1989 cr125 sputters mid range.

[Dan_1989cr125]

Hey guys! I have a 1989 cr125 for my wife. It has an fmf gold series fatty and a powercore exhaust. when i purchased it it had an awful sputter that would improve slightly with a hotter plug and run better on a br7 but still sputter at high rpms. I jetted the bike and it now runs on a br9 but sputters very briefly at high rpms. is this a result of the pipe? is it an ignition problem? any help would be greatly appreciated. Thanks!

 

[helio lucas]

are the reeds in good shape? silencer packing? crank seals? engine with good compression?
clean carb and good needle and seat?

any of this could be the cause and are the most common source of that kind of problem...

 

[Dan_1989cr125]

Well originally when i purchased the bike it would sputter constantly. after changing the jet to a 170 main and lowering the needle 2 notches and putting in a br9es it only sputters for maybe a second or so and then seems to run normally through the powerband after that. Thank you very much for a great answer!

 

[helio lucas]

i don´t feel that the bike´s problem is in jetting, you have to be sure on the mechanical side. :nod:

either way, on pro circuit or boyesen site they list the stock jetting and the recomended... it shoud help...

 

[Dan_1989cr125]

Thanks guys! After many hours of toying around i replaced the ignition coil and the sputter is completely gone now! I have been racing a few guys that have new bikes and it beats them! Gotta love the old 6 speed trans! it beat a 2008 yz250f by a longshot!