bottom end sputter

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bottom end sputter

Postby kinganu » 03:31 pm Jun 16 2017

Hi there folks at KDX rider. I have been all over this site and learned much useful info about my top favorite ride....my kdx 200.
I have a bottom end sputter that I just can't seem to get rid of. Have tried every low end jet from a 40 to a 50 with no result. Turning the airscrew has no effect at all when it is idling. from 1/4 to WOT it rips yer arms off and runs great but it has this sputter from idle to 1/8 throttle. Also have tried all the needle settings and the clip is now at the highest point on the needle (dropping the needle to its lowest position) the needle is the one ending in 73. It is stock with an FMF gold series pipe on it. Right now it is running a 45 low speed jet and a 150 high speed jet.
The air box is clean and the crank seals seem to be ok as when it is running at high rpm there is almost no visible smoke and I am running it at a 32 to 1 fuel mix. Nothing I have done seems to have any effect on it.
If you have any advice or suggestions I would be much grateful.

And....I love this site....you guys have done GREAT JOB.
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bottom end sputter

Postby SS109 » 05:58 pm Jun 16 2017

Make sure your idle speed (not idle mix) screw isn't adjusted too high. If too high you are always running on the main jet and the idle mix screw would have no affect.
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Re: bottom end sputter

Postby bufftester » 11:35 pm Jun 16 2017

Agreed, your airscrew should be affecting changes when adjusted. Needle is not really in play below about 1/4 throttle. Ensure your intake and exhaust tracts are mechanically sound then follow the jetting guide.
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Re: bottom end sputter

Postby Jason » 01:33 am Jun 17 2017

Welcome to the forums.

Which year model??

Which country is the bike from??

reeds ok? dirty carb?

ethanol / gasahol??

let the fuel set long in the bowl??

float height is ... ??

TMI is not enough. :grin:
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Re: bottom end sputter

Postby jjavaman » 10:10 am Jun 17 2017

I would check your float height. I had the same problem with my 220 blubbering at low throttle.
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Re: bottom end sputter

Postby kinganu » 01:47 pm Jun 17 2017

Thanks for the replies guys.....
The carb is clean and spotless, The reeds are perfect and the float level looks fine. I went over your jetting guide till I have it memorized (very useful guide indeed). I have ordered a jet block gasket just in case. It is a 1992 American model. I am running standard grade regular gasoline as I havent had any problems with it in the past in my other 2 strokes.......hmmm....first time for everything maybe?.......I am also at about 4500 feet elevation. The engine case is clean and dry with no leaks anywhere.

The silencer does not have any packing in it but it looks it never was supposed to have any......just a turbo looking insert in an aluminum housing.
Lots of black spooge dripping on my swing arm and brake caliper....very annoying...
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bottom end sputter

Postby kinganu » 01:54 pm Jun 17 2017

SS109 wrote:Make sure your idle speed (not idle mix) screw isn't adjusted too high. If too high you are always running on the main jet and the idle mix screw would have no affect.


I will go play with the idle screw and see if that gets any results........
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bottom end sputter

Postby Jason » 06:39 pm Jun 17 2017

Which silencer or spark arrestor is on there? In stock form, it did have a bit of packing in it. Check out the parts diagrams online if you have the stock one.
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Re: bottom end sputter

Postby kinganu » 03:15 pm Jun 23 2017

Well....I played with the idle screw and still no results from it or the airscrew. I have to push start it when it is cold. the other night it got a bit cool around here and it would not start with the kick starter so I had to push start it. It started right up but it should have started easily with the kickstart. I wanted to test out the new LED headlight replacement I got off of Amazon which kicked butt it works so well.
Anyways.....I am still waiting on the jetblock gasket and that is about my last idea before just going ahead and tearing down the engine for complete rebuild. I'm going to pressure test it as soon as I get the time before I tear it down. It smokes way to much when it is at an idle and when twisting the throttle (when in neutral) it bogs like it is fouling out but then cleans itself out after about a second or two and makes a pretty good cloud.
Sorry I could not get back sooner but I'm working 6 days a week so not much time........

Thanks guys at KDXrider.........
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Re: bottom end sputter

Postby kinganu » 03:18 pm Jun 23 2017

I still don't know what kind of silencer is on it but I think the problem is way to bad to be just a silencer packing problem.
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