Scorpa 125 with Yamaha engine questions

[halfway]

Hi, got an unknown age 125 4 stroke with a yamaha engine, monoshock. Trying to find out some servicing info or links to manuals for these, engine oil, brake fluid, carb settings etc. 

It does have quite a loud ticking from the top end, which comes and goes a bit but is there right through the rev range. It runs ok except a bit hesitant at low rpm. Any obvious problems with these engines that would give the ticking?

 

[konrad]

Regarding ticking, have you checked the valve clearance?

Regarding low-rpm hesitation...

[halfway]

Valve clearance and cam chain were going to be my first checks in a couple of days, hopefully just the valves not adjusted to spec. Any ideas what spec should be?

[konrad]

TT-R125 manuals are available online.

Valve clearance (cold)

IN: 0.08 ~ 0.12 mm  (0.0031 ~ 0.0047 in)
EX: 0.10 ~ 0.14 mm (0.0039 ~ 0.0055 in)

Check the cam chain tensioner too.

[Tr1AL]

@halfway www.birkettmotorsport.com - scorpa - parts books - halfway down the page. SY/TY 125F info.

Edited 19 hours ago by Tr1AL

[lemur]

Screw adjuster valve clearance tightens with wear as the valve wears into the valve seat. Valves do travel at half speed of the crank, is the ticking in time with the crank or valve train, that can help to narrow it down some times.

Your bikes parts manual shows only one spring on each valve, most have 2 springs wound in opposite direction to each other (stops the valve from rotating), I'd be looking for a damaged valve spring if it turns out to be a valve noise.