Starter speed

[jforgo]

Ok , this morning I pulled my 1980 RT out of garage. It was about 35 degrees. Turned on gas, let it flow into bowls . Set choke. When I hit the starter button, it cranked pretty slowly - did that a couple of times. Then I decided to stay on starter, it began to go faster, gave it a bit of throttle, and it fired right up.

I suppose I was expecting instant fire up - like a couple weeks ago when the mornings were 25 degrees warmer. My question here, is, why does the starter run so slow - then speed up as I continue to run it? Is this even an issue that requires action?

[20774]

35 degrees...slow starter...I don't think this is an issue. It can obviously go too slow to the point that it won't start. As long as it starts, within a reasonable number of seconds, I wouldn't worry about.

At that temperature, everything is cold and drags...the transmission fluid, the battery is not as powerful as it would be at higher temps, there may be grit in the starter motor that adds to the drag. Your situation sounds normal...

[jforgo]

I understand the thicker lubricants at lower temperatures. But why does the starter run slow, and then speed up, with the same cold sluggish lubricants? What is the dynamic here?

[Guenther]

In my R100GS/88 this was the start of a problem with the Valeo starter. At that time I wasn't smart enough to find the replacement bushings so I ended up with a new one and kawoom...a rocket start again.

Btw. does it turn faster with the clutch pulled (so no cranking of the transmission in-shaft)?

/Guenther

[Yarddog]

If you don't already do so, keep your scooter hooked up to a battery tender... something that will trickle charge only as required...I keep both of mine hooked up, all year long, and not only will this prolong the life of the battery, but they'll always have a hot battery...

[AnnapolisAirhead]

I understand the thicker lubricants at lower temperatures. But why does the starter run slow, and then speed up, with the same cold sluggish lubricants? What is the dynamic here?

You could also have a starter Bendix that is dirty and sticky and/or dirty connections either outside or inside the solenoid. Not a huge deal to clean and rebuild, but set aside a Saturday. Greg Bender has an excellent site that walks you through it. I've rebuilt 3 so far heeding his advice:

http://www.thisoldtractor.com/gtbender/print/print_loopframe_electrical_starter_and_solenoid_re pair_-bosch-.htm

[AnnapolisAirhead]

Btw. does it turn faster with the clutch pulled (so no cranking of the transmission in-shaft)?

I think so at least on lightened flywheel models ('81 and newer). On the old, heavy fly wheel bikes I don't think so. In fact, if I pulled the clutch in on my '72 /5, the starter didn't always engage 100%. I thought it was the battery, until a friend asked why I was holding in the clutch during a start. Once I stopped, all was right in the world. Go figure.

[rinty]

..why does the starter turn so slow...jforgo

According to Joe Minton's seminal article on boxers: "Black Tie Boxer", airheads pump about twice as much oil as ordinary motorcycles. So my theory has always been that it is the pumping losses caused by cold oil, that result in the low starting rpm's.

Just for fun, put a jar of 20W - 50 outside for a cold night and see what it does in the morning. :D

I put an AGM battery in my previous boxer, and there was a dramatic difference in starting rpm.

[PGlaves]

I understand the thicker lubricants at lower temperatures. But why does the starter run slow, and then speed up, with the same cold sluggish lubricants? What is the dynamic here?

The battery has greater capability at warmer temperatures. Like at 0 degrees only 1/2 what it has at 80 degrees, or some similar number. I can't find that chart offhand.

But as you start to crank the battery warms up internally increasing its ability to crank even faster than you are discharging the battery - for a short period of time at least.

Note - I am not saying the longer you crank the better it is. Output goes up initially as it warms but then drops of as the battery discharges.