friend wants to built a CB 450 racer

Anyboby out there racing a CB 450 Black Bomber. A friend of mine wants to built one for vintage racing. I tried to talk him into running a RD but he hates 2 strokes! Why I don't know, I guess he's not right in the head or something! Any way he has 3 450's( '65,'66 and '72 ) and thats what he wants to race.
I told him if anybody could help it would be you guys.
Oh Yeah 2 strokes Rule!!!!!!

 

Hmm lets see......
1. disconnect cam chain and weld all valves shut.
2. cut several big (bigger is better, right?) holes in the side of the cylinders.
3. Bolt some reeds to the intake manifold.
4. replace silly stock exhaust w/ cool expansion chambers.
5. get ready to kick some butt on the track!!!
6. Be prepared to replace pistons on a semi/regular basis.


Hope this all helps your "freind"!

 

Friends don't let friends race 4 strokes.

 

Carl, Mark (authors of the 2-stroke communist manifesto?) I can't believe you two are encouraging someone to smoke!!! Shame!!

 

Bean oil is the opiate of the masses!

 

Enough of the chatter already!CB450s can be a potent racebike,but not for the timid.Be prepared for lots of teardowns from rocker wear(probably)and blown rod bearings(definitely).The American expert on 450s is Bob Gerberich,racing them for over 10 years,and one of my mentors and colaborators.One of his 60HP engines beat the winning streak of Moony in AHRMA 500GP recently.Not the cheapest bike to build.Reach him at his buisness-Wadsworth Transmission Service (330)336-3515

 

If you want to learn how to work on 2 strokes, by all means, get one.

If you want to spend you time on the track riding & honing your skills & drinking beer after the day is spent, get a 4 stroke...

For under a $1000 you can buy, prep & race a GS450. You will only have to "jet it" once.(beer factored into price)

The debate never stops

 

CB450 comes with big ports and carbs and dynoed over 43HP stock on the rear wheel ! thats more than stock RD400 , it actually too fast for its frame and brakes , the frame weights a ton so start with hacksaw and grinder , cut off the down tubes let the engine hang , you be cutting and grinding and removing things for days , put pair of Longer shocks from wreck yard from a bigger later model bike then do something for front ,its 19 inch so use metezeler or k591 or just swap the front with anything that fits , install a drop bar if you cant find them just cut bicycle handlebars and weld up a drop bar , put those cheap pipes from JC whitney cataloge , it make harley guys envious

 

I tried to tell him to get a 2 stroke but some people just refuse to see the light. Anyway if he builds the old black bomber thats another 4 stroker to shame on the track.
Thanks for the suggestions and the sources.
All kidding aside the more people on the track the better off the sport will be.
I'm 46 and just got my license at Putnam this pass weekend and I have to say I have never met a bunch of nicer people.
Thanks for the ideas and keep them coming.

 

I don't think these are advisable tips... sounds more like a recipe for disaster.

Sorry if this was a joke and I merely failed to see it as such because a "smiley" wasn't attached.

 

cut off the down tubes let the engine hang...

sorry if it sounded sadistic but just look at MZ250 or honda MB50 frame , all you need is single back bone and 3 mounting point , frame wil flex anyways ,those are thick pluming pipes and i cant resist getting ride of them , i did it to few bikes including cb350 and cb175 etc with no problems ,they were not racers but it made light fun bike to ride around

put pair of Longer shocks from wreck yard from a bigger later model bike...

this will quiken choper like handling and give you more ground clearance

just cut bicycle handlebars and weld up a drop bar

i got one on mine which i made up , its like a clipon but extends 2 inches forward to put more weight on the front and improve handling , the best tip would be to move the engine forward one inch but its easier to make the drop bar

 

I believe there's more to coverting a frame to using an engine as a stressed member than just cutting off the downtubes. Don't forget, we're talking about racing old bikes with old tech frames that didn't handle well to begin with. I too modified my CB175 frame, but I made the frame stiffer because it flexed at certain tracks. The MB5 you mention was an inexpensive lightweight and wasn't meant for racing so it's frame didn't need to be stiff. Hell, even the 920 Virago I raced a little last year only had a pressed steel spine frame. It was designed to use the motor as a stressed member yet at racing speeds the damn thing flexed pretty bad. Look at competition motorcycles using the engine as a stressed member. Their frames were specifically designed for the purpose and use either huge backbones (such as the Egli frames) or perimeter/trellis style frames ala MZ, Ducati or Buell.

