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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