Boxerworks.com

When I bought my 1978 R100/7 project bike, the seller claimed that he had torn down to the motor to check the condition of the crank bearings and found that they were OK. He also claimed to have "freshened" the top end during re-assembly....whatever that means. At the time, it did run, albeit rough, and several other issues with it prevented me from riding it then. That was good because it would not have made it around the block had I tried. It has sat since then while I bought and rebuilt new carbs, collected missing parts, etc. I realized halfway through that I needed something to ride because the rebuild was taking a long time and was alot more extensive than I anticipated. Fast-forward a few years and I'm riding a '88 RT and have pretty much written off the rebuild of the /7. I am in the process of parting it out so that others may live on.....

Anyway, so I'm dissecting it and learning loads about these bikes....One thing I noticed is that the PO did not install a gasket at the cylinder base (it's a non-o ring style barrel). Nor did he install one at the cylinder/head when he re-assembled it.

Anyone encounter this before? Can these bikes be run without these two gaskets installed? He apparently used a silicone-type sealant at both locations....Seems like the compression would be way too high for it to run right. I seem to recall a discussion here a couple years back that talked about this but I couldn't find anything in the archives.

Any thoughts are appreciated....



I

/7s did not have cylinder base gaskets, at least mine never came from the factory with any.

As far as head gaskets, I'm suprised that it ran for any length time. Re-useing the old head gaskets is much better than silicone. I wonder what else he "freshened up"?

A silicone seal head gasket???? Did you, by any chance, buy this bike from a man named "James"?????

I'm in the middle of a topend on my Sept 1977 build R100/7. No base gasket and no large base o-ring. Head gasket definitely!

Kurt in S.A.

Actually it could run really well without a head gasket (at least for a short time), compression would be increased substantially if the mating surfaces were smooth enough (dry without silicone). Aircooled VW's didn't have head gaskets, of course the barrels fit into a recess in the head that seals things up pretty well. I would not recommend it on an airhead though, because of the major oil leaks that would be created by the PR tubes that pass through the head. What was he thinking?
My aftermarket barrels from Siebenrock do not use gaskets or O-ring either. The silicone needs to be applied with care so that none of it gets into the oil passages that run out at the base of the upper cylinder studs.

Locktite 515 Flange sealant works OK with the copper head gaskets on Brit Iron, particularly round the oil ways and push rod tubes which might not get a even pull down.

Stays liquid outside of the joint too, so it is not going to block many oil ways either.

So how big of a bead to use so I don't make a mess?

driggs wrote:So how big of a bead to use so I don't make a mess?

No bead. Thin shmear.

Major Softie wrote:

driggs wrote:So how big of a bead to use so I don't make a mess?

No bead. Thin shmear.

Yet enough to ensure no leaks. I've not used enough once or twice and used products that were not the best, although not cheap stuff.
Three bond is one product that is up to the task.

Isn't Yamabond supposed to be the cat's meow?