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Fighting Jeting problem

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Hey guys, I am really fighting this jetting issue on my bike. Its a 2005 and when I got the bike late last year it had been jetting with a JD kit, the air box had only the snorqual removed and the exhaust was stock. It has a quickshot pump cover also. It seemed to run good like this but I cant leave anything along and decided to do the honda track use cut on the air box and removed the entire spark arrestor and baffle out of the exhaust. I then fabbed a new spark screen for the exhaust and a loud mouth intake system and a RD flex fuel screw. The carb has the red needle with the clip in the center, 170 main jet, stock leak and stock pilot. The bike takes about 3 full cycles of the throttle to start cold and runs fine on the stand. When I notice a problem is when riding to work in the morning when the temp is about 35-40*F, when I hold the throttle steady it feels like its running out of fuel. On the way home when the temp is warmer around 55-65*F it runs fine. My fuel screw is about 2-2.5 turns out and I am at sea level.

I have not pulled my plug since cleaning it a week ago but will do that tonight and see what it looks like. I am thinking its running lean but I am not sure what jet to change.

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Your not going to get it to run good with that wide of a temp difference. JD I believe recommends the blue needle from 50 degrees on down (Blue needle is supposed to richen the bottom end) and if I remember right, they tell you to move the clip position down by two.

<<when I hold the throttle steady it feels like its running out of fuel.>>

At what throttle position? It's the position of the throttle that will tell you what needs to be changed.

<<My fuel screw is about 2-2.5 turns out and I am at sea level.>>

You slow jet is too big or you haven't adjusted right. You should be down in the 1 - 1.5 turns out range.

When you get that adjusted right, you will most likely need to change the leak jet to a 50 or 55 (stock is 60 I believe).

Jim.

Edited by JimDettman

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I dont really want to have to buy a new JD jet kit if I can help it by buying individual parts that I need. That said, I want it to run good also.

Holding the throttle steady when I am just staying at a static speed going down the road, it seems to be around the 3000-5000rmp range anything over that and it seems to really shit and get and anything below that I am rolling on the throttle to get up to speed. Its just when I am cruising at a steady speed and I am not twisting the throttle it chugs like its getting low on fuel.

Sequence of jets is SLOW - LEAK - MAIN correct? There is not way I would get away with 1-1.5 turns out on my fuel screw. It seems to run better in the cold with about 2.5-3 turns out but I know this is not the way it should be. I have also played with the clip on the needle by moving it down one notch to the 5th from the top and it seemed to run smoother also. I dont want to cause a ritch condition either.

Per rockymountainatvmc OEM parts schematic factory jets are Main=142, Slow=45, Leak=70. I know for sure it has a 45 slow jet but I have not pulled the leak to confirm that it is a 70.

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<<

sequence of jets is SLOW - LEAK - MAIN correct?

>>

No. Slow, Needle, and then Main is the progression from zero to WOT. The leak jet is just for the AP circuit, which is what squirts a bunch of gas in when you whack the throttle open. And sizing is opposite of the norm; going to a smaller Jet gives you more gas for the squirt, not less.

There are also two other jets in the carb; starter jet and possibly a slow air jet (depends on year).

Here's a picture what controls what for a given throttle opening.

KeihinFCRCarbTuningComponents.jpg

<< There is not way I would get away with 1-1.5 turns out on my fuel screw. It seems to run better in the cold with about 2.5-3 turns out but I know this is not the way it should be.>>

Then your slow jet is two big, making your fuel screw adjustment less effective.

<< I have also played with the clip on the needle by moving it down one notch to the 5th from the top and it seemed to run smoother also. I dont want to cause a ritch condition either.>>

Rich is better then too lean. You have to run a motor really rich before it becomes a problem. Going the other way (too lean), you'll have problems sooner.

Moving down a position or two is what I would have suggested.

Jim.

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Note, if you ride often at cold temps, you might also want to consider a larger starter jet, which is used when the choke is on to help with starting.

Jim.

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This may be unrelated but I had an issue with my 2005 seeming like it was running out of fuel. I know the jetting is good. Fuel filter is clean. If I run the petcock on reserve then it's fine. It's on my list to swap out.

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You definitely need a larger pilot jet. Don't know why JD doesn't address that. I went up one size on mine and it made a world of difference. Mine is a 2005 with the top of air box cut. Doesn't matter if I'm running the stock muffler or the "R" muffler with spark screen, both setups carburet very clean.

