of experience screwing with things!

Back to pure basics:

Isolate the problem, insure things are tight, and fact is that a good sealer can work wonders on this type of thing!

Why thanks Cope (I think) heehee

Just had the top off the fuel control on the backhoe

It still runs,,,,,,

[copemech]

Why thanks Cope (I think) heehee

Just had the top off the fuel control on the backhoe

It still runs,,,,,,

That is a good thing Al, you see, I never get to have any fun anymore, I have to have all this crap in certified and warrantable condition and all that.

Of course, with the auto industry in turmoil and all that, we may get back to some good old fashoned "Obama Riggin" here before long!

We can fix the world! With enough money!

[neo]

Just an update on this......And just to let you know that you guys are my HEROS!!!

There was no gearbox leak after all....it was Two stroke oil residue from petrol dripping out of the vents on the Keihin.

Anyway along the way I did a few jobs that I should have done months ago. Cleaned and polished the bash plate and put 3 tubes off of he Keihin.

I also do the Fuel Valve Standpipe Modification (Sherco Mod suposively for 03/04 bikes) which has cured a lean running problem I had for some time.

Long story short my bike has never run so good....It's like a New BIKE!!!

So I bow before you ... yea great ones

Next time your passing through Sydney your more than welcome to ride my bike at my place....In between drinks that is..

Best of balance.

Neo

Edited November 24, 2008 by Neo

[alan bechard]

Cope, I know what you mean.

Neo, glad you got it sorted out, nothing quite like working on something a whole bunch, to realize you missed something simple,

Not that I have ever done it, I think Cope told me about it once

I will have to forever Ban SWMBO from seeing this thread, as she will ask your adress and send you our flight # as what better reason to go One day we need to come visit your country though.

Glad it is straight.