Harbor Freight 670 sale

[raydhd]

I see the on line flyer for harbor freight has the 670's on sale for $669. One dollar per cc

[BIKERMIKEYBLACK]

So why don’t you buy one

[raydhd]

Why ? I am a pavement runner. It would take some bigger $'s to match my VC 460's top speed of 45 mph. And more $'s yet for the razor sharp throttle response I now have. But for somebody just starting a build especially with the current parts supply it might be just the ticket.

[csason]

Seems like. Good deal

[kellett5261]

my buddys yamaha runs 45+ with a HF 670.

[slonomo]

Originally Posted by kellett5261

my buddys yamaha runs 45+ with a HF 670.

Let's see it.

Speed is a function of engine rpm and gearing. Your buddy's 670 is obviously modified. That's what Ray's point was, it would take $$$ to get a 670 to 45 mph.

[BIKERMIKEYBLACK]

And don’t forget the razor sharp throttle response how Much would that cost

[raydhd]

Perhaps you have a solution for razor sharp throttle response on a V twin ? The Original VC adjustable idle circuit with an adjustable main jet added worked great on the single cylinder clones. A Shepard modified 3 circuit VC carb also with an adjustable main jet worked even better on my VC 460. I haven't seen a economical solution for either of the V twins. Enlighten me.

[slonomo]

The Vtwin carbs are terrible when it comes to performance. The run nice at constant 3600 rpm, and maybe some variance from 3000-4000 rpm. But low rpm and high rpm performance are terrible.

[Shepard]

Originally Posted by raydhd

Perhaps you have a solution for razor sharp throttle response on a V twin ? The Original VC adjustable idle circuit with an adjustable main jet added worked great on the single cylinder clones. A Shepard modified 3 circuit VC carb also with an adjustable main jet worked even better on my VC 460. I haven't seen a economical solution for either of the V twins. Enlighten me.

l've been do some research on Harley's Keihin 40mm CV carburetor. They used the same carb on the 500cc Buell Blast all the way up to the 88 inch Twin Cam till they went to fuel injection. From all l know about this type of carb, IMO it could be used on a Predator or Briggs V twin.
The air moving through the carburetor travels at speeds of 200 mph for any fuel circuit [idle or power]. A Constant Velocity carburetor does this by having a Variable Venturi. The air speed is "Constant" through the smallest openings - first the butterfly at idle - then the main jet under power -- different jetting for different displacement engines - but the same carburetor. l don't think you'd have any issues after jetting with this carb. There cheap on ebay and there's all types of tricks and parts to make then run better and adjust easier.