Topic: Building of a CB500 classic racer

[Howell]

Hello,

I am René from Holland and I am new on this forum.
I am building a CB500 Classic racer for my eldest son.
My eldest son wil ride the bike in the national dutch classic championship in 2010.
At the moment we are building up the chassis and a good friend of my will tune up the engine.
He is very experienced in tuning classic Honda fours.
He has already made two CB750 engines for me , one with 820cc and one with 860cc.
Another friend of my is already racing a CB500 with a engine of him with 65 hp at the backwheel.
My son has made a website for building the 500 racer , it is in dutch language.
But there are many pics on it.
www.yrjo.nl




Chassis specs:
Stock Honda frame
CB750 type Dresda swingarm
Frontfork Yamaha RD350LC
Alu yokes from Voxonda (member on this forum)
Yss shocks
Honda RC162 replica frontbrake from Budamotor Racing in Hungary:http://budamotor.hu/index.php?language_id=2&menu_id=1
Honda XL250 hub and rearbrake with AFAM sprocket 520
Tarozzi clipons and footrests

Some things to get more power out of the engine:
Head flowed and ported
Camshaft from Webcam
Renault car valves
Honda Dax pistons
Lightened CB500 crank
Suzuki GSX1000 rods
Barnett clutch plates
Close ratio 5 speed gearbox from :http://www.mpe07.co.uk/
CB650 oil filter pan
CB650 oil pump
CB650 outer clutch
Keihin CR29 mm carbs
4 in 1 exhaust with WRP alu silencer

At the moment we are waiting for the gearbox which will be delivered in the second week of januari.
The chassis is almost ready and after that we have to spray the chassis and the tank/seat and fairing.
I will update the topic frequently.

My Honda CB750 with the 820cc engine:

My CB750K2 1973:




Regards René

[bwaller]

Welcome Rene. 

Nice project, lots of good pictures, should be a great race bike. I am curious about the Dax pistons & Renault valves? Can you elaborate please? (bore, valve sizes) Looks like a nice light option for a rear hub.

I have Ellis doing some transmission work also and I'm excited to see the results.

[Howell]

Welcome Rene.  

Nice project, lots of good pictures, should be a great race bike. I am curious about the Dax pistons & Renault valves? Can you elaborate please? (bore, valve sizes) Looks like a nice light option for a rear hub.

I have Ellis doing some transmission work also and I'm excited to see the results.

Sorry , but I promised my tuner not to give any detailed information about the tuning.
So you have to do it with some pictures.

[bwaller]

I know, I know, you could tell me then you'd have to kill me.....

That's ok, my cylinder head and pistons are already sorted anyway!

[Howell]

I know, I know, you could tell me then you'd have to kill me.....

That's ok, my cylinder head and pistons are already sorted anyway!

Here a picture of the crankshaft , it is ligthened 5kg

[bwaller]

Looking gooood Rene.

Another member here Soos discovered GSXR1000 rods would replace his 650 rods which I thought are 5mm longer than 500 pieces. 

[MRieck]

Looks very good. Don't worry....none of us will be stealing secrets and starting out own companies.

[turboguzzi]

Hi Rene

Welcome to the small block racing club! Is it a 500 or bigger?

We already heard about you from Ellis, we know all your secrets

Was wondering why you have to use a drum in the front. Is it the same situation in NL as in the CRMC in the UK? Backwards retrograde logic....

Some really extreme weight removal on the crank! Wonder how it will work, crankshaft mass is somewhat beneficial for good drive out of corners. there is a yoshimura crank picture in the forum and it shows much less weight removed

Brent, The Honda Dax has the good old flat pushrod motor like the Honda monkey, so I guess its a piston form one of the common big bore kits out there kits out there. Takegawa has some really tasty 57mm ones, but they are really expensive!

And tell your tuner not to worry too much about industrial espionage on tuning 35 year old bikes which are raced for just a little tin trophy.... you are welcome to show him some of my secrets, they are all here in the site.

TG

[Howell]

Hi Rene

Welcome to the small block racing club! Is it a 500 or bigger?

We already heard about you from Ellis, we know all your secrets

Was wondering why you have to use a drum in the front. Is it the same situation in NL as in the CRMC in the UK? Backwards retrograde logic....

Some really extreme weight removal on the crank! Wonder how it will work, crankshaft mass is somewhat beneficial for good drive out of corners. there is a yoshimura crank picture in the forum and it shows much less weight removed

Brent, The Honda Dax has the good old flat pushrod motor like the Honda monkey, so I guess its a piston form one of the common big bore kits out there kits out there. Takegawa has some really tasty 57mm ones, but they are really expensive!

