Topic: One more thing ... ... another small block racer

[kos]

Anyone know what carb inlet rubbers (between carbs and head) to use ti fit CR31mm CR Keihin Specials on CB500/550 fours. I want to use the alloy original manifolds.

KOS

[Howell]

Anyone know what carb inlet rubbers (between carbs and head) to use ti fit CR31mm CR Keihin Specials on CB500/550 fours. I want to use the alloy original manifolds.

KOS

On our engines we use home made manifolds with the special inlet rubbers also of a Honda minibike.
But why 31 on a 500 ?

[von_Wanderlust]

I have milled my CB650 head round about 2.0mm down.

Do you know what the volume of the combustion chamber is, either before or after milling, or both? Specifically, just the chamber itself, not including calculations for your pistons. I already have some NOS 750 pistons to do the Gentleman's Express mod and money is tight so don't want to have to find/buy another set of pistons if I go for the 650 head. I'm really hoping that milling the head may bring it back to a decent compression ratio.

Do you think that 2.0mm is the maximum you could mill the head?

[MRieck]

I have milled my CB650 head round about 2.0mm down.

Do you know what the volume of the combustion chamber is, either before or after milling, or both? Specifically, just the chamber itself, not including calculations for your pistons. I already have some NOS 750 pistons to do the Gentleman's Express mod and money is tight so don't want to have to find/buy another set of pistons if I go for the 650 head. I'm really hoping that milling the head may bring it back to a decent compression ratio.

Do you think that 2.0mm is the maximum you could mill the head?

You are probably way into the intake seats at that point....that's an offhand guess. There is angle milling but.........

[von_Wanderlust]

I have milled my CB650 head round about 2.0mm down.

Do you know what the volume of the combustion chamber is, either before or after milling, or both? Specifically, just the chamber itself, not including calculations for your pistons. I already have some NOS 750 pistons to do the Gentleman's Express mod and money is tight so don't want to have to find/buy another set of pistons if I go for the 650 head. I'm really hoping that milling the head may bring it back to a decent compression ratio.

Do you think that 2.0mm is the maximum you could mill the head?

You are probably way into the intake seats at that point....that's an offhand guess. There is angle milling but.........

Thanks Mike, looking back at CBJoe's pics from the previous page seem to confirm that. I didn't know what you meant when you mentioned angle milling so looked it up, interesting. Yeah, I don't think that is an option for me! 

[CB500Four]

I have milled my CB650 head round about 2.0mm down.

Do you know what the volume of the combustion chamber is, either before or after milling, or both? Specifically, just the chamber itself, not including calculations for your pistons. I already have some NOS 750 pistons to do the Gentleman's Express mod and money is tight so don't want to have to find/buy another set of pistons if I go for the 650 head. I'm really hoping that milling the head may bring it back to a decent compression ratio.

Do you think that 2.0mm is the maximum you could mill the head?

Hello von_Wanderlust! (German ancestors?)

Unfortunately i don´t remember the exact measurements but i think it was something around 27-28ccm.
By milling down the head by 2.0mm  you will reduce the chamber about 5.2⁺ccm.
That gives you a chamber volume of something around 23ccm. That´s a nummber i could remember.
But with flat pistons it won´t work because you must add the volume of gasket thickness (+ >= 2.8ccm).
You must have pistons with a "dom" (right term???).
Milling down the head by 2.0mm is really near the limit.
Like MRieck mentioned you will run into the seats if you do more.
But in this range you could do.
By the way my CB650 head works for me since somthing over 60000km on street and track.

Regards,

[CB500Four]

Hoi Heinz,

My question wass obviously not clear enough , did you have problems with the primary chain without the tensioner.

gr.René

Hoi René!

Personally i don´t have had problems with the primary chain without a tensioner.
When i have done the mod my thoughts were to prevent chainsucks at the oilgallery under the chain.
I used the bike a long time/distance also on street.
Now i am in my thaughts on the way back. Means to remove the tensioner and some other things
to lose some weights. (I think a total weight of bike without petrol around 143kg is possible)

Regards,

[CB500Four]

Heinz, das motorrad ist fantastisch! (Hope I got that right!   ) The fact that it is already in the SOHC race bike gallery goes to show just how impressive that bike is!  

You've used the shorter 650 rods, i'm guessing because the DOHC pistons are taller? Any other reasons? I'm looking forward to the next update you have mentioned so that I can find out more.  

Hi again von_Wanderlust!

Thanks for your compliment. (You have got that right)

The 650 rods are 5.0mm longer than the 500/550 rods.
I have taken them because i would use the longer 650 cylinder
(larger cooling fins and smoother look in combination with CB650 head).
And they will give a lower angel accelerate in TDC and DDC. Fine for longer durability and fewer stress.
And the DOHC pistons are a little bit taller but you need the tallness for creating a "dom" to get an usable
compression ratio.

Regards,

[Howell]

Hallo Heinz,

You have Nicky Haydens number 69 and do you know why Nicky chose that number ?
I think because when you make a tumble and you are lying upside down , we always can see that it is number 69 who crashed 

[bwaller]

Not sure that's why he chose that number.....but who knows!

[CB500Four]

Hallo Heinz,

You have Nicky Haydens number 69 and do you know why Nicky chose that number ?
I think because when you make a tumble and you are lying upside down , we always can see that it is number 69 who crashed

Hoi René!

Sometimes i need the advantage of the number.  
But not often. Results see pic below.
By the way, i wish i had 10% of Hayden´s driving skills.  

