carb setup

[zman]

Is the only way to work out which jets work best by keep changing them till you get it right
my 900 is now 1015 with 4into1 and a k&n in the air box.Never run 100% before my rebuild.
i had 125 mains.But was wrongly told to change to117.
i have now been advised to go back to 120 or 125 and move clip to centre position.
as i gave away my 125 i don't want to keep buying new jets.
Is there a better way

Does any one now what air flow should be

Thanks david

[njwmct]

Quickest & most accurate way is to get it set up is on a rolling road.
Towcester Tuning Shop (TTS) based at Silverstone have a lot of experience with air-cooled jap multis

[Garn 1]

There should be a more methodical way.... I don't know it, but someone must!
I start by putting the standard main & pilot jets in ( From Manuf data sheet).
Balance carbs then with new spark plugs and correct ignition timing, road test.

I look for, or listen for "pooping" at carbs (usually too lean at idle).
Smoothness and power through gears and revs up to 3500 look at pilots.
Smoothness and power through gears and revs at higher range, look at mains.
Any bogging down, probably too rich!

Only make small changes...Bit bigger jets than standard if larger capacity, air pods and 4 into one.

Not very scientific!
Last item, get as many mates to see what they think!
Someone must have a good method? A good procedure list.
RegardZ.

[gray]

slow but sure way is ok if you've got plenty of jets to play with , and time, and good weather to do a fullbore test then plug chop . Not easy in UK in Jan.
professionals would have all the knowhow , all the the equipment and alllthe jets likely to be useful.
Expensive but could be the best money you'll spend for years in the increased riding enjoyment and improved economy and rideability.
i like DIY but this is 1 case I'd hand to the experts

[Garn 1]

I guess we will have to go and get a Dyno check.
They usually work out what you need... I think you would still have to have the carbs pretty close to correct, to carry out the test.
It certainly would be nice to get a graph back of HP v's RPM and air/petrol ratio v's RPM.

On that subject , I was wondering if, we just have a small exhaust analyser, clip it on the exhaust tail-pipe, feeding into a computer stick, with an electronic Tacho input also connected and go for a ride... Come home and plug it in to our computer. The readout would be Air/petrol ratio v's RPM.... We are half-way there! We will just have to judge power by the thrust we feel.
REgardZ.

[zman]

Thanks for your help guys.
I think i will talk to TTS and put it on a rolling road.
I have been told that they can be pretty brutal Hope it doesn't blow up
Im not to far from having it back on the road.You can see it in projects under,zmas cosmetic rebuild