Trouble with Valve Clearances

**klous-1** · #1 20th April 2009

Hi guys,

I have adjusted the valve clearances on my YBR 125 (EFI), and now have problems.

If I set the inlet valve to within tolerances, when cold it seems to run rich, any opening of the throttle and the engine splutters and dies. It ticks over slow, but adjusting the idle screw doesn't help matters.

So I have to increase the valve clearance, but of course get a horrible loud tapping/clicking. Runs OK, but still doesn't start great, power and repsonse seems ok, but worried about ruining the engine on this long trip.

I'm in Kenya, wondering if it is a coincidence that just before the adjustments I filled up with fuel, so maybe bad fuel?

Should I use two feeler gauges and set both valves at the same time?

Or some ideas?? Would be greatly appreciated.

Have taken it to Yamaha dealer here too, who checked the valves, which were ok he said (but he wasn't the greatest mechanic), by which time the engine was warm anyway of course and so started ok.

Stumped. Should have left well enough alone!

Thanks,
Nick

***Touring Ted*** · #2 20th April 2009

How was the bike running before you started playing with the valves ???

Why did you adjust them ??

Seeing as you have adjusted them (and maybe incorrectly), you really have to get this right first.

You need to leave the bike for at least 8 hours to cool properly (in the shade in Africa I guess)..

Get the correct clearance for your bike and be CERTAIN you have the correct timing mark set on the crank. (usually a T) and that the piston is at the top of the bore (Top dead centre) at the same time. Poke a long screwdriver down the plug hole to check...

You set one valve at a time !!

I'm guessing your bike is a 4 valve SOHC 4-stroke ??

If you havn't got any good feeler gauges, you cant do it PERIOD !!

**Kennichi** · #3 20th April 2009

Ha just thank yourself lucky you aren't Sjaak Lucassen , his Yamaha R1 has 5 valves per cylinder and its an inline 4. And as if to add insult to injury it uses bucket shimmed valves which mean the cam shaft has to come out.

But let the engine cool down 24 hours at least , one at a time and check it is at TDC by using a soft piece of wood like a chopstick...

I'd probably change the jet to make it very slightly leaner if it runs super rich or just let the bike warm up a bit before going riding anywhere.

**klous-1** · #4 4th May 2009

OK, bought some new feeler gauges and tried again, being a bit more gentle on the adjustments, seems to have sorted it and running pretty good....poor fuel doesn't help of course but it is running sweet now!

Thansk VERY much for taking time to answer, really appreciated, was getting in a bit of a flap there!

Nick

***Touring Ted*** · #5 4th May 2009

Glad its sorted out..

Safe riding fella

Ted