My yam ybr 125 will not rev out fully. in top gear at 50 mph 7000 revs that's it . the spark plug looks lean more white ish .but all setting are to the manual .thanks

ollie reece-jones

• 1167 Answers

SOURCE: WILL NOT REV

hi mate it sounds mechanical side instead of electrical have you changed the air filter or cleaned it also check to make sure the oil and petrol are being mixed correctly and check the air screw on the carb is the right amount off turns out if its incorrect it will either be to rich or to lean it normally says the amount of turns in the manual also check to make sure the jets are clear and the reed valve is closing propally many thanks

Posted on Apr 03, 2009

Graeme Ross

• 1512 Answers

SOURCE: yamaha ybr 125 top speed

Hi les
Not much to start with here unfortunatly mate. A free flow muffler will help top end speed, change the factory airbox to a K&N style pod air filter, other than that, hugging the tank at top speed :) If you do change these parts, you may also need to increase the main jet size to richen up the mixture for better tuning of the motor with the better flowing parts. This bike has a top speed of 100kmp and produces 10 hp, so you may only expect to get at best less than 1 extra neddy, and perhaps another 5 km/hr.... I suggest upgrading to a bigger machine of you feel the need for speed :)
If its 125's you are into, test drive a Honda CBR 125R 6 speed fuel injected 13.4 horsepower, and good for 120km/hr
regards robotek

Posted on Jul 10, 2009

Wayne Thomas

• 301 Answers

SOURCE: iv just bought a tzr 125 belgarda its smokes like

There are two places where gearbox oil can leak into the combustion process: from the gasket between the two engine case halves, or from the crank seal on the right hand end of the crankshaft. The most likely culprit is the crankshaft seal.

Posted on Nov 15, 2009

SOURCE: yamaha xt 600e 1995. won't rev above 4000 under

sounds like it may be running out of gas under aload it might be carb trouble

Posted on Jul 29, 2010

SOURCE: 2008 Yamaha YBR 125 Custom. Does

I would start with pulling the carbs, and cleaning the jets. run a wire from a wire blush , so you dont damage them, thru them, with some carb cleaner. should be fine after that. pull the jets and clean then, dont just spray carb cleaner thru them.

Posted on Mar 14, 2011