For lack of anything better to spend my money on I think I will try this project. I found a 1999 Rotax 600 twin. I'd rather have the 583 or 670 but the carbs are mounted too low and would interfere with stock sprocket location (400EX frame), even the new 600 might not work, I need to measure one to be sure, I might have to go with an older piston port motor which have higher carbs. Yeah its a tight fit but I don't really want to buy a banshee or quadzilla for this, and to have the same 2nd quad I can steal parts from is nice.

At any rate, I've found older message from people that have done it, 800twin, killerkx327, but I'm not sure you guys log on here any more, and killerkx327 the e-mail on you're web page didn't work.

The questions I have:

1) cooling. most applications for this are hill climbs and drag races, and a small rad with a fan would surely work for short runs, but I'd like to ride around more than short races, and am wondering just how hot they run. I figure I can fit a motorbike rad like a goldwing 1200 might fit behind a raptor shroud, and I also figure if it can cool a 1200cc 4cyl it'll work on a 600 twin, but you never know. I've thought about an idea of a thicker head gasket that I could put on for most riding, lower compression should run cooler, I don't need 100hp all the time, 40-50 would make me happy, then I could run high compression for the drag racing weekends and ice racing.

2) gearing. from what I can find, a snowmobile clutch system is at or near 1:1 at top speed, which should be pretty close gearing to my 5th gear I would think, since engine top RPMS are also similar, (5 which is 50-60mph depending on tire size, yet the drag machines I've seen have a huge rear sprocket which should gear it even lower but they still do some 130 mph, so there must be something different on them. My secondary will be mounted on a shaft with drive sprocket at stock location, no 2nd shaft or 2nd jackshaft chain scenarios I hope, unless the secondary would be too close to the ground but I don't think it will be.

3) Belts. I've blown belts in winter before and their remains were hot enough to burn you (well the first one did then I got smarter), so I'm not sure how well they hold up in summer heat in a sealed cover? MOst utility quads run snowmobile type clutches, and those drakarts seem to use the same clutches as the Rotax 583 skidoo motors, so they must work okay I'm thinking.

4) Pipe. I will use the stock 2-1 pipe, hopefully I will only need change the angle it comes off the motor on the header pipe and cut the pipe in a "round" location to change its angle again to come back straight like a 250R pipe, then add a longer end pipe ("stinger"?) to connect to silencer. A problem might be if the stock pipe is too long, which I think it will be, I will need to shorten the distance from the motor to expansion chamber which I imagine will completely change the tuning of the pipe, and am wondering if anyone has any experience with this kind of tuning. Maybe its easier or better to get a whole custom pipe made?

5) sealed clutch cover. Any ideas welcome here, haven't put any thought into it yet.

Thanks for any help and feedback guys. I'll post pics of the 3D cad dwgs once I get the 600 motor measured.

 

I have 900cc 4cyl. street bike motor in an lt500. For cooling I am using the stock lt 500 rad with an electric fan. I can ride around all day long slow or fast if that helps. Go to macdizzy.com for your pipe info...lots of info there on 2 stroke pipes. Good luck!

 

yeah I'm gaining confidence in the cooling, a couple of people have said the Sport 400 rad kept a highly modified triple cool, so thats good news. I will probably start with a rad/fan from the motorbike parts place and then maybe try a thicker alum aftermarket Banshee rad if it runs too hot.

Jammer, I am confused on the gearing though, I'll post a message on a snow forum, but I think the clutches are around 1:1 which means the secondary will be doing around 8000 rpm, which is also what the quad motor does, and I think a 400EX is around 1:1 in top gear, so the drive sprocket should turn at about the same speed mounted on the secondary? I would think if anything you would need a smaller rear sprocket to get up to 100+mph. Ah well I suppose if I end up needing the massive rear sprocket I probably won't need a skidplate on this one anyway. What kind of chain/sprockets did you use on the Polaris machines? A stock 400ex uses 520 chain which is 5/8" pitch but only has 1/4" clearance for sprocket thickness, but a #50 (5/8" pitch) sprockets are .343" thick. hmm!

sandman, awesome quad! Actually you have a bunch of awesome quads. how much weight did that 900 add? I am thinking of using a quadzilla since I might even be able to race that one MX. To fit in the 400 needs a couple of frame tubes cut out which definitely would not hold up to MX. I guess you used the honda 900 chain, what kind of rear sprocket do you have?

Thanks for the help guys,
Rod

 

The 900 weighs just under 400lbs. I use a 520 chain with sprockets from sprocket specialists.

 

I,m new to this forum thing, so forgive my spelling. I,m building a Lt-250 quadracer wiht a rotax l/c 440 engine out of a ski-doo blizzard. Hey killefitt, your questions about the gearing. A sled has no gear reduction except for the cvt. They do run a reduction between the driven shaft and the track, usually about 2 to 1. Most tracks are about 6 and half inches to 8 inches in diameter. That is in effect the diameter you are turning. A quad tire is 3 times that tall. You have to make up the gear ratio in the sprockets. I,m puttting a 74 tooth rear sprocket on my bike, with a 12 to 13 in the front. I have aaen,s performance clutch tuning book, which is of great help. Olan can also set you up with a pipe kit , for around $400.00 . THe clucth cover should be made out of light weight alum. Another word on the cvt. Most sleds engage around 4000 rpms, then they shift to 8 to 9000 rpms, where they stay until the shift from low into overdrive, which is about .75 to 1. I hope this sheds some light on your project.

 

I have seen and talked with many guys that have the snow motors in Banshee frames. When they run a jackshaft the rear sprocket is huge. Powerfreak is correct also, the CVT will obtain an ovderdrive of roughly .75 to 1. They also start in more underdrive than the ATV's which is why they take off good and fly on the top end.I say importance factors should be on the cooling, pipes, then clutch cover. If you ride a lot in the sand you do want a cover that will keep the sand from eating the clutches up. Improvise the best you can, but I think you will be VERY HAPPY with the results. Grab some throttle and hold on!

 

damn you have the sweetest quad ever sandman, the same weight as a rappy and an extra 240cc, bigger carb, all around bigger, and still light weight. What kind of ponies does that thing pull? have you dino'd it?

 

yeah that doesn't weigh much more than a Quadzilla, awesome. I am curious how much weight mine will add, with clutches, bearings, 1" shaft, frame mods, hopefully not too much over 425lbs.

Powerfreak, I was planning on using a bilzzard or cat 440 too but I'm getting carried away. I might end up with a 900cc twin. What is the centre-centre distance on your clucthes? how are you going to mount your secondary? Who is Olan?

Ah so a secondary clutch does some 10,000rpm! wow. Well with my front 14T doing 10K and a 39T rear I figure 192 mph with 18" tires, yes that would be geared a little high I think. But if a 400EX in 5th gear is 1.182 reduction thats a 7000rpm on front sprocket which is 55-60 mph. Hmm I am missing something but anyway its clear that people do gear them down quite a bit. I wonder if there is a way to gear down the clutches with a wider belt, which would sit lower in primary and higher on secondary? It might take some luck to find the right belt for clutch centre-centre distance though. I am planning on a couple of simple pillow block bearings for the 1" shaft with secondary and front sprocket on, which will have a little adjustment in them.

Rod

 

Thanks! It puts out 128 at the wheels, but I'm working in the shop on some more hp for it right now!

 

Bet that is one scary ride.... Any idea how fast it can go??

Travis