Thread: stroker motor

was wondering if any 1 knew what is needed for a 110 stroker motor?have a1974 ct70 that needs to have the case replaced,so i figure might as well look into a stroker crank.from what i read you need the 88cc big bore kit with cylinder and head and 52mm crank for 110cc.is there any thing else 1 might need?How well will the 3 speed auto work with this setup?or will i need to run a 4 speed with manual clutch?are wheelie bars gonna be mandatory(lol).want the bike to have some torque for the hills around here on and off road.any input greatly appreciated.

This one keeps coming up. If you search through older threads (this year's, not ancient history) you'll likely find more details.

First off, you'll either need to source a 6v crank, if you want to retain your flywheel & breaker points, or you could do a 12v CDI conversion.

You'll also benefit from running a slightly hotter cam, such as the Honda "fast road" cam. I wouldn't go much wilder than that with a semi-auto & 3 gears. You should be able to get at least 60mph even with a compromise between torque and peak hp. I'd install a Trailbikes billet semi-auto clutch, with HD springs. I wouldn't expect your stocker to get along with the huge increase in torque.

With 110cc, I'd do some modest porting, mainly on the exhaust, concentrating on the short turn radius and pocket. You don't want to go a whole lot larger, just remove the restrictions, without killing flow velocity through the port.

Add a 22mm intake and 22mm carb, such as a VM22, free-flowing exhaust and the motor should breath well. You'll also want to add an oil cooler, dipstick oil thermometer and high-output oil pump kit (be sure to enlarge the orifice to match the pump, as per the kit instructions)

Lastly, you'll have to experiment with gearing. Stock was around 5 mph/1000rpm in top gear. I'd start off around-7.0/1000rpm with your 110 stroker and expect 60-65mph top speed, with 50-55mph cruise speed. These are only rough guestimates. Good luck, I look forward to reading about your progress.

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Originally Posted by mike649

was wondering if any 1 knew what is needed for a 110 stroker motor?have a1974 ct70 that needs to have the case replaced,so i figure might as well look into a stroker crank.from what i read you need the 88cc big bore kit with cylinder and head and 52mm crank for 110cc.is there any thing else 1 might need?How well will the 3 speed auto work with this setup?or will i need to run a 4 speed with manual clutch?are wheelie bars gonna be mandatory(lol).want the bike to have some torque for the hills around here on and off road.any input greatly appreciated.

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You'll really enjoy the extra power . Probably will want to put a Mukuni carb on . You'll also want to change gearing . Talk to Fatcaat , he's the man when it comes to HP . I attached my beast 120cc stroker w/ 26mm Mukuni .

In addition to the good suggestions you already have, you might also want to add a second case vent to get rid of the increased pressure.

No big deal while you have the cases apart anyway. Just drill a second hole besides the original vent and glue a piece of brass tube in.

Regards,
Markus

thanks guys for the input,60-65 mph top speed would be nice to get for the highway.i live in the mississippi river valey and the roads around here get a little steep(500- 575ft) in elavation to get to flat road

The deck height of a high performance off-the-shelf 88cc piston will probably increase the compression ratio with your 72cc head to about 10:1 or even higher.

If you mix that with a stroker crank, you might end up with a much higher, probably excessive compression ratio (due to the longer stroke).

I'd either try and get a complete, proven 110cc kit from a single source or take the additional effort of measuring and adjusting the resulting compression ratio.

mfro, i was gonna get the 88 cc kit that comes with a head and cylinder then buy a 52mm crank.for a displacement of 110cc.

Thats probably easiest mike, dratv has a 6v 52mm stroker crank #200002 if you plan to keep the points, or if you do 12V you can just use the TB 88cc kit and their 51mm stroker crank, that's what I did and it goes together pretty nice. I think they have a 108 'kit' with a larger carb if you want to but it all together.

whats with the 12volt crank anyway,i mean is it added cos?12 gotta be better than 6,lol.then i would need a 12 volt battery and change the light bulbs any thing else i'm missing here?minds set on that 52mm crank,iwant a full 110 cc"s

Originally Posted by mike649

mfro, i was gonna get the 88 cc kit that comes with a head and cylinder then buy a 52mm crank.for a displacement of 110cc.

The stroker crank increases compression ratio nevertheless. Is it too much? Only measurement will show. Or ask your vendor.