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Old 09-27-2013, 12:33 AM   #16
disston
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Had an idea this might be the case.

Not sure how close this is to you but it would be advisable to take that transmission to somebody that does Airhead transmissions. There are several operations that should be done by Airhead experts. This is one of them.

http://www.beemershop.com/

Ted Porter is not only one of the Airhead Gurus he is one of the transmission rebuilders recommended most often. There are only half a dozen mechanics that will get regularly recommended for this work.

While the transmission is being done has the clutch been measured and the rear main oil seal replaced yet? This work is usually done while the transmission is out.

If the flywheel is on the engine it has to be removed to get at the rear main oil seal. Make sure the crank is blocked up front under the engine cover so the crank can't be moved while the flywheel is off.
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Old 09-27-2013, 07:42 AM   #17
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Personally, the transmissions on these bikes are pretty easy to get in and out. I'd just rebuild the transmission and plop it back in, assemble the bike and see how it does. I wouldn't pull the clutch and I wouldn't pull the flywheel without good reason. If there's black oil everywhere and dripping on the floor, that's good reason. Just idle curiosity, that's not a good reason.

If you go looking for trouble, you're going to find it.
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Old 09-27-2013, 11:57 AM   #18
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Originally Posted by Pokie View Post
Personally, the transmissions on these bikes are pretty easy to get in and out. I'd just rebuild the transmission and plop it back in, assemble the bike and see how it does. I wouldn't pull the clutch and I wouldn't pull the flywheel without good reason. If there's black oil everywhere and dripping on the floor, that's good reason. Just idle curiosity, that's not a good reason.

If you go looking for trouble, you're going to find it.
lets say your transmission was having problems and you had your choice between two mechanics:

One is a seasoned pro with a well earned reputation for solid work. he has all the needed tools, does lots of them, tons of experience and excellent judgement. He finds a problem here and he knows what else is going to be weak and ought to be fixed there to avoid future failures.


The other is a complete beginner. He's never done one before but he's eager to learn and make all the beginners errors---on your box. He has no supervision or anybody checking as he goes along, no one to show him the olds pro's tricks or supply the judgement that only comes with having made the errors already. He doesn't have the measuring gear to set it up but figures, hey, how complicated can it be? BUT, he's willing to work for free if you just buy the parts. Your transmission is his little learning project.



You just recommended he take it to the second guy.

If you're flipping it, what the hell. Throw some sawdust in it to shut it up, shine it up and get it on craigslist. You'll be long gone. That's as old as used car lots. But if you plan on depending on it...


I don't work on BMW transmissions because I know I will never be as good as the guy I want working on my transmission. I'm not a professional and I don't have the opportunity to get the kind of experience that I want in my transmission guy. And, having worked on different kinds of transmissions, I have a whole lot of respect for what these particular boxes need. I can set up a Rover 4 speed with a transfer case and rear PTO with a set of feeler gauges. You don't play that with a clamshell gearbox. I've also made the mistakes. The sound of a layshft thicker than your wrist snapping in half under your butt is ...mmm...memorable. Didn't seat a bearing right. Expensive bit of tuition. I don't care to have that experience on the other side of the country on a trip. I don't want to lay out a lot of cash for tooling I'll use extremely rarely (If I do things right)...it's cheaper to take it to any of a number of highly qualified individuals and know it'll be thorough and right and I can count on it 98.7%..
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Old 09-27-2013, 12:04 PM   #19
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Originally Posted by dilandau View Post
thanks for the replies.

1. It was cheap yes. so if i have to spend even 2k on the transmission id probably still be ok on resale.

2. I do not plan to sell.

3. I have heard they need rebuilds every 60k or so (on average) so I figured why not start fresh than deal with one that might go in 10k.

4. thanks for the rundown on transmission that will work. exactly what I was looking for- appreciate it. I have some time- so i'll be keeping an eye on ebay and making some calls.

5. I might have it tomorrow depending upon his schedule- otherwise next week. but i'm impatient and want to get a jump on the issue.

6. I can do most the heavy lifting mechanics myself- but might send the unit out for a rebuild depending upon how hard it is- and how much it is for someone else to do it.
Where did you get 60k from?

I get 110-120k on a 4 speed then you turn the shift forks around and throw in fresh bearings just because and do it again.

I have heard 5 speeds are not quite so durable. I have about 100k on one now with no issues. But I also have a backup in a crate so I'm not down while it's being worked on.
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Old 09-27-2013, 03:09 PM   #20
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?????

Who said anything about having a noob work on a transmission?

How the heck do you turn shifting forks around to wear on the other side?

