Needle selection

[deeeebeeeeee]

For those of you who aren't content to with a stock needle in your modded blaster and have moved to different ones , How did you go about choosing needles to try?
What needle and clip are you currently running? With what mods?
What did you do to test various needles ?
What was it that caused you to choose the needle that you ended up going with.
I am sure you guys have
Story or two detailing how you come to go with a different needle.

 

[Awk08]

I've run the stock carb on 2 different blaster engines in various states of tune, from stock, stock w/ pipe-filter, just port cleanup, to my KOR fully ported, modded head, 165# compression engine w/ all the goodies. and 5 different pipes and various reeds, tested on both bikes.
nothing works better than the stock pilot and needle.

 

[Blaaster]

Never have had to use any other needle with the stock carb!

 

[deeeebeeeeee]

Definitely food for thought, yet with a Q-2 needle jet in the 28mm mikuni vs. the leaner P-6 in the stock 26mm carb.
And now that I have found out that the vm28 I have uses a 332 needle which is limited to oem Yamaha sizes. I feel like I might want to use a different needle size.
then again the larger needle jet might be ok since the carb is slightly larger and should have a slightly weaker signal?
I am really interested if there is a better way than just extensive trial and error?
Obviously if it's on at 1/4 or so and lean at just under 3/4 then you wouldn't use a needle with less taper, and would try to go shorter or use a needle with more taper.

It just doesn't seem right to me (not that I really know about these things), that one needle could be so versatile as to be ideal for so many different configurations.
Is it that the smaller 26mm carb or good venturi action allows for a strong enough signal to provide fuel flow at the same ratio in a wide range of conditions?
Could ease of jetting be one of the reasons went with a 26mm carb on a 200cc motor when even a yz 80 uses a larger carb.

I am just trying to understand what I am dealing with and why or how it works so well from bone stock all the way to wild mods? I Was under the impression hat it is usually not that way as far as needles are concerned and that as a general rule as the amount of drawing force to pull in air at various throttle positions changedso did the shape of the needle?
I am obviously lost on the subject . Can anyone point me to a good read on this that goes beyond a simple explanation I would appreciate it.

 

[Awk08]

I have found out that the vm28 I have uses a 332 needle
the larger needle jet might be ok since the carb is slightly larger

your thread heading, and our responses to it, all are stock 26mm carb related.
now you flip the script and say 28mm

 

[deeeebeeeeee]

your thread heading, and our responses to it, all are stock 26mm carb related.
now you flip the script and say 28mm

Lol sorry my question was for general info on needle selection, wasn't aware that it wasn't required on the stock carb.
Seems the pilot jet is simple to set your airscrew will "tell" you to go up, down, or leave it alone.
Main jet and even needle position changes are plain as the nose on your face once you cut the threads off a properly run (wot or 1/2t) plufg.

But there are so many possibilities,and thing that can throw off needle selection, a pilot jet that's a size off, or a main jet that a couple sizes rich or lean can really throw things off, (so I hear anyhow).

My plan is to simply, pick a needle set it at mid clip, get the pilot, airscrew and main (pc verified) on. And then experiment from there concentrating first on getting a good chop at 1/2 throttle then on he sounds and feel of 1/4 to 3/8 throttle and right around 5/8 as well, holding each position for as long as possible from rolling rpm to where it stops pulling, in 4th of 5th for low throttle and 5th or 6th for higher 5/8 throttle.
Might also fan the clutch at moderate rpm as see if or how well it comes on the pipe.
My thoughts are that if the needle chops nicely at half throttle, then the clip will need to stay and the needle itself will be responsible for whatever happens on either side of half, and should give me a good idea of more or less taper, starting sooner or later???
I haven't a clue whether the above plan will actually work in practice but based on my limited knowledge, and barely workable sense of rich or lean, it sound like about the best I can do toward figuring it out.

My guess is I will carry a couple spare plugs and needles with me when I go out to the trails, because it about the only place I have now that I can run it enough for anything funny to show up.

I used to have a little powe line right of way at the end of my neighbor hood that worked pretty well for testing, but some punks spun it up with their little 2wd s10's and now it's gsted.

Anyhow let me know what you think of my general plan, as I am sure there is plenty of room for improvement, and hope their is an easier way to do it.

Thanks deebee

 

[jvb]

I used to have a little powe line right of way at the end of my neighbor hood that worked pretty well for testing, but some punks spun it up with their little 2wd s10's and now it's gsted. LOL


Get it jetted on the rich side, that it starts and idles good and good WOT
Now you can ride it safely WOT, then you'll notice everything in between throttle positions, then jet/ fine tune accordingly.
(at least , that's how i do it)
You've got enough knowledge to get it spot on , sure of it!

 

[deeeebeeeeee]

I used to have a little powe line right of way at the end of my neighbor hood that worked pretty well for testing, but some punks spun it up with their little 2wd s10's and now it's gsted. LOL

/\ no way.......what would make me grin from ear to ear would be to catch up with one of those little twits, with a bag of grass seed in one hand and my leather in the other, and tell them to choose one. Lol , but yeah would be my luck.
I got the little track behind the house but it has a n up hill curve that you can't come through wide open as it will break loose and if you keep it from spinning out then it picks up speed and lifts the front wheels before you can finish turning, as it is with the uphill switch back.


Get it jetted on the rich side, that it starts and idles good and good WOT
Now you can ride it safely WOT, then you'll notice everything in between throttle positions, then jet/ fine tune accordingly.
(at least , that's how i do it)
You've got enough knowledge to get it spot on , sure of it!

Appreciate the vote of confidence, ultimately if I get through it without major issue, then I will be happy.
I hope it's easier to jet than when it was leaking randomly throuh the carb gasket and apparently just under the exhaust tunnel once it got good and warm.

 

[jvb]

Appreciate the vote of confidence, ultimately if I get through it without major issue, then I will be happy.
I hope it's easier to jet than when it was leaking randomly throuh the carb gasket and apparently just under the exhaust tunnel once it got good and warm.

That's gonna make all the difference, a leak free engine
Now jetting changes will respond accordingly

 

[jvb]

And the 28mm isn't getting a weaker signal.. i hope your engine will flow at least the same as the 80 engine wich the carb.originally came of..

 

[deeeebeeeeee]

And the 28mm isn't getting a weaker signal.. i hope your engine will flow at least the same as the 80 engine wich the carb.originally came of..

By weaker signal I meant versus a 26mm on the same motor.
I noticed someone had picked up a bone stock blaster w/ a. Vm30 and was running a 250 main jet or 2 sizes over stock.
Sss
Looks like maybe 1 size larger main jet than expected with a stock carb s is about where I should start.

Lol I would ove to have a welder, a handful of bungs and plugs, and a decent egt setup. Not that there is anything wrong with the way I learned to do it from here, in fact even those that use an egg, say to verify with a plug chop.