Jump to content

100 Pilot Air Jet - Need a 2018 Discussion

Recommended Posts

Hey guys,

     I think its time to ask a 2018 FRC MX 39 question. I know theres a thousand discussions on this (But most prior to 2011 and its 7 years later... just saying) Do you leave the 100 Pilot Air Jet in or not??? Look it up and you get different answers (Both with good reasons). Just want to know leave it in, and why? Or take it out and why?

My Elevation 1,200ft

Temp = Pennsylvania (Means it could be 80 degrees today and 40 degrees tomorrow)

My Mods

MRD Exhaust

160 main jet

45 pilot jet

EMN needle

clip 3

200 main air jet

100 pilot air jet

2 turns fuel screw

o-ring mod

Share this post


Link to post
Share on other sites

Bought my fcr from JD 5 years ago with no paj and  a 45 p j in summer . Few years back I did try to add the paj but did not like it , even with a 40 pj I could not kill engine with mixture screw so took it off .this year I did a new standard bore top end and for some reason the 45 pilot is too small , need to go 48 . 

Share this post


Link to post
Share on other sites

Leave it in. Why, because there is no reason to omit any jet. If the pilot is too rich then buy a smaller pilot. If the transition off the pilot to needle is rich then get a larger diameter. Try the EMN and then try the included EMR. Use which ever feels better at 0+1/4 throttle.

 

2 turns on the screw is a starting point. Buy the R&D Flex jet, it's worth it's weight in gold.

 

Double check the float level and set it to 9mm if needed.

 

I bought a TT 39mm kit in 2016.

  • Like 2

Share this post


Link to post
Share on other sites

Thank you. That makes a lot of sense (You know now that I am an google carb expert now. I stayed at a Holiday Inn Last night too...LMAO). The only thing I haven't messed with is the float height. I do have the R&D Flex Jet (Got real old, real quick, to jump under a hot bike and try to adjust mixture). 

Maybe you can help me a little here:

I ride with two other guys

One has 2015 and the other a 2016 and mine is a 2017

2015 SM = Powerbomb (Only difference than mine) I know this because i do the work on his

2016 SM = Same exact set up but has stock carb with rejet (Dont know his jet settings)

2017 SM = Listed above

When I ride their bike's, they seem to have a little more pep and thier bike doesn't pop on decal

When I do the below method, it doesn't stall when all the way in OR out 

 

Share this post


Link to post
Share on other sites

Your tuning is likely way too rich with that jetting.The James Dean JDS010 is a much better jet kit for that carb imho.

Share this post


Link to post
Share on other sites

At a total loss now....UHHHHHHHHH

I started this season with a 42 pilot jet and if i screw the mixture full closed or 3 turn it ran the same. Now this afternoon i put a 45 pilot jet (Kept the PAJ in) and it stalls at about 2 1/4 turn and runs fine fully closed. Should I have gone down in pilot jet instead of going up? With the 42 or 45 a throttle blip almost stalls the bike

Problem I am trying to fix is that 0 to 1/4 throttle (Want it more peppy). PLEASE HELP! Its a PIA to keep taking the carb on and off

Share this post


Link to post
Share on other sites
5 hours ago, Shaun Small said:

At a total loss now....UHHHHHHHHH

I started this season with a 42 pilot jet and if i screw the mixture full closed or 3 turn it ran the same. Now this afternoon i put a 45 pilot jet (Kept the PAJ in) and it stalls at about 2 1/4 turn and runs fine fully closed. Should I have gone down in pilot jet instead of going up? With the 42 or 45 a throttle blip almost stalls the bike

Problem I am trying to fix is that 0 to 1/4 throttle (Want it more peppy). PLEASE HELP! Its a PIA to keep taking the carb on and off

You have to adjust the fuel screw with the lowest idle speed possible. If you try to adjust it with a normal idle speed, you will likely be slightly on the needle which makes setting hard, if not impossible.

Here is my write up on the full procedure:

Fuel screw settings in the 'book' are recommended starting points. Every bike is different, as is the temp and altitude. Set the screw according to this method. Do it with the bike fully heated up.
Gently turn the fuel screw all the way in. Now back it out two turns. Start the bike and fully warm it up, go for a 10 minute ride. Set the idle knob to speed to 1,500~1,800 RPM as best you can (I know, without a tach this is tough, just set it to were it idles relatively smoothly).  Once warmed, slow the idle speed (knob) to the lowest possible speed.
*** When turning the fuel screw, keep an accurate 'count' of the amount you are turning it and record it in case you have to reset it for some reason. Makes life easier when you can just set it from notes Vs. going through the procedure again.***
Turn the fuel screw in until the idle becomes rough or the bike stalls.
if it stalled, open the screw about 1/4 more turn. Restart it and slowly screw it in till you can just perceive a change.
If the screw can be turned all the way in and the bike still idles perfectly and does not stall, then you need to go down a size in pilot jet.
Now very slowly, open the fuel screw till the idle is smooth. Blip the throttle, let the bike return to an idle, wait say ten seconds. Confirm it is the same smooth idle.
If the screw has to be opened more than 3 turns to get a smooth idle, you need to go up a size in pilot jet.
If you find it does not stall with the larger jet but has to be open more than three turns with the smaller pilot jet, put the larger one in and set the fuel screw at 1/2 turn.
If the idle speed increased, adjust the idle speed knob to return the bike to a real slow idle speed. You must then re-visit the fuel screw. Keep doing this till the fuel screw is opened just enough to provide a nice steady idle at the lowest possible RPM. Once this is done, increase the idle speed to the normal one for your bike, typically about 1,850 rpm, but go by the spec in your manual.

  • Like 2

Share this post


Link to post
Share on other sites
On 6/14/2018 at 2:52 PM, Shaun Small said:

Should I have gone down in pilot jet instead of going up?

I'm over in Ohio, and have a slant FCR rather than the MX, and my airbox has a MUCH larger than 3x3, so take this with a grain of salt. When I started dialing mine in I found the recommended settings to be WAY too rich. I tested every jet from 160 down to 148, the bike made the most power on 148. I'd rather be on the safe side of rich I stuck the 150 MJ in when I was finished. On the PJ I'm running a 38. I'd have to dig up my build thread on here, my pilot air jet is adjustable, but I think its like two turns out. Once this was set my decel popping was gone.

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:


×