And tell your tuner not to worry too much about industrial espionage on tuning 35 year old bikes which are raced for just a little tin trophy.... you are welcome to show him some of my secrets, they are all here in the site.

TG

We have to use drum brakes by the dutch CRMCH.
The pistons are from a big bore Dax.(about 512cc)
Here a picture of the Cb500 racer of a friend of my and from the crank and rods.
Nr 46 not Valentino
The same crank and rods are used in the no 46 bike

[Howell]

Some pictures of the no 46 engine:

[bwaller]

Thanks Rene, pictures are always well received!

Different racing association class rules are sometimes puzzling to be sure. As much as big drum fronts are kinda sexy and can be really strong, why when almost all production stuff went to discs.... 

Yet another approach to improving intake flow too, at 65hp definitely some magic lurks beneath!

That crank will definitely spin up quickly, I expect it just makes them a little peakier to ride fast. Like TG mentioned I'm hoping a little flywheel effect might help haul my ass off the corners. 

Another good looking race bike.

[Howell]

I found these pictures on a french site , look for the clutch control.
Very nice.

[JIMLARCH]

Very nice.

For those who need to translate www.yrjo.nl,  just go to google translate. Very simple.

[turboguzzi]

Rene,

I remember looking at this guy's clutch plate (CL2.jpg) when I was building my own mechanism.

the main problem I see there is that all the force of the clutch pushrod is feed into a single 6mm bolt that holds the oil pump.

in my solution (CL1) , the plate is secured by two of the oil pump 6mm bolts, so i think its safer and more robust without having to add these two "ribs" like he did. sorry that you cant see the whole plate in this photo...

By the way, I really recommend you go for external oil feed lines to the cam like I did, makes life much easier and lets you use thin copper head gaskets for better heat transfer.

I also totally chopped the crank and fitted a very flat cover, otherwise you have to make a strange and ugly cover like this guy did that bends very easily if you fall. if you run total loss ignition, you dont really need the left taper at all.

TG

[Howell]

I do it this way , easy and reliable.

[Howell]

The last fourteen days I worked on many little things which took plenty of time.
I installled the special made Voxonda alu yokes and also made brackets for the fairing.
Yet al the big frame work is done and now we have to finish some welding by an experienced welder.
And then the bike is ready for spraying.
I hope the engine is ready at the end of januari.

[Howell]

My son and me in the early days.
Me on a Honda CB750 in 1977 and my son Yrjo who is gonna ride the CB500 on a Aprilia RS250 in 2002

[turboguzzi]

I do it this way , easy and reliable.

Wait till you mount heavy duty clutch springs.... 

beautiful shot of your 77' 750!

TG

[Howell]

I do it this way , easy and reliable.

Wait till you mount heavy duty clutch springs....  

beautiful shot of your 77' 750!

TG

That's no problem , my friend with the no 46 Honda uses the same with heavy springs during two raceseasons without any problem.

[Terry in Australia]

G'Day Rene, that engine looks great mate, tell me though, why the fancy carb adapters? I recently rebuilt Al Harpers 550 engine, he bought new Keihin CR carbs, and after trimming 3 or 4mm off the ends of the CR's spiggots on my lathe, they fitted perfectly into the 550's intake rubbers? Are those adjustable clipon's Rob's work too? Cheers, Terry.    

[Howell]

G'Day Rene, that engine looks great mate, tell me though, why the fancy carb adapters? I recently rebuilt Al Harpers 550 engine, he bought new Keihin CR carbs, and after trimming 3 or 4mm off the ends of the CR's spiggots on my lathe, they fitted perfectly into the 550's intake rubbers? Are those adjustable clipon's Rob's work too? Cheers, Terry.    

These carb adaptars are used because the original manifolds have a bend in it , and with these straight adaptors it gives the best flow, this is measured with a flowbench.
The clipons are from Tarozzi ,not Rob's work:http://www.tarozzipaolo.com/inglese/homenets.htm

[Sam Green Racing]

Looking good Howell, keep the pics coming a lot on here can't read but like looking at pictures.

Sam.

[Howell]

Looking good Howell, keep the pics coming a lot on here can't read but like looking at pictures.

Sam.

Oké Sam , here are some more pictures for those who can't read.
This are pictures of my CB450 classic racer I raced in the ninetees for the dutch classic championship, I sold it in 2002.

[Howell]

Some nice pictures of Cb750's

[Howell]

And here is a special one , me and one of Valentino Rossi's 2008 Yamaha's.
Forgive me it's not a Honda.