KR-1S.co.uk Forum

Hi, anyone done back to back tests running open carbs versus with an airbox ?
I am currently running PWK 35mm carbs with v force reeds into an airbox with a ram air tube feeding from below the headstock (above the radiator) into the airbox. I know open carbs = less engine life etc but thats how we always ran TZ350's and wondered what people's opinion's on this are ?

always better with airbox, but I wouldn't bother presurising it. if yours is built that way I'd drill some holes in the back to bleed of the presure.
why is it better ? most important is to get cool air in that's not heated by the engine, also less turbulent air.

The reason why TZ350's didn't run airboxes back in the day, is because people didn't know better back then. Even airboxes designed in the early 90 are considered crude by modern standards. So much more R&D went into designing airboxes to improve performance.

Just to echo what Jan has suggested, the key to a good setup is cool still air.

I won't argue with people who have superior knowledge to me on this subject but I like a healthy debate
Myself, my brother and a few others ran highly tuned YPVS's with the crmc a few seasons back and they also ran 'open' carbs (upgraded to 34mm or 38mm), they ran superb and generally gave around 68bhp at the rear wheel with a good spread of power. Some guy's even locked the power valves wide open arguing that they were only needed for road rider's and when racing these YPVS's the rev counter should never be below 7,500 rpm anyway, in other words ridden like a piston port TZ. What's people's opinions on this ?

Hmmm I suggest trying that out on a dyno is all I'm going to say.

they are correct. on track in the powerband, exhaust valves are unemployed.