Ybr 125 valve clearances adjustment?

[tom_m]

Hi,
i have a 2012 ybr 125 and in the last 14 months i have done most of the servicing myself; chain/sprockets, brake pads, brake shoes, brake bleeding, spark plug, oil changes, air filter etc...

However i have never touched the valve clearances as ive always had it done by a mechanic, but after having a look at _Iain_'s 'how to do' guide on his ybr - https://www.bikechatforums.com/viewtopic.php?t=240845 , i think i may have a go for myself. Just bought a set of feeler gauges off fleebay.

Is it an easy/straightforward process, and is there anything else i need to know?
____________________
Current: 2005 Kawasaki Er-5 C5P
Past: 2012 Yamaha Ybr 125, 2004 Yamaha Neos 50, 1994 Suzuki Gn 125, 2005 Aprilia Sportcity 125, 1988 Yamaha Tzr 125
Theory: Passed... Mod 1: Passed 22/08/12 Mod 2: Passed 22/10/12

[Islander]

It's pretty straightforward. Make sure the crank and valves are in the right position, check gap with feeler gauge, if slack or tight, loosen lock nut, adjust for correct gap and tighten locknut while holding adjuster to prevent it turning. Feeler gauge blade should be a sliding fit in the gap neither gripped tight nor loose.

[YBR Ric]

To be honest, that's far too involved for a simple valve check.
You only need to remove the inspection caps with a 24mm ring spanner and with the bike in top gear rock the engine into place so both valves are at the loose point and ready for adjustment.
As the wheel is rotated you'll see the valves open and close and just rock it to set the midway point. The engine should come to stop on the compression stroke anyway so you're halfway there!
If you don't feel confident enough to know everything is in the correct position, then remove the smaller inspection cap on the left hand engine case as a confirmation that you're in the ball park.


I prefer to use three imperial gauges to check/set the clearance gaps - 0.002", 0.003" & 0.004"

For the inlet, 4 is fine, 5 is loose, 3 is tight.

For the exhaust, 5 is fine, 6 is loose, 4 is tight.


Once the engine has racked up a few miles, adjustment will be a rare occurrence unless something is going drastically wrong.
My engine hasn't needed the clearance adjusting for over 10,000miles