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'91 GS500 Cafe/Tracker

Started by larsensp, March 22, 2023, 08:44:35 PM

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larsensp

Got this '91 GS500 several years ago, and thought it was about time I started documenting the build process. I'd love to hear your thoughts and ideas along the way!

Here's how the new subframe turned out, which was heavily influenced by SK Racing's build. It's not perfect, but I'm overall happy with how it turned out.



I went with a gloss black powder coat for the wheels and fork lowers, and popped in an R6 shock as well.

I gave fiberglassing a more minimal front fender a shot, and it turned out decent. I essentially just cut the original fender in half, trimmed it down, and glassed a copy. Then joined the copy to the original with more glass. Sanded down the resin hot coat plus a little Bondo on a deep low spot, and it's nearly good to go.  I plan on hitting it with some filler primer to see if there are any more lows/highs to take care of.




I think the next project will be mocking up the rear cowl. Going to use medium gauge aluminum wire and hot glue to create a sort of structure. It'll let me see if I'll have enough clearance to place the battery under the cowl before shaping something out of foam.


-Spencer

larsensp

Been working on shaping the tail, using green florist's foam. Stuff gets everywhere. To try and cut down on rust, I also primed the bare metal frame.

When fiberglassing the tail, I went with chopped strand cloth instead of a weaved cloth. I'll have to redo it,  but it was a good test run and I managed to salvage the foam template. Also gave me a better idea of how the bike is going to look. Glued down some cheap walmart craft foam to mock up the seat as well.








Next go around I'm going to decrease the length of the tail a bit. Doesn't look right to me with the seat and tail being just about the same size.


Ghetto Garage

Im really digging it. The tail reminds me of my old 77 KZ1000. I cant wait to see your progress. Its really taking shape.

Cheers!
Mike

larsensp

Ended up going a different route with the fiberglassing. I couldn't get the right shape in the tail section, while playing in nicely with the round frame of the tail.





The new design does allow for an integrated tail light, however, so pros and cons. Still haven't decided how I'll end up doing the license plate. This light (off ebay) was originally attached to a license plate bracket, which I cut off. It does have a white light included that would illuminate the plate. I may opt to mount it directly under the tail light, with a slot cut out to let that light shine on the plate to be street-legal.



Rear fender is also in the works. It attaches to the 2 existing holes under the swingarm where the stock small mud-guard went. Definitely needs to be reinforced with more layers of glass. I think I'll also end up shortening the top portion.






The rear brake master cylinder is off of a '13 GSXR600/750. Mounting holes were a direct fit. Banjo bolt is in a different orientation than stock, but I was able to make it work with the stainless lines I had already purchased. $23.96 off ebay, cheaper than replacing/rebuilding the stock reservoir. I also grabbed some TYGON line and a Honda breather plug to delete the rear res.




The throttle and right side switches are off of a '20 something CBR500R. Technically a push/pull setup, but since I'm only going to need 1, I'll just seal up the other.

Left and right controls, as well as the front master cylinder, are off of a 2003 R6. I'll have to fix the right-hand lever, as it's a little bent from the PO. No big deal.






The bottom end of the engine has been rebuilt and all buttoned up. I did forget the washer that goes under the oil pressure regulator, but I don't think this will cause any major issues. If anyone can convince me otherwise, I'll open the cases back up and redo it. I've also considered trying to back-off the regulator from the oil gallery holes and adding some gasket sealant, but I'm not sure I'd be able to get it torqued back on enough.

Lapped in the valves twice, but just wasn't able to get the intakes to seal, according to the poor man leak down test (water in the combustion chamber). The head and valves are off to the local machine shop tomorrow to resolve it.


That pretty much catches up with the last 5 months of progress. As soon as all the top end pieces are sorted, the engine will be going back in. Hopefully will be able to start it up for the first time ever shortly after that.





larsensp

Bent my valves while setting the timing.. Found this info after the fact:

1)set up timing, count the pins, rt mark etc. When setting up the initial cam timing, be sure to draw to chain taught to the exhaust cam.
   After timing, any slack in the chain should be at the backside/tensioner side of the engine.

2) Install cam caps on the intake.

3) Very carefully rotate the engine backwards, if your wrench is pointing straight up on the timing bolt, it needs to go 90 degrees to the left.
     You can watch and just rotate enough that your left exhaust lobe releases the bucket. Install exhaust cam-caps.

4) ***********Stop!!, do not attempt any more rotation of the engine until you install your cam chain tensioner****************

5) With the Cam-chain tensioner installed, there should be good tension on the chain and it's safe to slowly rotate the engine forward to RT. Now re-check your timing, pins etc
     before rotating through a full cycle."


But that's what you get for rushing it.

Found a head on ebay for about $120, off to the machine shop for another valve job. Sick  :hithead:

Bluesmudge

Its very easy for the chain to jump timing while installing the cam caps because one of the valves buckets is going to be depressed by the cam lobe, which can slip and cause it all to spin and then jump time. You have to count the pins many times during installation to be 100% sure the engine is still in time. The Haynes manual has a very good step by step procedure. I've successfully done it 2x now and I have no idea what I'm doing.

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