YBR 125 (2005) - Engine dies after some time for no reason

[wazka15]

Hi,
I've got a problem with my good old ybr 125. I have had this bike since it was new. Recently the engine started misbehaving. After running for some time (5-20km) the engine dies. I'm driving 70 km/h and suddenly it drops revs as if I turned the key off. I happened many times. When I start it after that I get nothing but If I wait more than 5 minutes the engine starts beautifully but when I continue driving the problem repeats more often (every 2-3km) and then i have to repeat my breaks. I thought that it may be a problem with fuel delivery and that I am running a dry carburetor but my friend told me it is probably the ignition coil overheating. Bike has done 20k km and i haven't replaced any major parts yet. Can you please help me figure out what's wrong with it?

[Rogerborg]

If it's cutting out immediately rather than struggling for a while, that sounds more like electrical, so I would suspect the coil (or the CDI or the HT cap or...)

Next time it happens, immediately shut off the fuel tap, then drain the float bowl. If it's empty, that's your problem. If not, you're on to electrical issues.
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[Jardine]

I had a very similar problem with my YBR, mine was fuel injected though so im not too sure how helpful this maybe.

I had a corroded wire coming from my ignition barrel, if you look just under the light there is a black tube which contains some wires. In there i found a wire that had just been destroyed by the lovely British weather. I'm not sure if this is the same thing you are having but i definitely wouldn't rule it out. Also, my alternator gasket was perished at one point to the point where i was loosing oil, this did a similar thing to the point where i needed to get the bike recovered to home.

Give the whole bike a look over it might be something very simple.
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CG125 1991[Sold] YBR 125 2009[SOLD] SV650s 1999-CBR600F-H 87
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[zark]

When my generator melted, the battery would flatten while riding, giving lumpy running and cutting out.
Check there's electricity coming off the white alternator wires when running... An 05 still has kick start, right? Does it start on that, or are you waiting a few mins and pressing the button to restart?
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[wazka15]

Well I don't think it's the generator. The bike used to run on flat battery. For now i changed the spark plug (didn't help) and ordered ignition coil. If the coil doesn't help i will check wiring in the whole bike.

[RhynoCZ]

Rule no. 1 = always check what you have before you go and buy spares.
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[Teflon-Mike]

Work LOGICALLY, not by voodoo, hearsay, presumption or random component replacement! Hoping to fix it. Don't think, go CHECK.
At this moment absolutely NO reason to presume your coil is faulty, so why replace it?

Start at the top, do the stuff Yamaha say you should at regular intervals, like change the oil, clean teh filters and adjust the tappet clearances....

that one, tappet clearances IS actually number one, top most favorite explanation of the symptoms you describe; gap opens up as engine gets hot, valves stop opening as wide or for as long till engine stops running... cools.. lets gap shrink... then runs again to repeat cycle.

DO a FULL and thorough BASIC SERVICE... no new parts required; o Chrystal balls need be consulted, no incantations to the gods of internal combustion need be recited... JUST follow the instructions that came with the bike when you bought it!

GOOD chance your 'problem' will just go away. If not... then a chunk load off possible problems have, at a stroke, been removed from the list of what MIGHT be wrong to go CHECK, not guess, think, presume or simply replace in hope; but CHECK, measure, inspect, test, assess! KNOW if not what's wrong, at least what definitely isn't!
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