Topic: more 500 racer developement

[dave500]

i rebored my 500 1st oversize and used after market xl125 pistons,i had the combustion chambers relieved to lower the compression.

[DresdaHonda]

About XL125 pistons
1. Is there a differens in XL125 and XL125s pistons ?
2. Is there any idea of drilling holes (5 (6mm) holes on both side of the "skirt"
-Old school tuning tips less weight and better oiling ??

About Dax or other minibike 57mm pistons
1.There is the pin size problem (normally they are 13 or 14mm)
-but that can be solved by bushing in small end of conrod.
2.Normely they are very low (from pin to dome top)
-That can be solved by milled the block or use longer conrod, like CBX1000R or maybe just CB650.

About CBX1000R conrod
1. What size is the big-end ?
2. Width ?

Dresda

[Howell]

About XL125 pistons
1. Is there a differens in XL125 and XL125s pistons ?
2. Is there any idea of drilling holes (5 (6mm) holes on both side of the "skirt"
-Old school tuning tips less weight and better oiling ??

About Dax or other minibike 57mm pistons
1.There is the pin size problem (normally they are 13 or 14mm)
-but that can be solved by bushing in small end of conrod.
2.Normely they are very low (from pin to dome top)
-That can be solved by milled the block or use longer conrod, like CBX1000R or maybe just CB650.

About CBX1000R conrod
1. What size is the big-end ?
2. Width ?

Dresda

There are Dax/minibike pistons with 57 mm size and a 15mm pin.
I placed the links where to get them.
 

[sebatje]

Iff you need takegawa pistons... just contact me, I'm an authorised Takegawa dealer 

[kos]

Iff you need takegawa pistons... just contact me, I'm an authorised Takegawa dealer 

I am interested in these pistons. What is bore size and pin diameter.

Mark @ M3 Racing

[Sukin]

i rebored my 500 1st oversize and used after market xl125 pistons,i had the combustion chambers relieved to lower the compression.

Hallo could you tell more about this. I think about  xl 125 pistons for my cb 500 racer

[turboguzzi]

hi sukin

welcome to the forum

some pics of your racer will be appreciated

XL125 piston  is the easiest solution for high compression in a 500. it's not a light piston, needs some work, but in all, easy to adapt.

It's hard to say how much you need to remove from the piston crown, you will have to build your motor and then measure how much final chamber volume you have and then adjust to get say 12:1 compression ratio.

Quite a few Czech guys come to our national race in adria, have you ever been there?

[Sukin]

Hi here is any photo
In the first picture, there is me with my Honda 250 1976 on Hořice Tourist trophy Czech rep.
Second picture is my CB four , when I bought it, bike was in very bad condition. I had to take out some parts( rear hub with disc, marzochi rear springs), because it was very young.
Third picture I make today, somethink more about CB: Modfied frame, Tank and seat made from steel sheet(I think last owner had steelworks ), rear fork is original Bimota. Rear brake drum is from Cb 750, I wanna use Cb 750 koni rear units (on picture are stock CB 500 units). I have bought cb 550 front forks, because stock was totaly wrecked. Fairings and front fender I made at home. Exhaust is Marving, engine is fully stock yet. Yesterday I bought steering damper. Rearsets - Gimbel replica, handlebars- telefix, front brake master cylinder- CB 250 N. For championship to 1972 year, I have to take out one front disc or buy front brake drum.

[turboguzzi]

neat bike, nice tank

a 350 rear brake/hub will save a few tons of weight....

Some people around here race with just one disc but bigger than stock, not a bad option if they let you do it.

Are you doing regularity or proper racing?

TG

[bwaller]

Good looking bike Sukin, welcome to the madness. 

[Sukin]

For next season I will ride regularity, but for future proper racing. I wanna set up suspension, test brakes and try handling for first season on it. Changing disc for bigger isn´t problem, I think rules don´t solve it, only calipper must be with one piston and master cylinder original Honda only. I know about races in Italy, itś UEM cup (for vintage bikes) I think, but I never been there. In Czech regularity championship start one Italian, Giovani Macchi with ducati single, do you know him?

Ifound on ebay this pistons:
http://cgi.ebay.co.uk/56-5mm-15mm-PISTON-KIT-CB-CL-SL-Honda-125cc-/190499664674?pt=UK_Motorcycle_Parts&hash=item2c5aaa3322

[turboguzzi]

not a bad piston, rings are a bit thick at 1.7mm  but looks like you could get good compression ratio with it.

the UEM races in italy are only the endurance ones. the classic championship here is run by the national federation, the Federazione Motociclistica Italiana, FMI