Help with sprocket choice.

[Commonrail]

Hello guys,

I'm curious on selecting a sprocket front and back on my doodle bug. To start out I've got the 212cc predator engine and just received the OldMiniBikes stage 4 hemi up grade performance kit and I add the ARC billet fly wheel with it so when I remove the governor, I'll be on the safe side of things. I've got a TAV2 torque converter setup that's going on it and I need to order a front and rear sprocket. As of now with just the bone stock 212cc predator engine with a 12tooth max torque sprocket and the large rear stock sprocket, it will easily lift the front tire and she tops out at 39mph per GPS, I know the Torque converter will be extremely torque plus having the added HP with the kit will be on the scary side of things, I want a good sprocket setup that will have great topend speed (way more then 39mph) and still have some lowend. So this is where I wanna ask for some input on this from you guys that have done this before or have a better understanding about it.

Thanks.

 

[Bbeachmobile]

you will need a sprocket adapter for the doodlebug then you can use split sprockets and you should buy a good chain i would go with a 60 tooth rear

 

[Commonrail]

What size front sprocket would go with a 60 tooth rear and should I keep the #35 chain or jump to a #40/41 chain?

 

[davidlamb78]

You can figure speed easily with a speed calculator. Those can be found on the web. I always used this one.

AGK - Top-Speed Calculator - Affordable Go Karts

You'll need to know rpm's to figure that out. If you are running a gov, then the top rpms will be between 3500 and 4000. I'm not familiar with the stage 4 setup, but if you're running stock valve springs without a gov, you'll be between 5500 and 6000. I don't know how the torque converter works with the speed calculator, so that may mess the whole thing up.

I am running a 35 chain, and that is plenty for me. I have 35 on the go kart too, and that motor is pushing a lot more hp. The stock chain is junk, and it will stretch a lot, if it hasn't already. The split sprockets are great for changing sprockets quickly. Split sprockets are pretty easy to obtain for cheap, not sure about the TC sprockets. I bet you'll just have to buy a few combinations and play with them. You'll find one that works. Just start with the sprocket that it comes with, and go up or down. I think you'll be pleasantly surprised how much you'll like it.

 

[2SlickNick]

you will need a sprocket adapter for the doodlebug then you can use split sprockets and you should buy a good chain i would go with a 60 tooth rear

OldMiniBikes sells a stock 60t for the db. Mind should be in the mail box tomorrow.
No need for an adapter.
I needed it since I got the smaller wheels and my stock 72t hits ground on left turns.

 

[Commonrail]

Thanks guys. DavidLamb78 the stage 4 kit has
(1) Billet Rod, standard length
(1) Mod2 Cam
(1) Upgraded air filter adapter
(1) angled air filter
(1) choke hold bracket
(1) heavy rubber gasket
(1) long carburetor stud
(1) Race Ready/CNC Bored Box Stock Carb
(1) 8 degree advanced timing key
(1) underseat exhaust with screw on muffler
(1) exhaust gasket

No valve springs (only thing I can see is they have the upgrades valve springs for the non hemi head) mine being a hemi head, are the good for higher rpm like around 6k or so or will they eventually need upgraded?

 

[2SlickNick]

-correction on my above statement .... Beachmobile is very...correct.
Lol you do need an adapter I didn't pay attention when I ordered.
Sorry for any inconvience of confusion this may have caused.
I will now be ordering me an Adapter and 53t sprocket split ring.

 

[davidlamb78]

Well, I haven't opened up my hemi to examine the springs. It's staying mostly stock...at least for now. I don't know when they'll start to float.

I can't remember what I got out of my blue clone before I did the billet upgrades with a new head. I think I was around 6k rpms. I think my cam has 265 lift. I'm hoping to bump up a bit more on my next cam, but I won't go there until my valve train is completely redone. Other than the springs, it's stock. I'm afraid to push the vavles and pushrods any harder than the 18lb springs. right now I'm between 7500 rpms and 8000 rpms. Springs are cheap. If you don't need to do any machining, you might as well upgrade to some better springs. Maybe not 26lb springs, but 18 or 22 might help with float. Who knows? You may get more than 6k rpms out of it? You can probably get them for less than $10.

 

[Commonrail]

So wonder why OldMiniBikes stage 4 doesn't put upgraded valve springs in there kit on the hemi head. Are they a lot better then non hemi springs or does the hemi head allow less of a piston to valve kiss due to the space it has?