Doing push rod tube seals-need advice

[Workinman]

Okay guys, I’ve finally gotten around to doing the push rod tube seals on the R90S. They’re dripping a fair amount at this point, as well as the oil pan (I think) so I’m gonna tear the top end down and address some issues. Unfortunately, the man I purchased this bike from had dementia and has since passed away, so I have no way of knowing what, if anything, has been done to the engine. So here’s what I’m thinking…
I think I’ll need to contact my local BMW dealer and see if they have a machine shop they use so that I can have the heads checked out and probably install unleaded fuel valve seats. Does this sound like the right move?
Also, the paint is chipped up on the cylinders and I’m considering having them powder coated or even ceramic coated. Jet Hot is only about an hour from me and they do great work. My concern is this…
This bike is 95% original and in wonderful shape, with just the slightest bits of patina here and there. Normally I’m not a big patina fan. I like to restore my stuff to showroom fresh condition. But this bike is too nice to do that to. So should I leave the chipped paint on the cylinders for originality, or should I make them look pretty again? You can see the chipped paint here, as well as the condition of the rest of it.

And my final question concerns the oil pan. I’m going to replace the gasket down there and I’m wondering if I should procure and install a deeper oil pan. Are they even available? Would doing this take away from the bike’s originality or would it be considered an acceptable update?

Once again, thanks for your guidance on this project. I value your opinions as you know WAY more about these airheads than I ever will. I’ve no doubt that I will have more questions as I progress.

[schrader7032]

My thoughts:

- not too many people are doing BMW heads correctly these days IMO. I'd contact Max BMW or possible Tom Cutter at Rubber Chicken Racing Garage for their input.

- On my R69S, I had some rusting issue on the cylinder fins, so I cleaned them up and used Dupli-color DE1613 (Walmart) Black 500 deg F to spray them. Has been holding up well.

- as for a deeper pan, you will need to ensure that the oil pickup is lowered to the proper level as well. Then you have figure out what to do about the dip stick. You can fill the new pan to the same height on the dip stick, so more oil. However, this maintains the same air volume above the oil in the case. The wind created can cause the oil to foam or whip up and go out the breather. You can just put the same amount of oil - 2 liters - in the pan and vastly create more air above the oil resulting in less whipping. Or you can do something in between for best of both worlds.

[srankin]

I concur with Kurt, far too few places to get BMW airhead head work done. A LOT of machine shops claim they can do the work BUT there are nuances to airhead heads they fail to account for.

LOL, Tom Cutter has retired and last I knew was asking or charging donations for his advice. Ted Porter has stopped doing heads, I am not sure if he will answer a request for shops he feels can do the work. Max BMW has the shop.
Other people to try to ask would be Brooke Reams and Anton Largiader.

I wouldn't bother with a deep oil pain. Lots of R90S bikes have lots of miles on them with the stock pans. Maybe in a race bike a deep pan is a good idea but on the street, it seems to be an expensive gimmick. LOL, lots of modifications have been done to airheads over the years that didn't pan out. St.

[Workinman]

Thanks, guys!
So I’ll scratch the oil pan idea. As much as this bike is going to be ridden, and the way it’s going to be ridden really doesn’t warrant all the extra work and expense.

With that being said, and considering the trouble to ship the heads to Max BMW and back, should I really worry about the valve seats? It’s always possible that they’ve already been changed but I have no way of knowing. This bike will get MAYBE 500 miles a season on it, and it’s ridden fairly gently, maybe just leave the heads alone? What about a fuel additive to put the lead back in there? I think I’ve seen stuff like that out there. Your thoughts?

Last question (for now)

Who is a good supplier for the gaskets and PRT seals? I see some on eBay, but would rather not go that route if I can find a reputable supplier.

[Workinman]

Now that I’ve looked again, the gasket kit on eBay is from Euromotoelectrics. They’re one of the good ones if I’m not mistaken. Seems like I remember buying my caliper parts and master cylinder parts from them.

[schrader7032]

If you think the valve seats have been changed, and hopefully the valves themselves, then just go about your business and monitor the valve clearances on a regular basis, maybe every year or couple of years. If the clearance values (0.6mm intake, 0.8mm exhaust) remain at those levels, you aren't experiencing any valve recession. But if they begin to close up rapidly between measurements, they time to consider some head work.

