crf 50 head

[cracka50]

ok so i was wondering what is the capacity of a stock head, like what barrell size can u run before your going backwards, also with carb and manifold size im sure it can only flow to a certain capacity does this make sence?

[BOXY]

Nupp No cracka that don't make any sense at all. I will try to give you some info to help. A crf50 head will handle a 20 mm carb ok if the capacity of the engine is upped to either 75 or 88 cc. I don't think a bigger crb will do much if the motor is stock. A couple of people put 70 stock carbs on their 50's but I haven't done it myself.(kinda big bore fan myself). Hope this helps.

[cracka50]

yea thanks boxy, was kinda hard to explain what i was sayin. was just wondering u know how generally heads are measured by flow in H.P what kinda set up would max out the head? I purchased a xr 70 carb for my crf from you ( by the way its awesome) and the inlet manifold so much larger than the stock inlet on the head. At what point in size does the engine suffocate from not enough flow in the head and a larger capacity bore? And is there a point in puttin a carb and mainifold the size of a 10cent piece on an opening the size of a 5 cent piece? sorry for the rambling i just get curious, cheers.

[OZ FMX]

when i did the SDG motor it ran a stock 22mm carb and stock 3valve head, i had the head flowed and ported to suit a new mikuni 26mm carbwhich took it from a potential Hp 14.3 to 17.8 from memory new carb and new pipe jetted to suit it runs unreal on fast flowing tracks but tight stuff its useless you realy have to ring its neck just to keep the power on.
a few nights ago i bolted the stock pipe and stock 22 carb back on and ran that and its picked up so much, tight stuff isnt an issue and its got mounds of torque so now i've got a set up doesnt matter where i race

[BOXY]

Yeh i guess it would max out the capacity of the ports so to speak. Flow is normally measured in Cubic feet per minute or CFM. So if you know all the techo info on the flow of your hed and you can get a match with a larger carb then go for it. As far as i know a 70 carb would be about it for a 50cc with a stock head.