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Hey guys, I am really fighting this jetting issue on my bike. Its a 2005 and when I got the bike late last year it had been jetting with a JD kit, the air box had only the snorqual removed and the exhaust was stock. It has a quickshot pump cover also. It seemed to run good like this but I cant leave anything along and decided to do the honda track use cut on the air box and removed the entire spark arrestor and baffle out of the exhaust. I then fabbed a new spark screen for the exhaust and a loud mouth intake system and a RD flex fuel screw. The carb has the red needle with the clip in the center, 170 main jet, stock leak and stock pilot. The bike takes about 3 full cycles of the throttle to start cold and runs fine on the stand. When I notice a problem is when riding to work in the morning when the temp is about 35-40*F, when I hold the throttle steady it feels like its running out of fuel. On the way home when the temp is warmer around 55-65*F it runs fine. My fuel screw is about 2-2.5 turns out and I am at sea level.

I have not pulled my plug since cleaning it a week ago but will do that tonight and see what it looks like. I am thinking its running lean but I am not sure what jet to change.

48 PILOT

45 OR 50 LEAK

80 OR 85 POWER JET (COLD STARTS)

Merge racing apump spring upgrade <<< you need this

Three + twists is totally normal when cold.

Long warm up time is always pretty normal

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Krannie, I am assuming that the pilot jet is the same as the slow jet, #42 in the schematic? And also is the Power jet the "By-Starter" jet, #45 in the schematic?

where is a good place to one stop shop for all these parts?

Edited by Maverick26

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Also, I am assuming that I will need to at least verify the timing of the AP squirt with the slide once I am all dont cleaning and installing the new spring. How can I do this the easiest way? Can I do it on the bench or do I have to do it on the bike with gas hooked up? I dont really even know how to do this so maybe someone could help me with the steps to do this.

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Rotate the subframe so you can see the carb inlet. Then use a flashlight so you can see good and twist the throttle.

Ok easy enough. If it needs adjusting what do how do I do that? Is it the screw next to the AP spring?

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Ok easy enough. If it needs adjusting what do how do I do that? Is it the screw next to the AP spring?

Your goal is a squirt that is 6'+ in length, and 1 second in duration, that JUST BARELY misses the slide every time.

You will see residue on the bottom of the slide if it hits.

When you get it corrected, you will be AMAZED at the difference.

Distance is from the diaphram and the spring upgrade

duration is from the amount of fuel (leak jet size)

Timing is adjusted under the black throttle wheel cover. Clock wise delays.

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I just got all my jets and AP spring so I plan to pull the carb and do a full clean and install all the new jets either tonight or tomorrow. I just got back from a ride this weekend and put 62.1 miles on doing mostly fire roads with some rough sections. Mostly just exploring a new area. Anyway, I almost ran out of gas! I had to hit reserve at about 51 miles. I filled the bike back up at a gas station and it took 2.16 gal. This maens I am getting 28.75 mpg with 13/50 gears and riding really easy with my wife. This seems low to me. Is a 170 main too rich for the main but all my other sercuts be too lean? Would a 165 main help lean out enough to make a difference? Is this normal mpg?

On road mpg is up around 48mpg with 17s and 15/47 gears.

I am looking at getting the IMS 3.2 gal tank but I want to be sure that the mpg is normal before I just add more fuel.

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Ok good to know. I would like to be able to get more then 100 miles from a tank but I hate the look of the 4 gal + tanks and the idea of all the petcocks and extra hoses so I am going to stick with the 3.2 tank and one or two 32oz fuel bottles. Im planning a back country trip accross Wa state for this summer and my longest span between a fuel stop will be 117 miles. First things first and that is getting the carb dialed in.

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Fire in the hole! Good lord this thing freakin rips... I almost crashed in my front yard... this thing has really found its self now... wow. Best $30 I have ever spent. I completely removed the carb and gave it a really good cleaning too. It had lots of grit inside it so I am going to look into a inline filter today. Also, after reinstalling everying the throttle feels tighter and maybe slightly sticky... I tryed to keep the throttle cables the way they were but I may moved the adjustments a bit. Is there an adjustment that tightens and loosens the tention on the thottle or is this the new spring I installed?

Im sketchy anyway and dont need a sticky throttle with all this new found HP.

Thanks guys for all the help on this.

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Ok so I am trying to dial the fuel scew in and it seems now that my pilot jet is too rich.. I only went from a #45 to a #48, I kept the clip on the middle slot of the red needle and installed a #80 power jet. When I go to adjust the fuel screw looking for the fastest idle I find no setting that raises the rpm. I can bottom out the fuel scew all the way and the bike still idles fine but If I crack the throttle it backfires in the intake it sounds like, then dies. I have it set at 1 full turn out and it does not backfire right now and seems to start really easy cold. Just choke and start button, no throttle imput. I have not got a chance to ride it yet and see how it really performs cause its raining buckets here but I will soon and report back.

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