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Installing a 686 kit from Chris at benchmark...wondering if I need to do any jetting or adjustments for this upgrade? Everything else is stock.

Thanks!
 

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You'll likely need to rejet. At least a 155 main, and while you're at it, replace the 40 pilot jet with a 45.

Also - might want to look into a set of allen head bolts for the carb bowl... the stock 'phillips' ones blow chunks and will strip the first time you open it... I had to slot two of them with my dremel tool to get them off after stripping them out with a #2 phillips.
 

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first thing I do is replace those dam screws....on all my bikes

ok with stock jetting I would def change it. what canuckle said should be a decent starting point.
 

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Mini jet kit 660

I agree with canucklehead and dbestduner...this mini jet kit is intended for those who mistakenly got a dyno-jet kit and/or have stock intake/exhaust...it will cover you for minor things on your intake that make a difference like a k&N drop in replacement filter or converting from 05-06 style and/or putting more holes in your air box/lid...comes with SS SH screws for cap, bowl...

Only I recommend a 50 pilot jet...can also split the difference and sell you a 47.5...or a 45 if you wish...

The biggest advantage of the 45 is that you don't have to unplug the idle a/f screw and adjust it...it is 2-1/8 turns out from the factory which is too lean for a 40 and about perfect for a 45...

IMO...you should leave the needle exactly how it is from factory...

You don't need a complete jet kit unless you have a hi flow intake and/or exhaust...in which case you really should get the complete kit...

I found that my before/after jetting going from 660 with high flow intake/exhaust was identical after going to 686 with ported head and +1 valves...

Dyno-tuned with a/f gauge both ways...
 

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Installing a 686 kit from Chris at benchmark...wondering if I need to do any jetting or adjustments for this upgrade? Everything else is stock.

Thanks!
Usually there is a minimal change in a/f ratios after just installing a +2mm piston. With no intake or exhaust mods I would say maybe just 1 up on the main to a 150 might be a good starting point.

Nate
Alba Racing
 

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Discussion Starter #8
You'll likely need to rejet. At least a 155 main, and while you're at it, replace the 40 pilot jet with a 45.

Also - might want to look into a set of allen head bolts for the carb bowl... the stock 'phillips' ones blow chunks and will strip the first time you open it... I had to slot two of them with my dremel tool to get them off after stripping them out with a #2 phillips.
Trust me...I have a strong hatred for those little screws as well. I actually use either an electric impact or an impact screw driver on those...works wonders with the right bit!

first thing I do is replace those dam screws....on all my bikes

ok with stock jetting I would def change it. what canuckle said should be a decent starting point.
I typically change them out as well. I used to part out jetskis so I have a ton of metric stainless bolts laying around...basically every size I could ever want!

Installing a 686 kit from Chris at benchmark...wondering if I need to do any jetting or adjustments for this upgrade? Everything else is stock.

Thanks!
Usually there is a minimal change in a/f ratios after just installing a +2mm piston. With no intake or exhaust mods I would say maybe just 1 up on the main to a 150 might be a good starting point.

Nate
Alba Racing
Thanks!

Mini jet kit 660

I agree with canucklehead and dbestduner...this mini jet kit is intended for those who mistakenly got a dyno-jet kit and/or have stock intake/exhaust...it will cover you for minor things on your intake that make a difference like a k&N drop in replacement filter or converting from 05-06 style and/or putting more holes in your air box/lid...comes with SS SH screws for cap, bowl...

Only I recommend a 50 pilot jet...can also split the difference and sell you a 47.5...or a 45 if you wish...

The biggest advantage of the 45 is that you don't have to unplug the idle a/f screw and adjust it...it is 2-1/8 turns out from the factory which is too lean for a 40 and about perfect for a 45...

IMO...you should leave the needle exactly how it is from factory...

You don't need a complete jet kit unless you have a hi flow intake and/or exhaust...in which case you really should get the complete kit...

I found that my before/after jetting going from 660 with high flow intake/exhaust was identical after going to 686 with ported head and +1 valves...

Dyno-tuned with a/f gauge both ways...
Great info! I really didn't see there being a need for too much of a change, but also know that these things often come jetted lean from factory. My old YFZ450 would turn the head pipe cherry red at stock jetting(with everything stock..no mods and clean air filter).

I typically pick up jets locally since shipping is usually more than the jets themselves...but if I have any issues I will contact you!
 
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