K guys,

I've had my original 1999 MXZ 600 for a few years now and I guess I never knew how good I had it.

I picked up an identical one (only in much nicer shape...like new actually), expecting it to perform the same. NOT!!! I had them both out tonight and my original one blows the doors off the more recent one.

My question is:

What could I look at that might make one significantly quicker and stronger than the other?

Ideas are:

Main Jets, compression, reeds, clutching (and how can I tell if one has different ones than the other?)

Thanks!

You've hit most of the things to check. Do a compression check. Should be in the 140 - 145 # range. Also, clean the clutches, and consider a clutch kit. Dymamo Joe on this site makes a great clutch kit. For short term good bang for the buck, Boyesen reeds are good, but IMO, wear out too quickly. V-Force 3's are more expensive, but last much longer.

Sounds like you're on the right track. Don't overlook the simple things, track tension, siezed idler wheels, brakes dragging, old gas etc...

Well, it has the same exact gas as the other sled. I don't think the brake is sticking, and I think all idlers are fine - it seems to coast down to 0mph at the same rate as the other sled.

Only differences I know of is the more powerful sled has an 1.25" track off a 99 mxzx 440 and the less powerful sled has standard track with a bunch of studs in it. The less powerful one seems to have trouble getting to 80 mph even...

Is there a quick and easy way to tell if one has upgraded reeds in it or not?

By "cleaning out the clutch" do you mean blowing compressed air into all of the openings or do you mean taking it off and disassembling everything?

I'm going to clean out the RAVE valves and see if that makes any difference too.

Remove the carbs and reed cages. The stock reeds are black, and have a brass "cage" over them. Aftermarket (Boyesen) are two piece and a tan colour. Your reeds may be deteriorating. Clean the carbs while you're at it.

The clutch has to be disassembled to clean it properly. Belt dust is a killer. If you're not familiar with the procedure, and don't have the clutch tools, by all means take it to a dealer, or someone that is set up to do it properly and safely.

Cleaning the RAVE valves, as you mentioned, is a good idea as well.

So far only able to do a compression test - got 120 lbs in each of the 4 cylinders so that's not it...