[NiInJa]

Team,

I have a ten year old Yamaha R15 which for the last 3 years have been used very sparingly for various reasons. I do activities like cleaning air filter, replacing oil filter and engine oil all myself since she is hardly ridden more than 2000 kms in the last 3 years (Total odo reads ~26000 km )

The bike has no problem at all except one big issue which has started cropping up in the last two years, and now its become a bit chronic.

Summary of Problem: There is arcing near spark plug with engine block at low rpms and it re-occurs even after changing : the battery, Spark Plug Cap, Spark Plug. The issue would crop after a few months earlier, but with recent change in Spark plug and Cap, it re-occured within a few days. The arcing starts only after the engine becomes hot and is idling. Does not occur at mid or higher rpms.

Details:

The bike starts fine irrespective of outside temperature, but when it gets warm enough it stutters once in a while, as if fuel was cut or spark didn't occur, in some cases it will stall. Initially I thought it was bad fuel or bad fuel tank as the bike was kept idle for long intervals, so got the tank cleaned from local garage, the pump too wasn't an issue, I regularly use Fuel Injector cleaner too and that has worked some times with the stuttering. However, this time, it did not solve the issue, then I changed the battery and the issue went away for some months. After a break of monsoon, I took the bike out after two months, the bike started normally and after a few kilometers started stuttering again. I started hearing a 'tik-tik-tik' sound near the engine and then I realized that its the spark that is escaping through the engine block which causes this misfire and stall. Got the spark plug cap changed immediately, then no problems for few months. Just to check, I warmed up my bike late night and saw that there was still some mild arcing, but it wasn't a problem. Then kept the bike for a two months as I had to travel for work, came back, charged the battery at home and started the bike, again no issues till it was warm. This time the spark plug cap had completely dried and it came off like peeling a cake. Got the spark plug and cap changed and rode the bike again, everything worked like charm and I was wondering that maybe spark plug would be the main reason. Then, just after a week of changing the spark plug and cap, the issue re-occured and the bike stuttered and stalled at low rpm. I haven't taken it out now for almost two months again as I am not finding time to repair it with my small kid around and office commitments. Plus, since my wife is on a break, I use her scooter for everything these days. I just cranked it today and she started without a fuss, but I am sure after a few kilometers she is going to stall.

Want to understand if anyone has faced such problem and what would be the solution. I am not willing to take the bike to Yamaha authorized service center just yet as I am sure they will recommend changing the whole wiring, alternator and everything that can be changed without diagnosing the issue considering my bike is 10 years old and haven't been ridden much.

Note: Despite the stuttering, the bike does not feel sluggish or slow to respond at any speeds, the only difference I can feel is the NVH levels change when I change the spark plug, it might be psychological or just that the engine runs efficiently. Also, the old NGK spark plug was not deformed/damaged or there was no carbon deposit, it was fairly dry with maybe just a slight increase in gap. The outer shell did have some marks showing it has been arcing for quite some time. Replaced Spark plug is of Bosch with same specifications.

[adrian]

Originally Posted by NiInJa

Team,

Summary of Problem: There is arcing near spark plug with engine block at low rpms and it re-occurs even after changing : the battery, Spark Plug Cap, Spark Plug. The issue would crop after a few months earlier, but with recent change in Spark plug and Cap, it re-occured within a few days. The arcing starts only after the engine becomes hot and is idling. Does not occur at mid or higher rpms.

Have you tried replacing the wires from the HT coil to the spark plugs ?

https://www.youtube.com/watch?v=4_EFGAFxi1w

[VijayAnand1]

Arcing happens when there is a crack in the conductor material, i.e spark plug cap, HT coil wire. This happens when the bike is old and the wire becomes brittle and develops minute cracks that aren't visible to the eye, but leak electricity causing arcing. Now that you've changed your spark plug, boot cap, it's time to replace the wire actually emanating from the HT coil to the spark plug.

Remove the HT coil along with the wire and boot, replace the HT coil going to the spark plug cap and use a heat shrink type insulator boot over the HT coil wire, easily available at local hardware shop, and it should solve the issue, at least from what I infer from your post. Strongly strongly recommend you check the wire from the HT coil to the spark plug.

Cheers!
VJ

[NiInJa]

Originally Posted by VijayAnand1

Strongly strongly recommend you check the wire from the HT coil to the spark plug.

Cheers!
VJ

Thanks for your valuable input, I will definitely get the wire changed. Is this something I can do by myself ?

But one question still perplexes me as to why does this start only when the bike heats up a little ? I just took her out today for a short ride and she behaved perfectly fine when started up, just when I was about to park her after my ride, I could hear small sparking sound again, she didn't stall though . (This is different from the tik tik sound that comes from exhaust due to metal expansion)

[ashwinprakas]

Originally Posted by NiInJa

Thanks for your valuable input, I will definitely get the wire changed. Is this something I can do by myself ?

Yeah, would take you a few minutes at best.

Twist and Pull Out for removal, Push and Twist for installation.

Ideally it's best to change HT cable along with the cap, dont bother if already changed, personally for me it's a mental block, if one is changed then the other HAS to be changed.

If by chance your HT Cable is permanently attached to the HT Coil then change the HT Coil as well, dont think twice, these things cost pennies to even consider diagnosis.

Heating does tend to cause electricals to act up, same goes for the Pulsar Coil, when they go for a toss they may run fine when the motorcycle is cold and start to act up when it gets hot.

Regards,
A.P.

[VijayAnand1]

Originally Posted by NiInJa

Thanks for your valuable input, I will definitely get the wire changed. Is this something I can do by myself ?

But one question still perplexes me as to why does this start only when the bike heats up a little ? I just took her out today for a short ride and she behaved perfectly fine when started up, just when I was about to park her after my ride, I could hear small sparking sound again, she didn't stall though . (This is different from the tik tik sound that comes from exhaust due to metal expansion)

Yeah, once things heat up, cracks expand and eventually things start acting weird. You can change it yourself, all it takes is to remove the fuel tank as the ignition coil is directly underneath the tank. Removing the tank is as easy as removing four allen bolts of the tank, and you have access underneath.

Then you can remove the side panel, remove the spark plug, cap and stuff. Just an hour's worth job, or if you feel a little boring, a local mechanic can do it for you.

Cheers!
VJ