Xl125 lacking power

[dune19670]

Hi all,
My 84 xl125 rc starts & runs fine but lacks any top end power.
Anyone got any ideas whats wrong.
Ive changed cdi
Checked timing
New carb
Its doing my head now ????
Thanks steven

[mid life crisis]

Fuel... new carb so unlikly to be that but chack the air filter and is there any wanter in the tank?? sounds stupid but i have had it happen before

Electrical...... cdi's are normaly reliable, but whats the condition of the coil, ht lead and ht cap and spark plug?

Then we are down to compression, and from what your saying, it sounds like that, you could do with getting it compression tested

[dune19670]

Hi there, thanks for the reply.
The coil, ht lead & spark plug are all new.
Ive put a new k&n air filter on,
But it was the same with the old standard filter. ??
So compression test is next, will this prove its the rings or could it be the valves
Any more ideas please join in, steve

[mid life crisis]

With a k+n have you jettered it acordingley? i found in my younger days that the small honda's did not like them, but that was a cg125 and a cm125.
if there is a compresion problem, its a head of job for investigation to see what the problem is.

[dune19670]

I havnt jetted up the carb to suit the k&n,
I'll put the standard one one again to see if it makes any difference.
I'll see if i can borrow a compression tester at the weekend, does anyone know what a good/ bad compression reading is.
Thanks for the input steve

[dune19670]

Well ive tested my compression today,
Cold, and it was 120-125.
Does anyone know if this is a good reading or not.???
The manual says the compression ratio is 9.4-1,
And ive seen a few conflicting exchange calculating figures.
So i would appreciate some help here please.
Thanks Steve