Here's my 1979 GS100L:
and here's the gallery of most of the images taken during the rebuild and detail shots of the finished bike: https://goo.gl/photos/TjhN5pXbQGKMkbQ77
I've owned the bike for almost 30 years, and when my kids were young we took road trips on it. Here's my son Ryan & I in 1996, wearing goofy looking rain gear in a storm on the way to Portland 200 Indy Car race:
As the years went on and I started my company and got remarried, I rode it fairly often (but in Washington weather that's not a lot - it only has 26,9XX miles on it). Over the past 5-6 years, I seriously neglected it, and it moved from the garage to outside for a year, which did it no favors and I'm still kicking myself for having done it. After feeling really guilty about not caring for it, I gave it to Ryan to try and get it running and start riding again. After 4-5 months, he gave up and it passed back to me.
As the weather started to get colder last October and I had some spare time, I thought I would try to get it running for him. After doing points and plugs, new gas and carb adjustments, it ran OK (kinda), but we found out quickly that the front master cylinder did not relieve pressure on the front pads - to the point that the brake was almost totally locked up - it wouldn't roll at all. It was at this point that I found out about this forum, which turned out to be a godsend!
To start off, I removed the front master cylinder to find out that the tiny pressure relief hole in the bottom of the reservoir had become rusted completely shut which was not allowing the pressure on the front pads to release. Using a small piece of wire, I was able to open this up to allow the front brakes to operate again. So far, so good – I could now ride and stop the bike! However, it smoked a bit at start up which I knew were valve stem seals, and with a pretty lumpy idle it probably needed some carburetor work so I thought the next step would be doing both of these operations with the engine in the chassis. The best laid plans always go awry...
I consulted this forum to get some ideas on changing the valve stem seals, and came up with the plan to use a tool that I had fabricated and the rope in the cylinder trick to keep the valves in place while I removed the collets/springs/seals. Although it was a little bit of a pain in the ass getting all of these removed and the new seals on, I had met my match when it came to getting the split collets reinstalled. If anyone on this forum has done this operation with the engine in the frame, you are a God! I couldn't do it.
So, it looked like I would have to remove the engine to reinstall the collets. Without ever having done this operation, I wasn't looking forward to it but after reading others' experience on this forum, it didn't look too difficult. It turned out to be a piece of cake removing the engine from the frame. I ended up using an overhead chain hoist with straps to suspend the engine in the frame and eventually moved the frame away from the engine. After fabricating a couple of aluminum brackets, I mounted the engine to an old engine stand which gave me stable access to start digging in.
At this point, I'm thinking "I'll just pull the head and freshen up the valves and seats while I do the seals", and the head came off super easily. This was a great idea and was a quick solution to the original problem, but then I had another great idea – "while I'm this far, I'll just pull the cylinders and re-ring it at the same time!" As everyone knows who has done this before, the head studs are a great place to cake on road grit / sand / gravel / mud / dirt, and everything the bike has run over for the last 30 years - I even found a feather in there!
So rubber hammer the cylinders to crack the bottom gasket seal and I start gently prying. Literally, once the cylinders moved 1-2mm, it froze and REFUSED to budge any more due to the buildup of all of this crap on the head studs! After consulting the forum again, I swallowed hard and soaked the studs to loosen the gunk on them and started hammering again - to say this was stressful is a massive understatement - it took 15-20 minutes of continuous pounding to remove the cylinders, which revealed that the pistons were in great shape and there was zero play in any of the rod bearings. But, since I couldn't slide a rag into the gap between the case and the cylinders as they were starting to move, all of the garbage that came off the studs had now ended up in the crankcase!
I have always been afraid of cracking the cases in any motorcycle I have ever owned, but once again, the forum came to my rescue - after reading through multiple threads, it looks like the bottom end of these motors is extremely simple – not at all something that should trip me up. So, off came the covers, out came the clutch and case bolts, and by the end of the night I had everything stripped and laying on my toolbox! Piece of cake!
After consulting the forum again and measuring all clearances, it looked like the crankshaft/main shaft/counter shaft bearings and gears were all good and could be re-used. However, the splines on the main shaft for the front sprocket were getting sloppy due to the old sprocket nut being so loose that once I bent down the locking tab on the washer, it spun off with my fingers - YIKES!), so I ordered another main shaft on eBay for a whopping $29 which gave me another entire shaft/sprocket/gearset.
At this point I ordered all new seals, o-rings and gaskets for the entire engine so that on reassembly, there would not be a single rubber part that remained from the original engine - by God, this engine will NEVER leak again! I also built my new favorite tool - a DIY soda blaster - to completely strip the engine case/cylinders/head/valve cover for repainting as well as to clean the combustion chambers, valves and pistons to make everything look completely new. I used rattle can Rustoleum engine silver and clear, baked it in the oven (****ing off my wife) and all parts looked brand-new for reassembly, but it doesn't stand up for sh*t to gas :- (
I cleaned everything so you could eat off of it, then replaced the right side crank seal and installed the crank, then swapped a couple parts from my EBay main shaft to the original, installed the new seals and plugs and reinstalled the transmission. Yamabond on the mating surfaces and it went back together a whole lot easier than anticipated.
Engine case reassembly went great except for one thing: I mistakenly used the wrong seal for the main shaft where the sprocket splines are (it had the same ID and OD as the correct seal, but the wrong lip arrangement for the main shaft spacer), so I had to crack the case again to replace it. Normally I would have gotten pretty bent out of shape about this, but the engine is so easy to work on, I got it done in under an hour - it was no big deal. I will never hesitate to get into this motor again if need be - it's WAY simpler than I had myself psyched up for all these years...
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