450 acceleration testing

[Bratman2]

I decided to do a little back to back acceleration testing on my MXU450i against my wife's 450 Grizzly. They are both similar sized and weight machines. Her 2010 isn't too long in the tooth and I just adjusted valves late last summer. Truthfully I already felt the Kymco was faster and a pair of unbiased people stated it was, oldest daughter and her boy friend. I remembered I had down loaded an app to my phone last year to check the accuracy of my Subaru Brat speedometer because I run tires 1.75" taller than were stock. Looking at the app yesterday I noticed it had 0-60 and 0-100 times. Took me a little to figure out but I was able to change it to kilometers per hour and checked it in my truck to see how it worked. Very good!!

On to the test, my wife's Grizzly has a winch, Kymco doesn't. So to balance it out I filled the tank on the Kymco to the top. Her Yamaha had 1/4 tank. I set all air pressures on 5 lbs. even. I started all runs at the road end of my driveway in the gravel, it is fairly hard backed. That allowed me distance into the yard if I needed it for braking. After launching one I set the other beside the tracks to have a similar hard pack surface to be totally fair. Without any further ado here or my results!!!

Kymco MXU450i = 0-60KPH in 6.33 seconds.
Yamaha Grizzly = 0-60KPH in 7.47 seconds.

To be honest with everybody I would have never thought the Kymco was that much faster. Riding them back to back the Kymco accelerates very hard out of the hole and has a very strong midrange. Even wanted try and fish tail a little!! With the Grizzly I was becoming glad at the end I had headed toward the yard. I slide to a stop 2 feet from the landscape timbers at the end of my driveway stopping. The kymco easily tripped the 60 kph timer and stopped easily with many feet left over and easy braking.

Some may wonder the point of my post. Well this year I intend to do a touch of modding to both. Now I have a decent idea of what they will do. Can retest and then mod and test again to see what gains. I posted this just for entertainment of our Kymco crowd!!!

[aaron8]

Nice results! great machine for the money.

Msrp on that machine is dropping to $4,999

[Bratman2]

Mine was a leftover 2014, I paid just a hair less than that. I feel Like I nearly stole it. The man I bought the Grizzly from said he paid just over 7K with a free winch included in 2011. The Grizzly is a 2010, they added the winch to help sell the leftovers. The MXU is a lot of machine for that kind of money.

[Bratman2]

I have rerun my 0-60 kph numbers to eliminate wheel spin. So this time I started on the pavement, 4 runs each and averaged the best two.

1. 2010 Grizzly 450 0-60 kph on pavement was 6.325 seconds.
2. Kymco MXU 450i 0-60 kph on pavement was 4.915 seconds.

For right now both are stock. I have shims to add between the sheaves to gear them both down some. Then I will most likely cut and weld the fixed plate that holds the rollers to get the top speed back the shims will lose. The Kymco is fast stock!

[Bratman2]

Finished with the 450 Grizzly shims and fixed plate mod. Total cost was $28.50 plus some of my time. CVT drives are super easy to work on, way easier than I imagined. Added 1.5mm of shims (the most you can add to a 450 Grizzly without the belt rubbing the cover inside) and cut the fix plate and bent the edges in 1.5mm. Just got the plate back from the welding shop this morning. Took it for a couple of runs down the road and driveway. The Grizzly produced 60kph on pavement in 6.28 seconds average, not much gain but a measurable improvement (.045 seconds faster). Shocked at my gravel driveway run, with a 7.11 seconds on the first try (.36 seconds faster). So no reason to do anymore gravel runs. The stock gravel runs stock I posted the best out of 4 with most of them bumping 8 seconds. I have more shims for the Kymco (2-1mm, .5mm and a .3mm) and I think I will stop the cuts at 1/2 inch, used 5/8" cuts on the Grizzly plate. Hope to have her done next week!

[Bratman2]

Got the cart ahead of the horse on the Kymco. I intended to do the CVT first but have not had a chance. Speedwerks listed an exhaust for an Arctic Cat XC 450 which is very similar to Kymco's Maxxer. The Maxxer is very similar to an MXU. I stepped out on a limb and bought the Speedwerk exhaust because the price was $100.00 off. It fit like a champ. Even though they list a different part number for the Kymco 450 ATV. So today I just finished another round of testing with the Kymco after installing the Speedwerx exhaust. On pavement the Kymco knocked out a smoking 4.37 seconds to 60 kph. On gravel the Kymco knocked out a 5.67 seconds with considerable more wheel spin and fishing tailing. It fish tailed so hard on my first try I had to back off as I thought I might loose it. I wouldn't have thought exhaust alone would make a significant difference. Definitely a little throaty sounding now but far from unbearable. the paperwork from Speedwerx claimed no modification or retuning of the EFI was required for this exhaust. I disagree, it does pop on when you let off of it. Probably look a fuel tuner for it and still going inside the CVT when a get a chance. The only other difference in the earlier runs were temperature and humidity. Best of my memory first stock runs were maybe 60 degrees, second that was on pavement was mid 60's. The Grizzly 450 with the shims I believe it was around 68-70 degrees. It was 82 degrees when I ran the Kymco today. Anyone have an idea if higher temperatures would be a plus or negative?

