The reasons motorcycles can be (very) hard to start - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 1 (permalink) Old 08-14-2019, 04:33 PM Thread Starter
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The reasons motorcycles can be (very) hard to start

Many riders wonder if their bike maker cheaped out on the starting circuit of their bike. It can certainly seem that way when the bikes are hard to start (often from new).

But the circuits are properly engineered for the anticipated electrical loads. But those calculations are based on Ohm's Law which does not take into account any adverse conditions which would impact the flow of the electricity.

So, if the starting circuit was set up in a lab, things would be fine. But put that same circuit on a motorcycle with its high vibration, high engine temp and (normally) intermittent use (not everyone gets to ride every day) and you have the recipe for ongoing problems.

Here are the 11 main reasons that most motorcycles are hard to start (we define hard to start as taking more than 1 second to start-up and/or taking multiple attempts to start).

1) battery is old, holds markedly less than 100% charge
2) battery is new but somewhat discharged
3) ambient temp is low, battery power is diminished, oil is thick
4) connections from sensors to ECU are old and now sub-optimal, so tune of the bike at startup is not optimum
5) starter motor is underpowered for engine size
6) starter motor is worn and draws excess current
7) sprag clutch is worn and dragging, causing the starter motor to draw excess current
8) intermediate gear is worn and binding on its shaft causing the starter motor to draw excess current

9) portions of the starting circuit are made of lower-cost metals which flow much less current than copper; steel (10% flow), brass (25% flow), tin (10% flow)

10) sections of the starting circuit are close to the hot engine or exhaust pipes, and the resistance in copper has increased

11) wire size in the starting circuit is under-engineered for a very hot and high vibration environment which results in inadequate current flow at all times

12) copper used in the starting circuit is work-hardened due to disruptions in the lattice (from constant wide-range vibrations traveling through the metal), and the metal now flows less current than required

9, 10, 11 and 12 are the possible causes of poor starting, - which the HICAP•SCDC 100% overcomes.

Overcoming those 4 issues adds enough capability to the starting circuit for the rest of the 8 issues to be moot.

Based on our years of experience of selling many thousands of HICAP•SCDC kits to riders in over 60 countries;

in over 99.75% of the cases of slow starting motorcycles,

overcoming those four issues enables the bikes to start up in 1 second or less - hot or cold.

On bikes that have problems with the engine dying at stops, that no longer happens.

On a sunny day with the bike sitting in the sun at 77 degrees, you will have the best starting because

the engine is not cold, and it is warm
oil is not thick as it too is warm
the battery is at standard temp and voltage capability, and battery specs are measured at 77 F
resistance in circuit wiring is not increased due to heat (added resistance can degrade current flow by up to 39% when copper is hot).

If your bike is difficult to start (taking more than 1 second to start or multiple attempts) our HICAP•SCDC kit will cure the problems.

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