I'm not questioning the idea of longer shocks... most of us use them on our bikes. My concern is with the suggested source. I have yet to find a junkyard shock worthy of a street bike never mind a race bike. Besides, a lot of OEM shocks were crap to begin with.

Metzeler... I loved them as a street tire but question their track worthiness. Dunlop K591... makes a great backyard swing.

Bicycle handlebars... Why bother? If you can get to a junkyard for shocks then you can find good thick walled handlebar tubing.

 

It appears the 2-stroke vs. 4-stroke lives again.
Since I race both I could argue with myself

See the following article regarding building a CB350
Honda twin which I believe the approach is good for
any motorcycle.

www.motorcycleshopper.com/articles/hondacb350/editorsnote.htm

I would start with suspension, wheels and tires, then (depending on rider ability and funds) move into the engine. Although the frame will cause handling problems, the suspension is more
critical to the handling of the bike. Two possible rear
shocks are Progressive Suspension and Works Performance.
Tires used are Avons and Dunlops (not 591s) which need to mounted on the correct rim size. Front suspension is more home grown as to what works and the cost. Race Tech will rework most
front forks based on supplied information for vintage bikes.
I would check the rules and use the latest model of the maximum
size that is legal for the class, then tune using springs, spacers and adjust the weight of the fork oil. The seat, rear sets and
handlebars are important to get set up correctly to work
properly and you feel comfortable. Finally, take the time
to properly build/install the exhaust, rear sets and oil
catch pan not to hit/drag at maximum cornering.

The engine needs to be in good condition and modifications
depend on funds available. www.m3racing.com has parts
for the CB450. I am sure there are several other parts
supplies.

Take Care

 

I forgot about AHRMA's Historic Production class,good for racing a stocker 450.I get caught up sometimes in the world of "competetive"fully-built bikes.Hey,Jim,I was waiting to see some comments from you on 450s.What's the story on your bike?I watched you win a V2race at Putnam,but never got over to see you before you split.Always interested in the "quote"(horsepower).Just tested some old Spec2 RD400 pipes on the dyno yesterday,not too impressive.I'll stick with the setup on my F-RD spec. RD400 that I've had for a year now,56HP (with lots of midrange).

 

Midrange ?? 2 stroke??

Dogs & cats living together???

 

Jim which dunlops you are recomanding and where to get them ? if you are talking about dunlop TT tires i dont know any source in us , everyone run R compound k591 at sear point and willow till few years ago , 250cc to 1200 cc , vintage or modern , BSA to GSXR1100 run 591s , %90 of modern bikes there actualy run bias ply 591s instead of radials which the bike was designed for ! ,no brand win more races than 591 , harley 888 cup used 591 as well with thier 19inch front ,they were cheap and warm up fast and slide predictably , dunlop stop making them so now they can charge you 2x more for radials

BTW ,Bassani or DG pipe on RD gives lotsa midrenge as long as you stay with original Y hoses

 

See hand made Dunlop thread.

Just talked to Mr. Barker on tuesday. 591's suck, compared to Avons, from what I've been told, avons suck compared to hand made dunlops.

I'll be having me a rear soon to see what all the fuss is about. Price be damned. Racer price $ 152.00 for the 110/90/18 + shipping.

When it comes to slapping down 2 strokes, only the best will do...

 

IPH:

The Dunlops are available through R. C. Barker at
352-378-3715 which are the special vintage racing
tires (KR series (124A, 124, etc.). I had used 591s
when you could get the R compounds, but switched
to Avons after Dunlop stopped producing the the
591. I believe the Avons are equal to or better
than the Dunlops, but in all reality both are very
comparable and may come down to personal
choice. I have seen some very fast (high corner
speed) riders on both brands. Getting the right
tire on the right size rim is very critical. Too big,
too small or wrong rim size costs corner speed
because of reduced traction, wheel chatter, and etc.
I spent about 2 years getting the suspension and
tires correct on the CB350.

 

Stan:

Decided to build a new CB350 engine from scratch looking
at everything. Mark and Jerry provided the specifications
for the engine along with the head and cam. At Daytona
it showed some good potential running with Tim, Buff and
Jesse in the 500 Sportsman on the banking. I had mechanical
problems and had to drop out. I have made a number of
mistakes in assembly and tuning that have keep the
engine from running like it should. This has been
very frustrating because I believe the engine should
be very fast once I can get everything sorted out.

I am trying some new parts this weekend at Putnam to
see if it solves a on going problem.

Are you planning on showing up at the September race
at Putnam?