I own a 2005 kvf 650. I even tweaked it a bit, (filters,pipe jets,high lifter modual ) I'm also running 25 " mudzillas. My problem is that I was getting up to 95-97km/hr and now I'm getting 82-85km/hr. Any ideas on what to check for or adjust. It only has about 70 hrs on it and about 700km. Anyone have a service manual for sale?

 

First question, were you running the mudzillas before the tweaking? Second question, is your jetting correct? Third question, can you unhook the highlifter module and see if your bike will run faster?

 

There is no doubt the extra weight of the mudzillas is holding back your top speed. It dosen't take much extra rotating mass to really effect your atv's performance. Also even though they are 25s I bet you mudzllas are taller than your stock tires which would up your gearing and make that exta weight even harder to pull. Did you follow the pipe manufactures recomendations for jetting? If not you probably should have, if so then your jetting should be ok. I used to run a hl module and it didn't change my top speed any so I doubt yours would. If you still have your stock wheels and tires try putting them back on for a couple of test runs. I would bet your quad would come back to life.

 

I disagree. Additional weight of the tires won't affect top speed, but WILL affect the time it takes to get to that speed.
It will have slower acceleration, but should actually have a little better top end, with taller tires.
Check to see that your other mods are compatible with each other. Some pipes also provide better bottom end, but take from top end, and vice versa. Maybe your main jet is too lean and it's not getting enough fuel at WOT?

I don't know anything about the module, and what type of issues it can cause.

 

rpxr400 try putting a set of 44" boggers on an s10 and see if you'll get the same top speed it just wont happen!

 

It will. It will just take much longer to get to that speed. All taller tires do is effectively make your gear ratio taller, therefore giving you a tad less torque and better top end. If you put smaller tires on, you will lose top end but gain torque.

Want a good (but extreme) example? Ever ride a multiple speed bicycle, and you put the thing in first gear, and you take off very quicky, but soon, you reach top speed and can't go any faster because your legs are moving as fast as they can. Shift the bike to it's top gear and stop.
Now accelerate as hard as you can. It will take you much longer to even get to that same top speed as in 1st gear, but you will hit that speed, and well in excess of that. Putting taller tires on is the same concept - changing gear ratios - except not as drastically as this example.

Now, let's say you put that bike back in 1st gear and hit...10mph. Now put 20lbs on your back. You don't think you can get to that same 10mph in that gear? It will take longer, but you will.

The one place you won't get more top end will be with a weak motor going up a hill - but if kvf650man is comparing his top speed numbers, I'll bet he's not checking it on a hill, but flat ground.

 

Hello, I've been running mudzillas since I bought it.I got all the other stuff put on after.With a set of 4 muds I was getting 95-97kms flat surface (hiway) I just put the stock front tires on to see if it would make a difference and thats when I noticed a power drop! I've had about 14-18 inches of snow up here in Canada and I was hitting the mountain trails maybe some moisture got in I also put a new skid plate on and the snow was coming up every where, I also forgot that I put screens on the top of the breather box.