Needle position

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Needle position

Postby Ed5786 » 05:08 pm May 29 2017

Is it unusual to have to run the needle in its richest position? I have had a persistent bog when I crack the throttle, and overlooked the needle until this weekend. I was previously in the middle clip, and it would bog if I cracked the throttle quickly. Rolling the throttle on it was fine. I also played around with pilots and main jets but the only thing that remedied the problem. The needle is a BEP, which was in the bike when I bought it and I believe it's just a tad richer than the 1173 needle. The bike has a fmf woods pipe, snorkel removed, 607 reeds 45 pilot, 154 main and 32:1 premix ratio. Elevation around 700" ASL. I tried a DEL needle as well knowing it's a rich needle, and it did the same thing. The BEP was more responsive though
1998 KDX200
Fmf gnarly woods
Boyesen reeds
13/49 gearing
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Re: Needle position

Postby John_S » 09:36 pm May 29 2017

Where is the air screw set to? First thing I would've tried if you haven't already is to have it 100% warmed up (3rd or 4th clip) and then turn the air screw all the way in to lightly seated. Keep the bike running with throttle input. Does it still lean bog when you whack it open?

A leakdown test or at least spraying carb cleaner around the air boot and gaskets while its running to check for air leaks would be good to eliminate other areas that could be causing a lean condition. Hows the idle?
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Re: Needle position

Postby Ed5786 » 04:48 am May 30 2017

John_S wrote:Where is the air screw set to? First thing I would've tried if you haven't already is to have it 100% warmed up (3rd or 4th clip) and then turn the air screw all the way in to lightly seated. Keep the bike running with throttle input. Does it still lean bog when you whack it open?

A leakdown test or at least spraying carb cleaner around the air boot and gaskets while its running to check for air leaks would be good to eliminate other areas that could be causing a lean condition. Hows the idle?

The air screw is at 1.25 turns out right now. I have not tried riding it with the stew turned all the way in. It idles fine, doesn't hang at all.
1998 KDX200
Fmf gnarly woods
Boyesen reeds
13/49 gearing
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Re: Needle position

Postby John_S » 07:31 am May 30 2017

When I was messing with pilot jets I experienced a lean bog whacking it open at 1.5, 1.25, 1, and 3/4. 1/2 turn out it started to go away and needed about 1/4 out to run good. A larger or two size pilot jet got me back to good at 1.5 turns out.
Also aftermarket pilot jets in my opinion are a no go. They were so much different one size to the next and drove me crazy for a little while on another bike.
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Re: Needle position

Postby Ed5786 » 08:15 am May 30 2017

That's good to know thanks. I will try going back to the 3rd clip and run the air screw in. The bike runs great, but uses a lot of fuel. One other thing I need to do this week is get a float level tool. I set my float level just using a measuring scale which isn't all that accurate. Not sure if that would play a part in a lean bog or not? I am no guru when it comes to carbs. What baffles me is it ran fine before I did the top end. I figured with a fresh top end I'd be a little leaner on the jetting
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Re: Needle position

Postby Ed5786 » 06:58 am May 31 2017

It turns out my carb just likes the mixture screw turned way in. Got home last night, adjusted float level more accurately (wasn't off much) then put the needle back in the middle clip. Warmed the bike up, and it still had a slight bog so I ran the screw in to 3/4 out, and the bog went away. Doesn't seem to load up as much either. Thanks again John for your input.
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Re: Needle position

Postby Jason » 07:05 am May 31 2017

If the "air screw" is only 3/4 turn out, time to go brass shopping for a new pilot jet.
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Needle position

Postby cornishwrecker220 » 07:49 am May 31 2017

Is the bike a 200 or 220??
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Needle position

Postby Ed5786 » 08:13 am May 31 2017

cornishwrecker220 wrote:Is the bike a 200 or 220??

It's a H series 200
1998 KDX200
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Re: Needle position

Postby Ed5786 » 09:39 am May 31 2017

Jason wrote:If the "air screw" is only 3/4 turn out, time to go brass shopping for a new pilot jet.

That's what's odd. When I do the "air screw" test, the idle picks up at 2.5 turns out. So I assumed I have the correct pilot.
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Needle position

Postby cornishwrecker220 » 09:39 am May 31 2017

You could try running 40:1 as appose to the 32:1 ...the extra fuel may help ... Keep your pilot /main/ clip setting as you have it & see how it runs.... You may have to adjust the air screw .
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Re: Needle position

Postby John_S » 11:11 am May 31 2017

Jason wrote:If the "air screw" is only 3/4 turn out, time to go brass shopping for a new pilot jet.


I'm with Jason. At 3/4 turns out to run good I would get the next size pilot (genuine Keihin 48) and you should be good to go. That should put your air screw about 1 1/2 out.

I experience the same thing with my pilot. Where it idles highest and where it has the best response don't really jive with each other. I don't worry about highest idle and go by the air screw setting when there's no longer a lean bog whacking it open in first just off idle. Less than one turn out, bigger pilot. More than 2 1/4 turns out, smaller pilot. I'm glad it worked out for you!
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Needle position

Postby Ed5786 » 05:23 pm Jun 03 2017

Went riding today, and the bog issue is cleared up but I get a bit of spooge from the exhaust. My buddies 220 has no spooge at all, and the jetting is stock. Do some bikes just get it while others don't?
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Re: Needle position

Postby Jason » 07:44 pm Jun 03 2017

Did you do anything to clear out past oil from inside the pipe and spark arrestor?
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Re: Needle position

Postby Ed5786 » 01:04 pm Jun 04 2017

Jason wrote:Did you do anything to clear out past oil from inside the pipe and spark arrestor?

I did not. However I did make a bad discovery today. The compression is only checking at 92psi. This really pisses me off because it's a fresh top end, including a new replate and piston. I'm assuming this explains why it's acting lean?
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Needle position

Postby cornishwrecker220 » 02:27 pm Jun 04 2017

Is it possible that the head gasket could be slightly leaking ?

Are you loosing coolant at all ?

Perhaps a piston ring may have broke ?

Check your plug for wet deposits ...
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Needle position

Postby Ed5786 » 02:45 pm Jun 04 2017

cornishwrecker220 wrote:Is it possible that the head gasket could be slightly leaking ?

Are you loosing coolant at all ?

Perhaps a piston ring may have broke ?

Check your plug for wet deposits ...

The plug is wet from the rich pilot/needle. Not losing any coolant either. But, I talked to my buddy today who assembled the top end for me (I had 2 broken fingers at the time)and he said he over filed one of the rings, but didn't think it would be an issue. So it looks like a tear down is in store. If I need new rings, do I have to buy pro x since it's a pro x piston or can I buy wiseco?
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Needle position

Postby cornishwrecker220 » 03:15 pm Jun 04 2017

I would buy the same as you currently have as they will match your piston ..

I would steer clear of filing down ring gaps too.... Just make sure they are the right way up & in the right order . :grin:
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Needle position

Postby Ed5786 » 03:22 pm Jun 04 2017

cornishwrecker220 wrote:I would buy the same as you currently have as they will match your piston ..

I would steer clear of filing down ring gaps too.... Just make sure they are the right way up & in the right order . :grin:

The way they came there pretty much was no gap w/ the pro x rings
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Needle position

Postby cornishwrecker220 » 03:32 pm Jun 04 2017

Pro x rings are made to OE spec so I'm surprised you had to file them.... Unless the new coating on the cylinder was slightly thicker .
Millennium or lancourt are probably the best & they can match the coating with the piston.

Some say not to use the expansion ring on the bottom ring .
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