Klx250s melted piston help?
#34
12-23-2011, 05:15 AM
Update on my situation, my 351 kit is on a plane to Australia as we speak!
What jets can you suggest I use and should I leave the carby as it is and put it all back together or should I rejet it while it's all apart now?
I've also got all new valves springs collets stem seals and everything for the head I just need to get the valve seats reset and new valves and stuff.
Oh and a suggestion on how many teeth sproket I should be using, I do 50/50 on and offroad. Onroad it's usually on the freeway so I need to be able to sit on 100 110Kmh without revving the *** out of it.
Cheers to everyone for helping me get to where I am now
What jets can you suggest I use and should I leave the carby as it is and put it all back together or should I rejet it while it's all apart now?
I've also got all new valves springs collets stem seals and everything for the head I just need to get the valve seats reset and new valves and stuff.
Oh and a suggestion on how many teeth sproket I should be using, I do 50/50 on and offroad. Onroad it's usually on the freeway so I need to be able to sit on 100 110Kmh without revving the *** out of it.
Cheers to everyone for helping me get to where I am now
#35
12-23-2011, 01:25 PM
On jets, Mr. Blue recommended +1 on pilot and +2 on main. I'm using the stock carb and bumped the pilot from #35 to #35 Kaw jet, and main from #124 to #132 dynojet. I also moved the clip down one on the needle (from 2nd to 3rd notch from the top).
#36
12-23-2011, 02:56 PM
Join Date: Oct 2009
Location: Sonoran Desert, Arizona
Posts: 262
For some reason, your down-under main jetting is quite a bit different than the jetting up here, so specific jet size recommendations from the north may not apply.
Usually with a big bore, you don't have to make much of a change with the main jet. The reason for this is that with a larger displacement more air is being drawn into the engine for the same piston speed. This increases the intake velocity. The increased intake velocity adds more fuel automatically.
If I remember correctly, the oem main jet for my 2006 was a 118. With the 351 a 120 main works best for me.
Ron
Usually with a big bore, you don't have to make much of a change with the main jet. The reason for this is that with a larger displacement more air is being drawn into the engine for the same piston speed. This increases the intake velocity. The increased intake velocity adds more fuel automatically.
If I remember correctly, the oem main jet for my 2006 was a 118. With the 351 a 120 main works best for me.
Ron
#37
12-23-2011, 05:17 PM
Ron:
My oem main Kaw jet was a 118 also. Bill recommends +1 on the pilot and +2 on the main. This recommendation should translate to the down-under folks too, I suppose. Who knows, Bill may be recommending a little on the conservative side to decrease the chances of lean running.
I can agree with your point on more air flow equals higher velocity in the venturi (carb) which decreases pressure in the venture which in turn causes more fuel flow through a jet. A jet operates on the orifice equation, which is a power equation so a given increase in pressure on the jet will result in increased fuel flow, but the relationship is not linear (e.g. 50% pressure increase on the orifice pressure can yield about 24% more flow on one example I just tried). Since the venture is also a power equation, maybe this all works out in a balance where a 25% air flow increase yields about 25% increased fuel flow. I dunno...just rambling thoughts.
My oem main Kaw jet was a 118 also. Bill recommends +1 on the pilot and +2 on the main. This recommendation should translate to the down-under folks too, I suppose. Who knows, Bill may be recommending a little on the conservative side to decrease the chances of lean running.
I can agree with your point on more air flow equals higher velocity in the venturi (carb) which decreases pressure in the venture which in turn causes more fuel flow through a jet. A jet operates on the orifice equation, which is a power equation so a given increase in pressure on the jet will result in increased fuel flow, but the relationship is not linear (e.g. 50% pressure increase on the orifice pressure can yield about 24% more flow on one example I just tried). Since the venture is also a power equation, maybe this all works out in a balance where a 25% air flow increase yields about 25% increased fuel flow. I dunno...just rambling thoughts.
Last edited by IDRIDR; 12-23-2011 at 05:25 PM.
#38
12-27-2011, 07:24 PM
Join Date: Oct 2009
Location: Sonoran Desert, Arizona
Posts: 262
Ron:
My oem main Kaw jet was a 118 also. Bill recommends +1 on the pilot and +2 on the main. This recommendation should translate to the down-under folks too, I suppose. Who knows, Bill may be recommending a little on the conservative side to decrease the chances of lean running.
I can agree with your point on more air flow equals higher velocity in the venturi (carb) which decreases pressure in the venture which in turn causes more fuel flow through a jet. A jet operates on the orifice equation, which is a power equation so a given increase in pressure on the jet will result in increased fuel flow, but the relationship is not linear (e.g. 50% pressure increase on the orifice pressure can yield about 24% more flow on one example I just tried). Since the venture is also a power equation, maybe this all works out in a balance where a 25% air flow increase yields about 25% increased fuel flow. I dunno...just rambling thoughts.
My oem main Kaw jet was a 118 also. Bill recommends +1 on the pilot and +2 on the main. This recommendation should translate to the down-under folks too, I suppose. Who knows, Bill may be recommending a little on the conservative side to decrease the chances of lean running.
I can agree with your point on more air flow equals higher velocity in the venturi (carb) which decreases pressure in the venture which in turn causes more fuel flow through a jet. A jet operates on the orifice equation, which is a power equation so a given increase in pressure on the jet will result in increased fuel flow, but the relationship is not linear (e.g. 50% pressure increase on the orifice pressure can yield about 24% more flow on one example I just tried). Since the venture is also a power equation, maybe this all works out in a balance where a 25% air flow increase yields about 25% increased fuel flow. I dunno...just rambling thoughts.
Ron
