At Last !!! I finally found a source for 'Performance' engine parts.
Carbs, Jets, Air Filters, Hi-Rev CDI's, Ing Coils, Multi-Winding Stators, Perf Clutch Packs, GY6 Perf Clutch Weights. Cams, Pistons, Etc, Etc.

Many, Many, 'How-to-Videos' on the Video Tech Page.

Link is for the 'ATV' page; BUT, make sure that you 'click' on the 'Performance tab' and the '4-Stoke Parts tab' and the 'GY6 Motor Parts tabs' to see all the stuff that is available !!!!

Performance Parts

Happy Engine Moding to you. !!!

 

Hey NJDALE,

Have you ordered any engine parts from here for your JM250???
Many this website has everything great job on finding this site!

 

No, I haven't had the 'need' to so far. I've got the quads pretty well tuned up right now. I did finally find a 'good' trail and had mine up to somewhere between 35 to 40 MPH. That's fast enough for ME !!! (especially when you think about the tires !! ).

Sometime in the future, I will be thinking about it for my grandson's quad - though that's quite a ways off. I already know what his needs (it needs to BREATH - larger carb and better flow exhaust) - but; for now, he has MORE than enough power.

 

Well i still want to try to add better performance on my JM250. My boss has a friend whos is an expert at ATVs and is willing do all that he can to add more HP and better Performance. And hell do it cheap or for no cost at all cause he loves to work on them and races quads on the weekends. I know for sure i want to add a aftermarket carb I read on here some guy added a Mikuni flat valve carb on a 250 Falcon and bought a jet kit and gave much more power. Do you know if the JM250 can only put a 30mm Mikuni carb? Thanks for your help

 

Well i still want to try to add better performance on my JM250. My boss has a friend whos is an expert at ATVs and is willing do all that he can to add more HP and better Performance. And hell do it cheap or for no cost at all cause he loves to work on them and races quads on the weekends. I know for sure i want to add a aftermarket carb I read on here some guy added a Mikuni flat valve carb on a 250 Falcon and bought a jet kit and gave much more power. Do you know if the JM250 can only put a 30mm Mikuni carb? Thanks for your help

 

It's really a process of taking the 'elbow intake manifold' off the head and measuring the diameter of the 'intake port' on the head. What ever the mm of the head port intake - then that is pretty much what you are limited to for the carb (unless you want to get into machining {port & polish} the head - both intake and exhaust). The 'head port','intake pipe', and 'carb' should all be matched in mm size. You can even 'gasket match' everything (meaning that you file each piece to match its 'mate' so the 'air flow' is smooth at each transition point.

After all pieces are matched in mm, the venturi area inside the carb will still be a few mm smaller in diameter that the rest - this generates the 'vacuum' that is necessary to 'pull' the fuel thru the jet and up & out of the carb.

The reason that the diameter match of all pieces is important is that you 'can't fit 5 pounds of shxt into a 3 pound bag'. (or having a 30 mm carb with a 26 mm intake port accomplishes 'nothing' and may actually be 'worse' because the venturi area of a 30 mm carb may only be 26 mm - in which case the venturi within the carb may not properly 'pull' the fuel up thru the jet properly).

 

And then - after you finish the 'intake side', you have to do the 'exhaust side'. Everything in the exhaust side has to be at least 80% (minimum) in area (formula, Pi R squared) of the the size of the 'intake side'. The reason for 80% is the 'expended energy'. You can then get into 'pipe size changes' (fat pipes) to cause 'venturi' effects to 'pull' the exhaust thru the exhaust valve (but these are only effective for very narrow RPM bands or ranges).

But, why would you even try to do all this on a Chinese motor ????? The Chinese motor is very good at what it was designed for - an 'inexpensive' power source for an 'inexpensive' ATV. Start going 'beyond' what it was designed for and you will end up with an 'expensive boat anchor'. Remember - above all; this is 'Chinese Metal', and you CAN'T change that !!!.