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Discussion Starter #1 (Edited)
Hi all,
Carby Thrux has been running (5-10km) after a recent makeover but does not have a consistent start.

Checked the specs on their website http://www.linkint.com.au/ and purchased a MOTOCELL LITHIUM GOLD LiFePO4 Battery 12.8 Volt Series - MLG14B 48WH.
Charges up to around 13.2v, hit the starter and sometimes it kicks over but more times just a click and whir of the engine trying to spin up but feels not enough oomph to get it to start.
Placed a multimeter across battery terminals, hit the starter and it drops to around 5-6v, no start, then it bumps back up to high 12s.
Swapped over and utilised a larger battery from another bike with same result.
New coil and plugs.
New wiring throughout using m.unit with two wires utilised from starter solenoid to START terminals on unit, this is the way many others also connect this circuit.
New R/R, recently purchased by Ricks for my set up.
Stator tested by checking resistance (20ohm) between each pin (1-2, 1-3, 2-3) whilst bike is off with no battery and reads starting at OL. to 0.00 after contact.
There is continuity between any of the three (1-2, 1-3, 2-3).
No resistance reading between any of the 3 pins to earth, checked with other earths.
Both connectors between rectifier and stator looks good.
Also noticed the battery earth cable gets quite hot to touch when attempting to start a few times.
Earth cable runs from battery to frame .5M and is around 6mm conductor diameter, no kinks or connectors.
Earth cable from starter motor to starter solenoid is 1.5M and again is around 6mm conductor diameter no kinks or connectors.
Seat not touching Ignitor.

If the bike does not start, I’ve also tried to rock bike in gear and reattempt, with some luck but not a lot.

Edit, altered text from relay to ‘starter solenoid’
 

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Maybe you should isolate the starter motor and bench test the motor. If a different battery does the same thing and you are sure of the wiring and correct connections, then I would test to eliminate the starter. Might be pulling too many amps.
 

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Discussion Starter #3
Thanks, In there a procedure for testing a starter, what am I looking for?

Also just removed the spark plugs and bike spins up a lot easier, put them back in and no change, will move on to Felony’s response.
 

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Try a voltage drop test. Connect one lead of the volt meter to the battery + terminal and the other to the battery cable stud on the starter. The meter should read .0. With the meter connected this way try to start the engine, the meter should read less than .5 volts. If the reading is higher you have a resistance problem in the cable, solenoid, or a bad connection in the circuit. Check the ground side the same way. Connect the volt meter to - battery terminal and starter housing, engage the starter and read voltage drop, should be less than .5 volts.
 

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Discussion Starter #6 (Edited)
Try a voltage drop test. Connect one lead of the volt meter to the battery + terminal and the other to the battery cable stud on the starter. The meter should read .0. With the meter connected this way try to start the engine, the meter should read less than .5 volts. If the reading is higher you have a resistance problem in the cable, solenoid, or a bad connection in the circuit. Check the ground side the same way. Connect the volt meter to - battery terminal and starter housing, engage the starter and read voltage drop, should be less than .5 volts.
I’ve disconnected the starter motor. Cable looks good and connection was clean and solid. Cable left off at starter motor for tests above.

0v with both tests and just the sound of a single click from the solenoid.
Battery fully charged.

Edit
Connected starter motor back up and conducted same tests
.08 with the + side and
.1 with the - side.
 

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I’ve disconnected the starter motor.

Edit
Connected starter motor back up and conducted same tests
.08 with the + side and
.1 with the - side.
Every thing has to be connected as normal to conduct the test. Removing the cable tells you nothing. When you did the test (with cable connected) did the engine turnover normally or you just got a click? Have you tried using jumper cables from a car to see how it acts?
 

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Discussion Starter #8
Every thing has to be connected as normal to conduct the test. Removing the cable tells you nothing. When you did the test (with cable connected) did the engine turnover normally or you just got a click? Have you tried using jumper cables from a car to see how it acts?
Maybe 4 out of 5 attempts I just get a click. The starter motor does spin sometimes, but usually only a few turns.
I haven’t tried jumper cables, but I did try a much larger battery with the same results.
 

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Sounds like a bad starter or battery. Try the jumper cables, that will eliminate the battery if it turns normally. You can also try hooking a good jumper cable from a known good battery from positive terminal to the cable stud on the starter. With a cable from the negative battery post momentarily touch the starter housing. This is direct to the starter bypassing all else. Make certain the trans is in neutral and ignition is off.
 

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Discussion Starter #12 (Edited)
Maybe you should isolate the starter motor and bench test the motor. If a different battery does the same thing and you are sure of the wiring and correct connections, then I would test to eliminate the starter. Might be pulling too many amps.
Try a voltage drop test. Connect one lead of the volt meter to the battery + terminal and the other to the battery cable stud on the starter. The meter should read .0. With the meter connected this way try to start the engine, the meter should read less than .5 volts. If the reading is higher you have a resistance problem in the cable, solenoid, or a bad connection in the circuit. Check the ground side the same way. Connect the volt meter to - battery terminal and starter housing, engage the starter and read voltage drop, should be less than .5 volts.
Isolated the starter from the starting circuit and tried jumper cables to the car. Starter had no engagement, no spin......no go.
I’ll be putting a kit through it.
Thanks Felony and rweb, my shout.
 

