Noob building a CB 350 racer

[legendary_rider]

I'm building a bike right now and would like to consider racing it in VRRA. It's a 1970 CB 350 twin.

I looked at the rules but they seem a little obscure. What's the rule with disc brakes if they didn't come stock but from same period? I'd like to use the front fork from a cb750 (35mm) with front disc.

Also I got my frame welded up yesterday but was wondering if there are any other mods I should be aware of.

So far I'm looking at

Bore tech 67.5mm pistons
X5 megacycle camshaft
32 mm mukuni's
lightened/balanced crankshaft
cb750 forks with disc brake
lightened 5.5mm valves with RD springs, titanium retainers and bronze guides
Head port/polish

As far as you guys know is there anything there that is non conforming in there?

I still need: connecting rods (no idea who is good)
Seat/tank. I was considering using stock tank but not sure.
tires (not sure of allowable width. I think the cb350 actually came stock with wider tires than
VRRA supposedly allows too). I heard someone mention Dunlop K81 410X 18's.

Any advice you can provide would be awesome. I'd really appreciate it guys.

[TimV]

I replied to your other post, but deleted it and stuck it here...

Nice work on the build! I'm building a bike right now and would like to consider racing it along side you. Mine's a CB 350 as well. 1970.

I looked at the rules but they seem a little obscure. What's the rule with disc brakes if they didn't come stock but from same period? I'd like to use the front fork from a cb750 (35mm) with front disc.

1973 CB350 had a front disc, as well as the earlier CB450s and CB750s.

Also I got my frame welded yesterday but read that you can't use additional frame support in VRAA. Yours looks like you chopped the hollow center support and replaced it with 2 side frame supports. Maybe I should do that instead?

I would think that you could brace it if completely new custom frames can be used, but get the OK from the tech chair to confirm.

I still need: connecting rods (no idea who is good)

I've been running a completely stock bottom end for a couple years with no issues.

tires (not sure of allowable width. I think the cb350 actually came stock with wider tires than VRRA supposedly allows too)

4k. WHEELS: Wheels must be wire-spoked construction, with a minimum rim diameter of 18 inches.
17 inch diameter wheels will be accepted if fitted as original size on machine. The maximum width of
the front wheel is WM4(2.5") and WM5(3") for the rear.

4m. TIRES: Maximum width 140mm, as stamped by the manufacturer. No radials.

I'm running 90/90 and 110/80.

Good luck, and see you out there!

TimV

[aly393]

hello new P2 Light
as far as my frame modification went, it was not as straight forward as the pics looked. I used a 360 frame to start, the 350 and 360 are really different motors. I had to make all new engine spacers and mounts to sit the motor correctly, so if you don't have a machine shop I'd stick to welding the stock frame. If you're going to do all the top end work you suggested, I'd also put in new high tensile strength engine studs, stock studs can break with high compression and high rpm. Carrillo rods are nice. bottom end a little lightening and weld the pin. I'm using Dunlop KR825 and KR124a
good luck and can't wait to see you out there
Allan
#393

[legendary_rider]

Hey, thanks guys


I wrote those down and will utilize it for sure. I heard about the engine studs once somewhere but it slipped my mind. I'll get on that. I actually sent an email to carrillo this morning about rods cause I didn't see them in their catalog. Wasn't sure if they were good but thanks for confirmation.

Cool. I'm glad that it's ok to just weld up the stock frame. I already dropped it of to get powder coated. They seemed pretty excited to work on it and I probably would have had to pry it out of their hands. lol.

The cranks in right now getting lightened if that's what you mean by bottom end. I went with a before/after photo of the Capellini crank. I also told him to take out the starter gear and I'll use kick start.

I'm not sure what you mean by welding the pin? Could you elaborate please Allan?

As far as the disc brakes go, I've watch some VRRA race vids and always see bikes with the drum brakes.
Doesn't it make a lot more sense to use disc on the 350's then if it's allowed. Aren't they much lighter and have better stopping power?

[aly393]

the counterweights ( rod cheeks ) are put together by press fitting, without welding the pin the cheeks can twist ( turn ) or spread apart. so they are tack welded to the pin
Allan

[MGill]

Regarding your question about brakes....
The cb350 is allowed in p1-350 but only with drum brakes
stock frame and stock motor.
Some people build to p1 spec and then can bump to p2
as well...
See you on the grid
Mat

[legendary_rider]

As far as I can see the P1 is only for bikes up to 1967 so I wouldn't qualify anyway with my 1970 350?

So I could still get into P2 and P3 then maybe an F series? So these other classes, would I pretty much have a death wish going up against larger bikes or would I actually stand a chance with a highly modified 350?

Another question, where do you guys get your tanks and seats? Are they just standard cafe race style from any site like "Dime City" or do you recommend somewhere in particular? Any tips?

[MGill]

Print this, and read it cover to cover...
http://www.vrra.ca/wp-content/uploads/2 ... -Rules.pdf

On page 17 under period 1 exceptions you will find....

HONDA CB/CL/SL/350 twin cylinder machines, in order to be eligible for Period 1 GP, are limited to stock original equipment engine internal and external parts as originally fitted to these models. No parts designed for another model of Honda or any other motorcycle may be used. No aftermarket components are allowed except for valve springs and slider style camshaft chain tensioner (as manufactured by Bore Tech or similar). Carburetors cannot be greater than 30mm choke size and may be any Period 1 legal model, round slide Keihin or Mikuni.. Ignition systems may be after market and/or electronic. NO MODIFICATIONS WHATSOEVER by any machining or chemical process may be made to the engine, intake tract, carburetors, or any other engine component. The only modifications allowed are the removal of the electric starter, alternator components and the fitting of a racing style exhaust. The rolling chassis must be of a racing style as per Period 1 rules. Modified Honda CB/CL/SL 350 twin cylinder machines, which deviate from the use of stock original equipment engine components, are moved to the Period 2 Supervintage Lightweight class.


Tim... Where does a P2L bump to -- mid production?

[TimV]

[quote=legendary_rider"] As far as I can see the P1 is only for bikes up to 1967 so I wouldn't qualify anyway with my 1970 350?[/quote]

No...read the rules that Matt linked to below. Save the file. I refer to it all the time.

You can run a drum brake if you want...a lot of the racers in the US do. I hear most of the early disc brake setups aren't much better than a really good drum brake, so do whatever you think is right for you.

Print this, and read it cover to cover...
http://www.vrra.ca/wp-content/uploads/2 ... -Rules.pdf

On page 17 under period 1 exceptions you will find....

SNIP

Tim... Where does a P2L bump to -- mid production?

Technically, I think a P2L CB350 can bump up to... everything, can't it? Enter as many races as your wallet and body can put out. But MWP and maybe P3L would be about it for me. Unlikely to finish on the podium if the fast guys are running good in those classes though....

[legendary_rider]

Hey I appreciate the link and advice. I read through the rules in entirety but it started getting dry at parts. I actually got the 1967 limit from the "FAQs drop down menu"- then "How do I build a race bike"- "race classes"-

"Period 1: For motorcycles up to model year 1967. GP style racing motorcycles with classes for: 200cc GP 250cc GP 350cc GP 500cc GP Open GP" * Maybe the open GP for 350cc invalidates 1967 then?