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backfill 11-27-2013 10:51 AM

The horror, the horror
I ride a 1992 R100R, but I just picked up a 1975 R75/6 as a winter project for $1500.

The good.

This bike is in good overall shape and ran great. It was cold when it was started but there was no hint of smoke. I rode it up and down the road a bit to be sure the transmission was working properly - it was shifting fine. The lights and horn all work and everything seems complete and fairly original. I think it was well taken care of for most of its life and hasn't sat outside too much. I even got a large envelope full of receipts showing what has been done to it. None of the receipts are recent.

The odometer shows only 16,000 miles, but I don't think it is working at this time.

The Bad:
Someone with anger management issues took a large hammer to the motorcycle. The right cylinder took the worst of the temper tantrum.

But the left didn't get off too easily.

The front hub even took a beating

And they even sliced the seat and cut out the BMW emblem from the back. I guess the emblem was taken as a memento.

Who does this to a perfectly good motorcycle???? I don't get it. I think it was done very recently too.

I decided to take the R75/6 home and give it some love. In the light of day, I am wondering if this was a mistake. But it is mine now, so I move forward. I will list what I think needs to be fixed, so feel free to correct me if I am wrong.

After that beating, it astonishes me that this bike even runs, but runs perfectly, with no clatter or weird noises at all. Someone on the Old's Cool Forum commented about their old Moto Guzzi; they had never had a bike with so many things wrong with it keep running. I guess I can say the same about this old BMW.

I need to clean the gunk from the rocker covers and replace the gaskets; I believe this is pre - temper tantrum gunk. Perhaps this seemed easier than changing the gaskets.

My main concern with the broken fins is overheating in the summer and uneven heat distribution (besides the fact it is pretty ugly with broken cooling fins) so I want to replace both heads. To the best of my knowledge, the R60, R75 and R90 heads are all the same (perhaps not the R90S head) so I just need to find /6 heads or later and they will fit this engine.

The left cylinder appears to be in good shape, but the right is missing some fins so it should be replaced. Among the receipts I found one for two first oversize pistons, so I am assuming they are already in the engine. Given this, any cylinder I find will have to be bored out (if not already). Once the heads are removed, I believe the size should be marked on the top of each piston so this will confirm the size. I think both the left and right cylinders are exactly the same, so i just need to find an R75 cylinder in good condition.

The front hub obviously needs work; I am not sure if it can be fixed or has to be replaced. Google will be my friend. The mufflers are a bit dinged up, but serviceable at this point.

I will also do the usual fixes, including oil, brakes, etc. I haven't yet lifted the tank to look at the master brake cylinder. If it is wonky, I think I can replace it with a later bar mounted master cylinder, but I need to check what year and style will work. The tires look good, but they date to 2005 so they should also be replaced.

I am hoping not to spend too much money, but that is probably a crazy notion at this point. I suppose, to be really cheap I would just ride it as is, but I don't think that is a good idea. I will watch IBMWR and ebay for parts, but if anyone has any leads or suggestions, I would really appreciate hearing from you.

When I am done, this will be a runner not a show bike. But I would like it to have it in good, dependable shape before riding too far.

Sigh. What have I gotten myself into. :eek1


Padmei 11-27-2013 10:54 AM

Well have to admit there are a few times I'd have liked to take a hammer to some of the BMW engineers who designed things - but to the bike- nah:D

I've wondered at times what exactly would happen if the fins were shaved off.

ozmoses 11-27-2013 11:22 AM

Man, that's sad! Divorce?

Make her purty all over again.

Pokie 11-27-2013 11:55 AM

If you take a course at the local college, you could build up or replace the fins by welding them. Unless you have a friend that's a welder, maybe you could ask him to help save the cylinders and heads. They arn't junk, they just need help.

Kai Ju 11-27-2013 11:56 AM

That does look like divorce generated anger....or the PO really pissed somebody off

usgser 11-27-2013 12:04 PM

R75's are great standard motorcycles and worth fixing to have a good rider. Granted he broken fins are pretty weird but not a game ender.

picinisco 11-27-2013 02:10 PM

I only had one fin to be repaired but multiple should be just fix, repeat.

Looked like PO had used a crowbar to try and remove the cylinder but to no avail.

Slipped a piece of aluminium (3/16 thick if I remember) between the vanes and followed the break and estimated the outside edge.

Cut the piece out on a bandsaw, chamfered the edges and gave it to a handy welder that I keep as a friend.

Good as new.

crazydrummerdude 11-27-2013 02:29 PM


Damn! Someone knew what they were doing when they banged that one up! You'd expect a belligerent ex to just take a baseball bat to the tank and headlight, not a hammer and chisel to the engine. Ouch.

But, like has been suggested, I'd try to have the fins repaired. You already have a complete bike and all the correct parts. See if you can just take the heads/cylinders off and have them repaired. There's gotta be some old school guys around who would like the challenge, if not yourself.

That wheel needs to be replaced, though.

SculptD 11-27-2013 02:52 PM

It's those long Canadian winters!

Stagehand 11-27-2013 06:44 PM


Originally Posted by Padmei (Post 22872952)
Well have to admit there are a few times I'd have liked to take a hammer to some of the BMW engineers who designed things - but to the bike- nah:D

I've wondered at times what exactly would happen if the fins were shaved off.

Our German friend Manuel shaved off every other one, for weight savings :deal

It would create local hotspots is the concern.

Normally I'm a fan of fixing fins, but thats quite a bother. Easily comes up against the cost of new/used heads.

Id replace that hub for sure.

hardwaregrrl 11-27-2013 08:24 PM

Wow! What a fucking shitbag....I've never seen a motorcycle so damaged in anger. Cars....Yes. Seems like a screaming deal for a Canadian bike, seeing as it runs and rides just fine. Sorry about the shitcan crap you've got to fix. I think you'll be in the black when done.

bmwhacker 11-27-2013 08:34 PM

nice find.:clap
Someone had a vendetta.(?)
Replacement cylinders / heads can be found pretty cheap on EBay.....wheels too....I wouldn't screw around welding on fins. Cheaper / easier to replace the heads / cylinders....just my $.02.
You could boost her up to 900 cc if you wanted.

tlub 11-27-2013 09:34 PM

Anger bike- need correct heads
Just thought I would point out that the R60/6, R75/6 and R90 all had different heads. Different volumes and maybe different valves on the R60. Certainly different diameters. They will not cross-fit.
If you buy replacements, be really, really sure you match the outer diameters of the cylinders. All /5 and /6 built before September of 1975 were one diameter, later were larger in anticipation of the R100 bores. You could (not ideally) put a smaller cylinder in a larger hole if you somehow shimmed it or aligned it in some way; to put a larger cylinder (like an R100) in a pre-9/75 block will require machining.
Good luck.

ME 109 11-27-2013 09:47 PM

Sledge hammer attack.

R100LT 11-28-2013 04:30 AM

A couple of my ex'a threatened my bikes ... But they were more of kicking the bike over and a match in the tank sort of girls .

That's why my bikes were the first thing to be removed or hidden before the break up talk ... " it's not you ... It's me ... I just think I can do better "

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