Dr Pulley or MRP or ??? 250cc Clutch Upgrade

[lvflyer]

I would like to know who has installed any of these clutch upgrades on a 250cc buggy and how much more speed and/or torque you have witnessed?

I have two 200cc Baja mini bikes (fat tires) that I upgraded from the STOCK centrifragal clutch to a BELT torque converter and I saw a MAJOR difference in speed.

I was wondering if I would see that MAJOR difference in speed by upgrading the STOCK clutch on my Kinroad 250cc

[chuckorlando]

From my experiance, I would'nt buy anything from MRP

If it's a cfmoto then DRP. If it's a CN then find a molossi

[kliff]

Ditto, MRP....junk.

Since your kinroad already has a CVT transmission, changing out the clutch is doubtfully gonna increase your top speed, Top speed is controlled by the variator, and how high up on the pulley the belt can pull. If it is already at it's max height, then you are getting all the gear mutiplication available, and your top speed is set, until you either change some final gearing,(sprockets) or increase the tire size. Either of these is going to put more load on the engine, and may then require clutch and variator mods to return the belt to full extension. In some cases, you will even need to mod the engine for more power to get the belt back up on the variator. Just depends on the tire size, and or sprockets you choose.

A clutch change CAN allow you some adjustability though, with different "shoe" or pad > pillow springs. And a slightly stiffer torque spring can be beneficial as well. IF you are not currently getting the full belt extension, sometimes a stiffer torque spring can allow engagement at a higher RPM, getting the engine in the torque band, before it starts loading, which can allow full belt extension. The CVT has quite a few variables working together, and you can go from a higher speed(top end) to a lower speed, but with stump pulling power, just by changing some weights, and or springs.

But expecting a MAJOR difference, simply by changing out the clutch, ain't gonna happen, unless your present clutch is completely worn out, and slipping throughout it's RPM range.

[chuckorlando]

I also would not believe all the hype of light weights + heavy spring= more torque. What it does in reality is hold you in a lower gear ration and often does not allow the belt to ride all the way up like Kliff is talking about. I tested 11g, 15g, 17g, 19g, and 22g weights with every spring in 300ft runs. The absolute best combo cam out to stock spring 17g weights and second best was blue spring and 17g. For folks who climb, 15 is light as I would go 17 with a white spring is likely the hill mans combo.

These were tested in timed 300ft runs. 3 runs per set up and then avg time of the 3

[lvflyer]

Thank-you Kliff - I will look and see how high up on the variator the belt goes when I have the buggy jacked up off the ground. I saw on GO KART USA the the MRP or Dr. Pulley and/or variator was supposed to increase speed UP TO 40%. I thought since my 200cc mini bikes REALLY increased in speed and torque like GO KART USA said it would AFTER I went from a CENTRIFICAL clutch to a TORQUE CONVERTER, I thought they would not be leading me a stray - can you explain anymore?

[metalstudman1]

FYI-Your noticable increase in speed on your mini bikes is because you went from a single speed clutch to a variable clutch & driven that changes the speed ratio with rpm increase & not with clutch engagement.You went from direct drive to a transmission!!

[lvflyer]

Thank-you metalstudman1. I quess after I see how high up the variator the belt is going, then I will ask all of you if i should look at upgrading the variator. Is the HIGHER the belt goes up on the variator with INCREASE of speed what I am looking for?

[metalstudman1]

Yes- but most variators are made for the belt to ride at the top of the pulley already!! Your aftermarket parts make an attempt to allow for the belt to rise slightly higher on the pulley sheaves to get that extra 2 mph's on the topend, or lighten up the assembly for quicker response, and try to keep it running cooler with their newer designs.

[chuckorlando]

There are far better ways to spend your cash. I would suggest you leave the vari and clutch alone untill they wear out. They are right up there with perf cdi's and coils. They do something, but if you say you feel it, I'll say your either lying, or had an issue with the other part.

Best money you can spend is on a cam, head, and pipe. Or on the cheap end best bang is a sprocket change.

This is assuming you've done a uni, rollers, and rejet.

[lvflyer]

Thanks Chuckorlando. Could you please expand on your suggestions starting with the sprocket change. I am sure there are other people who are or will be looking at this thread learning from all of you as I am on improving performance as economical as possible. Once I would do the sprocket change - per your instructions, can I JUST replace the 250cc head with a 300cc head with no additional machining?

[chuckorlando]

No you dont replace it with a bigger head. You have the head ported. If your real nice to Kliff he might be able to handle that for a very fair price. More air/fuel in is more power.

The first thing I would do is decide what I wanted. You want more low end? Or you want more top speed? Or do you wanna break out the check book and get them both?

Now you need a game plan. No buying crap just to buy it. If long term you plan on a ported head or a stroker crank, then dont do much of anything till you can afford them first. Same with a cam or BB kit. If you throw a 42T sprocket on and get good low end, then you add a lowend cam or head, you may have wasted money on the sprocket. If you set up the cvt for a stock engine so it has more pep, then do some mods, all could be for naught.

I'm an all in kinda dude. It's big or it's trash. So I would start with a ported head, torque cam, and an exhaust even if just bore out the flange and weld on bigger header and muffler. UNI filter and a rejet. I would do it this way cause thats where it's headed anyways for me and this set up will spin 24in mudlites with stock gearing on a crossfire 180r. It will also out run a bms300 and onlt loose to a kinroad300 buy 6in in 300ft drags.
Let alone talking a 250. In a 250 this set up has won 2yrs running in the drags

If you dont plan to throw 600-1000 into it, then take the head off the table all together as well as the cam(unless yu have a cn) In favour of a larger bottom sprocket, 17g sliders, blue main spring, uni and a rejet. If you do have a cn then it wont have a sprocket. In this case I would pony up for the torque cam with everything else minus the sprocket

In this case I would buy