[srankin]

I missed how many miles you have on the bike? Even with the stock seats you should get quite a few miles out of them before they would need replaced.
BMW did have a problem with bikes in the early 80's due to either bad seats, or what ever, and I had to have mine done on my 84 R80RT at low miles.

If you have low miles confirmed, and the valves and stuff look good, no knife edges or damage, ride it. Kurt brings up a good harbinger of seats going bad. Normal valves subjected to normal riding should be adjusted at about every 15K miles. If you find yourself adjusting them more frequently, it would be a sign they are going and work would be done. My R80, started idling poorly and valve adjustment was the cause. Readjusting the valves brought back idle to normal. BUT, when I started to have to adjust valves every 5K miles, it was time to tear things apart and have the heads rebuilt.

Yeah everything is apart right now and it is tempting to get the job done but sometimes it is better to ride for awhile and see what shapes up. 500 miles a year is not a lot in some cases and if you are like me, you can better spend the money you save on something else.

Oh, yeah silly me, I should have put in first, a leak down test when you get things back together or at a later date is the best way short of tearing the bike apart to find bad valves. Since you already have the bike apart, bypass this until you have some miles on the bike or it doesn't seem right. Good luck and a nice looking R90S, St.

[Workinman]

Thank you again, Gentlemen.
Mileage right now is just over 29,000 miles.
I pulled the heads and jugs off today, and the cylinders didn’t want to come off too easily. I got them off and noticed two things. 1) the base gaskets seemed to have some very dried up sealer of some kind on them. It was black and crusty, and somehow I doubt that it came from BMW that way. Regardless, this tells me that the cylinders have been off before for some reason. Maybe to have the heads converted over to lead free. Who knows?
And 2) there were two base gaskets per side. That doesn’t sound right to me, but maybe it’s an airhead thing… two thin metal base gaskets under each cylinder.
Cylinders and pistons don’t look bad. No scoring of any kind, but not much of a cross hatch pattern evident either. As soon as I get a chance I’ll measure everything and see what I’ve got to work with.
By the way, ordered all my gaskets from Euromotoelectrics. They seem like good people.

Thanks again!

[schrader7032]

Should not be any dried sealant on the bases. Usually a non-hardening sealant like Hylomar, Permatex Ultra Gray, Yamabond, and others, is used. It creates a seal but lets things move as needed.

As for the double base gaskets, that was something that could be done to lower compression ratio. The R90S has high compression and if getting good gas is a problem, this was a way of protecting the top end.

Not sure what you plan on doing as for reinstallation. Things to consider:
- you'll need to put on the right sealant but be sure you don't get it on the small holes at the base of the upper head bolts. Those holes allows oil to run out to the heads for rocker arm lubrication.
- If you choose not to reuse the two gaskets, then you're likely going to have issues with the ridge of combustion materials that have deposited at the extreme end of the piston rotation. If you remove them or use one or whatever, the piston is going to travel farther and you could break a ring.
- if you don't see any cross hatching, you'll need to use the tools/hones to put that back. The cross hatching is there to help seat the rings during initial start.
- be sure the rings are installed properly. Don't allow the gaps to align along the same line...this will allow compression gases to bypass the rings easily. Typically the three rings are installed at 12:00, 4:00, and 8:00.
- break-in after reinstall is important as well as retorquing the heads over time. Don't exceed say 25 ft-lbs when you do that.

I'm sure there's more things that I've forgotten.

[srankin]

In all seriousness, a mileage of 29,000, could be just that or 129,000, darn BMW for not installing that one extra digit in the odometer. I am getting a bit concerned the bike has higher mileage on it than you think. 29,000 is just about broken in for a R90S. Sorry to hear the previous owner has passed away, did you know him very well? How well do you know the history of the bike?
I agree with Kurt the extra base gasket could have been installed to lower compression a bit. I personally can't give any advice as to reinstalling it upon rebuild or leave it out. I have never had issues with pinging in my past airheads except my R75/7 and it only pinged when the timing got out of range due to the bloody points going out of adjustment.

Perhaps at this point you want to do a ring gap measurement as well as checking to see if the bores are cylindrical and in specification.

Did you do a compression test before tearing things apart? It would have given a better idea as to the condition of the engine.
Yeah, lots of help hindsight, sorry, St.