Jetting

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RoscoeP

New member
Just put a JD jet kit in my 625 smc this week. I dragged my feet on doing it all summer. It was pretty easy to do on the bike. The bike runs so much better. The first thing I noticed when I started it(with choke) was there wasn't as much vibration.
Second I didn't have to leave the choke out as long and it didn't stall this time before I got going.
The bike ran perfect and seemed to respond better to throttle imput. Felt like there was more power. Besides the jet kit I have the mufflers drilled out to 1.25 inches and installed a KTM air box cover, which is basically a screen. I used the blue needle with the 170 main jet and 45 pilot jet. Should have done it sooner.
Cheers Roscoe:hb:
 
C

caribooster

Member
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I was considering doing the same for my 640. Where did you pick up the kit and what was the cost.

Brad.
 
R

RoscoeP

New member
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caribooster wrote:
I was considering doing the same for my 640. Where did you pick up the kit and what was the cost.

Brad.
Click to expand...
I got the kit from Munn racing in Texas, can't remember price.
see munnracing.com
 
Island Hopper

Island Hopper

New member
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The jets are pretty cheap thru KTM , about $8-$10 for the mains and the same for the pilots.

For a 640 if you opened the airbox and uncorked the stock exhaust you could probably move from the stock 152.5 to a 160 main and maybe go from the stock pilot 45 to a 47.5 the rest could be done by float height adjustments and jet needle clip adjusting. Some guys drill the slide to speed up throttle response but that's optional.

I found that moving from a 152.5 to a 155 main with my 640 in stock form made it run much better as it seemed a little lean with the factory setting. It also helped cold starting as it would no longer periodicly stall when you first shut the choke and it idled down.
 
Island Hopper

Island Hopper

New member
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Stenhouse Racing in North Van can supply you with a finger adjustable low speed fuel mix screw for around $30. The stock setup is a real pain to adjust with the carb in place... even with a 90 degree screwdriver.
 
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