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Teardown of a R75/7

P

pops

Pops
Hi I am Pops and I have a problem.

I am becoming an Airhead.

I have studied the bibles - both the factory and the Clymer versions.

I have listened to the preachers here in the forum.

I still made the conversion and I acquired a 1976 R75/7 which has been sitting for a dozen years. My son and I have taken on the resurrection of this fine Bavarian Beast to bring it back to its former glory as a project this year. The plan is to strip it down to the frame and start with a paint job/ bearing replacement and move forward.

Here is where we have run into what I figure will be the first of many hurdles. The exhaust nuts were frozen on and after trying Kroil for a few days and heat and the exhaust nut tool it became apparent that they were not going to cooperate. Have read much about this problem I cut them off - one quick zip with a hacksaw and a couple of sharp smacks with a cold chisel and both came off clean an the threads are in great shape.

What has us scratching our heads is that the pipes will not come out of the heads.
I have tried Kroil, heat, large deadblow hammer (gently) and cannot move the pipes.
It almost looks like the PO had sealed them with muffler epoxy (?) or they are an extremely tight fit. I cannot find any info on this and the manuals say nothing about it being so tight. Anyone have ideas or suggestions as to how hard I can push(hit) or twist these to get them out? Here is where we found it buried - with all the paperwork up until it was parked in 1999.

BarnFind.jpg


Thanks for any ideas.
 
I think Kroil and time is the answer, but... Have you removed the mufflers and rear clamps. That will give you some more wiggle room. How about the front crossover? I know it can't be removed until you get the headers off, but maybe you can loosen it or if nothing else, sacrifice it by cutting it off. With the crossover off and the mufflers off, you will be able to move the headers independently and find a position where they will slip off. And with any movement, the Kroil can work in deeper.
 
Thanks

Thanks Kurt,

I was trying to avoid cutting the cross member but I think it is going to happen.
I have been dosing with Kroil and trying to wiggle getting the crossover pipe free or
loosening the header - eventually something will move.
 
The crossover pipe is the simplest and least expensive thing to sacrifice...if you don't want to pay for a replacement OEM part, just trot on down to your local muffler shop and they can build a replacement that will clamp into place...so I think you're on the right track by cutting it gone and using the leverage you'll gain to loosen everything up...
 
Kurt is right above. I'd recommend starting with removing the two bolts on each side that secure the muffler to the subframe at the rear. Then remove or completely loosen the exhaust clamp at the muffler/header joint (just forward of the footpegs). Leave the front end secure for the time being. Now work on trying to twist and pull the mufflers off the header. If the header is frozen in the head, muffler removal will probably require lots of brute force as well, using a band wrench and maybe even some heat at the joint. Once you've finally wrestled the mufflers off, proceed to:

Work on removing or at least loosening the engine mount nuts holding the muffler clamps. Those engine mount nuts are torqued to 55 foot pounds (and are probably frozen as well, so use a breaker bar if needed). Once you have that header hanger clamp loosened proceed to the header itself.

When I remove my exhaust (to renew the antiseize paste in order to avoid this kind of problem) I use about a two foot long 2x4, hold it in the forward curve of the header, and whack the other end with a BFH. It can work really well if you have your son or a buddy standing on the other side and you can hand the hammer and wood back and forth to bring the header out about a half inch at a time. In your case, the key will be to just break the corroded bond between the header pipe and the head. I'd suggest the application of heat on the head, and then some good whacks. Best wishes for a great project.
 
Last edited:
Bill - That is what I needed to know- a 2X4 with a BFH. I didn't think it would hurt but it sure boosts the confidence to know others have done it. Tomorrow after work we will give it a go I'll let you know how we make out.

Thanks for the input.
 
75/7 Model is a 1977

Pops if your bike is a true /7 it is one of 1450+ units brought in to the US and the last of the 750's made.
I did a frame up clean and replace all worn or damage parts job on my 75/7.

Will follow the thread and help as necessary.. Patience and time will prevail.

What does the clock read? Does the engine roll? Are the carbs # ending in -13, -14?

Keep us posted.:lurk
 
jforgo said:
Someone on here posted acetone as being very good on corroded fasteners and such
Click to expand...

I never knew about that before, but yer right, somebody did report good results a while back...I'm with the gentleman who suggested Kroil, it's the best stuff I've personally used, BUT I've also got it on good authority that PB Blaster is excellent too...What is pure crap for this is WD-40!!!

Actually, I think somebody posted a comparision a few month ago on how effective different materials were on freeing up fasteners, and if I remember correctly, I THINK...not certain...that acetone WAS the best!
 
Ron Miller posted this a while back:

Machinist's Workshop magazine actually tested penetrants for break out torque on rusted nuts. Significant results! They arranged a subjective test of all the popular penetrants with the control being the torque required to remove the nut from a "scientifically rusted" environment.

Penetrating oil .......... Average load
None ..................... 516 pounds
WD-40 .................... 238 pounds
PB Blaster ............... 214 pounds
Liquid Wrench ............ 127 pounds
Kano Kroil ............... 106 pounds
ATF-Acetone mix............ 53 pounds

The Automatic Transmission fluid (ATF)-Acetone mix was a "home brew" mix of 50 -50 automatic transmission fluid and acetone.

