yamaha sr125 losing power without notice. HELP please!!

[Guest]

I have a yamaha sr125, 1992 model i think The problem is that it just loses power without any notice and no matter how much i open the throttle, it will just not go any faster than 40/45 mph and acceleration becomes unbearably slow. The power loss will usually clear up after about a mile or after a LOT of revs which cant do it much good. I have already cleaned out the carburettor and fuel tank but the problem is still there. Please help me someone, it absolutely drives me crazy!!

Thanks, Max

[Guest]

say hello in newbies.. and add you location to your profile, TY.

hello and welcome..

fuel issue, have you trapped the fuel pipe, or the vacuum pipe... i take it you have plenty of fresh fuel.. otherwise it could be low fuel and/or picking up crud of the bottom of the tank..

[Guest]

thanks for your quick reply, much appreciated . I have checked the fuel and vacuum pipes already and they are fine. I'm guessing the problem must be the crud in the tank as i poured all the fuel out today and filtered it and just put it back in. I probably should have washed the whole tank out with a load of petrol. I then filled it up and took it for a ride so i'll have to wait till i've used all that again to wash it out i guess. Thanks again

[Guest]

you could always fit a clear in line filter, stops the crud getting into the carbs..

[Guest akey]

you say the power loss clears after a mile or so, is this happening the first mile or so of your journey?

If so I would suggest that the bike is still cold, and to let it warm up a bit more before trying to get max power out of it.

[Guest]

well the power loss just sort of randomly happens. It sometimes loses power after even about an hours riding so i'm guessing thats not the source of the problem. I'll try swilling out the tank with petrol and i'll also try and get hold of one of these filters. Thanks again

[matty6660]

I had kinda that same problem as this. Try letting the bike fully warm up before riding, like 5-10 mins or so. Also, putting fresh oil and water in it because this will help it to get around the bike quicker. Other than that, I'm not sure.

[asharin]

I had kinda that same problem as this. Try letting the bike fully warm up before riding, like 5-10 mins or so. Also, putting fresh oil and water in it because this will help it to get around the bike quicker. Other than that, I'm not sure.

SR125 is air cooled, putting water in might not be the best thing to do!!

[uktriggersm50]

spark plug ?

[Guest]

ive checked the spark plug, thats all fine and i washed the whole tank out with a loada petrol yesterday and its STILL doing it i then rang up a motorbike secialist and he reckons it could be the ignition coil? would this be a sympton of a failed coil or not?

[matty6660]

I had kinda that same problem as this. Try letting the bike fully warm up before riding, like 5-10 mins or so. Also, putting fresh oil and water in it because this will help it to get around the bike quicker. Other than that, I'm not sure.

SR125 is air cooled, putting water in might not be the best thing to do!!

 

Oh yeah didn't know it was air cooled.

[uktriggersm50]

if its easy to remove and put back on then find someone near to where you live and then try it on theres thats what i do with my bike only problem is when you thought you found out whats wrong and test it and it works you get annoyed lol but just check at a local breakers unless they are cheap then buy new:)

[Bogof]

The power loss will usually clear up after about a mile or after a LOT of revs which cant do it much good.

 

either i'm missing something, or this could be clutch slip? lots of revs but no power?

[Guest]

The power loss will usually clear up after about a mile or after a LOT of revs which cant do it much good.

 

either i'm missing something, or this could be clutch slip? lots of revs but no power?

or the revs are clearing the crud out of the carbs.. basically flushing the system by forcing fuel through it..

[asharin]

Thinking about it I had a similar problem a while back, but not sure what fixed it as I did a whole load of stuff to the bike (also a Yamaha SR125) at once.

I cleaned the air filter, bought a new spark plug (old one looked fine but it's age was unknown so I figured I would replace it iridium plug now, not sure it makes much difference) changed the engine oil, pulled out and cleaned all the electrical connectors (and replaced!) redid a few dodgy looking connections as the wiring was very tatty.

Runs much better now, and only seems to bog down a little when it's cold The engine and carbs could do with a good clean and service, but that can wait til Feb/March when I have no council tax to pay and therefore have some spare cash.

The only other thing that needs to be done is replace the battery, it doesn't hold charge so well anymore, but then, I have no idea on it's age. It's a genuine Yamaha part so could well be as old as the bike (13 years) unlikely, but possible. I don't fancy bump starting my bike all winter, the last 2 mornings was bad enough