Topic: my cb400

[Sam Green Racing]

welcome to the club, but maybe introduce yourself before shooting questions?

Member Howell is running 13mm pin pistons in his 500, they're off a Honda mini bike big bore kit i believe

member ttr400 sells yoshi big bore pistons for the 400/4 too or at least used to.

TG 

Yoseph, you mean to tell me you don't know xtof He's world famous, welcome to the club Christophe.

Sam.

[xtof]

Hello,

Sorry, I forgot to introduce myself... : my name is Christophe Huet, I won the 2010 french championship in classic 500 cc.

And I was probably not very clear in my previous email : my engine already has pistons in 56,5 mm (cg 125). I have the connecting rods small-end 15 mm, oil pomp cb 750 and a close ratio gearbox.
I am looking for forged pistons (for exemple wiseco).

 Do you know why  specweld  didn't use the wiseco pistons shown on the picture ?
is it possible to have the name of the contact in wiseco netherlands ?

Thank you all
Regards

[turboguzzi]

Hei Cristophe

nice bike, nice pictures! and congrats on the championship.

Been trying to contact your organization as i wanted to do one of the french rounds across the border, but never got a reply...

Do you have any events in the south of france?

If you already have a 15mm pin you have a slightly better range to use but cant think of anybody doing forged ones other than wiseco.

take into account that wisecos are a bit heavy and not very modern in design

Have you run into trouble with the cast CG125 pistons? Bike seem to be smoking heavily in one of the pics

i've been running very light pistons with modern design but they had low crown height, they are th eones in the left

in th emiddle these are CG125 that didnt work so well..

http://forums.sohc4.net/index.php?topic=55162.0

 

TG

[specweld]

xtof,
I got the Wiseco pistons from Col Stockdale,(IOMtt9) who got them from a friend in the Netherlands.
I have phoned Colin this morning, he will contact his friend to find out if any more are  available and we can take it from there.
Very nice motorcycle BTW.

Dave. 

[Howell]

Welcome Cristophe,

A beautifull bike and congratulations winning the classic championship.
Dou you have technical/tuning specs and engine pictures for us.
our cb500 racer

merci René

[bwaller]

Oui felicitations Christophe. I have seen your bike in the gallery on Kevins site. (TTR400)

Nice race bike.

[fasturd]

.... Man I love these 400 race bikes... I love what you guys are doing!

[specweld]

[specweld]

Finally got the engine back together and managed to get a quick session on the dyno (between other peoples bookings) I just asked the guy to give me two readings, one, max power (63 bhp at rear wheel) , and two, where power drops off (10,500) so I don't to waste time revving beyond.
no time to do any tweaking on dyno, but still quite pleased with the results.

ignore camera date it is well out, real date of run is written on the report.

[Industrial Rat400f Killer]

63 is pretty impressive. I hope mine is close to that when it's done.

[Tim2005]

That's a very impressive result, particularly nice curve too- what cam are you using to achieve it?

[turboguzzi]

nice dave!

cant remember, are you are running a 460 kit or full 500?

TG

[specweld]

Hi guys,
cam is webcam #69, Honda 125 pistons make it 500
full gas flow by Jim Norman
CR 26mm carbs
1mm oversize valves, in. & ex. (Kevin TTR400)
Dyna ignition & coils
Robson conrods
CR gear box (Nova)
lightened , polished, balanced crank

cycle parts include Yamaha TZ front end and same at the back with Maxton suspension.
AP brakes back & front .

Kevin Mullen also provided help .

Specweld...

[bwaller]

I can see this is a highly developed engine, very impressive. The output figures are also bloody awesome Dave. 

Overall a gorgeous package man. 

[turboguzzi]

Hi guys,
cam is webcam #69, Honda 125 pistons make it 500
full gas flow by Jim Norman
CR 26mm carbs
1mm oversize valves, in. & ex. (Kevin TTR400)
Dyna ignition & coils
Robson conrods
CR gear box (Nova)
lightened , polished, balanced crank

cycle parts include Yamaha TZ front end and same at the back with Maxton suspension.
AP brakes back & front .

Kevin Mullen also provided help .

Specweld...

so what size inlet valves did you end up with?

great performance indeed, but just like with the CB500, you seem to run out of puff at 10.5K too.

the reason I am saying this is that i still believe that with 28-29 mm inlets, these little motors could still be making power at 12K

mechanical they sure can stand it,

when i am filthy rich i am going to build one with re-angled valves

BTW, did you ever posted pics of it? could be nice to see it in your own thread.

