After riding my friends 88cc the other day i'm looking for some more power out of my lonely fiddy. I have access to some of the older honda bikes, such as old ct70s. What parts from these older bikes can i use on my xr? I know the ct is a 4spd tranny. There is a transmission without a head or piston sitting in a friends garage not being used, would it be worth swapping my fiddy head onto this for the extra gear? Is it possible to put ct70/90 heads on a fiddy tranny, what swaps what can i do for more cheap power/speed?

 

the only ct engines with 4 speeds were the ones that were a manual clutch. so take a peek at the clutch cover to find out for sure. 4 speeds in a stock 50cc engine is a bad idea. every gear in the 4 speed has a higher ratio. therefore the motor will really feel like its lacking power. in 1982 honda changed the length of their connecting rod. so unless the engine is newer than 82' (highly unlikely) the piston wont work in your fiddy. however, you can use the cylinder if wanted to purchace a 70cc piston. just make sure the piston is for a 1982 and up and for a stock xr50 head. the cylinder head will also work on you fiddy if combined with a piston that is designed for the 70 head. these pistons have a higher dome to accomodate the larger combustion chamber the 70 head has. personally, i would hit a dead dog in the *** with an old 70 head. especially one that is that old and prolly been beat on in its day. that head most likely needs new seals and might even need a valve job. the old 70 heads also use a non roller bearing cam which isnt as friction-free as the newer style roller bearing cams. do yourself a favor and save for a new bore kit. it will save you some headaches in the end.

 

OK thanks for the info, sounds like with the time i'd spend messing with stuff and fixing it up, plus the money i'd spend, it would just be easier to buy a big bore kit. I've seen some 88cc kits on ebay from "fiddy boyz" they say they are made in the same factory as the name brand kits and these are just packaged differently. Are these things worth a damn?

 

lol those are my auctions. do some research and read some threads around here. seems to be alot of mixed feelings about all bore kits. if you want one, just PM me. i can save you some loot rather than using ebay

 

I was over at my friends house tonight and he has an old ct70 engine laying on the floor in pieces in the corner. I'm like i'll buy it from ya, he said i could just have it. So i might just mess with it and maybe swap the whole thing in. Its only the 3spd auto, but it still has a stator so i could have lights plus i'd have a 70cc. It doesn't run at the moment though, has bent valves. I saw some heads on ebay for like $30-$40 shipped. I figure i'd probably be less than $100 to get this thing running... trying to decided if its a good idea or not.

 

that engine is a points motor. you will have to get a new coil, lose the cdi box, and pretty much make a new wiring harness. it just isnt worth messing with it. you will spend twice as much on that old broken motor in the end.

 

JOhnny GSXR, I just noticed your in nebraska...duhh

you should come to omaha today, hit my cell phone if you wanna come bomb out on a dirttrack or whatever (fiddy's of course) plus if your really wanting a 70 motor to run, my friend prolly has what pieces you're missing

850-3166 omaha #

 

well the 70 motor is in pieces on the floor... but the old ct70 is sitting in the middle of the garage ready to be parted out. So all the electronics i would need are right there. I might start messing with it with a budget of $50 or something and see what i can get.

Turbo i can't make it out today i've got some plans. If you've got aim or msn messenger though send me ur screenname. I can send u the dirt fiddy vid we made the other day!

 

find the best cylinder out of what you have, and buy a gasket set and piston from DRATV. put that stuff in your 50 motor. problem solved.

piston.. $39.99 http://www.dratv.com/xr70pikit1.html

gaskets.. $12.99 http://www.dratv.com/topgas.html

total.. $52.98 $3 over your budget and you retain your CDI xr50 motor

 

Can i use the stock head and carb then? So all i need is the piston, gasket, and cylinder? I'm doing this tomorrow if thats all i need!

 

So am i right in thinking all i need are those two parts u listed??? How will this run compared to a big bore kit? Like am i really gonna notice the extra power?

 

thats all u need man. and it is a big bore kit. its a 72cc cheater. they run awesome man. ohh, yer gonna need a 62 main jet as well for the stock carb. DRATV has those as well

 

Sweet, i'm ordering the parts today! Thanks for the help bro

 

So you can use the stock 50 head and cam chain. And use a ct70 head and buy a new piston? I understand all the piston and all that, just onwdering if the stock cam chain still works fine?

 

cam chain is the same. the CYLINDER is the only thing you are using from the old 70 motor, not the head.

 

Sweet...my boy has some **** laying around so I may tool around with that. Thanks!

 

so i take it the stroke of the xr50, and the ct70 are the same? if not, just swapping the cylinder over won't work, the cam chain would be too short, since you'd essentially be pushing the head away from the crank.

 

stroke is the same

 

Thats a sweet idea.. Now where to find a 70cc cylinder?

 

there was a guy with a complete 05 xr 70 top end for 100 bux on pm the other day.piston head cam and gaskets, carb intake and airbox.
you might check around if your gonna do the cheater 70 stuff use the whole top end. or for 250.00 buy a whole 70 motor. they r on ebay too. the head on it with a 70 carb would even do wonders,youd be surprised.