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apt13 01-28-2012 05:31 AM

spline lube and transmission questions
after a successful fork rebuild a couple weeks ago, i thought i'd try my hand at the famous "spline lube" while i have some garage access this winter. i've been reading up on a ton of posts and forums about the process of just pulling the transmission back an inch or so and doing it that way, but i've been thinking about going "all in" and taking it completely off and poking around a bit.

as i've mentioned in previous posts, i have zero history on the bike so i've been trying to get all the main parts checked out when i have the opportunity and i assume this will be the perfect time to check on other things while i have it all apart.

i haven't been able to find any posts where anybody does this specifically and was wondering if anyone could give me a general list of the "easy" things to check while i'm in there. i've got the clymers and haynes books which i assume will give me the process in getting the trans apart, but i'm not really sure what i'd be looking for and what would look bad or not.

things i can guess i should check (from what i've heard) would be the flywheel, rear main seal, neutral switch. lube the splines as my intention in the first place. anything else? what would i be looking for in those areas listed?

also, is there anything i should be careful with or avoid?

thanks in advance!

disston 01-28-2012 08:41 AM

Depends a little on the mileage this machine has. A little on whether this is hard or easy miles, judgement call. And whether you want to do the rear seal just because you are the get it out of the way now kind of guy.

I recommend that you pull the trans out to do just the spline lube. Use Honda Moly 60, available at Honda dealers but they usually have to order it, or on line. You will be also greasing the rear wheel bearings and the swing arm bearings so you need wheel bearing grease, get the tub of grease that looks like a colorful margarine tub. You also need the gasket for between the swing arm and Final Drive, that's cheap. And before you take it apart look at the drive shaft boot and it's two clamps. If the boot is cracked replace and the clamps should be in good order.

The spline lube grease goes only on the male splines of the transmission input shaft. DO NOT put grease on the female splines of the clutch disk. You have been warned.

Also grease the splines of the rear wheel and away you go.

LonerDave 01-28-2012 08:51 AM

Based on my very limited experience:

Look for oil leaking onto the shelf below the bell housing, if it's engine oil, the rear main seal or oil pump cover gasket is leaking. Might consider replacing both if you're in that deep. If it's hypoid oil, the gear box input seal is leaking.

If you determine that the RMS or oil cover is leaking and must be replaced, BLOCK THE CRANKSHAFT before you remove the flywheel. Some folks have trouble getting the oil cover screws out. An impact driver helps. Northwoods Airheads sells allen head screws to make this a non-issue going forward. You'll also have access to the clutch plate and spring, which you can measure for wear.

If you remove the swingarm to completely remove the gearbox, you'll have the chance to inspect the final drive splines. Use new bolts (short, without washers) when reattaching the driveshaft to the gearbox output.

I'm sure there're are things I missed. But I just went through this on my /6, and these were my learnings.

Good luck.


Bill Harris 01-28-2012 09:50 AM


i've got the clymers and haynes books which i assume will give me the process in getting the trans apart
No. Do not disassemble the tranny based on having Clymers and Haynes. Not a good idea.

supershaft 01-28-2012 11:33 AM

The famous spline lube? Does your clutch have grabby engagement? If it doesn't, it doesn't need the splines lubed. Regular spline lubes are probably the biggest waste of time you can do for yourself since they don't help the bike. In my experience from working on tons of airheads, chances are highly likely that your bike needs some other maintenance way worse. Sure, I do it when people insist. I happily do it when they need it but that is rare. It is usually after the bike has been sitting for a long while. That has a lot more to do with grabby splines than mileage. Spline wear? I have seen just as many worn splines on bikes that got regularly lubed as not. Personally I never lube mine other than when I have my tranny out anyway for something for three decades now and have never had any worn spline issues.

Oil pump cover? Always heat the bolts/screws before you loosen them. Some people put red loctite on them! Those threads are often buggered for whatever reasons including people over tightening them. Use the proper inch pound torque wrench. The threads often need cleaning. Clean them with a thread chaser or a roll tap. Do not clean threads with cutting taps because they remove too much material during each pass. That's my advise. :D Good luck!

pbarmy 01-28-2012 11:35 AM

Maybe block the crank,if messing with the rear seal?:ear

disston 01-28-2012 01:32 PM


Originally Posted by pbarmy (Post 17854873)
Maybe block the crank,if messing with the rear seal?:ear

It is a $2000 mistake to remove the flywheel with out first blocking the crank. The way it happens is that everything is going along just fine and the new seal is installed but nobody noticed the bike got bumped and because the flywheel is what positions the crank, the crank moves. If the crank moves forward, about the only direction it can go, the inside thrust bearing may be pulled off it's perch, or it may fall but once this bearing moves you have trouble. If you notice there is a problem and want to fix it before bolting everything back together you can remove the Left (I think it's Left) cylinder and heads and pipes and pistons and rings and rods and bearing, to make enough room, to reach in with a long sharp pointey thing and put the thrust bearing back in place.

That's why you block the front of the crank to prevent movement anytime the flywheel is removed from the crank shaft.