TG


TG

[specweld]

TG , inlet valves stock are 26mm, I got a set of 27mm from kevin @ttr400.
you can also use cb500 stock inlet valves but they need cutting down to size,stellite tip and re machine collet groove.
Jim who does the gas flow and head work told me a long time ago that there is more power to be had from this little engine but then the further we go with it the more peaky it will get and will end up with a narrow power band, he thinks a longer power spread is more important and what we have at the moment is a good happy medium.
The pics are up near the beginning of this thread

BTW col ran out of petrol at spa

[Yrjo#54]

BTW col ran out of petrol at spa

It was not his weekend, he had also some problems with ground clearance
with his 4 in 1 exhaust.
I finished 8th in the same race after a terrible start and was 1st in the 2nd Qualify (Rain)

[Tim2005]

TG , inlet valves stock are 26mm, I got a set of 27mm from kevin @ttr400.
you can also use cb500 stock inlet valves but they need cutting down to size,stellite tip and re machine collet groove.
Jim who does the gas flow and head work told me a long time ago that there is more power to be had from this little engine but then the further we go with it the more peaky it will get and will end up with a narrow power band, he thinks a longer power spread is more important and what we have at the moment is a good happy medium.
The pics are up near the beginning of this thread

BTW col ran out of petrol at spa

The power curve does look great, would have expected that cam to make it peakier. With that engine and those chassis mods (what's the swingarm with the Seeley-type adjusters?)  it must be an absolute blast to ride. Which clubs do you race with/ which circuits do you get to?

[specweld]

sorry for late reply, have been away for 3 days in Kent.
the swingarm was made by ron williiams (Maxton) , I took it off the TZ doner bike with all the other stuff many years ago.
the bike handles like a dream.
This was my race bike in the late seventies ,I did 3 Manx Grand prix on it , the 1st year it was a 460 and then I rebuilt it as a 500 for the next two. the 500 engine was used both for both events '78 & '79 and didn't miss a beat and it wasn't even stripped down between the two years, it was super reliable.
Then moved on to TZ's and the Honda was loaned out to various lads to play with (inc.Andy Macgladdery in formula 2)
We now jump forward about 25 years and I discover my old honda is in a barn in North Yorkshire and the farmer was quite happy to let me take it back , it looked like a basket case, but with the help of a good mate (Eddie) we  got it back to a reasonable condition
I decided to go a bit further with the engine and got a local engine tuner (Jim Norman) to do a lot of head work  on it  but then came the start of the blow ups as in the pics earlier in the thread (not Jim's fault) .It turned out to be the futura cams, the lobes on one side of the cam were ground back to front so the valves were going in on the fast ramp and out on the slow ramp and once i hit 10,000 it would explode, the old engine had a lot bigger tolerances and that is how we had gotten away with it , we never thought for 1 minute it could be the cam after all those trouble free miles in the isle of man.
So now it has been rebuilt but this time with #69 webcam and you can see the results of Jim's tuning on the powerchart above.
the old engine produced 52 bhp , so for Jim to hop it up to 63 and still keep a good power curve is a massive improvement (old engine had bored out stock carbs)
So , hopefully , it's first outing in it's present form will be at east fortune 28 May, but it is me who will have to get up to speed as the last two seasons most of our time has been spent at race meetings looking at a heap of broken bits.
Circuits will mainly be East Fortune, Knockhill,Croft , but first we have to test it out.
Will be with north east club, and may do the classic club Knockhill to try it out in the 500 aircooled (if it survives).

Yrjo
Well done at Spa,
 Col is to bring his bike to my workshop at the weekend and I will modify his exhaust..

[turboguzzi]

nice story spec,

Spotted them now, got confused by cristoph's pics.....

best luck with your comeback!

TG

[specweld]

thanks TG.

[turboguzzi]

And tell Col that we spotted him with his knee sticking out (he'll understand )

[xtof]

 hello SPECWELD,

Having more or less the same motor's specifications than you, I would like to ask you few questions :
- during my last race, I have twisted my Crank Shaft. Did you have this kind of problems ?
- could you please give me your jetting configuration (main jet, slow jet, needle jet,VALVETHROTTLE, main air jet)
- do you have an oil cooler on your motocyle ?

Thank you in advance for your answer
Best regards
CHRISTOPHE

[specweld]

Hi Christophe,

with regards to the crankshaft, this is a problem I have not encountered so I really cannot advise , I would think this sort of thing would happen at very high revs (what do you rev it to ?)
One of the reasons I took mine to the Dyno was to find out where the power drops off so I don't waste time with excess revs which are taking me nowhere and potentially causing damage.
I read somewhere that Yoshima used to rev his bikes to 13,000 but they had a lot of crankshaft trouble.
As you can see on the power chart my power tails off at 10,500 so I will set the rev limit to 11,000 .
My friend Colin (iomtt9) races a 500 honda and our bikes are very similar on the dyno results, his power drops at 10,500 so he has done the same. (He used to rev it a lot more) .
At Philip Island, as an experiment, he tried a couple of laps at 12,000 and went round slower than when he had the limiter set to 11,000.
Perhaps this is worth looking into.. perhaps you know this already, and I apologise.

The carbs (CR26mm) came to me already set up for the bike by Sudco , I have never looked to see what they have done, but according to the dyno man I should leave them as they are because I could end up spoiling something that is pretty damn good already.
I am sure someone on here will have the sudco settings and will post them here for you, however if nothing turns up , I will take them off the bike and find out for you.

I have not run an oil cooler on this bike, but after talking to Gerrit Lether (classic bike tuner) at Assen this weekend it is now a priority and one will be fitted very soon.

Regards ,

Dave

PS. Mon Francais est tres petit, mais, bon chance avec votre engine.

[turboguzzi]

Dave

As someone who is not really into oil coolers, I would be interested to hear what Gerrit had to say on the subject....

TG