Thread: new member

Hi, I am new in this forum.
I live in the Canary Islands, Spain and I go crazy about honda ct70.
I recently bought a 1972 CT70HK1 from a guy in St.Louis, Mi.
I decide to restore it and install a 85 cc piston.
Any reccomendation for the carburetor size?

Congratulations for the forum

Hello! And welcome to the forums!

As for carb size, a 20mm or 22mm would be plenty big. If you want to look around and get more details you can check out www.dratv.com

Any more questions, please ask!
Happy Trails
-Tiedgen

Small world, isn't it? St.Louis, MI is only about 125 miles north of me, unless you meant St.Louis MO (the one with the big arch), but onto business...

I'd recommend an 18mm carb for this engine. 20mm would be about right for a stock 110cc, 22mm is pushing the limit even at that displacement. 20mm is way too much for a mildly built 85cc CT70 engine. To effectively utilize a 20mm carb with 85cc you'd need a ported/big valve head, race cam and a free flowing exhaust.

If you stab-in a slightly more aggressive cam and replace the restrictive stock airbox with an open-element K&N air filter the bike should be capable of around 50mph(about 80kph) with the proper gearing.

Unless you know someone in the US, you'll have to forget dratv and most of the other US dealers because they don't ship outside the USA.

You are right racerx, it was in St.Louis, Missouri. Fortunately one of my brothers lives in Little Rock, AR and I can get the parts through him.
The only thing is that it takes 4 weeks to get to the Canary Islands.
Since the stock carburetor is a 19mm, what if I change the jets to a bigger ones? do you think that this will work?

As I recall, the stock carb was 16mm. That's the inside diameter of the venturi, not the O.D. of the air horn to which the air cleaner attaches. Rejetting the carb will not only work out fine, it'll probably be necessary with the bore-up kit. I've installed 88cc kits on otherwise stock CT70s with good results.

I'd start out with a main jet 3 or 4 sizes larger than the original and the jet needle height set to the middle groove. Once the engine has been broken-in, find the jet that is just large enough to prevent the engine from revving-out cleanly. From that point, reduce the main jet size one number at a time until you find the one that will allow the engine to rev-out cleanly. This will leave you with full needle height adjustment in both directions, should that ever be needed, and keep the engine from running too lean.

Not too sure about delivery time to your locale, but for small parcels the USPS offers 3-5 day, 6-10 day and 4-10 week delivery. Those are all less expensive than UPS and FedEx and I've have good luck with them between here and Europe. Checkout usps.com for details