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I’ve made several individual posts concerning the various parts I’ve made as this project progresses. As those posts accumulate, I’ve decided to put them under one heading. I neglected a project log until now because this has been a sort of piecemeal undertaking. I originally brought the major parts home more than five years ago never intending it as more than spare parts for the more-or-less complete bike that it came with. The frame & engine discussed are seen here on the ride home flanking the sister bike.
The sister bike has a title. This frame does not. The sister bike had a complete, but at the time non-running engine & trans. This one was incomplete. I didn’t know at the time and I still don’t know yet if this one is even going to run and drive. While it is intended as “a race bike,” I have not done any performance work to the engine. First, I want to know if it’ll even work! As for racing, I’m 60 years old. I haven’t been on a track since I was 15. “Performance” is subjective at this stage.
I began with a 1971 K1 SL 350 engine and frame, that’s about it. Along the way I picked up a front end I’m not totally sure of the heritage of, a pair of mismatched 19” wheels, a Kawasaki 250 Ninja rear brake and probably a few other odds and ends I’m forgetting. I’m using a 75ish era XL350 tank and a modified fiberglass tracker seat/tail I had on hand. Many other parts have been shop built mostly because I wanted to. This is first and foremost a project to kill time and especially learn. Hopefully, without breaking the bank.
If you’re looking for guidance on how to restore your bike, how to recreate obsolete parts, save money, go fast, or a million other legitimate goals in working on a vintage Honda, this probably isn’t the place to look. If you’re in search of expert advice, you’re definitely on the wrong page. If however you are looking for entertainment, I just may be able to fill the bill.
Before getting too far into the project I stripped the frame down and checked to make sure it wasn’t tweaked. Looked good. Unnecessary bits were removed, with some left on because they would be repurposed for attachment of new parts and some… just because I hate cutting up old bikes.
The tank like several other parts was originally intended for another project. Since the XL is a one-lunger, some means had to be contrived to feed both SL carburetors. The XL also has a slightly smaller bung/threads on the tank so you can’t simply screw on an SL petcock. You can buy plastic “Y” fittings cheap enough from the usual vendors but what’s the fun in that? I turned the applicable parts in brass and soldered them together. My single spout XL petcock now feeds twin SL carbs! I was originally concerned about volume delivery, but previous testing on another SL proved this to work. You really only need enough fuel flow to maintain the bowls at (about) ½ full, so the worry about volume is really overblown in my opinion.
The SL tank also uses slightly smaller front “bumpers” than the SL/CB/CL tank. An adaptor was easily fabed out of 12ga. Steel, formed to the frame backbone, two “nubs” welded on and the whole tack welded to the frame after establishing where I wanted the tank to sit. The tunnel is smaller. It does not allow the tank to seat completely on the frame, but I wanted it higher anyway. An attachment point for the rear of the tank and front of the seat will be worked out later in the process. Falling off your motorcycle is never a good thing. It is typically less expected to happen in casual and recreational riding than on the track though, so for this project making absolutely sure the gas tank is SECURELY attached to the bike is maybe more critical than usual.
I don’t plan to fall off. Falling off is still an exception rather than a rule, but the prospects of it happening increase. Not being ready if it does is unacceptable. Helmet, gloves, boots and leathers? Check! All parts attached securely? Check! Insurance — health & life, paid up? Check! 

The sister bike has a title. This frame does not. The sister bike had a complete, but at the time non-running engine & trans. This one was incomplete. I didn’t know at the time and I still don’t know yet if this one is even going to run and drive. While it is intended as “a race bike,” I have not done any performance work to the engine. First, I want to know if it’ll even work! As for racing, I’m 60 years old. I haven’t been on a track since I was 15. “Performance” is subjective at this stage.
I began with a 1971 K1 SL 350 engine and frame, that’s about it. Along the way I picked up a front end I’m not totally sure of the heritage of, a pair of mismatched 19” wheels, a Kawasaki 250 Ninja rear brake and probably a few other odds and ends I’m forgetting. I’m using a 75ish era XL350 tank and a modified fiberglass tracker seat/tail I had on hand. Many other parts have been shop built mostly because I wanted to. This is first and foremost a project to kill time and especially learn. Hopefully, without breaking the bank.
If you’re looking for guidance on how to restore your bike, how to recreate obsolete parts, save money, go fast, or a million other legitimate goals in working on a vintage Honda, this probably isn’t the place to look. If you’re in search of expert advice, you’re definitely on the wrong page. If however you are looking for entertainment, I just may be able to fill the bill.
Before getting too far into the project I stripped the frame down and checked to make sure it wasn’t tweaked. Looked good. Unnecessary bits were removed, with some left on because they would be repurposed for attachment of new parts and some… just because I hate cutting up old bikes.
The tank like several other parts was originally intended for another project. Since the XL is a one-lunger, some means had to be contrived to feed both SL carburetors. The XL also has a slightly smaller bung/threads on the tank so you can’t simply screw on an SL petcock. You can buy plastic “Y” fittings cheap enough from the usual vendors but what’s the fun in that? I turned the applicable parts in brass and soldered them together. My single spout XL petcock now feeds twin SL carbs! I was originally concerned about volume delivery, but previous testing on another SL proved this to work. You really only need enough fuel flow to maintain the bowls at (about) ½ full, so the worry about volume is really overblown in my opinion.

The SL tank also uses slightly smaller front “bumpers” than the SL/CB/CL tank. An adaptor was easily fabed out of 12ga. Steel, formed to the frame backbone, two “nubs” welded on and the whole tack welded to the frame after establishing where I wanted the tank to sit. The tunnel is smaller. It does not allow the tank to seat completely on the frame, but I wanted it higher anyway. An attachment point for the rear of the tank and front of the seat will be worked out later in the process. Falling off your motorcycle is never a good thing. It is typically less expected to happen in casual and recreational riding than on the track though, so for this project making absolutely sure the gas tank is SECURELY attached to the bike is maybe more critical than usual.