Topic: Building of a CB500 classic racer

[kos]

My youngest son came back today from a holliday at Kreta, Greece with eight pistons in his luggage.
These are 57 mm pistons for our Cb500 racer, original for the Honda DAX minibikes.
They are very cheap in Greece , 25 euro each ( = $32,50 and GBP 21,= )  , complete.

What is pin diameter on those pistons?

KOS

[Howell]

My youngest son came back today from a holliday at Kreta, Greece with eight pistons in his luggage.
These are 57 mm pistons for our Cb500 racer, original for the Honda DAX minibikes.
They are very cheap in Greece , 25 euro each ( = $32,50 and GBP 21,= )  , complete.

What is pin diameter on those pistons?

KOS

The pin diameter is 13mm ,we use Suzuki GSX1000R conrods for a pin diameter of 15mm.
We use bronze bushings in the small end to fit the 13mm pins.

[Howell]

The arms are clocked incorrectly: they should be at 90 degrees with the connecting rod. They both should be rotated counter clockwise.

Why and what is the difference ?
If I understand you correctly they should be mounted like the ones on the picture below.

[turboguzzi]

The arms are clocked incorrectly: they should be at 90 degrees with the connecting rod. They both should be rotated counter clockwise.

I tend to agree with you, the angle is not efficient like that.

rene, i have 4cm like you in the small arm but about  6.2cm in the lever so my linkage requires 20% less movement than yours....

[turboguzzi]

and put some lockwire in the sprocket!! 

[scottly]

Your 4/5 ratio is only valid when all 4 pivot points are at 90 degrees. At 45 degrees, your 4 cm arm is equal to a 2 cm arm. Your angles favor down-shifting, at the expense of up-shifting. The angle of the shorter arm is more critical. I would rotate it one spline anti-clockwise, and see how it looks, then shorten the connecting rod to fit.

[oily.tom]

Better late than never! The angle of the backcut is 5 degrees. I have made ALL my backcut clusters/gear pairs with this angle and this causes no issues. In Rene's cluster it is the same angle on 2nd, 3rd & 4th gears also.
Regards, Ellis.

[Howell]

and put some lockwire in the sprocket!!  

Is not necessary , I ride my CB750 and CB820 still many years without.

[Howell]

The arms are clocked incorrectly: they should be at 90 degrees with the connecting rod. They both should be rotated counter clockwise.

I tend to agree with you, the angle is not efficient like that.

rene, i have 4cm like you in the small arm but about  6.2cm in the lever so my linkage requires 20% less movement than yours....

I can't make the lever arm longer because it is an original Tarozzi lever , otherwise I have to make a complete new lever like the Tarozzi and that is difficult because of the shape of it and how it is fit.
But I can change the angle to 90 degrees.
See the picture for the Tarozzi  lever.

[turboguzzi]

the arm with the holes looks like mild steel. would cut it and simply weld a 10mm extension.

it will not look so nice but neither did pops bikes look nice

But if you dont want to cut them, just try a CBR900 (the "929" model) lever. you witll only need to turn on a lathe a steel spacer for the lever to turn on.

And if you dont like it you can go back to your tarozzi's

but you surely can change the length of the rod so your arms are at 90 degs anyway.

[scottly]

I would try setting both arms as close to 90 degrees as splines allow; if 90 is between splines, choose the more anti-clockwise position to favor up-shifts. I would not worry about changing arm ratios unless you have too much travel at the shifter pedal.   

[Pasolini]

Hello,
I am new to this forum, my name is Michael and I live in Belgium.
I have not a CB 500 racer but a Benelli 500 Quattro one which had a stock CB 500 engine in when I got it  and is coming back next year on track with a Benelli one  .

Rene wrote:
On saturday there was a free practice and a timing practice , on sunday there were two races.
First practice we missed again 3000 revs, after inspection I found a overheated coil which was melting.
I think this was the cause of missing in earlier races some revs , the coil was probably already bad.
I had no spare with me , but there was a motorpartsmarket in the paddock with all kind of things and I found a pair of second hand 3 Ohm coils.
Second practice the revs were back again , but the engine was not running really good above 10000 rpm.(max 11000)

I think you should consider the coils. Me too I have an ACCENT ignition, also bought from Rene van Maanen (very good). It is, like the original Honda ignition, designed to run with 5 Ohm coils.

