Running lean on mains need some advice

[zillakilla02]

Hey bhq so the banshee was running tittays in august I mean spot on perfect I had the mains dialed in and she ripped but the last few weeks it all of a sudden got really lean on wide open throttle to the point where it has me worried. since I had 160 mains in during the summer and that is what it liked best I thought maybe just because it cooled off slightly that I just needed to go up a few sizes. Well I'm up to 185 mains and it's still lean when I plug chop. I just did a leakdown test because I figured there must be a leak and it's holding 6 psi like a champ all day long. Is it possible that a leak only occurs when it's hot or when it's under full throttle? Or should the leakdown test have failed if there was any leak? It really hasn't cooled off temperature wise all that much it was probably 85°F in august and now it's maybe 60s here in wisconsin. Does the drop in temp require that much of a jetting change? I didn't think 20 degrees would cause it to lean out that much even with 185 mains compared to 160s... I'm going to keep going up with the mains I just haven't had much experience with temperature changes and how much the mains will differ. Thanks guys for any advice

353cc dune port with boost ports

34mm keihin pj carbs

185 mains 45 pilots

Chariot reed cages, chariot intake manifold, boyesen power reeds, uni dual stage direct mount filters, rocket exhaust

 

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[CycleTech]

If both carbs are running lean then check for a fuel starvation problem. Fuel tank vent?

[zillakilla02]

If both carbs are running lean then check for a fuel starvation problem. Fuel tank vent?

Thanks I will check the vent. Can an inline fuel filter cause too much restriction? It's only a couple months old and never had that problem before and looks clean. Also another possibility is that my pickup coil is too big of gap can that cause a lean condition wide open throttle and a stutter?

 

 

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[Bennett131]

Thanks I will check the vent. Can an inline fuel filter cause too much restriction? It's only a couple months old and never had that problem before and looks clean. Also another possibility is that my pickup coil is too big of gap can that cause a lean condition wide open throttle and a stutter?

 

 

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It is possible for a fuel filter to do that, but it would have to be a pretty long pull.

[zillakilla02]

It is possible for a fuel filter to do that, but it would have to be a pretty long pull.

Yeah this is pretty much instant as soon as I crack it wide open.

 

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[CycleTech]

Check the carb vents also.

[trickedcarbine]

No way that motor will eat 180's main jets. You got other issues for sure.

[zillakilla02]

No way that motor will eat 180's main jets. You got other issues for sure.

That's what I thought so I got out the leakdown tester and it held like a champ for over 20 minutes until I let off the pressure. It's gotta be somethin with the bowls not being full. You know what the spec is for float height on keihin 34mm pj's?

 

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[zillakilla02]

And both cylinders are the same color for plugs

 

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[zillakilla02]

Unless it's a leak that only occurs under full load if that's possible

 

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[sleeper06]

Pj are 16mm float height make sure you measure them properly tilted on 45 just so float tab touches needle pin

[zillakilla02]

Pj are 16mm float height make sure you measure them properly tilted on 45 just so float tab touches needle pin

Ok thanks will do

 

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