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Won’t idle off choke

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Picked up a used ‘08, fairly rough shape but it was cheap enough and would start. Anyway, can’t get it to idle off choke, will run off choke if rpms are kept up high enough.

 

PJ: 45

MJ: 165

Clip: 4/7 from top

LJ: 65

FS: 2T

Small jet that goes to the accelerator pump is a 50 I believe. It was quit clogged but I cleaned it well. I have a new one that’s a 70. But I figure my problem lies else where, maybe not though?

 

Only mod is a FMF Q4 slip on, stock header.

 

New jets, cleaned carb multiple times, checked and used dielectric grease on all electrical connections.

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Blocked fuel passage (pilot / fuel screw)

ream all passages with a single strand of copper wire

if in doubt, replace rather than clean the pilot jet.

 

If applicable, perhaps the fuel screw assembled in wrong order (o-ring/washer etc.)

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Around 500ft above sea level, up to 2,500ft at most

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Blocked fuel passage (pilot / fuel screw)
ream all passages with a single strand of copper wire
if in doubt, replace rather than clean the pilot jet.
 
If applicable, perhaps the fuel screw assembled in wrong order (o-ring/washer etc.)


I have not tried to run an wire through the passages. Just going to have to tear it down again. But yeah, it’s got new jets other than the accelerator pump jet, don’t know if going from a 50 to a 70 will work out too well. It came in the Pro-X kit I bought (KX450F kit). Fuel screw should be correct, but I’ll double check when it’s apart again.

Also, I shimmed the valves, all good there.

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by looking at the plug all you are doing is getting a snapshot of the tune when the engine was shut off,if you shut the engine off at idle that is what you are looking at,if you shut the engine off at full throttle then look at the plug you are getting a read on the main jet.I wouldn't use the plug as a fool proof way of trying to diagnose the problem,instead use it as an indication of where to start looking

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by looking at the plug all you are doing is getting a snapshot of the tune when the engine was shut off,if you shut the engine off at idle that is what you are looking at,if you shut the engine off at full throttle then look at the plug you are getting a read on the main jet.I wouldn't use the plug as a fool proof way of trying to diagnose the problem,instead use it as an indication of where to start looking


Thanks for the advice, never thought of it that way as far as idle vs opened throttle. This pic would have been from an idle condition.

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Any chance the hot start plunger is not snapping back in all the way?  That stuck on me once and it was a big air leak to the intake and would only run when fully choked.

I had to pull the carb, drill out the stuck plunger, polish the bore, grease and put the new plunger in.

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Any chance the hot start plunger is not snapping back in all the way?  That stuck on me once and it was a big air leak to the intake and would only run when fully choked.
I had to pull the carb, drill out the stuck plunger, polish the bore, grease and put the new plunger in.

It doesn’t seem to be sticking or anything. I have taken it out and cleaned all through it and it appears to be functioning just fine. Is there anyway to to test it other than if the lever with pull it and it pulls back? Maybe it’s pulling most of the way back? Anyway, I cleaned the the carb again, ran some small gauge wire through the pilot and starter circuits and it seemed to help some. Will idle rough with the choke off but still dies less than a minute later unless I hold the throttle cracked a tad. I could screw the idle adjust in more but I just feel like it should idle at a lower rpm than it would take. So maybe running it some will clear some junk out and another good cleaning. Tells me it’s the carb though I feel like. Only other things I think it could be is excessively worn valves/head and/or worn piston/cylinder. Really hope not either of those!

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The go to checks should always be checking the grey stator plug,do a valve check,and check the fuel screw hasn't wound out on you,some aftermarket ones easily wind out by themselves or incorrect order of spring/washer on the fuel screw can cause issues

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The go to checks should always be checking the grey stator plug,do a valve check,and check the fuel screw hasn't wound out on you,some aftermarket ones easily wind out by themselves or incorrect order of spring/washer on the fuel screw can cause issues

Stator plug is good, fresh dielectric grease in it. Valves are in spec, and fuel screw installed correctly and turned 2 full turns out from fully seated.

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If it were me now at this stage I would increase the idle speed screw until it stays running and then run the fuel screw in and out till it is at its highest RPM, then lower the idle speed screw and repeat. I like my idle a little high anyway because it help fight the hanging idle syndrome, not sure what RMP it is but it is about double what my XR650 is. 

Caution: this adjustment process must be done after the engine is fully warmed up and hot (10 minutes of wheelies and roosts should do).  Adjusting when hot is why an RnD flex screw is so nice, you don't burn your finger tips trying to reach between the bottom of the carb and the top of the starter to get to a straight fuel adj screw.

How I tell if my hot start is working properly is three things.. 1) the idle changes when you pull it  2) snaps back when you remove your finger quickly  3) there is the correct free play in the cable after snapping back.

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How is the crankcase breather hosing routed? There’s two nipples at the bottom of my airbox, the crankcase breather connects to one, what goes to the other?

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Mine came with a short piece of clear tubing on the nipple, crimped closed on the end (about 2"). I have to pull it  and clean it out every now and then. It getting plugged with air filter oil and dirt.

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So I'm assuming the bottom nipple is the drain then. Is it possible if this doesn't have some sort of hose/filter attached to it, I'm ingesting too much air and causing some of my jetting issues? Doesn't seem that should be the case but who knows.

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Missing the bottom drain hose won't cause any jetting or driveability issues but I would still replace it,

the end of it acts as a 'one way valve' to allow water to drain but not enter the airbox.

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Got it, thanks! Went back to a 48 pilot. Idles with the choke off now, but getting a bad hanging idle now. Suggestions?

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