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1978 R100/7 Topend Overhaul

Ted Porter told me the rings/cylinder should be dry but oil on the piston skirts. I do plan on starting it and holding a high RPM (say 3K) for 45-60 seconds, then take off for the first ride while varying throttle and keeping the speed down somewhat.
 
The amount of screeching noise the motor makes in the first two strokes gets your attention, but it should settle down after 2 or three long seconds. There is a lot of friction to overcome, so it's best to have a fully charged battery.

I went with lighter wrist pins, checked the weight on everything and tried to balance it the best I could within reason. I don't know if it made a difference, but I felt better about it.
 
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Based upon my previous measurements, the wrist pins and pistons are very evenly matched. I'm not planning on removing the conrods, so I don't know about their balance. I'm thinking that the items which are farthest away from the crankshaft will have the greater impact on balance.
 
Sure looks pretty!!

your gonna have 2 big jugs stickin out all new and pretty kinda reminds me of an old stripper I know but that is a different story!!!:blush
 
The two base gaskets provided to reduce the 9.5:1 to 8.8:1 compression measure about 0.66mm or 0.0026" thick. Part number on the package is 11 11 1 335 650. That matches R60/6 and R60/7 gaskets which were used for the very same purpose, to reduce the compression on the R60s and help with pinging.
 
Dropped the oil pan today...fairly clean inside, nothing unusual in there. I pulled off the pickup screen by removing the wire clip...found the bolts holding the pickup needing tightening. After putting it all together, I gave myself a dope slap and figured I should have pulled the pickup bolts and reinstalled with a drop of blue loctite. Oh well, I'll do that in a few days...I don't want to lose sleep over the pickup possibly loosening.

Found something interesting...the forward right side of the pan flange has a nasty dent in it...probably from someone using a screwdriver to wedge the pan off. I didn't put use any sharp tools to loosen the pan...just tapped it with a dead plan around the edges. And I don't recall ever having the pan off before, so it must have been the PO who owned it for two years before I got it. That's my story and I'm sticking to it!!!
 

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It's always fun to discover something about yer bike when taking it apart. Usually a PO has done something careless. last year before sending speedo out for a fix, took it apart for a look see and found the tell tale shards of glass from an obvious previous Crash? Never know what these old bikes have seen. Rear drive on my R90 is marked '77 and it's a 3 to 1 ratio with perfect splines. More evidence of something or another. Caveat emptor, I guess.
 
Safety clip for the sidestand.

I like the extra clip to hold the side stand.. can you show more detail..

I have installed a weaker spring on my side stand so that it can be deployed easier as I have as shortage in the inseam. I have been using a bungee.. and i hate it.. but it works..
I would like to build a clip like you have installed. It looks like the proper trick to keep the sidestand in place when riding.

Can you elaborate..

thanks.

Jim, Ketchikan
 
Oil pickup and gaskets, my suggestion.

Replace the gaskets and inspect the strainer (bell) for fatigue fractures. My R100S with 80K was severely fractured and one bolt was lying inside on the perforated plate. RePsycle had what they thought was a good used strainer but it also was fractured. These parts are cheap new!

Really enjoying your informative thread!
Tom
 
Tom -

I wasn't going to disturb the pickup gasket...I figured I'd just remove one bolt and loctite it, then do the other. I suppose it would be a good idea to check it out since I don't plan on doing this again for another 30 years! :laugh
 
I'm getting ready to fit the topend this weekend and got to thinking about the piston orientation. I know about the arrow on the crown...it must be facing the front of the bike. The piston has an offset wrist pin location relative to the top and bottom of the piston as it is installed on the rod...I did some measurements and confirmed that. Is there a left piston and a right piston?? At first blush, I would say no.

But, I got to looking at that. If I take one of the pistons and hold as if were the left piston, the arrow points to my left which is the front of the bike. If I hold that piston in that orientation, and walk around to the other side of the bike, the arrow now points to the back of the bike. So, to use it on the right side, I must rotate the piston 180 degrees. Fine, except that the location of the "short" side of the wrist pin has now also rotated 180 degrees. So, for example, the "short" side might be on the upper part of the piston the left side, but if I orient the piston for use on the right side, the "short" side of the piston is now on the bottom.

Am I goofed up on this? Is it all OK just as long as the arrow points to the front?
 
I slept on things and may have figured out what needs to happen. I'm still unsure about the wrist pin offset, but will confirm that.

Here's a picture of the two new pistons. Basically it comes down to ensuring that the piston pockets are oriented correctly. My intake valve is 42mm while the exhaust valve is 40mm. On the left piston, it should be evident that the left pocket is smaller than the right. On the right pistion, the right pocket is smaller than the left. So, what I will do is installed the left piston on the left side so that the Siebenrock lettering is upright. The right piston will be installed on the right side, again so that Siebenrock is readable. I have to pick something, so that's what I'll choose.

The thing that is still confusing is that I could reversed the pistons from left side to right side and then rotate them 180 degrees and the valve pockets would be correct but the Siebenrock lettering would be upside down. That changes the location of the offset. That is what still has me wondering.
 

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The arrow on the front coincides with the smaller pocket for the 40mm exhaust valve. The pistons can be switched provided the arrow and smaller pocket coincides with the exhaust valve (front of engine). Otherwise, the intake valve will interfere with the smaller cut-out in the piston. Unless the wrist pin hole is off center, the letter orientation should not matter. Given the choice between having the lettering oriented as readable or upside down, I too would go with readable. Good luck!
 
Stan -

Ted Porter confirms that it doesn't matter which side the pistons are installed on, only that the arrow must point forward. So, I'll do as I thought...install to the lettering is right-side up just so I have a point of reference for the future.
 
Boy oh boy oh boy those pistons are truly beautiful. Golly, one would be tempted just to sit one of them on the coffee table and just become one with them........lol..........YOU are doing fantastic Bud.....The arrow situation is totally standard and the way to go.........God bless .........Dennis
 
Dennis -

That's the last time they'll look that clean! Maybe even the last time I even see them!!
 
Made quite a bit of progress today...at least it's going back together! The new pistons and cylinders are on and the heads are on and have been torqued. I think I figured out that I'd never make it as a mechanic for a living! :banghead I'm kind of beat up today...I hope to post some pictures in the morning.

A big shout-out to Bill (aka jusbill) who came by and did more than kibbutz. He helped providing moral support, finding my tools, seeing things that I didn't see, and even getting a little dirty! Thanks! :thumb

The lesson I learned is "we don't need no stinkin' internal snap rings"! My thumbs will never be the same. Stay tuned....
 
Can't wait to see the thread that says "She started up and runs great"

Nice project you've got going, Kurt - may the force continue to be with you!
 
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