There is a speed limit sensor which generates pulses that are a funciton of the output shaft rotational velocity. The CDI monitors the output of this sensor and (with stock tires and gearing) retards ignition timing when speed nears 75mph to prevent riding much above this speed. Due to gearing, this should only occur in 5th gear.

The speed sensor can be modified or eliminated to increase top speed (if engine mods are enough to provide power to exceed air drag above 75mph). Search 'speed limiter' in the 660 areas for more info.

What is your RPM limit in lower gears?

7000 rpm every gear, will not go above this limit even in neutral, perhaps I was just expecting more having been used to riding superbikes, I just expected a little more top end. Bottom end is great since I got it back a few hours ago its done nothing but slide as I've hit the throttle, its a lot of fun but just feels like it wants to go more and is stopped dead at 7000. If anyone else with a 660 could let me know if there's goes passed this point that would be great.

I, honestly, forget what the stock RPM limit is, but 7k seems possible. Remember, it's a LARGE single piston moving, not four small ones... the RPM's simply can't reach anything near what you are used to on a superbike without grenading. They are very different animals.

You, on the Raptor, have a hell of a lot more frontal area to cause drag than you on a superbike. Drag is what will ultimately limit top speed. Power required to overcome drag is a function of velocity CUBED so even small increases in velocity require significantly more power .

Since we're 9 pages in, here, I'm not going to go back and try to find your mods. If your bike is stock, you will need everything going for you to make 75 - a tail wind, bit of downhill etc.

If you have the big 3, then the speed limiter is keeping you at 75 and 80-85 is within your reach with decent big 3 mods.

The 660 should rev higher than 7000 RPM, BUT with a single plug it will not make much power past 7000 RPM's. Even with all the mod's in the world, unless you add a 3 plug head, then you WILL make power till the motor hits the limiter & then some.... My limiter is set around 10,000 or so...

Thanks for reply guys, I think I'll stick with it as it is for awhile as not had it for a month and itching to ride it, thanks for the input especially QM and WillyKiller who have helped direct me in getting this thing to run correctly, cheers.

On closer inspection the quad seems to get to around 6000 revs before I have power issues probably around 5000 rpm in first gear and seems to be not as bad when getting to the higher gears, should I drop down one more size to 150/155? as I'm now running 155/160 and it has improved dramatically since moving down from 170/175, cheers for your patience guys. I've been having problems with the indicators so might aswell change em again whilst the plastics are off.

Willy? QM? looking for your input here, change jets or make adjustments elsewhere? Needle position? fuel mixture screw (they are extended now and easy to alter), thanks guys.

You took such a large jump (from 170/175 to 155/160) that you may have gone through the sweet spot... from rich to lean.

The only way to tell is to change jets again OR change operating conditions and see what happens. If you have holes in your lid, cover half of them with duct tape. If you have no lid, cover half to 3/4 of the opening with cardboard and duct tape, if you have a lid, unclip it and hold it open a 1/4 inch with some cardboard...

Then ride again and see if the 'issue' gets better or worse. This will tell you whether it was due to being too rich or too lean, and then adjust mains/needles accordingly.

When you get this close to being right on, it can sometimes be a bit of a dance to get the rest of the way (unless you methodically change jets by one size at a time until you go through and beyond the sweet spot, then move back one size).

The high rpm power falls off very quickly on these 660s, like it hits a wall...........

Just another thing I would like to add, when i ran the quad the other day I was a little naughty and blasted straight throught the gears when the engine was cold. It ran perfectly and shot straight upto 85 mph! No lag, no backing off it opened up properly all the way through, what does this mean to me, wot do I need to adjust? I'm going to try the jets 1 up and 1 down to see the difference.