Why does my starter slow down?

If it's broken or just needs tweaked

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DammitDan
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Why does my starter slow down?

Postby DammitDan » Tue Jul 18, 2006 10:49 pm

1982 CB650 std with an '82SC engine.

I've noticed (more like feared) a peculiar phenomenon when my bike gets nice and warm after a long-ish ride. If I stop somewhere for a few minutes and cut the engine (like at a gas station), when I try to start it again the starter acts like it's "tired" and just Whirrr.. whirrrrr...... whirrrrrr's like the battery is dying. However, if I hit the starter with the throttle slightly open it will turn over instantaneously. I don't think it's the battery going cause it runs plenty strong after it turns over and I keep her charged and maintained correctly. And if I let the bike cool down for an hour or so the starter will spin the engine and turn it over effortlessly.

I've got an extra starter at home, and I know they can go bad, but why does mine only go bad when the engine is hot? I initially thought the damn thing was getting hot enough to slightly sieze (making the starter have to work very very hard), but then I found that I could turn the engine while in gear by hand with the rear tire.

What could my problem be? And why the hell didn't they give 650s kickstarters?!

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Chris
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Postby Chris » Tue Jul 18, 2006 10:57 pm

Hey, funny you should mention that! Mine does the exact same thing. Maybe there's pressure in one of the cylinders causing it to crank harder? I dunno, just guessing. I never tried cracking the throttle when it does it. I just let it crank and it fires after 2 or 3 "whirrs". :)
1980 CB650c

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Ibsen
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Postby Ibsen » Wed Jul 19, 2006 12:39 am

This is not uncommon. There are a couple of reasons why this happens. One is that the compression is rising when the engine is hot. Another is that heat will increase the resistance inside the windings in the starter and the current will be slowed down, pluss the metal in the starter will expand, causing more friction. Also dirt inside the starter can be a third cause.

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Volker_P
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Re: Why does my starter slow down?

Postby Volker_P » Wed Jul 19, 2006 1:24 am

When the battery gets weaker, hot starting may become difficult first although the starter is cranking fastly for a long time when it is cold. Cleaning all connectors and the starter itself from black stuff inside may help, but usually your CB wants to tell you this way that you should start to save some money for a new battery next year. :P
Opening the trottle maybe reduces a bit of the sucking load of one cylinder thast falls together with the compression of another cylinder.
When it gets worse, you may use second gear and clutch to start. When it is flat and your legs are long enough, you can stay on the seat for that. Two or three steps should be enough. I did this sometimes to stretch the investment on a new battery to next spring. :wink:

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kbailey
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Postby kbailey » Wed Jul 19, 2006 1:43 pm

My own experiences are similar. I found that the brushes in the starter had disintegrated into dust. there are 4 brushes inside and one of them was GONE meaning I was working on only half a starter. It would start OK cold but never hot. it finally failed completely when a second brush was destroyed and the starter didn't work at all. I just replaced it with one I got on ebay for about $50. you can have them rebuilt for about $80. I don't have a good reason for why the throttle position matters at all. I'll be interested to hear about it when you get it figured out.


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