1981 R65 Top End Rebuild

[matthewjp14]

So, I could dive into all of the past work and history of this motorcycle, but this thread is going to be my effort to rebuild my 1981 R65.

Long story short, exhaust valve and seat on the right side exploded taking big chunks of the head with it. I consulted with Ted Porter over email and he recommended new ones since the damage was so extensive, (find that image in my intro post if you wanna see). Ordered apparently new heads and the ebay seller confirmed they were compatible with their 1983 r65, so ideally they'll work. I'm planning on taking them to Porter's to be lapped and reseated for an unleaded valve seat conversion since I want this to last. Other than that I will most likely need a new piston or two and rings, right?

Specs for pistons and cylinders:
R(damaged): piston-81.96mm cylinder-82.04 at widest point of the mouth      cant feel or see any scoring so is boring them a necessity?
L(no damage visible): piston-81.96mm      cylinder-82.07 at widest point of the mouth      only concern is HEAVY carbon buildup on piston and head, could this be a sign of anything important?
Other than obvious damage, I have no idea of the history of this bike, apparently someone from Marina Del Rey, CA worked on it but seller gave me zero information or maintenance history and it likely won't be possible to place a true mileage on the engine since the odometer hasn't worked since before the last owner.

Currently the piston seated in the right side moves after taking out all the shrapnel and seems to have no scoring along the cylinder. Rings are still smooth, no catching anywhere, and move without any extra effort so I want to assume minimal damage occurred. Since I'm already getting a full valve job can I get away with getting everything blasted clean and buying one within spec piston and balancing them? Is that a bad idea? What is typical +- range on this model? and please give me any other engine building advice or knowledge you have.

Pics in order: right piston face, left piston face, left side cylinder bore, left side cylinder head

[dogshome]

1. Carbon buildup looks normal.
2. There is some wear in the plated liner. You need a ring and some feeler gauges to measure at a few places near the top ant at the top where there is no wear. It is 0.2mm variation max I think. Please check that! But you will not feel the traditional iron liner lip for the bore to be worn out.

[georgesgiralt]

Hello
If your engine is post 1981, the bores won't stand re-boring. They are Nikasil plated. And all aluminum.
If you had shrapnel in the cylinders, a thorough cleaning of the engine is mandatory in order to ensure there is not a tiny bit of metal clogging an oil passageway... So not just a top end job. Triple check that the oil filter is changed a couple of times when turning the engine back into use and change the oil often in the first 1000 km....

[matthewjp14]

Triple check that the oil filter is changed a couple of times when turning the engine back into use and change the oil often in the first 1000 km....

Youre saying I could do fine with frequent oil and filter changes for the first few thousand miles? I can replace filters no issue and I will be having the whole top end including barrels, at least everything being reused, steam cleaned to avoid grime and metal where it shouldn't be. Hopefully that would account for as much of the possible issues on that front as possible.

Secondary question, there was nothing metallic when I drained the oil, but would I benefit from dropping the entire oil pan and double checking no flakes of anything there? too much work?

[dogshome]

Getting the oil pan off is very easy with the centre stand. All you need is a gasket and a gentle touch when putting the bolts back in.

If there is shrapnel or glittery bits, that's the first place they will be.

[Tony Smith]

Firstly, that's not a valve drop, see below for a real one......

If the heads you are buying are 1983 then they are already lead free fuel compatible. Instead buy new valves, have the guides k-lined and a 1st class 3-angle cut performed - on the whole a much smarter use of your money.


P.S. the piston pictured came from my R65. The deaf as a post previous owner had been having coil problems and thought the loss of power was a continuation of that.

To my very great surprise the rod was straight and the bearings undamaged - these are tough little engines.

[georgesgiralt]

The main problem is not in the biggest of the shrapnel bits you will find in the sump. IT is in the small bits that will at the worst clog some oil passageway or embed themselves in soft journal metal... This is why I advise changing oil a couple of times in a very short interval and change the oil filter in the hope those bits get caught in it and not in the engine...
A local long time BMW Guru says it is better to find a used engine block when such an accident arose. HE has a lot of horrors stories with pictures....

