I started building CB350 and other vintage race bikes in the 80's as a mechanic, then started racing myself in 1992. There were no "Supersport" type rules until USCRA introduced them mid-90's with the stock CB350 down graded from Lightweight Supervintage (Sportsman in WERA and AHRMA) to 350 GP class.
Your engine has very low wear and was not abused. My personal and customer Stocker CB350 builds are as follows:
-Clean and degrease all engine parts, especially cleaning the crank oil-slinger "sludge trap" groove with a pick and spraying a can or two of contact cleaner through the big end pins to clean. You can rotate the con rod and feel the debris getting loose and washing out. Inspect all parts for replacing. Stock intake and exhaust valves will need to be replaced in most cases.
-Bead blast all cases, clean again to remove all blast media, then wash the cases with S-100 or Bike Brite to remove more media dirt stains if needed. Cut/dress the valve faces and check the seal as per my video. It is critical to thread a sacrificial bolt into every threaded hole to keep the media out during blasting. If beads are blasted into a blind threaded case hole, throw out the part and start over.
-Assemble with all new gaskets, o rings and oil seals. All oil seals need grease in the ''groove". Include an upgraded camchain tensioner, Ken Miller KA slipper type is my preference, I have not tested or used the newer roller types on the market. It is not necessary to use a flat sided chain with the KA tensioner, the stock chain is good. Beef up the shift drum detent with my mod as per my video.
-You need a good electronic ignition, crank mounted PVL type is my preference. Stock CV carbs are fantastic, run without filters like a real vintage race bike. You may change the Primary and Main jets for tuning. Be advised that all of these carbs now have eroded needle jets and good O-rings need to be sourced. You will want long tapered megaphones on each headpipe. 2 into 1 exhausts will loose power.
The engine output will measure 27 rear wheel HP on a Dynojet 250i.
What I don't do:
Do not slot the cam sprocket, stock timing is optimal.
The stock oil circulation is excellent, no need to modify in any way, even up to a 11,000 RPM 48HP engine.
Completely stock clutch is good.
The stock drum brake is garbage. The GT500 Titan drum brake will crack and try to kill you when the wheel collapses. The CB450/CB77 drum sucks. The only affordable brake that I have not destroyed or make fade into oblivion is the 4LS GT750 drum. It is NOT too heavy, and I promise to wave to you when I pass you on the brakes if we ever meet on the track.
Read what I wrote about chassis mods:
Sweet Mike.....will work for beer:up: I'll know tonite if I'm in.....thanx.....I'll pm yall. Hey CP.....I thought the same thing....its like front...
forums.13x.com
I do no extra welding or boxing or bracing to the stock CB350 frame. I still hold the lap record of 1:48:9 at Mid-Ohio 2011 for this class of bike, plus the next class up. I'm not the fastest rider, do I have the best handling bike?
I like 35mm CB500T forks simply because the have chrome all the way up. Straight weight springs, Gold Valve emulators.
Stock fork clamp offset will allow the bike to fall into the corners, trail needs to be increased.
Here are the numbers:
Steering head angle 27°, front tire radius 310mm.
Stock offset 58mm/ ground trail 92.86mm
48mm offset/ 104.08mm ground trail.
There is a CB750 clamp that has this offset.
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Curiously enough this particular bike was built for Larry Macoskie in 2008, it was then raced by another racer, and is currently raced by Andrea Blake. The engine has never been apart.
Cheers, Stan