Planet Minis

smiffy

hi guys,

im building a engine for a 50 class, however its a bit of a cheat.

the spec is:

takegawa 50mm crank
powroll 15:1 hc piston
takegawa h/d oil pump
takegawa c/r gearbox
takegawa r10 cam
takegawa 18mm carb kit
stock 50 head

to make the setup work i have had to cut the base of the sleave off about 5mm so that the conrod doesnt touch the side.

however the increase in stroke length has meant the piston skirts come out the barrel by 4mm at bdc.

do you think this is a problem?

need someone with some real tech knowledge here!!!!!

the engine will be running at full tilt 12,000 rpm for an hour at a time, a cant afford for the piston to come through the side of the jug.

PLEASE NOTE IM USING 98 OCTANE WITH 10% METHANOL MIX

fatcaaat

I personally think youd' be better off with a big bore cheat kit than a stroke cheat kit. You can get an 85cc top end marked 49cc and it will run circles around this setup and be much cheaper to boot. Your stroke to bore ratio isn't likely going to let you run 12k all day and a stock head probably won't allow it anyway. Your clutch isn't going to hold at 12k either if you run it like that all day.

If you are going to run a powroll 15:1 piston what will the compression ratio be when you put the stroker in? 17:1? Did you check to see that a takegawa crank has the same connecting rod length in that the piston comes to TDC? I think the takegawa crank is different than the stock....not sure.

As for the skirt sticking out the bottom, I'm a believer that as long as the piston pin is covered you should be ok. If you are trimming the skirt anyway, may as well trim it up further. Just make sure you get the edges perfectly smooth or your cylinder wont last long.

smiffy

hi there,

the takegawa crank comes up a bit shorter at tdc than the stock crank, so i will machine the jug down 1mm.

i definately want to go down the route of the stroker crank so on inspection when the head is taken off the piston measures 39mm.

i have cut 4mm off the skirt of the piston and it runs ok up the bore.

the question is will it run at high rpm and last do you think?

cheers

fatcaaat

If they are going to tear your motor down to inspect the piston, it only takes about 5 seconds to turn your crank and discover you have a stroker in there. No need to take the motor apart to determine that...If the top end comes off the motor, they'll know if you have a stroker crank anyway if they actually do any type of inspecting.

I don't think it will run 12k at all. I also don't think it will run maxed out for an hour straight with the amount of cutting you plan to do on the skirt unless you had it machined at a shop. Your compression ratio is going to be so high that you are going to have detonation unless you run a completely different fuel. 15:1 is doable. But when you put the stroker in there you are going to get up around 17.5-1.

smiffy

the crank comes up shorter at tdc so the compression ratio will be lower i think.

i have worked out the comp ratio and its about 11.9:1.

i think i might leave the skirts and just machine the sleave down the required amount.

firepower354

The Tak rod is 88mm, 6 shorter than a 50, and only 4.25mm more throw, so it's about 1.75 lower than with the stock crank.

Fatz is right.
Head won't flow 12k.
Clutch won't survive 12k

smiffy

do you think the spec below would work then?


kitaco 41.4mm race crank
powroll 15:1 hc piston
takegawa h/d oil pump
takegawa c/r gearbox
takegawa r10 cam
takegawa 18mm carb kit
stock 50 head - flowed
kitaco inner rotor

cheers

moto234

also if they take the head off it obvious its not a stock piston, the dome is huge on that. youre going to get caught if they inspect so do a good job of cheating.


get the 85cc marked 49cc and stroke than then get an HD auto (w/ weights??) and lighten the flywheel. work the head over, get a cam and upgrade to a crf70 carb with a uni if you can and you'll be fast like a nascar

chasetheface123

dude just buy a dratv 88 kit for 100 bucks and be done with it!

dieselthemeatbag

Or if you were fast you would not have to cheat

chasetheface123

lol or, you could just buy a dratv 88 kit for 100 bucks!

minirdr

or not! not marked 49cc, and not black.

chasetheface123

oh really? i thought that they were

cmktech

You could have saved a lot of money and bought the cheater 70 kit I have in the classifieds . Marked 48cc

firepower354

Just 72 and 85cc kits, marked 49cm3 and black, from the Dr.

I do have an aluminum 88 jug marked 49 though, that mated to a stroker will make a nice 106cc "50"...

moto234

buy it whoever started this!! does it have big fins tho? that will tip them off if they pay attention at all