Hi guys,

I bought an SR 125 a couple of weeks ago and all was good until it began to struggle to start up. Then during a ride around town it cut out a few times, and only just managed to make it back home. Now it won't start at all.

The electrics all seem to work (lights etc) and the starter motor will crank over happily enough but it doesn't ever "catch".

Tried to troubleshoot a few basics:

• Inspected the air filter which is clean
• Changed the spark plug and checked its spark
• Took apart the carb and gave it a good clean
• Did a compression test which seemed healthy (a needle's width under 12 bar)

So now I'm very confused. Apparently I have all the ingredients for a working engine: Air, fuel, spark and compression, but no luck..

Any suggestions as to what I can check next would be much appreciated!

Graham

Hi Graham, so how do you know you have the fuel ingredient...is the plug getting wet with fuel?

Taking apart the fuel doesnt mean It's getting in the cylinder if theres something wrong with the supply,,,Filters...Fuel tap etc

Hi,

You're right, it was a bit of an assumption that the fuel is actually getting into the engine.

The plug does seem to be dry. There is a slight fuel smell coming from somewhere, but not the plug.

I checked the fuel tap - seems ok since the carb bowl is filling up and fuel comes out when I turn the drain screw.

I'm fairly sure I put the carb back together ok, I set the mixture screw at the bottom 2 turns out. There are a couple of electrical connectors on the side that I'm not sure what they are for?

Is it worth just replacing the carb altogether? There's one on ebay at the moment, but from a '93. Not sure if they are compatible?

try squirting a bit of petrol down the plughole, see if she catches

maybe try a bumpstart too...it should be easy enough on that bike?

edit...I'm not familiar with the haves and have not's of every bike of course...is this one elec start only?

SRs are electric start only .

i would suggest that you manually tip a couple of teaspoons of petrol down the plug'ole and see if it will catch that way, if it does then that indicates me a fault in the inlet tract.

also, make sure your choke lever is fully out, most of the ones i have seen do not have the retaining function and so need to be constantly held out until the engine is warm.

OK then, elec start only...It may benefit from a bump after squirting in a little fuel (10cc) or charge the battery fully and try the button

I had a similar issue on a long run recently in that whenever I stopped at junctions etc, if I didn't keep the revs up, she would stall. I adjusted the idle / throttle stop clockwise about 1/8 turn and touch wood she's been fine since. Having said that, the other guys on here know a lot more than me!!

Is the petrol cap clean and letting the tank breathe? If there's a vacuum it can hinder fuel getting through.

Ok, good news!

The fuel down the plug hole helped and she's started, albeit reluctantly with a bit of help from the throttle (choke didn't seem to do much), so possibly not getting enough air.

After it has warmed, the idle is a bit erratic, so i suspect I have a vacuum leak somewhere, and looks like the exhaust manifold is blowing a bit too.

But at least it's not cutting out and starting a lot easier when warm, so that's something.

yeah you should do a good job with sorting out the exhaust next as it may contribute to the problem

I have a 1991 sr125, has good consistent spark, new carb which I cleaned out etc, it runs but it does not sound healthy, sounds very tappety or something, checked timing and its absolutely spot on, it does rev but i shut it off quickly due to noise, any ideas what I could be? I am stumped with this one. Cheers, Matt.

https://youtube.com/shorts/S7jwJtyIAtw?si=huL1ZtzBqrXCuuku

Hi there Matt,

Resurrecting a 10 year old thread is not seen as good forum behaviour , You really should consider starting a new thread for your problem even if it does relate to the same machine.

I suggest commencing a new thread and one of the mods can delete these posts and lock this 10 year post as it never got resolved anyway.

We call it Thread Necromancy: raising the dead! lol
Maybe we should sit down some time and look at all the old, still open, threads...