Are we all talking about BMW motorcycles here?

Am I missing something?
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Old 09-27-2013, 03:35 PM   #21
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The OP is not trying to rebuild the transmission himself. He is willing to take it to somebody. It's important at this point to suggest what most of us know by now that the local gear head is probably not a good choice for someone to have look at your Airhead transmission.

"Ill probably bring it to an experienced local hand and pay for an opinion."

It can be an expensive lesson to learn about these bikes.

No mention of how many miles yet on this bike. The original rear oil seals are 37 years old. They almost always leak by the time the transmission bearings are going out or the clutch is worn out. But a figure on mileage or suspected mileage may be helpful.

No word yet on how much oil is under the trans on the shelf. The trans is already out. Was the shelf area cleaned? This is sometimes used to determine if further investigation would be advisable.

Part of the original post was mention of "noise" suspected to be transmission bearing and the PO has already pulled the transmission because of this. There was also a mention of "loosing power" This sounds more like a slipping clutch than any transmission problem.

Send the transmission in the box or take it to Ted Porter. Is this trip doable for you? It looks like an hour away to me on the map but maybe it's two hours. If they know you are coming they can probably look at it and give you advice on what to do next that will fit the situation and condition of this box.

If you take the transmission to Ted make sure you have all the pieces with you. He will attach the output flange when the rebuild is finished but if you forget to bring it it becomes difficult for you to have to do because it takes a special tool to take this part off or put it back on.

They will be able to mail the completed trans back to you.
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Old 09-27-2013, 03:48 PM   #22
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Originally Posted by disston View Post
The OP is not trying to rebuild the transmission himself. He is willing to take it to somebody. It's important at this point to suggest what most of us know by now that the local gear head is probably not a good choice for someone to have look at your Airhead transmission.

"Ill probably bring it to an experienced local hand and pay for an opinion."

It can be an expensive lesson to learn about these bikes.

No mention of how many miles yet on this bike. The original rear oil seals are 37 years old. They almost always leak by the time the transmission bearings are going out or the clutch is worn out. But a figure on mileage or suspected mileage may be helpful.

No word yet on how much oil is under the trans on the shelf. The trans is already out. Was the shelf area cleaned? This is sometimes used to determine if further investigation would be advisable.

Part of the original post was mention of "noise" suspected to be transmission bearing and the PO has already pulled the transmission because of this. There was also a mention of "loosing power" This sounds more like a slipping clutch than any transmission problem.

Send the transmission in the box or take it to Ted Porter. Is this trip doable for you? It looks like an hour away to me on the map but maybe it's two hours. If they know you are coming they can probably look at it and give you advice on what to do next that will fit the situation and condition of this box.

If you take the transmission to Ted make sure you have all the pieces with you. He will attach the output flange when the rebuild is finished but if you forget to bring it it becomes difficult for you to have to do because it takes a special tool to take this part off or put it back on.

They will be able to mail the completed trans back to you.
There are at least a couple of other well qualified airhead tranny guys around the Bay area. I use to be one of them but I am not one of them right now. Then, of course, there are plenty others outside the Bay area. You just don't see their names all over the net.
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Old 09-27-2013, 05:05 PM   #23
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Originally Posted by supershaft View Post
There are at least a couple of other well qualified airhead tranny guys around the Bay area. I use to be one of them but I am not one of them right now. Then, of course, there are plenty others outside the Bay area. You just don't see their names all over the net.
I only have what I know or hear about to go on. I had forgotten that you were in the Bay Area SS. But I have no other contact info or Web Page or address to say where your garage is. Everybody is getting busy right now or getting ready to be busy. What, are you retiring SS?

I know Ted porter personally and I know how to contact him. I also think he is a cut above even good.

Suggest somebody closer to Oakland.
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Old 09-27-2013, 09:19 PM   #24
supershaft
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Originally Posted by disston View Post
I only have what I know or hear about to go on. I had forgotten that you were in the Bay Area SS. But I have no other contact info or Web Page or address to say where your garage is. Everybody is getting busy right now or getting ready to be busy. What, are you retiring SS?

I know Ted porter personally and I know how to contact him. I also think he is a cut above even good.

Suggest somebody closer to Oakland.
I was always busy enough while trying to stay off the radar. I suspect that is the case with others I know in the Bay area. I would want to call up the couple of people I would recommend and ask them if it was alright to mention them on the idiotnet. I suspect it wouldn't be. There's an inmate here that I would recommend but he quit working on trannies. I can't say that I blame him. Hypoid stinks!!!! His good work has made a good name for a number of businesses in the Bay area. Good work is almost always not about where but who? Unless, of course, it's a one man operation. Personally? I am on sabbatical. I am shopping for a house and I could NEVER afford one in the Bay area and, if I could, I would never want to put myself in a corner like that. I have seen what it does to people and it usually isn't good.

