Yam SR125 pinking!

Feasty · World Chat Champion Joined: 01 Nov 2006 Karma :

Hey all

my bike has been misfiring/popping for a while now, recently I've worked out it's only under stress when this happens. Accelerating, higher speeds etc.
I've filled up with a full tank of Esso Supreme plus additive and since, whilst I ride gently without harsh acceleration, the bike is smooth as anything. Especially since topping up the transmission oil! I've also noticed a bit of black spitting from the exhaust that wasn't there previously...
However, the minute I push the bike - reaching speeds of 50+ or accelerating highly, it misses and pops. Which leads me to saying the bike is definitely pinking.
My next idea is to fill up with normal unleaded and see what happens for the next few days. I have just bought a new chain and rear drum shoes which I'll be fitting over the weekend...

If it still misses and pops after all this I'm thinking of adding some Redex - in particular to the carb. I've heard spraying a fine mist of this directly into the air intake for the carb while idling can work wonders - I'll be asking round a bit more before doing this though!

Anyone any ideas what else I could do, or thoughts on what I'm thinking of doing?

All much appreciated!! Thumbs Up

Blau Zedong · Banned Joined: 26 Jun 2006 Karma :

Strip the carb and clean all the internals untill they are surgically clean.
____________________
18:54:48 Rob Fzs: jews don't give away stuff for free

18:54:59 Rob Fzs: unless its their clothes/ hair/ golden teeth

Feasty · World Chat Champion Joined: 01 Nov 2006 Karma :

Paddy Blake · World Chat Champion Joined: 29 Jun 2006 Karma :

Check the air filter

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

How old an SR125? Does it have a points ignition? Have you or anyone else attempted to 'tune' the engine to get more speed out of it?

Definately pinking and not a misfire or piston slap?

Do a plug chop at full chat and report back on the colour of the sparkplug electrode. (Put a plug spanner in your pocket, take the engine up to temperature, go for a blast at full throttle then pull the clutch in, kill the engine and come to a stop using the brakes. Whip the sparkplug out and inspect the electrode.)

Feasty · World Chat Champion Joined: 01 Nov 2006 Karma :

Thanks for all the ideas, I checked the air filter the other day and it's all nice and clean. The bike is 12 years old but I don't believe it has points ignition and I haven't touched anything to try tuning for more speed etc.
The weird thing is, last night I filled up with Jet Unleaded (not the super stuff) and the bike has been brilliant since! Last night went for a longer ride home and again later on, no problems - even got it to touch 60mph! (With my weight that is impressive lol). And again this morning, no missing/popping or anything!

I've never known different petrols to make that much difference before though I have heard some people mention it from time to time. Thing is, I'm not sure what the science is behind the improvement - any ideas?

Razz

element · World Chat Champion Joined: 23 Jan 2006 Karma :

doesnt the higher octane stuff combust at higher temp? Anyhow an sr125 wont be tuned to run on it!

Stick to the normal unleaded Wink

____________________
04' DT125RE (run-a-bout) // 89' DT125R (rebuilt + supermoto conversion)
SPARES FOR SALE. 2RK TZR // 82 DR125 // DT125R/E .... PM ME...

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

You wont do any harm using high octane fuel. In fact, small bikes sometimes return a sufficiently increased mpg to actually justify the cost of it.

I reckon you had some water in the bottom of the float bowls and the 'pinking' you were hearing was actually the engine misfiring.