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I am contemplating shaving a small amount off of the bottom of the carb to emulate buying a leaner slide, I'll have to take it apart and have a good look first though!

a video of the bike running would be good!

In the words of a complete twat, "I shall try my utmost"

Definitely needs a larger pilot jet, will get a few on order 2moro

moto_psycho wrote:Definitely needs a larger pilot jet, will get a few on order 2moro

That doesn't surprise me. Weaker signal....

I have fooled with carbs a LOT on boat motors. Not so much on motorcycles, but theory is the same.

From experience - 44 cubic inch 4 cylinder outboard with 2 carbs:
Motors come with two 1" carbs. Mercury made several other sizes of carb for different motors - 1 1/16", 1 1/8", 1 3/16", 1 1/14".... The motors were designed to turn ~ 5500 RPMs stock. We turn them ~ 8500 RPMs on our hydros. We can't do ANYTHING to increase compression ratio. We can port them all we want to (in fact, we can remove all the metal we want to - just can't add any). The 1 1/4" carbs are way too big for anything. The 1 3/16" carbs are way too big for racing. The 1 1/8" carbs run good down the straights on a 1 mile course, but they give up too much coming out of the turns and they are too big for 3/4 mile. The 1 1/16" carbs worked out to be the best 1 mile courses. The stock 1" carbs are tough to beat or courses shorter than 1 mile. I run 1 1/16" carbs everywhere. Some of my competitors switch between 1" and 1 1/16" carbs depending on the course. The smaller carbs work better on the shorter courses. Why? The motors spend more time accelerating on the shorter courses. Even though I can run a Holley 4 barrel, it wouldn't do me any good. The motor can only use so much carb.

It is definitely a jetting issue at the moment though, it doesn't feel like too much carb atall (I've over carbed before!) this is literally a case off to small an idle jet, the bike is hunting at idle and I have a smaller jet installed than recommended for the carb.

But as you say, weaker signal, but with the carb being so much closer to the action I definitely believe it is made up for, as the second the needle comes into play (just over 1/4 throttle) the bike takes off like... a powerboat

Interesting, when I snapped the throttle shut the needle got jammed in the main jet had to make a shim up for it.

Also, fitted 50 pilot jet, has cleaned up the bottom end, but I really think I need to get a leaner slide so I have more adjustment on the needle. Then from that I need to get a needle that is slightly richer at 1/4 throttle.

The bike feels nigh on perfect atm, but there is always more to be had

Video;
Needs a larger main jet atm, I went down 5 sizes on pilot and it affected WOT rather severely, so its not revving out as much as it had done before hand, but there you have a video of it running :)

45 Pilot
CEL Needle top clip
180 Main (changing to 190 2moro)
[youtube][/youtube]

Sounds like a turd bike to me
Did you give it more than half throttle on your
way down that hill ?

Not worth my time.

perhaps the main jet being on the leaner side of correct?

bit of math for you

pilot 50
main 180
WOT - 230

pilot 45
main 180
WOT - 225

Don't forget to post the before and after dynos

Good work on that adapter though.

Not worth my time.

Do me a favour and get me a schematic of the valve that shuts off the idle jet at anything over 1/4 throttle then please mate...

And no, my idle is perfect, if you really want I could use a timing light to find exactly how many hundred rev's it is idling at. Air screw is 1.5 turns out which is directly in the middle of the adjustment range, it is perfect.

Also, the idle circuit on this carb bypasses the slide completely, at idle the slide is 100% shut.


Pilot jet 45
Needle CEL top clip
Main jet 190

best setting so far :D, gonna try 200 main 2moro, though I doubt it will improve, but I'll never find out if I don't try!



Quote from a well known jetting guide;
"It's very important that you start with the pilot circuit. The reason is simple. The pilot circuit affects the entire throttle range. When you are at full throttle, the main jet is the primary fuel metering device, but the pilot is still delivering fuel as well, adding to the total amount of fuel that your engine is receiving."

Source - http://users.conwaycorp.net/virtus/page ... etting.htm

Not worth my time. Good luck to you and good bye.

Hah! How am I not worth your time? You've learned something quite important about jetting from me, what have I learned from you?


I find it quite funny, before I fitted the carb half of the forum was swarming on this thread, itching to read of my absolute failure, now it works far better than expected, everyone buggers off.

Also, I will next try shimming the needle to see if that provides any better performance, and should give me a ballpark figure on what slide I need to buy!

TWMOODY wrote:Sounds like a turd bike to me
Did you give it more than half throttle on your
way down that hill ?

Like I said, top end was upset at that point.

moto_psycho wrote:Hah! How am I not worth your time? You've learned something quite important about jetting from me, what have I learned from you?


I find it quite funny, before I fitted the carb half of the forum was swarming on this thread, itching to read of my absolute failure, now it works far better than expected, everyone buggers off.

i havent learned anything from you.....you put a carb on your bike and made it run{somewhat}......but, did you not take a carb off your bike that was running?
i just dont see why you want to go thru the trouble to install that carb, when you could have jetted the stock carb.
but, i guess if your THAT bored, go for it.

moto_psycho wrote:Hah! How am I not worth your time? You've learned something quite important about jetting from me, what have I learned from you?


I find it quite funny, before I fitted the carb half of the forum was swarming on this thread, itching to read of my absolute failure, now it works far better than expected, everyone buggers off.

As far as I can see, it's working about as I expected.