Jetting change needed?

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Re: Jetting change needed?

Post  SkidMark on Sun Mar 31, 2013 8:33 pm

ok got my jets now - all the talk above is about checking the main jet. Anyone know what kind of speed/gear/throttle opening to check the pilot jet?

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Re: Jetting change needed?

Post  BuRP on Tue Apr 02, 2013 10:55 am

Yes: closed!
Get idling right first, then mark your throttle and keep below 1/8th & go testride - an exercise in self-control if nothing else but this works well. Look at your front sprocket and see if there's 'surging', and if so find a setting that surges least.
Oh, the screw must be close to 1.5 full turns out, too much off means the jets are wrong.
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Re: Jetting change needed?

Post  SkidMark on Wed May 15, 2013 11:50 am

So put in the 68s and 170 with the mixture close to 1.5T outs. here its the plug after a full throttle plug chop (sorry the pics aren't great but hopefully good enough?)

[url=]pic 1[/url]



the second image overexposed so the brightness makes it look lean I think but really it was pretty even tan colour on the electrodes and the same on the top of the insulator. Spot on or a bit lean?

Thanks guys - heading to Rwanda friday on it so just want to make sure I'm not lean and gonna blow it up!

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Re: Jetting change needed?

Post  AURORA on Wed May 15, 2013 3:37 pm

SkidMark wrote:ok got my jets now - all the talk above is about checking the main jet. Anyone know what kind of speed/gear/throttle opening to check the pilot jet?

This is jetting is based on your mixture screw.
It should be about 1.5 turns out. If the screw requires say more than 2.2 turns out you need a bigger pilot.
If the mixture screw is say less than 3/4 to 1 turn out you need a smaller pilot jet.

You should be able to turn your mix screw and get the idle to rise and fall. If you cant, its simple, you don't have the right pilot yet.
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Re: Jetting change needed?

Post  SkidMark on Wed May 15, 2013 5:56 pm

here's another better picture of of the plug. I pulled it out again at the end of my ride and it basically looked the same and I got a better picture

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Re: Jetting change needed?

Post  Mauser on Wed May 15, 2013 7:49 pm

Looks good to me, slightly rich maybe but still good BRP smile

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Re: Jetting change needed?

Post  Mad Frosty on Wed May 15, 2013 11:34 pm

That looks about right .
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Re: Jetting change needed?

Post  BuRP on Thu May 16, 2013 8:46 pm

Def not rich, looks fine if not leanish.
If this was a new (white ceramic) plug you used then, if it runs well, I'd leave it at that. If this was a well-used plug (ie sooted darkish beforehand) then it's too lean - which I would test (a rough one mind) as follows: find a clean tarred quiet dustfree road, and ride (with a new/clean airfilter, with the excess oil squeezed out) the same stretch up & down until you know how the bike behaves there. Then remove the airfilter (but put back the sidecover) and repeat a bit. If the bike still runs good then it's jetted too rich, if it performs a bit less then it is fine, and if it seriously underperformes/misbehaves then it is jetted too lean. Mind, the idling will not be affected by this. As said a rough way of testing but a fair indication.
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Re: Jetting change needed?

Post  SkidMark on Mon May 20, 2013 6:59 pm

BuRP, it was a used plug (but probably only a couple hundred K's on it) but I had given it really good clean back to the white ceramic before I did the run. The bike just performed really well on the run to Rwanda and back up to altitudes of 6600ft, my jetting run was carried out around 3700ft. A friend arrives friday with 4 plugs so I will do another jetting run after those arrive to confirm.

Thanks for all your input. Will do a run to get the pilot just right too soon.

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5000 ft

Post  Chris_w_65 on Mon May 20, 2013 8:32 pm

I bought my bike from a guy at sea level, he had it on a dyno and they set it with 185 and 68 (different headers and tail pipe, airbox intake cut in side plastic). With being at 5000 ft I looked at the jetting chart and dropped to 175 and 65. I still need to get it on the dyno but already I notice if I blip the throttle from idle it is very responsive where with the 68 in it was not
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Re: Jetting change needed?

Post  AURORA on Tue May 21, 2013 2:55 am

SkidMark wrote:ok got my jets now - all the talk above is about checking the main jet. Anyone know what kind of speed/gear/throttle opening to check the pilot jet?

Idle
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