Topic: Building of a CB500 classic racer

[Sam Green Racing]

b

A new world record for the shortest 1st post, well done Nev and welcome.

Sam.

[Sam Green Racing]

Back from our holliday trip to Croatie.
Tomorrow we go to the next dutch classic race in  Oschersleben, Germany.
http://www.motorsportarena.com/default.aspx?ID=63
The bike is ready for it, I hope Yrjo also

Rene, how did Yrjo perform ?

Sam.

We performed not good.
It was very very hot in Oschersleben , Germany, 40 degrees Celsius (104 F) on saturday during the practices.
The tarmac was 60 degrees.(140 F)
Oschersleben is a very technical track , Yrjo had problems to get the bike trough the corners.
The bike wouldn't steer as he wanted , he couldnt get the bike on the lines he wanted.
Result 16th place.
Therefore we made a big change fot the second practice and setup the bike at the rear 2 cm higher.
This made a little difference, but still the bike was not going were he wanted it.
Yrjo was 3 seconds faster in this practice but that didn't help because everybody was going faster.
All the guys were worn out because of the heat.Yrjo was complete dizzy.
Result of this practice 17th place.
Starting place 17.
For the race on sunday we made another change to the setup and lowerend the front.
Race on sunday:
The temperature was now a 27 degrees C because of a shower in the morning.
Yrjo made a very bad start , I saw him starting as latest.
But the next lap ,he had already passed five riders.
Second lap he had already lost this places again and more riders passed him.
His laptimes went slower and slower I saw on the monitor , what was wrong ?
He finished as penultimate.
Cause: The clutch didn't work smooth at the start , no slipping but immediate grip , so the engine went down in rpm's and he had to declutch to get more rpm's to get away.Overheated ?
In the second lap he missed suddenly 2500 rpm's , max rpm was 8000 instead of 10500.
So he missed power and speed because of misfiring.
Yesterday after inspection of the electrical circuit I found a bad connection socket at one of the coils.
Tomorrow I will repair that and will see if the engine will run good again.
But the change on the setup before the race was the right one , the bike went the direction Yrjo wanted.
So another race with up and downs , but that's racing.
Now up to the next non championshiprace in Chimay , Belgium on 18 july.
There we hope for a better result.
http://www.circuit.be/manifestations_21_ClassicMotorcycle.html

HOLLAND WORDCHAMPION FOOTBALL 2010 ?  YESSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS

Don't worry Rene, the bike and Yrjo are still in one piece, there's always next time.
In 44 years racing, I've had my share of odd electrical failures and carb problems.
I only ever had a mechanical failure once when an experimental gearbox locked up on me around 85mph. It put a big flat spot on my rear slick but I walked away to race another day. now all you have to worry about is Spain

Sam.

[turboguzzi]

yeah, bad stupid electric connectors sure suck...

Hope that team orange doesnt suffer from any bad connectors this sunday

Hop Holland indeed (even if also the spaniards played nice yesterday)

TG

[Howell]

This weekend we went to Chimay in the south of Belgium near the French border for the 17th Trophee des Motos Classiques.
This is an open event for all type of classic bikes .There are many categories.
We subscribed for group 2 , 500cc twostrokes and multicylinders.
There were many fast riders from the UK , Belgium, French, Germany and Holland.
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)
Yrjo also had to get used to the track , first time here and it is a very fast roadtrack .
He ended this practice in the midfield.
For the race I changed the mainjets from 120 to 122 .
Race one: Yrjo made  a bad start ,almost last ,but finished 18th from 41 starters and his best lap was 5 seconds faster as in practice.
But at the start the engine stopped suddenly and then run again. No idea wat is was.
At top rpm the engine was now running better after the mainjet change.
Second race: Again a bad start , now finishing 21 th, race was stopped after four laps because of a red flag situation caused by a bad accident and not restarted.
Now the clutch was the problem , the clutch was slipping very much during the start and also during the race.
Now we have some weeks to the next race on the 28th august to solve the clutch problems and to inspect the whole bike complete.
Colin Stockdale was again present here , but he had no luck.
Fist missing the first practice, forgot the timeschedule and was walking and talking somewhere in the paddock 
Then his gearbox missed some teeth, he build in his spare engine but that engine seized up.
So end of the story for him .

[turboguzzi]

hei rene, doesnt sound too good...

maybe try to have a proper test day at a track so you can sort out all the little problems without the pressure of the race

take care

TG

[Howell]

hei rene, doesnt sound too good...

maybe try to have a proper test day at a track so you can sort out all the little problems without the pressure of the race

take care

TG

Hi TG,

Indeed a lot off little problems the last races , most of the time electrical (missing revs) caused now I think by the bad coil.
We will solve that , also the clutch problem.
The intention is to do some dyno runs when these problems are solved.
It is difficult to test it on a trackday in Holland because all the trackdays are fully booked.
We have also a problem from time to time by changing gear from 4th to 5th , I heard that's a normal CB500 gearbox problem.
When changing  to 5th gear it won't change sometimes , it feels like it stucks in 4th.
Our friend with the no 46 Honda has the same problem.
Do you recognise that  and how to solve it ?

