[Four-Fifty-X]

I'm running a 48 but need to go 2.75 turns out on the fuel screw or I get decal pop and hanging idle. 50 seems pretty fat though. Anyone running a 50?

'03 R cam
MRD R header, yosh can
Opened air box
JD red
170 main[/u]

[JimDirt]

Have you ever replaced your Needle Jet ?? , a worn Needle Jet will cause erratic idle and will cause the bike to be lean then rich , making adjustments about impossible , the hole will be ovaled out and its not something you can see or tell with the naked eye , if there was any wear noticeable on the old needle or on the new JD needle(discoloration/wear), then chanced are the Needle Jet is worn

Also look at the slide plate seal

Also a #45 should be good for just about any elevation , going richer with rising ambient temps will cause you more issues than running lean , you might try going back to a #45 , the hotter the temps get the leaner you should be , you might have thought the bike was lean when it was in fact too rich and went the wrong way with jetting , and i still think with the erratic idle that your Needle Jet is the main issue and your trying to compensate for it by jetting changes

The erratic idle is a clue not a symptom

[Four-Fifty-X]

Have you ever replaced your Needle Jet ?? , a worn Needle Jet will cause erratic idle and will cause the bike to be lean then rich , making adjustments about impossible , the hole will be ovaled out and its not something you can see or tell with the naked eye , if there was any wear noticeable on the old needle or on the new JD needle(discoloration/wear), then chanced are the Needle Jet is worn

Also look at the slide plate seal

Also a #45 should be good for just about any elevation , going richer with rising ambient temps will cause you more issues than running lean , you might try going back to a #45 , the hotter the temps get the leaner you should be , you might have thought the bike was lean when it was in fact too rich and went the wrong way with jetting , and i still think with the erratic idle that your Needle Jet is the main issue and your trying to compensate for it by jetting changes

The erratic idle is a clue not a symptom

Thanks Jim. Needle looks fine. I replaced the slide seal and fuel screw bits and checked for leaks. I think there is a partial clog somewhere in the slow circuit, probably about the pilot or fuel screw. I'll take it apart next week. In the mean time it runs great, the fuel screw is just out more than I'd like.

[JimDirt]

Usually when the idle hangs its because the Needle Jet is worn , it will be high one time then be low or stall the next time (if you keep fiddling with the Fuel Screw or Idle setting) , is this the case ??

It will also hang for a bit if the mixture is either too rich or too lean (be idling high then slowly drop to normal each time you rev the motor) Is this the case ??

I have ran a #48 when at 500 ft elevation , while i was in Washington state , i also had to run a #180 main jet to go along with the #48 pilot and 2 1/4 turns on the Fuel Screw , so it can happen , but its not the norm , you should be able to run fine with a #45 and the Fuel Screw 2-2 1/4 turns with no issues but you dont want it near 3 turns because the screw can vibrate out and then your screwed if you loose the O-Ring and washer , have you eliminated a header leak either at the head or at the muffler joint ?? , this will also cause popping and make you believe the carb is the issue , you can test it with some Incense (the long stick kind) and hold it near the head and at any pipe connection , if it flutters, then there is a leak

You mentioned the Needle looks fine (i am guessing the NEW JD Needle) , what about the old one ?? , is there any wear spots on it ?? , if so , again , i would look at the needle jet as a issue (Needle Jet is the long brass tube that the needle goes into and your main jet screws into), it makes a big difference on the low RPM running , where air and fuel mixture is more critical than at higher RPM's

Oh , and nice X , it reminds me of mine

[Kyle450x]

I actually based my jetting after my engine mods to yours, four-fifty-x. I have the 2003R cam, 12.5:1 piston, TRX intake valves, Pro circuit RC-4 header with T-4 muffler, twin air backfire resistant air filter with OEM airbox cage metal mesh removed, cut airbox, no smog, etc.

I settled on 170 main, 48 pilot, 50 leak jet, and R&D fuel screw 2.0 turns out and I experience no decel pop, hanging idle, or anything that would make me tweak with my carb any more. I'm stoked on how great it runs now! I should've just bought that R&D fuel screw a long time ago to make adjusting that much easier.

Has your bike always been running like this, or just recently?

[Leardriver]

Bikes that are perfectly tuned will still have decal pop due to free flowing exhausts, exhaust gasket leaks, etc.
No need to drown them in fuel to mask the problem.
A 45 pilot and 165 main will work great in about any bike, like Jim stated. If that jetting isn't working, there is another problem.

[Four-Fifty-X]

I actually based my jetting after my engine mods to yours, four-fifty-x. I have the 2003R cam, 12.5:1 piston, TRX intake valves, Pro circuit RC-4 header with T-4 muffler, twin air backfire resistant air filter with OEM airbox cage metal mesh removed, cut airbox, no smog, etc.

I settled on 170 main, 48 pilot, 50 leak jet, and R&D fuel screw 2.0 turns out and I experience no decel pop, hanging idle, or anything that would make me tweak with my carb any more. I'm stoked on how great it runs now! I should've just bought that R&D fuel screw a long time ago to make adjusting that much easier.

Has your bike always been running like this, or just recently?

Kyle,

Just seeing your post. My bike always ran spot on--instant start hot or cold, no pop, clean low-, mid- and high-end.

I just pulled my carb apart yesterday and blew everything out. One passage was clogged, so I'm hoping that was it. I'll know in a few days when I get it all back together.

[Kyle450x]

Sounds like that was the problem!

[Four-Fifty-X]

Bike is back to running awesome with fuel screw 2-1/2 hour and 48 pilot. There was one orifice (above slow jet) that was plugged with black smeege.

Also, the o-ring for the o-ring mod had broken and fallen off. I safety wired the bits together--AP squirt is strong and instant again.

Oh, and that was a pain in rear job...