[Bratman2]

Had a little trouble finding a tuner. The one I wanted was listed for earlier models of Maxxer ad MXU. Manufacture did not think it would be a plug and play on my 14 model. So, research, research, research, I decided to try and fool the IAT sensor (called a T-Map sensor on a Kymco) into thinking it was colder than the temperature was. I pulled it and tested resistance at 82 degrees, 76 degrees, 38 degrees and 0 degrees. Purchased a 10k POT resistor made by Allen-Bradley. Tied it into the wire coming from the sensor to the computer. After playing around with it some I found that adding 3k ohms resistance eliminated all popping on deceleration. So I have a set of new numbers for the Kymco.

Gravel 0-60 kph in 5.20 seconds.

For some reason I got faults four times in a row on my phone app running on pavement. Worked fine first try on gravel.

Overall I am pretty happy with the exhaust mod and fuel mod. By the way the POT resistor only cost $7!!!
Still have not had time to bust into the CVT. That is next, being my new Carlise tires are waiting to be installed!

[Bratman2]

Okay, I have been dragging butt for too long. Broke into the Kymco 450 CVT. Added 2 millimeters of shims to try and decide if I want to send the front pulleys off and have them machined. Got some puzzling results from my app. The fastest time I turned on gravel was 5.19 seconds. Only a .01 gain, more on that in a second!! On pavement the app messed up every single time I tried (5-times), it would continue to run even after I went well past the 60 kph. I decided for the sake of my belt and tires to give up on accurate pavement times. My thoughts on the gravel runs!!!  I believe it spins so hard taking off that it just isn't gaining speed. It takes off hard and you need to be sure you are pointed perfectly straight or the tail tries to come around. I also think it is possible that 2 millimeter of shims dropped the midrange down until you may have ran out of the midrange before 60 kph is reached. Just guessing on the second theory. Feel that the first theory is pretty accurate. Top speed dropped from 56 mph to 48 mph. Right now I have a second set of CVT pulleys for the Kymco MXU 450.  I think will send them off to Adam at Airdam and have them machined down. Then do the fixed plate mod. I'll start a new thread if I do and when I get them back. From all I have read he is running about 3 months behind and sucks at communication. Reason I obtained a second pulley set. No down time.

[MitchPeder7]

Just bought a 2013 xc450 and looking for any info on mods! Very good thread! Please keep posting!


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[Bratman2]

The XC is a pretty machine!! Hope you like it, does yours have the stock 23" tall tires or already been upgraded with bigger tires?

[MitchPeder7]

The XC is a pretty machine!! Hope you like it, does yours have the stock 23" tall tires or already been upgraded with bigger tires?

No upgrades yet! It's actually my wife's quad, not sure what we'll end up doing to it but it's good to see someone out there is modding a similar bike


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[Bratman2]

If you decide to go with an exhaust you can tune it in with a simple pot resistor like I did. It is doing the exact same thing the Ebay Dyno-Boost "chip" is doing for about $7!! There is an Arctic Cat moveable sheave, front pulleys on Ebay used also for $40.00 or best offer and shipping. If you wanted to go the AirDam route. I got pretty good results with the exhaust, T-Map mod and Airdam machined front pulley set. I think he can take right much out of them, that makes a big difference. Some moveable pulley sets on some ATV's are limited how much can be machined off. Like my wife's Grizzly, around 1.5mm max or the belt will ride up so high it will rub inside the case.  I think he may have machined 3mm out of mine. With 23" tires it would be a screamer!!!!

[MitchPeder7]

If you decide to go with an exhaust you can tune it in with a simple pot resistor like I did. It is doing the exact same thing the Ebay Dyno-Boost "chip" is doing for about $7!! There is an Arctic Cat moveable sheave, front pulleys on Ebay used also for $40.00 or best offer and shipping. If you wanted to go the AirDam route. I got pretty good results with the exhaust, T-Map mod and Airdam machined front pulley set. I think he can take right much out of them, that makes a big difference. Some moveable pulley sets on some ATV's are limited how much can be machined off. Like my wife's Grizzly, around 1.5mm max or the belt will ride up so high it will rub inside the case.  I think he may have machined 3mm out of mine. With 23" tires it would be a screamer!!!!

I read your post on the POT resister mod! Sweet idea, sure beats the $300+ I'd have to spend on a tuner here in Canada.
I know! It's already pretty quick on the low end, thinking I'll definitely need to go up to 25s though, to much mud up here!
She'll need a bit bigger tires to keep up to my 1000 on 27"s I think haha


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[Bratman2]

Very nice looking ride your wife has! Clean too!! Looks like brand new! I was going to tell you get a picture or it didn't happen, lol!

[MitchPeder7]

Very nice looking ride your wife has! Clean too!! Looks like brand new! I was going to tell you get a picture or it didn't happen, lol!

Only 360km on it! It is pretty much brand new. Excited to get some mods done to it


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