There ya have it!!!
 
Last fall, I had a derelict parts bike that had sat out in the rain for quite some time. Long story short, I ended up with the right head loose with the header still in it. I gave up after a weeks worth of running heat cycles and Blaster, having to cut the header close to the port and split the remainder of the pipe with a chisel working carefully down the inside of the port. The piston was also struck in the cylinder on that same side. One never knows how these things may turn out. Hope your luck is better than mine was on that score.
 
Well beat on it for 20 minutes or so the right side freed up the left is still frozen so more heat/Kroil , and then I am going to try the Acetone/Diesel concoction with a BFH.

At least I know the piston is free - haven't spun it far but I did move it a little to TDC.
Gotta love that!!
 
Pops said:
Well beat on it for 20 minutes or so the right side freed up the left is still frozen so more heat/Kroil , and then I am going to try the Acetone/Diesel concoction with a BFH.
Click to expand...

As Yarddog noted above, it's actually acetone/ATF fluid in a 50/50 mix that reportedly won the frozen nut contest. I can't confirm this because I've never tried it. If you do try it, be very cautious about storage and only use the mixture with no heat. As you no doubt know, acetone is highly combustible. And if you spill any and clean it with rags, rinse the rags carefully. Spontaneous combustion happens. Meanwhile, congratulations on the right side. Be patient and the left side will give it up eventually.
 
Bill Burke said:
As Yarddog noted above, it's actually acetone/ATF fluid in a 50/50 mix that reportedly won the frozen nut contest. I can't confirm this because I've never tried it. If you do try it, be very cautious about storage and only use the mixture with no heat. As you no doubt know, acetone is highly combustible. And if you spill any and clean it with rags, rinse the rags carefully. Spontaneous combustion happens. Meanwhile, congratulations on the right side. Be patient and the left side will give it up eventually.
Click to expand...

Good point on safety with rags containing high combustibles. I always put such in an empty coffee can and burn 'em.
 
woodnsteel said:
I ended up with the right head loose with the header still in it. I gave up after a weeks worth of running heat cycles and Blaster, having to cut the header close to the port and split the remainder of the pipe with a chisel working carefully down the inside of the port. The piston was also struck in the cylinder on that same side.
Click to expand...

Same story on my R90.. but opposite sides.
 
Pops-
You may not know it, but Todd Byrum, above, just made you an offer that you would be wise to accept if at all possible. Byrum is one of the top airheads in the country.
Just sayin'.........
 
Pops said:
Hi I am Pops and I have a problem.

I am becoming an Airhead.

I have studied the bibles - both the factory and the Clymer versions.

I have listened to the preachers here in the forum.

I still made the conversion and I acquired a 1976 R75/7 which has been sitting for a dozen years. My son and I have taken on the resurrection of this fine Bavarian Beast to bring it back to its former glory as a project this year. The plan is to strip it down to the frame and start with a paint job/ bearing replacement and move forward.

Here is where we have run into what I figure will be the first of many hurdles. The exhaust nuts were frozen on and after trying Kroil for a few days and heat and the exhaust nut tool it became apparent that they were not going to cooperate. Have read much about this problem I cut them off - one quick zip with a hacksaw and a couple of sharp smacks with a cold chisel and both came off clean an the threads are in great shape.

What has us scratching our heads is that the pipes will not come out of the heads.
I have tried Kroil, heat, large deadblow hammer (gently) and cannot move the pipes.
It almost looks like the PO had sealed them with muffler epoxy (?) or they are an extremely tight fit. I cannot find any info on this and the manuals say nothing about it being so tight. Anyone have ideas or suggestions as to how hard I can push(hit) or twist these to get them out? Here is where we found it buried - with all the paperwork up until it was parked in 1999.

View attachment 23293


Thanks for any ideas.
Click to expand...

I know it looks ugly and the initial urge is to fix everything, but....
Especially the lower ends of these machines were built like brick youknowwhats and the bearings can last 2-300k without major work. I agree with the "frame off" restoration but don't arbitrarily tear the engine all the way down unless you find it necessary to do so. As an example, I recently purchased an R51/3 that had sat in a rainy garage for many moons. The right hand head and cylinder were full of corrosion since the intake valve had sat open on that side. Once I got beyond the top end, however, the crank, camshaft and bearings proved to be in good shape and didn't necessarily need replacing. Also, the transmissions and final drives rarely suffer from corrosion problems as long as they remain sealed. Major work on them is usually the result of miles, not time. Sometimes these bikes can look terrible and still only need mostly cosmetic and tune up work. Just a thought....
Little Egypt Airheads
1951 R51/3
1966 R50/2
1980 R100RT
 
Thread Jack... Thread Jack...Thread Jack...Thread Jack...

Pops, Where are you? Send a PM so we can help out.
The crowd is gathering soon.
Click to expand...

Todd, I just went through your PRT seal replacement photo-article. Is the "H" fixture really necessary to align rockers on a '73/R75? I found the the subject thread on this site, but no definitive answer there.

Please ping with PM, Thanks. Lew

We now return to your regularly scheduled thread.... .

tv_test_pattern1.jpg
 
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