Bogging issue, should I change the gearing?

dragonlube

dragonlube

Got a 2001 YZ125, yesterday was my first time riding an MX bike (had a ttr230), the issue was that I found it incredibly hard to get moving from a standstill, if I stopped the bike at just a slight uphill it would just be impossible to get moving again because no matter what combination of clutch releasing / gas giving I tried, it would bog down and then stall, sometimes it would eventually pick up the RPMs after a couple of seconds while slowly moving and from then on work perfectly.

I weight 250lb and the gearing ration is 13/48, I'm not sure that's even the problem but 48 seems like it could be too low for my weight.

Anybody got any other ideas

Additional info: it happened from the moment I started riding until the end of the trip 3 hours later, hot or cold, didn't matter. oil/gas mixture ration 32:1
 
Mihylo33

Mihylo33

This leaves me with several questions....
When was the last time you cleaned your carb?
When was the last time the topend was rebuilt?
Does the powervalve operate properly and has it been cleaned lately?
How well is the bike jetted?

These could all lead to the low power you are feeling when taking off. Granted its a 125 and it begs to be revved to the moon, but in 1 st gear this thing should launch like a soviet missile.
 
dragonlube

dragonlube

here's a pic of the plug

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530ktm

530ktm

At your weight I wonder why you would go from a 230 down to a 125? The suggestions above would be a good start but I would have gone to a larger engine if it were me. :prof: Is the engine in stock form or has someone ported it and done things to it. If that has been done then it can take some time until that little things comes on the pipe and until then it is gutless.
 
bobkyle2

bobkyle2

My buddys that run 125's in the woods run 12/51 gearing.. And sometimes 13/51

Like others have said clean and check Carb and air filter. And if you plan on keeping the bike or a 2stroke. I'd invest in a compression tester.
 
CDA

CDA

Stock gearing on that 125 is 13/48 with a 6 speed trans. Hard to tell from your avatar, but looks like an after market pipe is installed so it should pull this gearing fine. This 125 tips the scales at around 196lbs and wants a small light rider so you will need to keep the Revs up all the time to get this bike to go anywhere.

But like any bike that you buy used, drain all fluids and replenish with new, replace spark plug with new, clean carb including all jets, clean or replace air filter, Remove top end and inspect piston and rings and possibly the power valves and clean them and never, I mean never forget to grease the valve stem bearings....I can't tell you how many people forget to do this simple maintenance procedure....
 
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