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Hi guys, I bought an FMX 650 in January before doing my A2 licence in February, It's got 8500 miles on it. Ever since I started riding it (25th Feb 15') it surges at constant speed and idle i.e. it's running uneven. I've done all the basics such as replacing the spark plug, oil and I've inspected the air filter, it is a k & n air filter which looks fairly new. The bike also has a set of arrow cans fitted to the standard factory headers. I've cleaned the carb and saw that the jets are still the factory jets - 168 main and 50 pilot. Any ideas on what to do to make the bike run smoother on idle and stop it from surging at constant speed? I'm about to order a bigger pilot jet - 55 as I believe that the bike is running lean as it backfires a lot, rides a lot smoother on choke and rides smoother as the bike warms up. Any ideas to what I should do with regards to setting up the carb and jetting? Not really bothered about massive power gains, just want a smooth ride. Thanks.
 

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Hi guys, I bought an FMX 650 ....Any ideas to what I should do with regards to setting up the carb and jetting? Not really bothered about massive power gains, just want a smooth ride. Thanks.
Remove the anti-smog cannister and blank the resultant holes...then do your carb jetting.
Also ensure valve clearance are on the "loose" side of the spec.
 

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Yes that is the one - it smooths out the power a little.
I look after my own bikes.
With regard to rejetting it is something I am just about to do - I am upping the slow jet (to a 55) and the main jet (to 170 or 175) as I have some other derestrictions on my FX (same motor, carbs etc) as the later FMX.
 

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One more question, the pilot jet will affect the idle and up to 1/4+- throttle, but the surging also happens at mid throttle, how can I adjust the mid throttle surging? I've read something about the jet needle but when I took my carb apart to clean it I could only find the pilot and main jet, not really sure where the jet needle is and how can I adjust it? Any input would be greatly appreciated.
 

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And since the needle jet is not adjustable, you could try shimming it to raise it slightly
- very small quality washers can be used
 

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And since the needle jet is not adjustable, you could try shimming it to raise it slightly
- very small quality washers can be used
Thanks a lot for the hint, I'll be swapping the pilot jet to 55 and adjusting the jet needle on Tuesday probably, do you happen to know where I could get some washers in the Hull area? Also I'm a newb to carbs so hopefully I will be able to work out where to put the shims, but would be great if you could give me a hint? I've attached the image with 3 possible positions (might be totally wrong). Also, from reading other forums about the XR 650 I see that the shims have to be big enough to raise the needle by 0.5-1mm? Also I doubt that you'll know off the top of your head but what sort of diameter should the shim be? (inner and outer).
shims.jpg


ps sorry for all these questions, hope that I'm not bothering you too much.
 

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I have a 2007 FMX. I was not impressed when I got the bike but after a full exhaust and Daves mods it feels like a different bike. Thanks for the info guys:thumbup::thumbup::thumbup:

I want a little more snap though.

What is the biggest rear sprocket one can use with the stock chain?

Are 13T front sprockets available?
Answering my own question for the next guy, no, 13T sprockets are not available for the FMX650. In the past JP made 13T sprockets that did fit, but those were thin and likely to damage the counter shaft.

However the Honda XR650R has the same spline pattern. 13T sprockets for the XR650R are available from several manufactures but they ARE NOT a direct fit. I got a MOOSE 13T sprocket. The XR650R sprockets are wider so they have way more surface area and therefore are less likely to damage the counter shaft. Very nice.

To make the XR650R 13t sprocket fit one needs to file a bit of the sprocket (mainly the splines on the engine side). Also, if you have the stock chain, go for allen head bolts for a bit more clearance, the stock bolts will touch the chain.

The change is very nice IMHO, the bike is a lot more responsive and will still cruise nicely at 100 kmph.
 

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Hi after years on a zx10r ninja i have bought an fmx650. I have remus silencers and bought arrow headers but they arent compatable. Anyone reccommend the cheapest place for arrow end cans. Also what are the best cheap performance mods and i want a tail tidy and rear hugger. Any feedback would be much appreciated.
 

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I've had a FMX for 5 yrs now. Bought it when it was only 18months old. I had the arrow front pipes which I found to be rubbish. Go for the ABP headers they are of miles better quality


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I'm also running with a k&n and air box mod. Mikuni flat slide and ignitec cdi. RP exhaust which sound awesome without the db killers. I've also fitted a large oil cooler which helps.


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i have a 56 plate fmx which i bought at christmas , tbh i found it a bit slow and lumpy to start so i fitted arrow headers with mivv gp cans , a k&n filter , i found that it ran very lean so lean infact that the headers were glowing red!! fitted a stage 2 dynojet kit which seems to have sorted it out runs much better and sound awesome with baffles out lots of noise and popping when riding hard , i am planning to change sprockets to 15/45 as this was a very popular set up on other forums will let you know how it goes with new gearing
 

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Hi, I've raised the needle jet by approx 0.8mm, changed the main jet from a 168 to a 172 but also changed the pilot jet from the factory 50 to a 'long style' 55 and the bike is stuttering like hell at low throttle i.e. 0-1/4 can you guys tell me what jet setup you're running? I changed this pilot jet when I had very little knowledge about carbs (thinking it'd sort out my mid range) and I did two mods at once i.e. changing the pilot jet AND raising the jet needle at once, so I think that my mid/top range of the throttle opening is running fine but I'm now planning to go back to a 50 or maybe a 52 for the pilot jet?

My setup is arrow cans with no db killers, standard headers and a k&n air filter.
 
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