02 YMF660 Yamaha Raptor won't rev

It is not recommended to change the bolt pattern on a Raptor 660. The bolts are designed to fit the frame and any alterations could weaken the frame and cause damage. If you are looking to change the bolt pattern, you should consult a professional mechanic or experienced fabricator who is familiar with the Raptor 660.

check fuel flow and check spark at spark plugs

According to an "ATV Rider" 2009 article, "When the Grizzly was introduced in 1998 as a 600cc machine, the top was blown right off the displacement wars of the time."
It was replaced in 2002 with Yamaha Grizzly 660, an even bigger engine derived from the well-established all-terrain vehicle (ATV) Yamaha Raptor 660R.
Grizzly's 660 cubic centimeter (cc), four-stroke, liquid-cooled single overhead camshaft, five-valve engine performs well in open country, but sometimes it causes serious problems for owners.
Before you call a Grizzly dealer, however, trying a few tricks in your garage can save you a lot of time and money.

Check the fuel level.
Locate the fuel meter indicator on top of the multifunction display.
If it does not work properly, open the fuel tank, and push the Yamaha 660 Grizzly side to side.
Ensure the fuel is not contaminated by water or rust.
If you have not driven your Grizzly 660 for a long time, drain the tank completely, and fill it with a fuel tank cleaner.

Check fuel hoses for cracks or leakage.
The hoses should be soft and simple to bend.
Replace those that show any sign of wear.

Check the compression.
Screw a compression tester into the spark plug hole, and press the electric starter button.
If no compression exists, contact a Yamaha dealer.
Wipe wet or dirty electrodes with a dry cloth.
The spark plug gap should be checked regularly

Correct the spark plug gap.
Measure the gap with a wire thickness gauge.
If necessary, adjust it to 0.8mm using a screwdriver or replace the spark plug.
Use only a Yamaha-specified spark plug.

Check the Yamaha 660 Grizzly's battery.
Operate its electric starter.
If the Grizzly starts quickly, then its battery is in good condition.
If the engine turns slowly, check the battery lead connections, and you may need to change the battery.
If the engine still does not eventually start, your Grizzly is beyond home repair.

need your carb rebuilt or your carb readjusted. sounds like you might have some mud in it. do you take it in the mud? if so check the top where the throttle cable comes through.

hi there.see if this link helps you get it sorted.
2002 yamaha raptor and it wont start Google Search

clean the filters on the petcock?

Seafoam try it autozone sells it..$10

As long as you haven't CHANGED any components like the exhaust or air filter (which typically require rejetting), you may want to try and clean and re-oil your air filter and air box. A clogged or dirty air filter will change your fuel/air mixture, expecially in the top end when the carb venturi is completely opened and needing to draw in the most air possible. hope this helps.

under air cleaner box, reverse switch, one green and white wire. needs good connection to ground through sensor for full spark. happened to me 3 times now, very bad connector by yamaha in my opinion. about every 29 hours of riding it will need to be tightened, hope this helps.

if it idles fine but when you give it gas you say you have no power? then you have a problem with your intake and exhaust valves.they need to be set.I have a 2003 660 raptor and it was doing the same thing and that fixed it.