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starting problems

Guest jesus joe

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hi, i have had a quick look around this forum and couldn't find anything that helped with my problem

basically, sometimes my bike will NOT start at all, i sit there using the electric start, which turns the engine over, but the engine jsut won't catch.

sometimes, the engine catches but then dies after about 3 seconds or so

sometimes, the bike starts absolutely fine first time and i ride away...

My mate's dad's a mechanic, so i took it to him one day when it actualy started, he thought it was the carburettor and had a fiddle, which hasn't really changed anything.

when i pull out the spark plug it looks fine, it is dry though - i don't know if that's a problem? it definately makes a spark though. I found that one out the painful way...

any body got any help, any ideas, any experience, anything? thanks - joe

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it's a yamaha SR125 1996. The previous owner changed the engine, carburettor, and battery from another bike, but didn't know the make of the other bike. The mileage of the bike is somewhere in the region of 55,600 but aparently the new engine etc has only done 10,000. I really don't know when all of the plugs have been changed and stuff, because I've only had it for a couple of months and I also haven't actualy had very much time to ride it.

I had a look at the battery, and the fluid level seems high enough, plus when i press the electric start I can hear the engine turning, which I have read is a sign that the battery is working (the lights, horn etc. are working as well).

I've tried starting with the choke in, the choke out, the fuel on and reserve, throttle closed, throttle open, clutch in and out, in gear, in neutral, sidestand up, sidestand down... thinking (hoping) it was just that the engine was too cold and being stubborn, I left it out in the sun for the day and that didn't do anything

checked the spark plug, fuel levels, battery, and my mate's dad done the carburettor for me, but being new to owning a bike, not to mention mechanics, that's pretty much all i understand...

Only thing i noticed was that the nut holding the spark plug in place is rusty to f*ck, which made me wonder if the problem was with the spark plug, but the plug itself is working painfully well, and the rust is only a cosmetic problem

[edit] ooh, also, there is a slight, thin bit of rust on the inside of the petrol tank if that makes any difference?

unfortunately, my mate's dad is on a rideout through Europe and won't be home untill monday, and i need my bike to move into uni halls of residence on saturday :x

hence, i've resorted to internet forums!

as some of you have said, there may be a problem with the fuel feed, how do I check the filter and fuel line, and what is the fuel vaccuum pipe coming from the engine?


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if you look at the fuel tap theres usualy 2 pipes a wider one comes from the tank and a narrow one which is the vacume pipe,take the fuel pipe off and follow it laong and the fuel filter will be inline before it reaches the carbs

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ok, I checked for the vaccuum thingymajig, and there's only one pipe coming from behing the fuel tap, which is about 4 inches long and looks like it leads into the carburettor. it does however have a small peice of crap floating in the fluid. How would i go about cleaning the crust out and how can i work out where it is coming from?

[edit] - I just had a look at the carburettor, and there is a longer, thinner tube (about 10 inches long) which isn't attached to anything - one end is attached to the carb, the other end is just hanging loose. What should be attached to the other end?

[edit again] on FURTHER inspection, there are two tubes hanging loose from the carb. in total, there are three soft tubes going into the carb - one comes from the fuel tap to the carb. one comes from the bottom, on the same side as the fuel tap, and is hanging loose. the third comes from the side of the carb, slightly higher up, on the opposite side from the other two.

where are these two mystery tubes supposed to be connected, and why would they be loose? they had been helpfully tucked away behind some sort of mudguard, and me pulling them out wasn't what disconnected them - i just used my fingers to feel where they were leading to and they came out with no resistance at all.

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