So far the only expense of this mishap is a bunch of new gaskets, head, base, maybe oil pan, and time. If you didn't notice that the thrust bearing had moved and bolted the flywheel back on it can, will, bend the thrust bearing. To replace this the crank has to come out. That's getting close to $2000, I think.


disston 01-28-2012 01:38 PM

I think it's good advice that SS gives. If the bike shifts and there is no symptom of dry splines, if there's no oil on the shelf under the trans, then there are usually other things that might need more attention.

I don't know where it comes from but we Airheads do get obsessed with spline lubes. Maybe it's the fact that "certain" problems with shifting can be cured by a spline lube. If you don't need it why bother, unless there for other reasons.

apt13 01-28-2012 04:50 PM

haha! thanks guys. i knew i'd get some good responses as usual. thats why i have grown to love this place.

here's the deal. i am not an airhead aficionado or anything. all i know about them is basically what i get from here and bmwmoa and i'm lucky i have nathan down the road at boxerworks when i get in way over my head. i know there is a lot of mention about the "spline lube" so i thought i'd give it a go.

like i said i have zero history on this bike. in general it rides great. there are weird things here and there that i encounter probably from various previous owners (like painters tape holding electrical wires together-yikes!), but all in all everything basically functions correctly, as far as i know. i fix things when they come up with the help of you excellent folks and it is a great deal of fun for me (and frustrating at times).

does the bike NEED the spline lube? haha. i have no idea. to be honest, i don't know what a "grabby" clutch means. i've never had a problem shifting the gears other than what i've understood as the usual clunkyness everyone says is normal. sometimes its more clunky than other times. but i don't know if thats good or bad.

iv'e been through and fixed most the electrical problems, starter problems, and whatever mechanical/carb problems i've encountered. i just rebuilt the forks. and i have the bike in my folks garage (i don't have one) so i figured "what the hell," a lot of people list the spline lube as routine maintenance, i have no idea if it has ever been looked at or done, might as well take a look while i have garage access.

if the consensus is "don't bother", haha, i would surely take that into account as you folks have lifetimes worth of experience and i have 2 years.

or maybe i should just wait for a local tech day and be a guinea pig? i'm down with that.

bmwhacker 01-30-2012 09:43 PM

An Airhead Tech Day would be a good idea....nothing like having a couple of experienced guys ridiculing / slobbering beer :freakyall over while you follow their directions.....:lol3.....No seriously, that is how I learned the technique, from a couple guys who could do it in their sleep. Whether your bike needs it or not, you'll have it done and learn something you'll always have with you....unless you are old like me and can't remember what I did this morning....:cry

These bikes are so user friendly that once some of the "mysteries" are exposed you'll be confident performing all your own work & maintenance. It is not rocket science and these old machines are actually pretty simple..

100RT 01-31-2012 05:49 AM

I'm from the other side of the fence on spline lubes. Since you have no history of the bike, I would have a look and lube then you know where you stand.
No surprise's out in the middle of BFE! It happened to me. Even the newer oilheade are experiencing the issue of failed splines.

Bill Harris 01-31-2012 10:24 AM

Lubing the splines doesn't hurt, and it give a good excuse to inspect the clutch, oil seals and bond with the bike. I'm on the "lube" side of the fence. I've seen dozens of cases where a grabby, sticky clutch was corrected by spline lube. Lubiing the rear wheel splines on a pre-Monolever rear wheel is an absolute must, OTOH...

And, when we run out of oil, tire and dual-plugging threads on cold Winter days, it gives us something to talk about. :lol3:rofl:lol3

So there.

thevulture 02-01-2012 01:46 PM

Just did one last weekend at the Fullerton Tech Day. I was very surprised at how simple it was. We followed Snowbum's tutorial, read it a couple times before you start and follow it as you go. One thing that wasn't in there that we did was, before tightening the trans all the way back on was to put the bike into to neutral and hit the starter about 5 times to make sure nothing got misaligned/bunged up. Had it done in about 3 hours, with help. Good luck!

bmwrench 02-01-2012 08:44 PM

I think the early bikes ('70-'80) need spline lubes far less frequently than '81 and on. Their felt seal on the pushrod allows a tiny bit of oil onto the splines in a kind of controlled leakage. The later bikes, with a proper garter seal on the pushrod keeps the splines very clean. I don't think I've ever seen an early bike with dry splines, unless it had been sitting a long time.

supershaft 02-01-2012 09:19 PM

I have but I don't think dry looking splines has anything to do with them needing to be lubed. They can look bone dry in a couple of thousand miles and they won't need to be lubed ever again if the bike doesn't sit too much. That is if the clutch action doesn't get grabby which they rarely do if they haven't sat for too long. From what I have seen time and time again lubing the splines does not help them from wearing as much as never lubing them makes them wear. What can go wrong lubing them besides most often wasting your time? Getting grease all over the clutch. That and what ever else it was that you should have really been maintaining.

If I bought a used bike and the clutch was grabby you can bet your boots I would lube the splines. When I bought my R100 I didn't lube the splines but the clutch wasn't grabby. I did lube the splines when I put my close ratio gear set in but that was the first and last time I have lubed the splines on that bike. That was right at 70,000 miles ago.

I am just trying get the flip side of the issue out there. Not too many do from what I read. I have worked with a couple of techs in my camp on this issue but alas my camp is rarely on the net. Imagine that! :D

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