Spit and Sputter and High RPM

[shanekyle]

I just got an HMF pipe for my 2006 Outlaw 500 and have been playing with the jetting. Trying to find 2 good setups, one with the airbox lid and one without. I have read alot of posts already about what others are running and cant find the perfect setting yet. So far everytime I have test road it sputters at High RPM. I started witha 155 main jet and read that the sputtering may be caused by it being rich so went down a size and get the same result. Could I just be hitting the rev limiter? I dont recall this happening to me with the stock exhaust. Any thoughts?

[realbadlarry]

Probably want to go richer with an aftermarket pipe...should flow more which means more fuel is needed. My ktm cleared up some by turning the fuel/air screw a little. I think you need to just play with them till they are good.

[shanekyle]

Anybody have the High Rev CDI box on there 500? I think this would help and it would get rid of that annoying reverse limiter that I hit everytime I get stuck. I can get one on ebay for $92. Is it worth it?

[katch26]

its not worth it on the fugi motors as it tends to tear up the one way bearing which breaks the starter gear which well you get the idea...the rev limit isnt the problem if this all started after you added the pipe, you just need to rejet.
155 should work pretty good (sea level) with the lid on
anywhere from 162-175 (seal level) with the lid off
where do you live?

[willb]

I would start at a 162 if you are not at a high altitude. 2 turns out on the air screw. Make sre your idle is set right and that the choke cable is not hung up. Cable can get pinched if it isnt routed right and cause the same thing.

I would leave the airbox lid on with a K/N- the carbs on the fujis like to be pressured fed to open right.

Do that and drop one tooth on the front sproket for more power or up one if all you do is drag race.

[shanekyle]

I live in Spencer, IA elevation 1200ft. The sputter occurs with every mikuni jet from 145 to 160 in all clip postions. (I spent rougly 8 hours yesterday playing) The pipe came with a 152.5 mikuni main jet. I am running a dynojet needle and a quite core in my HMF pipe. It runs great except for when I reach a high rpm up to 3rd gear, then it does not sputter anymore. It also has been starting hard now, but I may have messed up the float taking the carb on and off so much.

[chris hallett]

If you are useing a Dyno jet needle with Mikuni jets that could be your problem the needles are diffrent, the taper and how far they taper is diffrent, and I belive the dyno jet needle is a hair bigger.

[katch26]

you can use the dj needle with the mikuni juts just not the other way around.

youre problem is youre stopping at 160 when you should be starting at 160. I'm at 167.5 (with the stock carb running a little rich in summer) so I would realistically be at a 165 at seal level. Its winter now so you need to go bigger on the main to compensate for the denser (more) air that winter brings and then generally reduce one main per 1000 in elevation. Roughly. I would start at 165 then work up.
put the needle back to stock and work one circuit at a time. Start with a larger main and do WOT runs until it starts to starts to get muddy feeling then go back down. Then mess with the needle positions. JMO

[katch26]

also what gear it happens in is not important but what position in the rpm range it happens. It should be the same point in all the gears right?

[sleddog66]

Katch, true statement on the RPM, but there may be some varience just because of different loads on engine at different gears. An example of this is you may not indicate a lean sputter in neutral(no load), but may be very noticable in 5th gear climbing a hill, with a 250 lb rider. These are two pretty extreme differences.

[shanekyle]

Originally posted by sleddog66
Katch, true statement on the RPM, but there may be some varience just because of different loads on engine at different gears. An example of this is you may not indicate a lean sputter in neutral(no load), but may be very noticable in 5th gear climbing a hill, with a 250 lb rider. These are two pretty extreme differences.

This is why I dont think it is lean, but rather just the rev limiter. It will not act up under load. Also I adjusted the vavles today and I think that helped out a little too. I think the 152.5 is about right since I am running an airbox lid and a quiet core in my pipe. Seem everyone running a 165 takes the lid off. Thanks for everyones help

[katch26]

Originally posted by shanekyle
This is why I dont think it is lean, but rather just the rev limiter. It will not act up under load. Also I adjusted the vavles today and I think that helped out a little too. I think the 152.5 is about right since I am running an airbox lid and a quiet core in my pipe. Seem everyone running a 165 takes the lid off. Thanks for everyones help

yep true that. 155 at sea level usually does the trick with the lid on but drop one cause of the altitude and youre right at where you ended up. The 160's recomendations was more because you were looking at setups for both and that would be a good starting point for lid off jetting.