Originally Posted By Guten
Originally Posted By NJR
Originally Posted By GLLHG
Originally Posted By NJR
I have replaced the stock filter on my '83 CVH (XR3 n/a) with a nice Pipercross. Sounds good and much improved throttle response, but the car runs out of breath past 80 in top, and struggles to gain further speed. Can I cure this with adjustment or is it a gearing problem?

Many thanks.

I notice that you have taken steps to free up the inlet side ( ie the Pipercross) but what about getting the used stuff out ie the exhaust side

I'm not suggesting that this is a complete fix because the issue is wider and really involves how wide the effective power band is and where it is deliverd, but if you are still on OEM stuff, then a better quality exhaust manifold and a system with a smaller silencer would be worth considering

A s a final point ( and apologies becuase this is a real hobby horse of mine) is the Pipercross situated so that it is giving you a good supply of dense, cool air?

regards,
GLLHG


Breathing is improved at both ends, I have removed the tail silencer and put a straight through pipe ( single silencer box under n/s wing) but using stock exhaust manifold, which apparently is quite efficient. It has a 5 speed box but I get the feeling that top is quite 'long legged'. She pulls very well up to around 80 in top, then runs out of legs, but will cruise happily at that speed.

One thing, there's a small air pipe that that ran from the original air filter box to the base of the carb...should this be closed off, left fully open or remain attached to the small original valve, for best performance.

thanks for your help


I'm not clear what you mean here. The original set up has an emissions valve with the top connected to the rocker cover, the side to the filter and the small pipe on the bottom to the carb. As I understand it this uses the vacuum caused in the choke above the butterfly to open the valve and so draw the fumes when working hard out of the rocker box and in to the air intake, that's how I have connected mine. You often see photos of CVH engines with a filter connected to this rocker outlet. I tried this and got smelly fumes in the cockpit when accelerating so reverted to the original set up.
Regards
Simon


Hi Simon,

My mistake, not the base of the carb, but into the manifold just below the carb.

Its not the emissions valve, thats the large pipe that runs off to the right, this small pipe branches off to the left and up into a small valve fitted in the base of the stock filter box. It may just be an idle control as this seems to be the only effect that I can see. I'd just like to know what you did with this in the past, when you had the single carb set up.

rgds
Nick....just waiting for the sunshine...