I did not know neither but the ACCENT will overheat EVERY 3 Ohm coil. I also cooked at the beginning my 3 Ohm aftermarket ones, with the same problem as you describe. And especially at 40°C weather and running engine in standing bike waiting for the go!

ACCENT describes that problem on their German website (!) and states that the ignition needs 5 Ohm coils to avoid overheating.

I use now 5 Ohm (Dynatek Duo) coils, they run perfectly, cool and perfect firing even at very high revs. I can recommend them.

I got mine here:
http://classic-bikes.bikeside.de/

Go to the online shop and look for Dynatek. They have also some other nice tuning stuff for old Honda's, unfortunately not a lot for the CB 500.

[Howell]

Hello,
I am new to this forum, my name is Michael and I live in Belgium.
I have not a CB 500 racer but a Benelli 500 Quattro one which had a stock CB 500 engine in when I got it   and is coming back next year on track with a Benelli one  .

Rene wrote:
On saturday there was a free practice and a timing practice , on sunday there were two races.
First practice we missed again 3000 revs, after inspection I found a overheated coil which was melting.
I think this was the cause of missing in earlier races some revs , the coil was probably already bad.
I had no spare with me , but there was a motorpartsmarket in the paddock with all kind of things and I found a pair of second hand 3 Ohm coils.
Second practice the revs were back again , but the engine was not running really good above 10000 rpm.(max 11000)

I think you should consider the coils. Me too I have an ACCENT ignition, also bought from Rene van Maanen (very good). It is, like the original Honda ignition, designed to run with 5 Ohm coils.

I did not know neither but the ACCENT will overheat EVERY 3 Ohm coil. I also cooked at the beginning my 3 Ohm aftermarket ones, with the same problem as you describe. And especially at 40°C weather and running engine in standing bike waiting for the go!

ACCENT describes that problem on their German website (!) and states that the ignition needs 5 Ohm coils to avoid overheating.

I use now 5 Ohm (Dynatek Duo) coils, they run perfectly, cool and perfect firing even at very high revs. I can recommend them.

I got mine here:
http://classic-bikes.bikeside.de/

Go to the online shop and look for Dynatek. They have also some other nice tuning stuff for old Honda's, unfortunately not a lot for the CB 500.

Hi Michael , welcome on the forum.

3 Ohm coils are not a problem with this ignition , I use them on my CB820 for 4 years with the Accent ignition without a problem.
Also my friend with a CB500 racer uses 3 ohm coils still 3 years with this ignition without any problems.
But you have to use another rotor , this is what Accent says about it in the installation manual :

PREREQUISITES
To install this SYSTEM you may need some basic knowledge of how ignition systems work
on motorcycles. If you have not, common sense and a step-by-step instruction guide will
help you through the installation process.
This system is developed for running with standard 5 ohm coils. If you need this system
for use with lower Ohm coils, e.g. the Bol d’Or 3 Ohm types, you will have to order
another rotor type. This is concerns the 110 contact angle type. Please mention this
while ordering.

* …….your coils heat up heavily after you have installed the system, and did not heat up
before….
You may have installed non-standard coils; 3 Ohms instead of 5 Ohms. The coils take
more current, and therefore will dissipate more heat. Also in this case the system will
need another timing. You can order another rotor from your dealer. This rotor will
provide a contact angle of 110 degrees, instead of 180 degrees. Please mention this
while ordering.

Maybe you overheated your coils because of using the rotor for the 5 Ohm coils.
I opened my overheated coil and saw that there was rust in it ,so I think that was the problem , I bought them second hand on Ebay.
Now I ordered new DYNA DC1-1 3 Ohm Hi-Performance Ignition Coils with spark plug wires.

