Carb Question?????

mtnmaxman600

mtnmaxman600

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Jan 2, 2009
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Age
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Location
Wisconsin
I took my 98 SX 600 twin out for a trail ride tonight and the sled runs great at WOT and idles fine and start up on 2-3 pull when cold sitting outside. My only concern is that while trail riding and the engine running about 4800 to 5000 rpms there is what I call a hesitation ( not a BOG ) a part throttle and sometimes you can hear a little pop noise out the exhaust above 5000 rpms when you hit the throttle you better be hanging on cause its going. What could be causing this? I have 151.3 mains and 45 pilot jets in it the fuel screw is set at 1- 1/2 turns out Will changing the pilots up a size correct this issue? Not sure where my needles are set at going to look tommorow at that Would raising the needles one notch help? I did a plug check tonight half way thru my short ride and they look like there burning very good. Or do I have a cluthcing issue? My clutch engages at 4000 rpms and I have 8AB and a green spring in my secondary at 60 degrees with a 51/43 helixs my gearing is 22/39 Any thoughts

Thanks

Eric
 
Sounds like your hesitation is in the needle clip territory, idle is fine and wot (wide open throttle) pulls like it should; clip territory is part throttle (overlapping with both idle and main jets when closer to no throttle/full throttle respectively).

Have you or a prior owner been in the carbs before? If the sled is stock so should the needle clip positions. Sound like they need fatting up in the part throttle area ((lowering the clips), you think it would drown if too much fuel, pop if not enough), or a good dunk in a bucket of carb clean?
 
I have clean the carbs twice. I am not sure how to set the needles but I have a set of carbs that are for part that I can experiment with. Dont you want to raise the needle so it get to full fuel faster? It does pop a little out the exhaust in that 4800 rpm range more so when the sled is colder.
 
yes raiseing needle will richen the mid range it kind of depends on throttle position more then rpm i was guessing you where at around 1/4 throttle and richening fuel screw will still help there
 
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do one thing at a time. if your plugs look good at half throttle( that is very important here) i would start with 2 turn on the pilots and test ride it.If it gets better you are going the rite way then try 2-1/2 turn and test. if the burbble is gone your good to go but if it's still there but very slite go up one size pilot jet start that one at 1-1/2 turns. sounds to me like it's lean comming off the pilots to mid-rang. do you have pipes or air box mod?
 
I put a MBRP race can on it. And yes my problem is at 1/4 throttle. I did a plug check after I trail rode it about 20 mins trail was rough so I was up and down on the throttle and the plug looked good. I will try the fuel screws first and see what happens that will be easier than the needles.
 
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I took the pilots to 2 turns and that help a little bit so I think that I am going to put 47.5 pilots in it and see what happens. Also I am a little concern that maybe the mains need to be a little larger the plugs are looking a light brown/tan which I think is kind of on the edge of lean so I have a set of 152.5's that I will install and see how they look.

Thanks JTSX700 for the help.

Eric
 
Hay eric, coffee brown is very good (like coffee with creamer) but if your going to go up on the mains do that first as this will give a little more fuel at your overlap from pilots to mid.but the mains are checked at wot this should be done first to establish the rite size main (coffee color plug) then check 1/2 throttle and set midrange needles for the same color then work on your pilots. good luck
jim
 
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I want to go up on the main because I really haven't held it at WOT for a long run just short runs would rather be a little rich and come back to jetting down after I know what they look like on a long WOT run. But I will leave the 45 pilots in and the fuel screw at 2 turns and just change the main and see what I have. Thanks
 
Spark Plugs

Here is what I 've done I turned the fuel screws out to 2 turns but my hesitation so I took the carbs off and installed 47.5 pilots and 152.5 mains and turned the fuel screws back to 1-1/2 turns and here is how my plugs are looking after some short pulls and across the field I think I need to go one size up on mains because I haven't taken for a long WOT run yet. Looking for thoughts.
 

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Sled runs great rode today on poker run still going to play a little with jettting,clutching and gearing to try and get ready for some radar runs hoping to get 100mph out of it I had it up to 90-92mph across a open field today with a little throttle to go. Its and awesome sled.

Thanks

Eric
 
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