Regards,

[von_Wanderlust]

Thanks for the info! I don't have the pistons here, they're over in the old man's workshop waiting for me to do something with them, so I've had to do some 'guesstimate' calculations as to how whether the pistons could work with the 650 head. While the CB750 "300" model pistons are flat tops, thus have no "dome"  , they do need some height machined off to fit in the 550 block as per the "Gentleman's Express" mod (see here: http://forums.sohc4.net/index.php?topic=20601.0). I am hoping that there is about 3mm worth of height to play with, because then machining to suit the 650 head (ie steeper than the suggested 15 degrees) will give me a ratio of about 9.45, which is fine for my street usage as my goal is get more power through increased breathing and not compression. After reading other threads where people were concerned that they would have to much CR with the GE mod, this is reassuring me a little bit. I'll have to go over and take some measurements.

Thanks for the info on the rods too, I thought it was the other way around, I must have gotten mixed up somewhere . So re the easier acceleration of the piston, has this increased your revs as well? Out of curiosity, what do you run it to?

Also out of curiosity, what gasket are you using to suit the 62mm bore? Custom?

(And no, no German ancestry.)

[CB500Four]

So re the easier acceleration of the piston, has this increased your revs as well?
Out of curiosity, what do you run it to?

Also out of curiosity, what gasket are you using to suit the 62mm bore? Custom?

Hi!

I don´t knew whether this has increased my revs. I think if i had mounted the 500/550 rods
there were no significant difference. But my life had could been a little bit easier.  
In the gears 1-4 i run it up to 11Krpm and the fifth goes up to 10.8Krpm and a little bit more.
Pic below you can see my Vmax (km/h) which i reached at the end of the start/finish straight
at the race track in Rijeka/Croatia.
The gasket i use is as you guess custom made. Here in the area we have a manufacturer
who does at your specifications. He does a lot for historic vehicles.

Regards,

[turboguzzi]

So re the easier acceleration of the piston, has this increased your revs as well?
Out of curiosity, what do you run it to?

Also out of curiosity, what gasket are you using to suit the 62mm bore? Custom?

Hi!

I don´t knew whether this has increased my revs. I think if i had mounted the 500/550 rods
there were no significant difference. But my life had could been a little bit easier.  
In the gears 1-4 i run it up to 11Krpm and the fifth goes up to 10.8Krpm and a little bit more.
Pic below you can see my Vmax (km/h) which i reached at the end of the start/finish straight
at the race track in Rijeka/Croatia.
The gasket i use is as you guess custom made. Here in the area we have a manufacturer
who does at your specifications. He does a lot for historic vehicles.

Regards,

what gearing do you run in rjeka?

[CB500Four]

what gearing do you run in rjeka?

Ciao TG!

16/42 Teeth. But notice that i run also the CB650 clutch with its gearing (primary ratio 2,721:1).
And i run a 150/70-18 tyre (circumference 2098mm).
What´s your gearing? And max revs?

Regards,

[turboguzzi]

what gearing do you run in rjeka?

Ciao TG!

16/42 Teeth. But notice that i run also the CB650 clutch with its gearing (primary ratio 2,721:1).
And i run a 150/70-18 tyre (circumference 2098mm).
What´s your gearing? And max revs?

Regards,

sounds like its tottally different
with the stock rpimary i run 16/35 to 16/38 according to the track

[Howell]

what gearing do you run in rjeka?

Ciao TG!
16/42 Teeth. But notice that i run also the CB650 clutch with its gearing (primary ratio 2,721:1).
And i run a 150/70-18 tyre (circumference 2098mm).
What´s your gearing? And max revs?

Regards,

We also gonna use a 650 outer clutch and have front sprockets 15,16,17 and rear 40 and 42 with a 520 chain.
520 sprockets you can buy here:http://www.d-mengineering.co.uk/store52/agora.cgi?cart_id=7259915.30023&product=Sprockets&xm=on
My rear sprockets in alloy come from AFAM.

[Kurlon]

How much work was involved in adapting the GSXR swingarm to your machine?

[Ecosse]

dunno about that swingarm swap but this thing has been nominated for sept. botm.

http://forums.sohc4.net/index.php?topic=74975.new;topicseen#new

 

[FunJimmy]

Wonderful bike and great info for all us 500/550 owners.

Thanks
FJ

[FrankenFrankenstuff]

Another inspiring bike for all of us shade tree mechanics out there. Thanks for building it and giving us a peek into your recipe book.

[Retro Rocket]

How much work was involved in adapting the GSXR swingarm to your machine?

Its really not that hard. I have a "J" model 1100 GSXR swingarm on one of my builds and it slipped straight in, all i had to do was have the monoshock section removed and shorten the arm a bit...

Mick

[CB500Four]

Wonderful bike and great info for all us 500/550 owners.
Thanks
FJ

Another inspiring bike for all of us shade tree mechanics out there. Thanks for building it and giving us a peek into your recipe book.

Thanx for your kindly words.
But i think there are a lot of other members here around which have done
and do much more for us than i could do.
Unfortunately i am not so vivacious in posting here.
That´s a part i should change.


Regards,

[CB500Four]

For the people which want to provoke their eyes and minds.

Unexpected i am nominated for September BOTM by Ecosse
(One more thanks to you Sir, i am still very, very honoured).
By that reason i have loaded up some more pics which you
could inspect here:

http://forums.sohc4.net/index.php?topic=75581.msg844154#msg844154

I hope you will take pleasure in them.


Regards,

[turboguzzi]

what tires are you running in your bike? i think i could read bt012 in the rear, not sure.

thanks

TG