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General Category >> Rubber Side Down! >> Jet set up
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Message started by Tpot on 02/19/17 at 16:00:31

Title: Jet set up
Post by Tpot on 02/19/17 at 16:00:31

I live in south west Michigan. What jet setup should I use?

Title: Re: Jet set up
Post by Kris01 on 02/19/17 at 19:41:09

What's your altitude? What kind of mods on the bike?

Title: Re: Jet set up
Post by Tpot on 02/19/17 at 19:45:38

I am at 659' and the only mod i know of is the "white spacer mod"

Title: Re: Jet set up
Post by Dave on 02/20/17 at 04:22:06

I ride between 525 and 825 elevation.

The #150 main works very well with the stock air cleaner and a DYNA muffler, and a #50 or #52.5 pilot works.

If you have a "surge" when accelerating with low throttle settings, the raise the needle slightly by taking a bit more off the spacer, or using 2 or 3 #4 machine washers instead of the white spacer. Start with 3 washers, and it the surge is still there remove 1 and try running just 2.

Title: Re: Jet set up
Post by Tpot on 02/20/17 at 06:16:13

I believe I am running pretty lean because I have quite a bit of discoloration on the exhaust

Title: Re: Jet set up
Post by Dave on 02/20/17 at 07:53:38

022437203F25263922223324560 wrote:

I believe I am running pretty lean because I have quite a bit of discoloration on the exhaust

That is not always a proof of running lean - the blue can also be caused if you spend a lot of time sitting at traffic lights, riding at slow speeds through towns/cities/traffic.......all those can allow the header pipe to get hot.

Title: Re: Jet set up
Post by Tpot on 02/20/17 at 07:55:45

Is this because it is air cooled?

Title: Re: Jet set up
Post by Dave on 02/20/17 at 08:51:57

it doesn't make a much difference if the engine is air or water cooled - what makes a difference is how hot the pipe gets.

The exhaust pipe is cooled by air blowing over it......and if there is little or no air movement......the chrome turns blue. This blue color is a result of the oxygen in the air reacting (oxidizing) the elements in the chrome.

Title: Re: Jet set up
Post by Kris01 on 02/20/17 at 17:57:19

7A5C4F58475D5E415A5A4B5C2E0 wrote:

I am at 659' and the only mod i know of is the "white spacer mod"

I think I'm somewhere around 300' or so. A 52.5 pilot and a 150 main works great for me. I use 3 #4 washers in place of shaving the white spacer.

Title: Re: Jet set up
Post by Gary_in_NJ on 02/20/17 at 18:51:21

You can take two seemingly same bikes and jet them right next to one another and get two different results. Use the suggestions above as a guide for a starting point, but nothing will replace a good understanding and evaluation of the trottle position and the transition points. A proper plug read will confirm the throttle read.

Title: Re: Jet set up
Post by Tpot on 02/20/17 at 19:07:22

Is there a reference to throttle position and transition points on here?

Title: Re: Jet set up
Post by Gary_in_NJ on 02/21/17 at 08:01:13

As a rule of thumb...

Idle to 1/8 (or less) throttle = Pilot Jet / Air Screw Adjustment
1/8 to 3/4 throttle = Needle*
5/8 to WOT = Main

*there are a lot of variables with the needle circuit. Clip position, condition of the needle valve and the tapper of the needle itself all have an effect on this circuit - a circuit that you do 90% of your riding on.

The only way to tune the needle circuit is by feel and performance. Feel and performance include hesitation, lean surging, bogging, burbling - to name a few conditions.

By the way, a spark plug reading is really only valid for WOT operation and a new spark plug must be used. This is an easy test for a bike where the spark plug is easily accessible (like a dirt bike) but a challenge for a bike like the LS650 - and impossible for a fully-faired sport bike. As an alternative to a plug read, I like to get the bike to 5/8 throttle and roll to WOT. I'm looking for a linear transition with no reduction or surge in power delivery. A reduction in power delivery indicates too small of a main jet, while an increase indicates that the needle circuit is too lean.

Title: Re: Jet set up
Post by Kris01 on 02/21/17 at 17:47:53

143221362933302F34342532400 wrote:

Is there a reference to throttle position and transition points on here?

http://kawtriple.com/mraxl/carb/mikunicircuit.JPG

Not Mikuni speciific but will get you by.

Title: Re: Jet set up
Post by Tpot on 02/22/17 at 15:02:08

Well I kind of feel stupid now but one of the screws that holds the front boot on the intake of the engine was loose so I replaced the screws with 10mm bolts and everything is great now