Differences between crf 50 and 70 motors?

[Down2Mob]

So obviously the top ends are different, but I was wondering what the differences are in the bottom end. I have heard that the transmission is different.

[PlanetMinis.com]

[doopsx3]

I believe the trans itself is the same but the primary drive is different ratio and the 70 has a higher volume oil pump.............(I think)

[zwieblekopf]

what doops said plus heavier duty clutch

[doopsx3]

what doops said plus heavier duty clutch

yeah...4got about the heavier clutch

[sr20hardbody]

dont forget the 3rd bearing i think the 50 uses a seal instead



tranny's have same part # its mainly the primary gearing, oil pumps and clutch springs that differ

[dirtbkr188]

dont forget the 3rd bearing i think the 50 uses a seal instead

Would you like to elaborate a little on this, for those of us who haven't heard of the 3rd bearing, please?

[sr20hardbody]

sure thing



if you look at the difference between both pics you'll see the 70 has an extra part #14



Honda Yamaha Suzuki Kawasaki Sea-Doo Can-Am Ski-Doo Motorcycle Parts ATV parts Scooter Parts personal watercraft parts Accessories



Honda Yamaha Suzuki Kawasaki Sea-Doo Can-Am Ski-Doo Motorcycle Parts ATV parts Scooter Parts personal watercraft parts Accessories





i also forgot the 70 uses a thicker conrod but from what im told its not needed just extra weight.

[dirtbkr188]

Got it, the needle bearing for the shift shaft that's in the right side cover. It is just a machined hole inside the cover for the 50.



Thank you...

[sr20hardbody]

you're welcome but curious could that bearing be installed into the 50 cover or is that machined hole not the right size?

[dirtbkr188]

There is enough material all around the machined hole to enlarge it for that 1010 bearing, but it might be better to just get a 70 clutch cover. That is a precision fit, otherwise, the shift shaft will bind if the bearing is installed incorrectly.

[sr20hardbody]

hmm thats $95 shipped



i wonder if FPM would machine it for much MUCH cheaper

[Down2Mob]

okay cool, I am wondering because I have a stock 70 and want to just buy a mod 50 motor and throw it in there. I'm sure I wouldn't have any problems doing this right?

[sr20hardbody]

port your stock 70 head add a cam and get a tb 88cc bbk with the dome piston.



wish it were that easy for me i have to build my 50 motor to 70 status first which costs a lot!



and 50 motor will bolt right in if thats the route you choose.