Electrical starting problem 82 GS850G

[davidt]

Hi,

I've just bought an 1982 gs850g as a project bike. I am having trouble starting it. I bought a new battery charged it and installed it . The bike turns over a few times but wont start and the positive lead from the battery to the starter relay is really hot.Then it just wont turn over. When I first took the bike home it started straight away so I am not sure what is going on.
I have cleaned all the connections to the battery earth and positive leads.
I ended up push starting it just to give it a run.
Can someone please give me some expert advice on what to do?
Thanks

[SPARKSS]

Hi,

I've just bought an 1982 gs850g as a project bike. I am having trouble starting it. I bought a new battery charged it and installed it . The bike turns over a few times but wont start and the positive lead from the battery to the starter relay is really hot.Then it just wont turn over. When I first took the bike home it started straight away so I am not sure what is going on.
I have cleaned all the connections to the battery earth and positive leads.
I ended up push starting it just to give it a run.
Can someone please give me some expert advice on what to do?
Thanks

If JUST that wire is hot and not ALSO the wire from the relay to the starter OR THE BATTERY NEGATIVE WIRE, then replace that wire (and if it looks like it is not original, suggest you use an 8 or 6 gauge replacement with correctly installed ends). IF ALL WIRES are hot, and the bike runs normally when push started, AND the battery tests ok, then the problem is at or in the starter itself. The basic reason it won't start is that the engine is cranking too slowly AND/OR that the ignition may not have enough operating voltage during this event to fire the plugs reliably. I can help you further based on what you find above.

[SqDancerLynn1]

Most likley the brushes in the starter motor are bad

[davidt]

Thanks for your advice. I have replaced the positive lead still same problem, connectors are good. Is only positive lead into battery that is hot.

Is the starter easy to fix or are the brushes easy to replace?

[SPARKSS]

Thanks for your advice. I have replaced the positive lead still same problem, connectors are good. Is only positive lead into battery that is hot.

Is the starter easy to fix or are the brushes easy to replace?

Based on your reply, I'd want to confirm that other significant voltage drops aren't taking place in the starter circuit. Check the voltage drop from end-to-end of each of the 3 starter heavy-current cables AND across the starter relay as well (or substitute a jumper to rule this out).

Brushes.....Based on your description of one cable becoming hot (and thus replaced) the starter is drawing significant current and therefore it's unlikely that brushes are bad. What happens with brushes is that they DO wear shorter and at some point usually start to lose contact with the commutator segments (or slip rings in other devices).....once this starts heat generates due to the increasing resistance and further burns the brush which, in some cases, also may weaken the tensioning spring (pushing the brush against the commutator etc)......it goes down hill fast here - drawing LESS current and also turning slower until open circuit (no current = no cranking).

What also occurs to a starting motor is that the shaft bearings wear causing the armature (shaft) to deflect as it tries to crank the engine......this reduces torque and when very bad may cause the armature to contact the field poles mechanically binding it. This deflection also causes the brushes to push towards and away from the commutator during rotation......now throw in worn brushes and at some point what often occurs is that upon the starter motor coming to a stop, one or more brushes are bumped away and stick.....instant open circuit = no cranking. Often at this point a gentle tap with a hammer etc will bring it back to life in varying degrees (which may get you going in a pinch).

So what's your problem.......you can see that there's a few factors to consider when the results don't jump right at you.......a little more testing is required (or better guessing!).

[duaneage]

I'd say start motor brushes, I'm with Lynn.

[davidt]

When I get the chance I'm going to try to check voltage drops and then move to starter motor and check that out.

Thanks for all your advice.

I will keep you posted on my progress- which may be a little slow given work and family commitments.