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· Registered
4,025 Posts
That is the jet needle(not to be confused with the needle jet, lol, they Are 2 different parts).
The "hole" is the needle seat.
The needle hangs on the float tang, as the float bowls fill, the floats rise, and that needle rises into the seat and shuts off the incoming fuel(basically it's a valve).
Then as the fuel in bowls gets sucked out, the floats and needle lower letting more fuel in, and then it repeats.
The needle should not stick in the seat.
The needle and seats are one of the most common fail points in all motorcycle/atv carbs, they wear and can no longer seal properly. Then you get fuel running out of the overflow tubes, as the needle and seat can't shut of the fuel completely, and the bowls flood/overfill, so it runs out the overflow.
The only fix would be to buy a quality carb rebuild kit and use the needles and seats out of them(which are the Only parts other than o-rings and bowl gaskets that you should ever use out of a rebuild kit. Never use the jets or needle jets out of them, as they are rarely precision enough to work correctly, and they'll keep you running in circles trying to tune them).

· Registered
4,025 Posts
The pilot and main jet sizes will vary by any modifications.
If you want real power and throttle response from a 660, remove the airbox lid, you'll need an air filter adapter, as the filter attaches to the lid.
Then, two #25 pilot jets(stock is 22.5)
Get a DynoJet jet kit(no pilots are included)
It has 2 needle jets with a different taper than stock, and 6 grooves for adjustment, vs the stock 5. These are Only available in the kit.
If you have an aftermarket exhaust, you will use the 2 largest, or 2 second to largest main jets in the kit. The right carb main jet will Always be one size larger than the left, no matter what.
ALL other carb settings will be the Same, Always.
Start with both fuel screws at 2 turns counter clockwise, then adjust in 8th turns to dial in.
Vitos fuel screws make adjusting them so much easier.
Look in the Stickies for the 3mm clear tube method, this is the Only way to correctly set float height.
Set the floats between 13mm and 15mm, then put them on, and clear tubes off the float bowls.
The fuel levels should be even with the line where the float bowl meets the carb bodies.
This is a tedious adjustment, and can take several tries to get right, but is well worth doing.
You can also trim the float stops so they rise a little higher, and allow more fuel into the bowls.
This prevents fuel starvation at high rpms, it harms nothing to do this, but is usually only beneficial on highly modified engines.
I've done several 660's this way, and it makes a very noticeable difference in throttle response and performance.
There's alot of info on it all here, and there's a few of us still here that can help you with it.
Ask questions if you need to, and good luck with it.

Also, if you do remove the airbox lid, you will need a small autoparts store k&n style round filter to go on the end of the crankcase vent hose, as the hose normally connects to the lid.
A filter skin is a good idea too

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