searched for info on belt drives and decided to stop looking and start doing. Bought a 9hp briggs that is bone stock, had a symetrical comet and an A-symetrical comet from kids gocarts. already got the motor wedged in there (gonna post pics as soon as my wife shows me how). Ran into some issues with the recoil side but nothing a plasma cutter and mig welder cant fix. steering will remain stock, cylinder head hits near OEM fuel tank but i wanted to modify that anyway to hold at least a gallon. If there is anyone in the mid thumb region of michigan that wants to modify there kids sled, i would love to help for free. We are going to use juniors sled as the test dummy and see what happens. Got big plans for front and rear suspension that are much cheaper than most alternatives. know that i have the motor i will keep up with pics as i proceed.

Sounds cool,, only bad thing that I can think of is very recent closing of doors at Hoffco/Comet,, shortly the supplies for their systems is going to take a seriously drastic turn for the worse,, as their go-kart/mini-bike drive systems were just about impossible to locate at ALL their distributors from early July to early Sept

And not all of their commonly stocked items were ever brought up to speed (stocked up,,so to speak)

Some have claimed they've filed for Chapter 11,,

Time will tell I guess

I just purchased a belt drive and GX200 for my kids ZR120. I will be watching this thread closely.

that is interesting info on hoffco. Too bad they might close. if i HAVE TO i would buy a JR clutch assy.. just waiting for them to come down a little on price. hopefully the comet 40 series holds up through crash and burn...... I mean the trial and error stages.

Click to view attachmentClick to view attachmentClick to view attachmentHere are the pics as promised. Ricky's 2007 120 Z is being transformed into a 297 Z. The first pic is the bench full of parts that we have scavenged to perform test and engineering with. by the way, if anyone needs a good running engine with only 2 seasons on it, comes complete with wire harness cheap, make offer. the only reason we are doing the conversion is the clutch finally fried and that was mostly due to my 9 year old hauling his older brother around on a sled. Next pic, possible clutch and gear combos, probably going with the 40 series comet even though it doesnt fit as well. Going to use a heat gun on the plastic near near the clutch, push it out a little with a coffe can for clearance. I will let you know how that works. Next is clutch side view, gonna need to weld in new bottom plate to bolt engine to and cut slot larger for crank shaft to fit. Will build small plate to stiffen on clutch side. Next is recoil side, was going to build new plate to support jackshaft and the stock 9hp briggs is a pinch too big to fit with the recoil on so, gonna fab hole new side plate and heat the belly pan on that side also and push it out with coffee can to get the stock recoil in there and mount jackshaft and disc brakes. Next is stock steering shaft, thankfully it looks like thats gonna work without modification. next is one of the 2 major issues I ran into. the valve cover hits the left hand support for the steering shaft. To keep the engine flush with the left side frame i am going to cut the tube just high enough to let the valve cover in, weld a flat tab and rivet it to the side of the tunnel. The last visual issue is, when the seat and fuel tank assembly is tucked in under the steering shaft support, the valve cover also hits the front of the fuel tank. I really would have liked to get this done without modifying the fuel tank just to keep it cheap and then install something larger than the 2 quart OEM at a later date as finances in the family are the same as Michigan, very poor. BUT, since it hits,I have contacted a friend at the local weld/fab shop and he will weld an aluminum one that will fit. I plan to build a paper mache' of the outer shell and he will weld up something to fit with a bung on the front just like the big sleds, to install a fuel line and clunk. Bolt it to the tunnel and cut out the old tank, carefully cutting the fuel neck out and use an aluminum ring to secure it back to the new tank with some fuel proof silcone so that the only change in appearance is the ring holding it in its exact oem loaction. The other issues that are not visable are going to be the fuel tank will then be lower than the carb, hence a case operated vaccum pump that was used on older John Deere lawn mowers when the fuel tank was under the seat. Just gotta find a place in the crank case to drill and tap above oil level. I might also need to slightly restrict the oem breather vent to the carb to cause more case vaccum/pressure to operate pump. Need to custom build exhaust pipe and muffler. Engine does not have lighting coil, hope to find some blown up 10horse and rob the coils and flywheel to throw in there for the lights. Guaranteed to run into other problems along the way but it wouldnt be fun if I knew the future. The jackshaft looks like it will still fit under the head of the motor and all of the belt drive will look like others seen on this forum. Local bike shop has very reasonable prices on disc brake set ups. The one advantage is, this will all be stock. No screaming the engine at ungoverned speeds or spending $1000 dollars on the engine. This one came from Burdens Surplus shipped to my door for $375 brand new without fuel tank or muffler. I didnt need either any way. Disadvantage...........15-25 lbs heavier than other options. I will sacrifice the weight for reliability. I will keep everyone posted on progress with pics every step of the way and hopefully a video of the last pic I am posting, my little buddy Ricky tearin' it up across the yard.Click to view attachmentClick to view attachmentClick to view attachmentClick to view attachmentClick to view attachmentClick to view attachmentClick to view attachment

with a little help from some internet calculators I have developed a formula for a 7 tooth drive lug. The OEM is 3.125 dia. with 5 lugs and the one Rec motors has is 3.875 with 6 lugs. I did the math and there is 3.375 from center of OEM shaft to shortest point on tunnel. A 7 lug would end up at 4.375 diameter. Even with the track at .875 tall with a 1.100 stud in it, that would be a total over all dimension of 6.575. Divide that by 2 = 3.287. That would leave .088 of clearance between the tip of the stud and the tunnel. Its only a little more than a 1/16 of an inch. Maybe use a stud that is only an inch if they hit.

So I showed the OEM to my buddy at the steel shop and they have a bridge port. hes gonna try to build a 7lug to fit the OEM hex shaft and we are gonna test it. not sure about track adjustment just yet but i think there is room. Still gonna do the belt drive, but for some of you stock clutch guys, go to mph to rpm calculator by bowling and grippo and you can plug in numbers to verify ground speed with these changes. mess with the gear ratios too.
12t to 44t sprocket = 3.66 ratio @4000 rpm w/ 3.125 drive = 10mph
12t to 44t sprocket = 3.66 ratio @4000 rpm w/ 4.375 drive = 14mph
12t to 36t 3 to 1 ratio @4000 3.125 12
" " 4.375 17

If this works and anyone is interested in new drive wheels for an OEM shaft, maybe i could convince the steel shop to make a program for there CNC to print them out at a resonable price.
still hacken away at the 297cc machine trying to get it all in there. send more pics in the future.

OK, so I am running into more problems than anticipated. Started with the jack shaft. Need to keep it as close to the tunnel as possible to achieve proper clutch distance. having a hard time with the 1.375 bearings. They hit the front of the tunnel at the point that goes vertically up the side support. might have a little bit of the bearing inside the tunnel.