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Old 12-22-2013, 02:06 PM   #1
KxRuss OP
Joined: Oct 2013
Location: Isle of wight
Oddometer: 29
klx650 jetting

I have got a klx 650 c and i have done the usual things like remove the airbox lid and i have sorted out the exhaust. The bike now does not run well at full throttle and if you hold it at full throttle at about 70 it will die back and slow down. I have lifted the needle about 3mm with washers and this helped but today it was colder and i had the same problem.
I would do a plug chop but dont have the time in the day light at the moment.
How far can you lift the needle and what sort of main jet do people run with those mods at sea level?
I have a 148 main
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Old 12-22-2013, 04:33 PM   #2
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Joined: Jan 2007
Location: central komifornia
Oddometer: 1,145
If its that lean at 70 mph you might burn a hole in a piston at wot.I would try +2 or +3 on the main and +1 size on the pilot jet.If you can find a local bike shop with a dyno that has a wide band a/f ratio printout.There are modern inventions like wide band o2 sensor a/f gauges so you can actually read the af ratio-look up Innovate Motorsports.A modern 4 valve engine should be a very powerfull engine if tuned correctly.
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Old 12-22-2013, 04:52 PM   #3
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Joined: Jun 2004
Location: Nor Ca.
Oddometer: 4,976
I ran the open air lid, 148mj, 1 thin washer and a scorpion exhaust for a while. The bike ran like a rocket at higher rpm and lost a lot of low rpm power. It also surged at 65mph steady state. The muffler was loud, so I added a baffle and suddenly the surging went away and the low end came back.

I used a poor mans dyno to test what my mods were doing, by marking off 200 yds on an uphill road and did some top gear roll on's from 50mph. Stock the bike increased speed to 67 and would go any faster.
Modded similar to your bike it stumbled, then slowly accelerated, then took off like a rocket. 80mph and still accelerating. With the current scenario, both with either 142.5 or 145, the bike would accelerate with no stumble or delay and top speed is 77mph and still climbing. I can live with that.

The air box was a dust collector, it increased the exhaust noise, So I ended putting the lid back on without the snorkel, rejetted to first to 145 and later a 142 mj. Not much difference between those two, same for the washer.

The bike has great power high or low and I ain't going back.

There is a big difference in the jetting between C and R models. With a 148, I don't think you are running lean, assuming you are using Keihin Jets.

The R version carb has an adjustable needle. You can use one of those if you like.
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itsatdm screwed with this post 12-23-2013 at 02:08 PM
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Old 12-22-2013, 09:10 PM   #4
Beastly Adventurer
Joined: Oct 2004
Location: Anchorage, formerly Spenard (hub of the universe)
Oddometer: 5,874
kehin and dyno have different hole size with jets of the same number
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Old 12-27-2013, 04:35 PM   #5
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Joined: Jan 2008
Location: Myrtle Beach SC.
Oddometer: 350
Hi KX Russ,
where are you from. I am at the beach as well, but here on the east coast. Do most of my riding at higher elevations though.
Dont know if you have seen the KLX 650 Riders Unite thread, some good info there and you will get more replies as well - Itsatdm has tonnes of experience, I have learnt alot over there.

'07 R 1200 GS.
'96 KLX 650 R.
Keep It Real!
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