Needle Height Determination

[Auggie_1970]

Hey guys wondering if I can get some advice here on properly selecting the best needle height. I recently swapped out the cobra slip ons that came with the bike when I bought it with Dales complete exhuast. The bike had a dyno jet stage one kit on it with stock filter and dj 170 mains. I swapped out the mains with minuki 155's and added the K&N and removed the Y on the air box. Pilot screws are 2.75 out. I live in NJ in case that helps with altitude..

The needles were originally set at the third clip from the blun end so I left them there when I put on the holeshots and drove it for a little while like that...Seemed to have a stumblle at around 6-6500 rpms, but not sure how fair that is considering that I since found I had a small exhaust leak because I didnt tighten things down enough.

Anyhow I moved the clip to the 2nd from the blunt end and it seemed to run good, didnt notice any stumble. Didnt seem to notice any change in performance as she warmed up.

I then wondered what it would perform like if I richened it her up a little so I moved the clip down to the 4th from the blunt end. Also runs good, so stumble , and its smooth. No noticable change in performance as she warms up

Am I missing something. Seems to run good in both the 2nd and 4th clip posistion. Never re tried the 3rd position after I fixed the exhaust leak. Can anyone help me understand the best way to figure out what I should be looking for when comparing different clip positions.. She definately runs 100% stronger now vs when I had the cobra slips ons on her. Any advice would be greatly appreciated. Thank you

 

[gamorg02]

you want to keep going leaner until theres stumbling then back off one.

 

[Auggie_1970]

Does that generate the most Hp?

 

[gamorg02]

its not that simple. you need the a/f mixture correct throughout the WHOLE range to generate the most HP. if your needle is right u will have the most HP in the midrange. the definition of midrange also depends on what your throttle position is. at WOT its about 3k - 5/5.5k.

 

[Auggie_1970]

Ok , gotcha, just attempting to get as close as I can without having to try and find a dyno.

 

[gamorg02]

have u read the 'tuning CV carbs guide"?

 

[1967vmax]

put the y back in,then do a good carb sync, ride it and do a plug check where it stumbles . Also check the connections at the carb boots for air leaks,1 thing at a time,then test ride jim3933

 

[Auggie_1970]

Ok will try, whats the reason for putting the y back on , does that richen it up a bit? Just curious..Will have to wait till tomorrow its supposed to keep raining all day. Thanks

 

[Nicki66]

Garrett, where can this tuning guide for carbs found.

 

[KJShover]

where can this tuning guide for carbs found.

http://www.vmaxforum.net/showthread.php?t=1024

 

[gamorg02]

http://www.vmaxoutlaw.com/tech/cv_carb_tuning.htm

&&

http://www.vmaxoutlaw.com/tech/carb.pdf

 

[RagingMain]

You may not notice a seat of the pants difference between the 2nd to 4th clip position but your bike does.
Like it was said earlier you will want to run as lean as possible when just putting around town without surging or popping. This also gives you close to the a/f mix you need for max power when you whack open WOT.
This keeps the engine carbon free and gives you better mileage.
If you have crisp throttle response, no popping or surging on the 2nd clip then that is where you should keep it.
You will find out also after you do some of those carb tuning tips how it is running.

 

[Nicki66]

Thanks KJ and Garrett

 

[Auggie_1970]

Ok sounds good, I'll put her back at the 2nd clip position and test ride it. When you say popping , is that popping on decel, or popping while cruising or accelerating? Thanks for your advice.