Faulty start problem of cold engine

I have been riding a 2006 Yamaha R1. It never had an engine problem for 12 years.

The R1 developed cold start problem around middle of March 2018. The symtom is when the engine is cold in ambient temperature, it fails to start the engine with own battery.  Jump start using a big car battery is required.  Once the engine starts, run about 10 to 15 minutes at idle, ignition is fine.

The mechanic at the bike shop told me replacement of three year old battery would fix it. So I replaced the old battery with new one. But new battery failed to start the engine also. Every time I went to a tour, I did jump start the R1 and have managed bike riding.

If the battery voltage is low, charging voltage drops below 14 V on the battery terminals.  The mechanic seemed not to understand it and suggested to replace the regulator. I could do that if the engine went dead while I was riding.  Genuine regulator from Yamaha is 340,000 KRW which is not cheap!

I asked to the mechanic what if new regulator wouldn’t fix the problem. His answer was to replace the generator next, which would cost probably over 400,000 KRW. In my head ‘then what’s next?’ I’ve known the mechanic for six years and did not want to develop bad relationship.

Few days ago I brought the R1 to a local bike center which a rider fixed his bike. The shop was small and owner has worked as a mechanic over three decades. We discussed about possible cause of the ignition problem of cold engine.

  • Valve clearance is out of the specification
  • Faulty starter motor
  • Faulty relay of starter motor
  • Generator or regulator unlikely

The mechanic suspected the starter motor and he would replace it with new one.   New starter motor and replacement of the starter motor relay fixed the cold ignition problem. The day before yesterday I went to the shop and picked up the R1. The mileage was 43,530 km.

I disassembled it to look inside. The inside was covered with black liquid. There was a broken piece of magnet.







About janpenguin

Email: k2.mountain [at] gmail [dot] com Every content on the blog is made by Free and Open Source Software in GNU/Linux.
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