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Ride and ridden open class MX for years - top speed on any of them has nothing to do with HP, only gearing.
If you can't see over 90 MPH indicated, and you are near sea level with stock sprockets, you are not "tuned in well" enough.
im running 14/45. This puts me in higher rpm’s up top. I’m sitting on a 15t to bring it close to stock if I have to.
in in Los Angeles and work near the beach so I’m pretty much like 300ft above sea level. And I’m running the “near sea level” jetting w my power core 4. Fuel mixture screw is 2 turns out. My float is measured at 17mm. Manual recommends 17mm-20mm. Would 3mm make at 20mph difference?
Also still popping on decel.
Im trying to narrow down my mods to figure of what I could have done wrong.....?
Last edited by Don Tripas; 08-03-2018 at 06:20 AM.
2 out on a #40 pilot jet should not decel pop, so this is indicating a problem.
Given you gearing, if you can't make 90 mph indicated with no wind and tucked, I would think there is something wrong with the way the engine is running in the top end. You will need to tell me of any issues when your engine is running from 9k - 10,500 rpm at wide open throttle.. Also, what is the max RPM you get @ WOT in 6th gear ?
Both of those issues could be caused by a vacuum leak..
Also:
The decel popping could be a leaky exhaust connection - at the head or the header/midpipe connection.
The fuel filter inside the fuel line could be partially clogged - only choking off proper fuel delivery during WOT 6th gear runs - when fuel demand is the highest the bike will ever see..
Use the "clear tube method" to quickly verify correct fuel level without any disassembly. Level should be .5mm above carb/bowl mating surface, plus or minus 1mm.
The below pic is a proper fuel level - it is just above the green line ( which is the bowl to carb body mating point ) NOTE: carb must be indexed correctly ( properly installed straight up and down) and bike must be standing straight up.. And yes, this owner is using a bench Vice as an air cleaner..
Lets hope you will find the issue, once again, without having to delve into possible carb faults..
Given you gearing, if you can't make 90 mph indicated with no wind and tucked, I would think there is something wrong with the way the engine is running in the top end. You will need to tell me of any issues when your engine is running from 9k - 10,500 rpm at wide open throttle.. Also, what is the max RPM you get @ WOT in 6th gear ?
Lets hope you will find the issue, once again, without having to delve into possible carb faults..
Ran my KLX sat night. Idle is at 1000-1200rpm. Bike would bog between 9000 - 10500rpm. Max RPM in 6th gear was 9,200rpm. As you said, I suspected an air leak.
Double checked my work Sunday morning and found a crimped vent hose that had touched the exhaust. Replaced that and made sure the manifold's were sitting flush on the carb and the airbox.
After, the bogging stopped between 9000 -10500 rpm and my max RPM in 6th is only 9600rpm, putting me at 86/87 mph. Bike still pops on decel but not as much before Sunday.
To reduce or eliminate decel popping, get better throttle response, and improve low RPM power ramping, you must richen the pilot system ( on the KLX).
1. Remove (and cap off) the air injection system.
2. Insure that all exhaust joints are fully sealed and not leaky.
3. Set the fuel screw to 3.5 turns out .
Depending on your altitude, you've just eliminated all popping or (at sea level) reduced it significantly. To fully rid any remaining pops, install the #40 pilot jet and put the fuel screw to 1.75 - 2 turns out..
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Just my testimonial (2010, DJ kit, full FMF, K&N): 1 and 2 were already done on my bike, but I still had very obnoxious and annoying pop waaay too often--like every time I would drop the throttle or engine brake, it would pop pop ping pop....pop.....pop pop...…….pop. It was kinda laughable really--like there was a mad Japanese dude in there making popcorn.
I did #3--went ahead and bought the Kouba--and all is well. I get an occasional pop or series but they are rare and not obnoxious at all. I tried tuning it, but 3.5 was the sweet spot. Thanks, klxster
By the way, I am not under the impression that pop is bad so no need to educate me. I just didn't like what I had going on in this case.
I did #3--went ahead and bought the Kouba--and all is well. I get an occasional pop or series but they are rare and not obnoxious at all. I tried tuning it, but 3.5 was the sweet spot. Thanks, klxster
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Word. Im @ 285ft elevation running a #38 pilot @ 2 turns out. The pop is something Ive settled with but definitely still annoys me.
My float is at 17mm. Thinking maybe ill go up to 19mm in between the manuals specification of 17mm-22mm. Also might go from the K152 main jet do DJ140. Looking to eliminate these possible issues Ive diagnosed in my head.
Don, assuming your exhaust connections are air tight and your air injection system is properly removed and capped, relief should be simply backing out your fuel screw to 3.5 out - on your #38 pilot jet..
You are obviously running a slipon, lidless airbox, and a K152 with the needle clip at 1N - otherwise, you've got problems with your CVK setup and your fueling..
Resetting your float level to a lower/leaner setting does not make sense to me..
The DJ 140 main jet thing - I also can't make any sense outta that.. If you have a K152, a DJ140 should not effect any change to the fueling curve..
08-03-2018, 03:55 AM
