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yamaha SR125 cuatome start problems


o5otato5o
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When you bump her and have her going, does she rev ok? I've been assuming that when warm she doesn't idle but ok when running along?

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Important bits in red.

On the left hand side (nearside) of the engine there will be 2 slotted caps on the crankcase. You need to unscrew the top one to see the timing marks for tappet adjustment, the lower one to turn the crank and look through the top hole until you see the marks. Remember to turn anticlockwise.

Rotate the crankshaft anticlockwise to align the slit on the rotor with the stationary pointer on the crankcase cover. When the piston is Top Dead Center (TDC) Measure the valve clearance by using a feeler gauge.

Exhaust tappet is the one to the front of the bike near the exhaust.

Tappets (measured cold):

IN 0.05 _ 0.09 mm NOTE Millimeters not inches so check your feelers

EX 0.11 _ 0.15 mm NOTE Millimeters not inches so check your feelers

Spark plug:

NGK DR8EA 0.6 _ 0.7 mm

Carburetor:

Type Y24P

I.D. mark4WP-10

Main jet (M.J) #102

Main air jet (M.A.J) ø1.3

Jet needle (J.N) 4C9A-3/5

Needle jet (N.J) 2.600

Cut away (C.A) 2.25

Pilot outlet (P.O) 0.8

Pilot jet (P.J) #38

Bypass 1 (B.P.1) 1.0

Pilot screw (P.S) 2

Valve seat size (V.S) ø2.0

Starter jet 1 (G.S.1) #60

Starter jet 2 (G.S.2) #64

Float height (F.H) 28.5 mm

Engine idle speed1,250 to 1,350 r/min

Ignition timing:

Ignition timing (B.T.D.C.) 9 degrees at 1,300 r/min

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When you crank it over with the plug out and touching the cylinder head, is the spark a big fat blue one or a weak yellow one. I'll go down the route of the CDI (don't I always) and this is because my boys SR displayed the same symptoms. Wouldn't start on the button, but would bump start and run like shit

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Sorry, can't get to my tools in the shed right now, but looks ok to me. If she runs when blipping, says to me it's the air screw. I could be wrong, but mine was showing similar symptoms before I got the screw right. When you bump start it, you're already taking it off idle the minute the engine starts. How old is your SR and how many miles has it done?

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Sounds like low on compression,, :eusa_think: starts cold- not when hot... = valves burnt or worn rings,,

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Sounds like low on compression,, :eusa_think: starts cold- not when hot... = valves burnt or worn rings,,

Very possible John but someone has messed with the tappets - which may show the same symptoms - so that is easy to correct.

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It lives but its now.loud it was my exhaust tappet because id set it.myself.it was too tight got a freind to hold stem (adjuster) while.i tighted nut she fires but tappets are now very loud altho for some reason.lots of oil missing but no.leak anywhere??

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burning oil you mean,, :eusa_think: ,,how often are you checking level,,,doe she smoke,,,,

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No oils.fine checking it warm.like a tit she had an oil.change a few days ago i havnt had her long

Please not guys ur cam chain yensioner needs setting if it sounds.like.ur tappets are loud

SHES ALIVE!!!!

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altho for some reason.lots of oil missing but no.leak anywhere??

What did that mean then,,,, :spin2:

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