make a 70 out of the 50

[desratt]

everyone that is running a 70ss how did you build it??
simply bolt another cylinder on the 50 with a little case boring or what???

[gistmarrs]

I have two top ends for our bike. I can switch it from a 50 to a 70 in about 5 minutes. Would you be interested in buying the 70 top end? I am looking at selling two of our three cobras and all of the associated parts for them.

Marrs

[desratt]

what exactly is the top end and what do I need to do to make it work...

[gistmarrs]

There are probably different options, but mine is simply plug and play. I have only converted it once about a year ago from the 70 back to a 50. It was very easy. Take the one head off, remove the piston, put second piston on, and put second head on. That was it. Oh, maybe a quick jetting adjustment. Do you want me to send some pictures to you of what it looks like?

[qcitytile]

I think most use 70cc cylinders, but this requires a little case machineing. I think a stock 70 cylinder on a 50 lower end will make 65cc. Then you cam bore or stroke to get to a 70. I think Heath offers a top end kit to make a 70ss also.

[desratt]

Yea I can't find a cylinder that calculates to 70cc with the 50 stroke. You would have to change stroke and bore. Gistmarrs. What cylinder do you use for 70cc's?

[qcitytile]

heres a item# for ebay. This is Heaths 70kit.

[gistmarrs]

Yep. You are right. I forgot that it does calc out to around 65cc with the larger cylinder.

[desratt]

Can you try the ebay link again i've tried to google it. Can I just have a stroked 50 crank and the 70 cylinder?

[gistmarrs]

I believe Heath's id on ebay is 1fstvet. Or search under cobra ecx*.

[qcitytile]

heath 70ss item number 230735697024

[Ryko racing]

Call Paul at Wiley Mods. 609-387-3060.

We ran a 70 ss a few years back and it was virtually indestructable.
i think he has 3 natl cjhampionships from that set up.

good luck....

[chris grissom]

The best way I have found is a 44.7 stroke and a 44.5 cylinder. Crank is my custom (from Crank Works) cylinder is stock 70 shifter old style. Requires case work and additional work for national winning package. I can build this for you or call many of the Cobra people around such as John Heath, G-Force, Triple-A, Pittman Racing, etc. Wiley is one of my competitors and does a good package as well. I have tried some other packages as well but this seems to be the best all around and is 69cc and some change, not 65 etc which still needs case clearancing.
Call me if I can help, 731-642-0511. Chris Grissom

[heathmxracing]

There is really no "bolt on" option for a true 70cc. You can go 60cc, 65cc but for a true 70cc requires a little work. There are a few ways, you can go big bore with destroked crank, big bore with stroked crank, and big bore with slightly destroked crank. It all really depends on the type of racing your doing and the weight and size of you rider. We run one combaniation of a long top end track, and run something completely different for a tight bottom end track.

[desratt]

don't worry John your helping me out as we speak.