Hi All,

I thought I would start this topic following on from Steve's Ducati TT1 Street Conversion thread... where I learnt about Mikuni Pro-Series carbs on our engines.

What carb are you using? Have you had the opportunity to compare different carburettors on the same bike?

I have seen quite a few Keihin FCR 39 carbs fitted to 750 F1s in pictures. Does anyone here use them, recommend them?

Mike,

I have run both Mikuni and Keihin FCR carbs back to back on the dyno. There is not much difference in performance once the carbs and properly tuned (usually less that .5 horsepower). For cost and fitment the Mikuni TM series is the way to go, but depending on the engine setup will dictate the carb size. For small valve heads with stock or very mild porting, I have had the best luck with 36mm. For big valve and porting either 39mm or 41mm, have not seen much difference on the dyno. For the Keihin FCR carbs, fitment is an issue as intake manifolds, frames and gas tanks have to be modified to fit an F1. The Yellow Bike 1 has 41mm FCR carbs where as Yellow Bikes 2 and 3 have Mikuni carbs. Unfortunately for the F1, there is not an a super carb that is better then the rest as each as some drawbacks.

Palmer

i've had a look for these, but it's hard to work out what is actually available. this site lists only 39 and 41 for sale, but under the "Detailed Description" button it gives a big list that doesn't include either: http://www.power-barn.com/servlet/the-6 ... IES/Detail

palmer

do you only use pumpers? they appear to be available in 33, 36 and 40? hard to work them out.

i thought a pair of 33 might work well on the 400, but then i came to my senses.

this site doesn't even list the 39 or 41: http://www.jetsrus.com/carburetor/carb_ ... eries.html

they are cheap though. wacky, but i always thought they were much more expensive. maybe they sell a racked set for paso style motors that is much more.

my experience with fcr is a fairly small sample size, and it appears to me that the smaller the cc/carb dia ratio, the less flat the a/f curve is thru the rpm range. i tried the larger main air jet thing, only to find that it seems to make no difference at all once you go over the std (and maximum available) 200. the fcr are great for the later paso engines as the racked pair fits in just nice.

I am pleased that I asked! Great info Palmer and Black!

On the performance side of things it sounds like flat slides are the go!

On the road riding side of things how do they run? Errrr I am finding that the Monty (40mm dellortos) struggles a bit around town at anything less than 90Kph (55mph) e.g. it coughs and splutters and hunts quite a bit until I hit the highway which is 45 minutes away.

Now I do appreciate that it is NOT a street bike! Though I do wonder what options I have to make the first 45 and last 45 minutes of my ride a little more bearable?

Cheers,
Mike

Mike has sort of pre-empted a question on my mind. I was thinking to use Mikuni TM 36er's on my what will be a road bike.
I have noticed that the 4T carbs (pumper the only diff ?) carbs are about $150 each more expensive.
I know a 4T will run without a pumper & I remember reading that on Rutters ? TT bike they disconnected the pumpers to gain fuel economy, and he still managed to get around there at a decent pace.
So what are the pro's and con's, pumper vs non pumper ?

Mike if you ride your bike for 45mins on the road to get to the highway, then ride up and down the highway, it sort of sounds to me that your bike IS a road bike ?
but the other thing is when you get to the nice mountain roads, which is not a WFO situation - your bike must be horrible to ride ?

Hi Peter, The Montjuich was never designed to be ridden on suburban streets. It is a race bike with race cams and race sized carburetors. Yes, shame on me for putting her through these unacceptable conditions.

Anyhow, I live in Balmain which is an inner city suburb of Sydney - say like Richmond is to Melbourne. I have 3 basic ride destinations for a morning blast.
North to the Mt White cafe on the old Pacific Hwy (this ride is like heading to the Rock Store on Mulholland or Boxhill in the south of England)
West to Eastern Creek race track for a ride day where I can WFO - my favourite ride! and
South to the Nasho - Royal National Park - which is a scenic MUST for anyone visiting Sydney.
For each of the destinations I have no option but to navigate 45 minutes worth of traffic lights (45 out/45 back). Yup in this environment the Monty is not at all happy! 'horrible even .

However, once I am on the winding open road and the speedo says > 90 Kph (55 mph) there is no more delightful bike to ride! In a few moments my bike and I enter a spiritual space together of glorious harmony. The sound, the agility, the confidence of her feedback. She is like a race horse that is finally given her bridle as she opens up and settles into full gallop! Oh what a feeling

So, as you see I would like know if I can somehow ease the discomfort at the beginning and the end of the ride. Perhaps a 36mm DellOrto might do the trick? Or do flat slide carbs manage fuel better than a 40mm DellOrto at lower revs while maintaining top end performance also? Though nowadays I rarely ride flat out... So low to mid range performance would be primary requirement for the Monty.

The Montjuich P cams are probably the main show stopper for what I would like, but I ain't changing them 'cos they make the bike sound so exquisitely beautiful, raw and aggressive like a top fuel dragster staging at the grid. Yum!

Hi Mike

My F1 has 41mm pro series and they are really good. It has a no. 7 cams, a heap of head work and it is a pain in the butt riding around town,its want to blow the carbs off the intakes. I don't have to go through any towns to get to my favourite rides so i am happy with them.

Jon

I hear you! And the other motorists HEAR ME TOO at the traffic lights!! - if you know what I mean!!!

Last year Ian Gowanloch warned me against putting Montjuich cams in my 1985 F1 - if I wanted to use it on the road, so now I know what he was talking about!!

My F1 should be back on the road soon after a 20 year hiatus of being in parts as a consequence of being submerged in the Benalla floods of 1993.

I have left the restore for Ian to do. It will have some pretty delicious parts on it when completed.

Hello Mike,
My TT rep (750) has 900ie cams and these are good riding the 45 minutes to good roads in the hills behind Brisneyland. Also good once in the hills! (but the tight TT is the most uncomfortable bike I've ever owned around town )
Moving to Tasmania in 2 weeks then the good roads are only down the driveway.

Graeme

And 40's with the pumps disconnected

Mike, I spoke to a friend of mine today who is a bike racer and mechanic who keeps his cars/bikes very well tuned.
He didn't think that pumper carbs were necassary on a road bike if running flatslides : especially when smaller carbs were used as airspeed is high. Larger carbs could benefit becos of slow air speed.
He says that going to flatslides over round slide or cv carbs is going to make a big difference to engine response time after turning the throttle as well as a small gain in power generally.
How long is it going to be before you get your other bike back from Gowanloch ?