[Howell]

I would try setting both arms as close to 90 degrees as splines allow; if 90 is between splines, choose the more anti-clockwise position to favor up-shifts. I would not worry about changing arm ratios unless you have too much travel at the shifter pedal.  

I made some more holes in the Tarozzi lever to adjust the arms to 90 degrees.
Also I  bend the return shift spring (nr 18) of the shift arm to get more preload, so that the arm gets quicker and better in the right position.
 

[Howell]

In the paddock in Chimay a man came to us to take a look on our Honda racer.
I saw the man before walking in the paddock and recognised him then already.
It was Todd Henning , riding many years on Honda's CB450's and had many wins on it.
I spoke with him for a half hour about his career , his Honda's and his terrible crash.
Ten years ago, Todd had a serious crash while racing the AHRMA race at Sears Point Raceway in Sonoma California resulting in head injury and a long time in a coma.
It took a while, but thankfully Todd did recover. His racing career was over.
Now his sun Ari is racing on Honda's , in Chimay on a CB350.
I was very honoured having talked whith him.

http://web.me.com/thracing/THR/THR_HOME.html

On the left is Todd.

[bwaller]

Good you recognized him Rene.

He certainly has had difficulty in his life. When he raced he was very talented. I remember one event here at Mosport where he and a local talent on a CR750 had a real battle going, nothing vintage about the pace they set....tremendous.

[scottly]

I made some more holes in the Tarozzi lever to adjust the arms to 90 degrees.

Looks good to me! I suspect this will cure your up-shifting problems.

[turboguzzi]

howell, thats a good step.

I played a bit with arm ratios and when i went really high (6cm with 3cm shaft arm) it was like having a quick shifter! the only reason I went back to 6/4 was that it was becoming hard to hit second without going into neutral when downshifting, was too easy to miss it. but the way it is now, it works really nice.

TG

[iomtt9]

No problems here, gear lever is the other way round !!!
1 up and 5 down.

[fastbroshi]

  I was under the impression Henning had passed?  Good to know he's still alive and kicking.

[Howell]

No problems here, gear lever is the other way round !!!
1 up and 5 down.

No problems Colin 
What about your gearbox problems in Chimay and your spare engine ?

[iomtt9]

Sorry i meant no problems with the shifting, got gearbox back today, We were at Croft at weekend, i won the two 500cc races on Saturday, and was 4th and 2 nd on Sunday, Frank was there and David Martin. You should get your self over here some time. Croft is a great track. 4 races and 2 training sessions, and great weather, !!!!
With a bit of luck i will see you at Assen on the 24th of september........ Get the beers ready !!!!!

[Howell]

Sorry i meant no problems with the shifting, got gearbox back today, We were at Croft at weekend, i won the two 500cc races on Saturday, and was 4th and 2 nd on Sunday, Frank was there and David Martin. You should get your self over here some time. Croft is a great track. 4 races and 2 training sessions, and great weather, !!!!
With a bit of luck i will see you at Assen on the 24th of september........ Get the beers ready !!!!!

Congratulations Colin !!!
But the riders level there must be very low then  
What did Frank ?
See you at Assen and the beers are ready then.

[Sam Green Racing]

Congratulations Colin !!!
But the riders level there must be very low then  

 

Sam  

[The Fonz]

Why is it only us old guys have all the cool old sh*t?

because you "old guys" are the ones who can afford it 
nothing against you. i think its awesome that the elders carry on these hobbies so thanks.
im 19 and just picked up my first 2 project motorcycles (a 74 cb550f super sport and a 72 cb750f)... sadly it was because my grandpa had past away and i inherited them, but all the more reason to restore them!
my grandpa used to race old open wheel formula ford cars and won the senior championship in portland oregon just before he past (just a little history  )
so when finances give me the "green light", the project(s) will begin... and hopefully sometime down the road ill be out on the track with one of them.

... p.s. - hope this didnt come off wrong, im not asking for, or trying to get sympathy (just clarifying).
... Also, congrats on the bikes by the way!!! they look and sound AMAZING