Author Topic: VForce and Gnarly vs jets  (Read 3525 times)

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Offline tschisi

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VForce and Gnarly vs jets
« on: March 22, 2010, 07:33:07 AM »
Hi Guys!


I know the jetting-threads suck but i just didn?t find enough info...

Just got the VForce 3 for my 1990 k5 (but not installed it yet).
I?m also planning to get a GnarlyPipe.

FMF provides the jetting charts, but i don?t know if i have to change my setting ?cause of the reeds.

Can anyone tell me approximately what changes i have to expect with the VForce 3 and maybe the Gnarly?
I?m riding at about 800 feet above sea level and 40 to 80 degrees fahrenheit.

Thx!!!

2004 kx125
1990 kx500 (sold)

Offline Friar-Tuck

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Re: VForce and Gnarly vs jets
« Reply #1 on: March 22, 2010, 05:59:28 PM »
http://www.mototassinari.com/pdf/MotoInstruct04b.pdf

Q: Will I need to rejet?
A: Typically, there is no need to rejet after installing the VForce reed valve system. If you have previously jetted your machine to work well with your stock reed valve you should have no problems. However, we do recommend that you check the plug(s) after your first ride to make sure that there is not a drastic change in plug color. We do not offer individual jetting guidelines due to the numerous variables that will affect your jetting... such as climate, elevation, other existing modifications and more.


http://www.fmfracing.com/TechSupport/JettingCenter
 Jetting Center
We know how difficult jetting can be sometimes, that's why when we test our exhausts we also adjust the jetting to see what works best. Sometimes stock jetting works fine, other times a slight adjustment is needed. Here is what we've come up for in our area and is a great starting point for you as well. There are way too many variables in jetting to give you a recommendation that works perfect. Use these specs for a reference to help aid you with your specific bike. We developed these specs with a 32:1 fuel to oil mixing ratio of a 50/50 mix of race fuel and super unleaded, 0 - 1500 ft altitude at 70 degrees outside temperature.

Select your MAKE, YEAR and MODEL

Make:
--Select--  KAWASAKI
 Model:
--Select--  KX500
Year:
--Select--  1990
 
Jetting Information: 
Main Jet: 170
Pilot Jet:  62
Needle: N82L
Needle Position:  2ND
Power Jet:  N/A
Air Screw:  1.5
Fuel Screw:  N/A
Comments:

 Tuck\o/
   
« Last Edit: March 22, 2010, 06:28:37 PM by Friar-Tuck »
"The Truth Has No Agenda"

Offline tschisi

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Re: VForce and Gnarly vs jets
« Reply #2 on: April 27, 2010, 05:21:58 AM »
Sorry guys, i have to bother you one more time with this.  :oops:
I installen the vforce and the bike still runs  :wink:, but my spark plug an powervalce look like i?m running too rich mixture.
Unfortunately i can?t find jetting charts for my setting.

This is the situation:
Stock 1990 k5 with vforce 3.
800 feet above sea level and 40 to 80 degrees fahrenheit.
- Mainjet: 168
- Pilot jet: can?t get it out  :-(
- Needle: N82M
- Needle clip: 2nd from top
- Air screw: 3-1/2  :-o
- Spark plug: BR8EG
- Fuel: standard gas 1:40

I guess the air screw is much too widely outside?!
I got a new BR8EG and the gap is about 0.0016 feet (i measured 0,5mm). Ok?

Would be great if you could give me some values.

thx
2004 kx125
1990 kx500 (sold)

Offline blueoval

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Re: VForce and Gnarly vs jets
« Reply #3 on: April 27, 2010, 07:44:16 AM »
tschisi, it seems the pilot may be too rich if your air screw is 3 1/2 out.    IMO that pilot needs to come out to determine which one it is.   It's important to be sure the float level is correct also.   Am I understanding you right that the plug gap is  0.5 mm? 
« Last Edit: April 27, 2010, 07:48:03 AM by blueoval »
If some is good, and more is better, then too much is JUST RIGHT!  B.O.

Offline Friar-Tuck

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Re: VForce and Gnarly vs jets
« Reply #4 on: April 27, 2010, 11:24:57 AM »
Tschisi,
  Your going to have to change your main over that broad a range of temps, or run rich when it warms up and close when it's cold.    It doesn't take long to swap out mains by removing the 17mm plug in the bottom of the carb bowl. 
Use a 6mm socket to remove and replace the main.
  Re-install the 17mm plug and ride.

I agree with BlueOval, on the size of the pilot.
   The pilot and air screw actually have an effect on the whole range of your carb from Idle to W.O.T. 
(Read through this link for a refresher on jetting http://www.motorcyclecarbs.com/carbs101.pdf )

   If you can't remove the pilot, can you remove the carb and take it to a machine shop and ask them if they can remove it for you.

   If that is not possible there are some other things you may consider.
   Lowering your needle to the top clip position.

  A 7 heat range plug (BR7ES--G-EIX etc. Cheap one for test ride) Take a short ride and check the plug.
 
 Start going leaner on your main.
 You have to be careful obviously, how hard you ride and the type of riding you do is going to come into play.   Take some tools out with you and try a 165 main.   Take the bike out for a short ride and make sure you get up to operating temp, without going W.O.T.
   Pull the plug and see what it looks like.   If it still looks rich, get the bike up to operating temperature and do a plug chop to verify the bikes not melting!
 
You may be able to clean up your jetting by getting a leaner needle.
 An N82N is the next leaner needle (from Stock)  and a N82P in two leaner (than the stock(N82M)

 I know this is a pain in the rear, but you should be able to get pretty good performance working around the pilot.
The biggest thing to remember is to only change one thing at a time and take it easy until your sure the bike is not melting the piston.
  After a while you will know what you need to do to get the bike running right, it just takes a little time and patience.
 Every bike and rider are different, so there really is no magic numbers or jetting combination's.
   You CAN DO IT!
  Tuck\o/
« Last Edit: April 27, 2010, 12:08:14 PM by Friar-Tuck »
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Offline tschisi

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Re: VForce and Gnarly vs jets
« Reply #5 on: April 27, 2010, 04:49:13 PM »
Yes, the gap of my spark plug is 0,5mm.
I managed to open my carb and the pilot is 58.

For me it?s not really an option to try much settings because one jet costs me about 15 dollars.
But with the correction factor out of of tuck?s link; which is about 0,97; i will buy a new main jet and should be ok for the first.
The pilot is ok with 58, if 60 is stock i guess.

Another problem is that the bike won?t start right now.
I?ve got good compression, spark and fuel.
The engine won?t fire up, but pops and is flooded after about 8 times kicking, even when i just flushed it without the spark plug.
My float valve closes as it should.
Could it be possible that i have too much oil-soup in the exhaust?
« Last Edit: April 28, 2010, 05:15:42 AM by tschisi »
2004 kx125
1990 kx500 (sold)