FWIW, I think the four speeds being more robust than five speeds is an idiotnet/urban myth. I don't think I know anyone that actually works on and has ridden both say so. That is people I trust. For starters, the five speeds shift MUCH better than four speeds and that is just the tip of one big iceberg.

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Old 09-27-2013, 09:41 PM   #25
Plaka
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Originally Posted by Pokie View Post
?????

Who said anything about having a noob work on a transmission?

How the heck do you turn shifting forks around to wear on the other side?

Are we all talking about BMW motorcycles here?

Am I missing something?
You did.

Beats me, ask Matt, he did my last transmission. He's forgotten more about them than I'll ever know. I may also be mistaken and he was talking dogs or something. Tranny was popping out of 1st or second @about 110k miles. I'll ask him when I see him next. I have a crap 5 speed and rear drive that need attention. That garbage from Mike is really something. I'm tempted to crack the box just to have a peek, but I know how little mechanics like you bringing them them pre-monkeyed with stuff in boxes.

Yes.

Yes.

Any idea if the pushrod tubes through the heads are the same OD as the pushrods in the jugs?
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Old 09-27-2013, 09:53 PM   #26
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Originally Posted by Plaka View Post
You did.

Beats me, ask Matt, he did my last transmission. He's forgotten more about them than I'll ever know. I may also be mistaken and he was talking dogs or something. Tranny was popping out of 1st or second @about 110k miles. I'll ask him when I see him next. I have a crap 5 speed and rear drive that need attention. That garbage from Mike is really something. I'm tempted to crack the box just to have a peek, but I know how little mechanics like you bringing them them pre-monkeyed with stuff in boxes.

Yes.

Yes.

Any idea if the pushrod tubes through the heads are the same OD as the pushrods in the jugs?
They have two OD's. If I remember right, the smaller one is the same.
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Old 09-28-2013, 01:06 PM   #27
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The bike is a 1975 /6 with a 5 speed transmission. I suggest you do not consider any 4 speed transmission swaps unless someone gives you one of these free. This is a waste of energy and band width to consider this. The OP is willing to learn how to remove a trans and wants working bike. Not your Hot Rod BS. The GD 4 speed fans will do this every time a Noob shows up needing a 5 speed.

Do not buy a 1974 transmission. You will most likely regret it.

An option is a used transmission from Ebay. Not always the best option for somebody new to this. Better would be a used transmission from a wrecker that gives you a guarantee so you ended up with a working bike sooner. Another transmission from a wrecker should be a little cheaper than a rebuild but maybe not by much. You would have to call around and check prices and availability.

You mention a 60,000 mile figure for transmission life. This figure was used a number of years ago for the original transmission as a minimum. I think very few transmissions only lasted 60,000 but it may have happened. A rebuilt from one of the transmission experts should go more like 100,000 or close to it.

You have the opportunity to do this right. You have said the money can be available to build a reliable bike. One of the areas that needs attention on Airheads is the transmission. I mentioned Ted Porter as somebody I know is close enough to you and he is a BMW Guru, much respected with years of experience building these bikes. He is an Airhead transmission expert.

I forgot to put the link in the post I made mention of Ted so here is the link to his shop.

http://www.beemershop.com/

I strongly suggest that you do not try to have this work done by anybody that does not come with credentials for Airhead work.
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Old 09-28-2013, 03:41 PM   #28
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FWIW, I remember reading the "60K-ish means time for a rebuild soon" thing as well. I think it was Snowbum's site or a link from it. It also said that using full synthetic gear lube delayed this significantly.

He didn't pluck that number out of thin air.
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Old 09-28-2013, 04:12 PM   #29
Plaka
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FWIW, I remember reading the "60K-ish means time for a rebuild soon" thing as well. I think it was Snowbum's site or a link from it. It also said that using full synthetic gear lube delayed this significantly.

He didn't pluck that number out of thin air.
Can you find that on his site?

(better you than me )
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Old 09-28-2013, 04:38 PM   #30
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Snowbum edits his site so often that if it was there at one time it may not be there now. I do think he is the likely source of that figure tho. i think I have heard him write it years ago that way. It's not a bad figure for the lower limit of the OEM trans.

It is often said by many reliable sources that a transmission correctly rebuilt and accurately shimmed will be better that the original
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