Topic: Who knows cb450-500cc twins?

[Geeto67]

Anybody here mess with the 450-500 twins? Can you tell me the wristpin size? (in mm)

Also anybody have any expirence with the 450 into kz900 piston swap and what was involved? I am trying to go the other way with a set of kz1000 turbo pistons and would like to know what is to be expected.

[tbpmusic]

Piston pin for CB450 DOHC 5-speed - (4-speed lists a different part number, but may be the same size??)

outside diameter - 16.994 - 17.0 mm:::  replace if under 16.95 mm

inside diameter of piston (pin bore) -    17.002 mm - 17.008 mm ::: replace if over 17.1 mm

CB500T is same part.

Don't know anything about an alternate swap-out part.

[Geeto67]

kz900/1000 piston pins are also 17mm and an old timer told me he used to use cb450 pistons in his drag bikes because it gave them a bump in compression. The kz1000 stock piston is 70mm just like a cb450/500 honda.

I am building a turbo 450 to go LSR racing with and there are no forged pistons for the 450 with low compression. There are however stock replacement and turbo forged pistons for kz900/1000s.

My original plan was to use cb500T pistons in the 450 since the 500T has the same piston size and a longer stroke than the 450 so mating them with the 450 engine would give me around 8:1 comp. Kz turbo pistons in a Kz have a compression ratio of 7.8:1. If I knew the difference in compression using a cb450 piston in a Kz creates I can then figure out what these kz turbo pistons in my cb450 will give me.

I am shooting for around 8:1 because I only want to run 8psi with the turbo.

On a semi-related note: anybody know a set of bolt on carbs for the 450 that are not CV? I was thinking of running a draw through S&S super G but if I could go to a blow through carb I would consider it.

[bill440cars]

       Geeto, crazypj has some some swapping around of internal parts on several different bikes, might give him a shout and maybe he has some insight or might know where to send you.

        BTW, I wouldn't mind keeping up with your progress, myself.

                                     Take care, Bill

[Geeto67]

I'll give him a shout, right now I have a message into Big Jay since he used to make the old KZ big bore kits out of DOHC pistons back in the day. So far all the info I have is that they used to cut the honda pistons to accomidate the different valve angle of the KZ head but everything else is a bolt on it looks like. MTC has forged psitons in 70mm (450cc) and 72mm (464cc) with a 7.8:1 comp ratio which might work for me.

As far as keeping up with the progress you have my e-mail. everything kinda hush hush right now since we only just got the bikes that will serve as the basis of this endeavor in last Friday. I bought an AHRMA racer's partially assembled cb450 road race bike and parts bike, and the neighborhood guys have come up with an entire 450 in parts. We are moving shop space from Long Island to Brooklyn this weekend and then the fun begins. I hope to have the bike running on my birthday Feb 22.

Once we get rolling I am going to start a post on caferacer.net so people can follow along.

I just had a long conversation with a racer in Jersey who is running a 500cc turbo BSA and he is running the same turbo/carb setup I want to run so it is nice to have somebody who has tred this ground already, epsically when we are in different classes with almost the same setup (he runs in pushrod I run in non-pushrod).

[crazypj]

Hi Geeto,
Posted a reply on a forum but cant remember which one, either Do The Ton or Caferacers.com.
Do you know the biggest pistons you can fit and stay under 500cc?
 I have lists of stuff as I 'invent' big bore 'kits' for different bikes.
PJ

[Geeto67]

probably caferacers.net, do the ton pisses me off to much to surf there often. what is your name over there?

The largest I can go is 74mm which yeilds a 490cc displacement. At 75mm I am at 503cc with stock 450 stroke.  the only reason I was considering 72mm is I found a kz big bore kit in that size for $350 which is pretty cheap, normally they are $500.

I want to stay close to stock bore just because honda 450 parts are cheap and if I grenade an engine I can just grab the parts I need and go again. I am expecting to break a lot of stuff.

[crazypj]

GS500 is 74mm.
You can get complete cylinder/piston set on e-bay cheap sometimes (friend picked one up bored 1mm over, barely run for $75.00)
Pulled liners and fitted them into an XS400dohc motor. pic of GS500 pistons in XS400 block
Its up in NJ somewhere
PJ
 BTW, I stick with crazypj everywhere unless its already taken, then I use either 1crazypj or crazypj22