Starter motor drawing too much current !!!

[justaddmonkeys]

Hi all,
i have a basket-case '83 GS650 Katana i am trying to get running and have no spark at all. With the help of Bikecliff and other helpful posts i am now at a point where i can get the starter motor turning over the engine nicely but i seems to take all the voltage from the coils when it does so. i can measure 12.36 v on both sides of coil with ignition switch on, but as soon a i hit the starter button, it drops down to 8 volts approx. i have cleaned all the earth connections, motor to battery etc. but not sure what to do next...

presumeably remove starter and disassemble, but what exactly am i looking for in this case ? am i on right track or is this voltage drop a sign of another problem altogether ?

For background info, i have not got rectifier hooked up as i am only trying to get spark, the whole charging side with be another struggle i'm guessing. New battery and new solenoid, even borrowed a second-hand cdi before finding the problem more likely to be starter. i have taken a while to realise this as i am not good with electircal and as the starter turned the engine over, i had figured it was fine and tried other things...

thanks in advance for any pointers,
mike

[BassCliff]

Greetings and Salutations!!

Hi Mr. justaddmonkeys,

Welcome. I'll offer a few thoughts.

After you clean the solenoid connections, the ground connection to the engine, the fuse box connections, the ignition switch connections, and every other electrical connection you can find on the entire wiring harness, you can try the "coil relay mod" to ensure that you get a full 12v to the coils when starting. You might have a weak starter (clean it up and install new brushes?) or dragging starter clutch. Are you sure you have a good, fully charged battery? If the battery is old and worn out it won't hold a charge well. Have you changed the oil and checked the valve clearances? Compression check? There's lots more info below, but first let me say "HOoooowwDY!"

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[justaddmonkeys]

thanks for lightning fast response

yes, brand new battery and it "starts" fully charged but looses charge quite quickly. i just removed the starter and tried to disassembly but need a impact screwdriver... foiled at first hurdle. can remove one screw but not the other. wd40 and returned to computer for solace. this bike is a "barn find" and so i am at the start of a very long journey. i have compression but no spark. i will try all your suggestions of cleaning connections, and then do the 'relay mod' if that is the correct action to take. i really just wanted to validate i am on track and not "barking up the wrong tree" so to speak.

[reddirtrider]

If the starter is turning over the bike and not overheating, it's probably OK. They draw a lot of current, and if your bike isn't staying fully charged, then you've got problems elsewhere. I suggest you do an investigation of the charging circuit.

[Steve]

Try connecting your battery to a car battery (engine NOT running, if it's in a car) and try your voltage drop test again. If it still drops a lot, your starter needs some work. If it does NOT drop much, your 'new' battery needs to be replaced. Before trying your new battery in your bike, be sure to initialize it properly.

.

[reddirtrider]

The current through a spinning motor is limited by back emf. If the motor is turning over properly, then it's producing back emf and there's not a whole lot you can do to reduce the current draw and still have it function properly.

Check the charging system.