[turboguzzi]

hei rene, doesnt sound too good...

maybe try to have a proper test day at a track so you can sort out all the little problems without the pressure of the race

take care

TG

Hi TG,

Indeed a lot off little problems the last races , most of the time electrical (missing revs) caused now I think by the bad coil.
We will solve that , also the clutch problem.
The intention is to do some dyno runs when these problems are solved.
It is difficult to test it on a trackday in Holland because all the trackdays are fully booked.
We have also a problem from time to time by changing gear from 4th to 5th , I heard that's a normal CB500 gearbox problem.
When changing  to 5th gear it won't change sometimes , it feels like it stucks in 4th.
Our friend with the no 46 Honda has the same problem.
Do you recognise that  and how to solve it ?

have you undercut the transmission?

[Howell]

have you undercut the transmission?
[/quote]

Yes , we have a special made close gearcluster from MPE.http://www.mpe07.co.uk/
See the picture for the undercut.

[turboguzzi]

OK.... then the second solution is to use a CB550 gearbox+bottom end, with the two external forks on separate rods

[Howell]

OK.... then the second solution is to use a CB550 gearbox+bottom end, with the two external forks on separate rods

TG,

I don't understand exactly what you mean by the CB550 gearbox + bottom end.

[turboguzzi]

bottom end means 550 crankcases.

the cb550 had a much better gearbox design but it doesnt fit in the cb500 crankcases.

so you need to use basically a 550 motor "bottom half" with 500 cylinders/head.

if you also change the clutch actuation mechanism to the one of the 500, nobody will be able to see the diference...

the CB550 had a more modern rack & pinion actuator in the clutch cover.

TG

[scottly]

have you undercut the transmission?

Yes , we have a special made close gearcluster from MPE.http://www.mpe07.co.uk/
See the picture for the undercut.
[/quote]
This appears to me to be a very large angle on the undercut. Could the dogs be reground to a flatter angle, at a reasonable cost?

[turboguzzi]

have you undercut the transmission?

Yes , we have a special made close gearcluster from MPE.http://www.mpe07.co.uk/
See the picture for the undercut.

This appears to me to be a very large angle on the undercut. Could the dogs be reground to a flatter angle, at a reasonable cost?
[/quote]

looks like good angle to me,

TG

[Howell]

bottom end means 550 crankcases.

the cb550 had a much better gearbox design but it doesnt fit in the cb500 crankcases.

so you need to use basically a 550 motor "bottom half" with 500 cylinders/head.

if you also change the clutch actuation mechanism to the one of the 500, nobody will be able to see the diference...

the CB550 had a more modern rack & pinion actuator in the clutch cover.

TG

Okay TG,

Now it is clear to me wich parts must be changed.
But I have no 550 engine , only two spare stock 500 engines.

[turboguzzi]

well, i am running a 500 motor too. had missed shifts after one year of racing due to a bad middle fork which was obviously destroyed from the not undercut dogs putting constant pressure on it.

fitted a new fork, undercut the transmission and since then no problems but the 550 is definetely a better design, looks like honda understood there was a problem with the 500 gearbox (essentially a cb350 twin box!) and fixed it properly.

the 550 has also a cute little oil pump to feed the gears. if i keep running my 500 next year, i'll definitely build my next motor around a 550 bottom. a friend has one to sell.

TG

[bwaller]

Ellis told me he uses five or six degrees of undercut, I agree with TG, it looks perfectly normal.

I have three 500 engines here but none apart. What locates the shift drum, and is there any end-play? There is always some clearance for the shift fork pin in the drum track and if the drum has some end to end it may combine enough to cause an issue.

The 550 drum uses a bearing at the mechanism end and is firmly located for no lateral movement.

[scottly]

When changing  to 5th gear it won't change sometimes , it feels like it stucks in 4th.

This statement is what lead me to question the angle of the undercut.

[turboguzzi]

howell, here is one idea you could try....

I noticed big differences in shifting quality when changing the length of the arm that sits on the gear change shaft. if you run like me a sepearate gear lever with a rod to send the movement, you could use a shorter arm and that would increase the speed at which the shift drum is rotated.

a shorter arm will give you faster changes and will require less pedal movement. of course if you go too short, shifting will be too hard...

give it a try.

TG

[Bill/BentON Racing]

well, i am running a 500 motor too. had missed shifts after one year of racing due to a bad middle fork which was obviously destroyed from the not undercut dogs putting constant pressure on it.

fitted a new fork, undercut the transmission and since then no problems but the 550 is definetely a better design, looks like honda understood there was a problem with the 500 gearbox (essentially a cb350 twin box!) and fixed it properly.

the 550 has also a cute little oil pump to feed the gears. if i keep running my 500 next year, i'll definitely build my next motor around a 550 bottom. a friend has one to sell.

TG

That box is indeed better as you stated.I remember finding the little gear oil pump and was way impressed.Also first ran a CB 500 BE,but switched to CB550 and was much happier.Bill

[Howell]

howell, here is one idea you could try....

I noticed big differences in shifting quality when changing the length of the arm that sits on the gear change shaft. if you run like me a sepearate gear lever with a rod to send the movement, you could use a shorter arm and that would increase the speed at which the shift drum is rotated.

a shorter arm will give you faster changes and will require less pedal movement. of course if you go too short, shifting will be too hard...

give it a try.

TG

A shorter arm would be a possibility , how long is it at your bike ?

[turboguzzi]

I use a CBR900 gear pedal and it has a pretty long arm.

dont remember what bike is the gear shaft arm from, will measure both for you as the ratio is the result form the two arms length

TG

[scottly]

Could both of you gentlemen please post pictures of your external shift mechanisms?

[Howell]

Could both of you gentlemen please post pictures of your external shift mechanisms?

Here's a picture with the measured values in cm.

[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.

[scottly]

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