R1 carb jetting

[Bossie]

I have purchased a 1.7 as a small quick & dirty side project.
Will all be very low budget (mad camber, low, thick oil in shocks, gutted, short final ratio, welded diff etc). Will use the car for some drifting, spirited driving and maybe a track day if the race car is down.

Wanted to fit some 40mm R1 carbs I have together with a hotter cam (regrind) and an exhaust header. (The car will probably run on E85)

Which jets do the F7P guys use/run in their bike carbed setups? Where can different sizes be obtained?

[filthyjohn]

The thing about R1 carbs is that they're like an SU carb, in that they have a sliding tapered needle metering the fuel. It means they supply pretty much the right amount of fuel according to how much vacuum they experience from the engine, keeping the mixture somewhere near right in a vast range of applications. I have R1s on my 2.0 vauxhall XE and they work great, returning around 30mpg. That's in a <900kg car though.

[Bossie]

Aha, wasn´t aware of that. So you have not rejetted them?
Sounds great, if there that easy to setup, hmm

Nice mileage! Gutted 340 will probably weigh almost the same. Maybe just a bit more. C20XE however is known for it's efficiency, B172 not really

[samueljon]

sorry to pigy back your thread,

How hard are these to fit and get running properly on the valver engines??

[Chris_C]

The thing about R1 carbs is that they're like an SU carb, in that they have a sliding tapered needle metering the fuel.

But SU's still have something like a squillion needles to get good running which I'm guessing Yamaha never intended on making as they were soley used on 1 bike? Have you had a wideband on the manta dude?

[filthyjohn]

But SU's still have something like a squillion needles to get good running which I'm guessing Yamaha never intended on making as they were soley used on 1 bike? Have you had a wideband on the manta dude?

Never had the chance, but I can report no symptoms of bad mixture, no hesitation/smoking/run-on/pinking etc, just super smooth power delivery.

[volvosneverdie]

Whats a wideband?

(serious question of the day)

[filthyjohn]

Wideband lambda sensor. Lets you know the air/fuel ratio in numbers so you can monitor it and make adjustments accordingly. As opposed to older narrowband systems which can only say rich or lean, without quantifying it.

[volvosneverdie]

Wideband lambda sensor. Lets you know the air/fuel ratio in numbers so you can monitor it and make adjustments accordingly. As opposed to older narrowband systems which can only say rich or lean, without quantifying it.

Ah. Helpful.
Cheers.

Nearned something.