[dogshome]

My thinking is that if the sump is clean of glitter, then the chances of the rest being clean are good. it's such a simple task to get the sump off, it would be the first place I would look.

If there is a lot of small stuff in the sump, then I'd be looking in the filter. Or vice versa. Both anyhow! If the filter is clogged with little pieces, then engine out 



The pic of the piston above is worse than anything I have ever had to deal with, so I bow to those with direct experience.

[Kurt V.]

Before you do anything else, drop the oil pan and see if you have any metal particles in there. And I’m still not quite understanding what happened. Do you have any pictures of the damaged head? Particularly a picture of the top and bottom side?

[Bob_Roller]

The '81 model year bikes got new and improved valve seats .
They were made of some new alloy .
Only problem was that unknown to the engineers that the new seats acted like an insulator and prevented proper transfer of heat from the valve to the valve seat .
Valve recession occurred before 40,000 miles, my '81 needed a top end overhaul at 41,000 miles .
The shop that did the overhaul said that I caught it just in time before the valve head would have broken off .
That's the usual failure for this, destroys the head and piston .

[matthewjp14]

Hello all, thanks for all the comments and advice, college finals are officially over so it's time to really get some work done I think.

I did drop the oil pan, (attached pics) no glitter to be found. It had about 100 miles on the odometer since last oil change which is why the oil's so light, but I'm now feeling reassured that this is completely salvageable, I will still be changing the oil frequently once it's up and running.

To the person asking to see the damage, its posted somewhere on my intro post if you want to see, if that's not good enough, we can all check it out when I replace it with a healthy head. Speaking of the healthy heads, the ones I received are '83's in pretty healthy condition, at least better than the originals. Both steam cleaned already and the only damage possibly unsalvageable is a helicoil in where the spark plug goes. That can hopefully be fixed too once I send these in to be set up.

I think I am gonna go through with the full top end clean and rebuild here, will be taking rockers, valve covers, and cylinders to get blasted and steam cleaned to make sure there is 100% no glitter and then on to the reuild I guess. I will still need to source a piston, this right one is otched and from the comments here I don't have all the confidence that it will withstand running after rebuild. Either way its onwards and upwards.

If anybody has advice for special tooling feel free to bestow some knowledge to me.  If anyone has a source for matched pistons or one right piston I'd be happy to talk to them. Are they all $200?

[dogshome]

Looking good in there 

[matthewjp14]

Hey all!
It's been a while since my last update on this but as a college kid, time and the availability to get projects done don't always come at the same time. Fortunately that time is now, and the heads I bought to replace my destroyed one were garbage so I've suddenly got refunded and back to square one, dead bike.

Long story short those I bought over ebay had been worked on to the point of failure and should be left as scrap metal. Such is the life of ebay bmw parts.

I am reaching out to anyone on this forum who might have a lead/source; I'm in dire need of the right side cylinder head and piston for an r65 gotta be 1981 or newer. If anyone has other equally inexpensive options to recommend like a kit with new heads that I somehow haven't found yet let me know; but this seems like the only route to success here. I really honestly only need the right side as the shop I've got them in cleared the left for takeoff, no damage whatsoever. And as per my posts above, oil and passages are clean too.

This can be saved, please help

[Matt Chapter]

There are a few air head breakers out there, finding them is tricky.  There's a guy local to Austin that has a bunch of parts, he sells stuff on ebay.  Larry Chibira, I think his ebay handle was lamont sandford or similar.

https://re-psycle.com/ might have some parts?

[matthewjp14]

https://re-psycle.com/ might have some parts?

I have looked through re-psychles site to find a donor near me but unfortunately support for the r65 from almost any shops is practically nonexistent.

Luckily a generous member of this forum happened to be getting rid of a healthy 1981 r65 with a few things missing. his machine had no transmission or air system, but since a powertrain is all I need, a powertrain is what I'm swapping!

Thanks to a user on here I was able to pick this up and get it stripped down to an engine on a bench and a box of extras. Pics attached. This will likely be the end of this thread and I will be starting another attempting to document and likely troubleshoot the birth of frankenbike. RIP to this black 1981 r65, I'll be keeping forks and swingarm but if someone reading this is looking to pick up a pretty clean (mostly rust free) frame in Northern California please pm; happy to be of service.