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Isolated the starter from the starting circuit and tried jumper cables to the car. Starter had no engagement, no spin......no go.
I’ll be putting a kit through it.
Just something you said in your initial post:
Also noticed the battery earth cable gets quite hot to touch when attempting to start a few times.
Earth cable runs from battery to frame
The fact that the battery earth cable gets hot tells me that there is a high resistance connection, which would cause a severe voltage drop. If the cable runs to the frame as you say, this could be the cause because you should never ground directly to the frame. Here's how it should be to do it properly:

Battery cable goes onto the ENGINE directly, typically onto an engine case bolt (M6). Also on this bolt is a lighter ring connector with a substantial wire, perhaps 16 to 14 gauge (I'm no good with wire gauges but it should be a gauge or two heavier than the harness grounds), which connects to ALL the earth wires in the main harness. The engine case bolt connection must be spotlessly clean, perhaps using a bolt with a flanged head to keep the connection clean. The wire connection to the harness should have heat shrink tubing covering the connection of the wire to the ring connector. Same for the battery cable.

The problem with earthing to the frame is that frames are painted, then there is the problem of water and dirt ingress over time.
 

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Battery cable goes onto the ENGINE directly, typically onto an engine case bolt (M6). Also on this bolt is a lighter ring connector with a substantial wire, perhaps 16 to 14 gauge

Right. I made this annotated drawing to show where the main battery ground connection is, or should be. The bolt is a substantial M8 and the cable something like 8 AWG (10 mm2):


 

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Right. I made this annotated drawing to show where the main battery ground connection is, or should be. The bolt is a substantial M8 and the cable something like 8 AWG (10 mm2):
Spot on Mr F, and thanks for the illustration. I had thought the engine bolt to be an M6 since that is the size of the stock battery terminals. One thing is for sure, the battery earth cable should not even get slightly warm to the touch when cranking, even when it may fully deplete a freshly charged battery.
There are actually 2 ring connectors on that bolt, the other is less 'heavy duty' and is wired back to the wiring harness ground. It may be handy if you added that to your illustration since on some early models there was a further 'quick release' spade connector down by the engine. This was so that the harness could be removed without disturbing the engine case bolts, but the spade connector proved to be a bad idea and there were cases on here where the earth wire had rotted off and the connector itself was getting hot. I don't think they are used anymore but its something to always keep in mind, knowledge of it may solve someone's problem.
Still, this setup is far better than the usual one on Japanese bikes, where the battery cable was connected to the frame side of the rear engine mount bolt. I've rarely seen one of those without some rot and when the bolt is pulled it is sleeved in white oxidisation powder.
 

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Discussion Starter #16
Guys my apologies, earth from battery does in fact run to the engine, stock earth location.
Many thanks again for your in-depth review.

I’ve removed the starter motor and will drop in to an auto electrician tomorrow and see what can be done, or I’m looking into Holder, Sub Assy, Starter (part No T1310024) and whilst it’s out Ill also grab a new O ring.
 

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Guys my apologies, earth from battery does in fact run to the engine, stock earth location.
Maybe, but its still getting hot as you have stated. Have you made sure that the engine connection is spotless and tight, and there's no corrosion in the cable joint? Even if the problem turns out to be the starter motor itself, I can't see how the cable could get hot - the motor would burn instead since it is not protected by any fuses.
Do you have a meter? Try setting it on the low ohms range (20), and with the earth cable disconnected at the battery end, put the red probe on the battery end of the cable and the black probe on the head of an engine case bolt. The reading should be below about 0.2 ohms. Remember to zero the meter first if it has a calibration.

If both cable connection and starter motor check out okay, then my first move after that would be to look for anything which may be physically preventing the motor from spinning when power is applied, such as missing teeth on gear wheels or a jammed sprag clutch.
 

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Discussion Starter #18
Do you have a meter? Try setting it on the low ohms range (20), and with the earth cable disconnected at the battery end, put the red probe on the battery end of the cable and the black probe on the head of an engine case bolt. The reading should be below about 0.2 ohms. Remember to zero the meter first if it has a calibration.

If both cable connection and starter motor check out okay, then my first move after that would be to look for anything which may be physically preventing the motor from spinning when power is applied, such as missing teeth on gear wheels or a jammed sprag clutch.
Cable tested 0.00.
 

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Discussion Starter #19
Solution.

Took the starter motor (SM) out and thought I would have a look inside to see if there was any noticeable damage. Brushes looked fine and brush length seemed ok, motor has 8k. But there was oil inside. Cleaned throughout with metho and used fine grit paper to lightly sand the Armature Commutator. Rebench tested the SM and it spun easy. Took battery and SM to auto electrician and had battery load tested, again no problems and SM also spun up no probs.
Made a call to a bearing and seal company and picked up a cup or radial seal (24od x 15id x 5mm deep) and another outer O ring for around $11. The seal is in the cap of the spline end of the SM.
Put in all back together checking all the bits n pieces that I had apart, turned on fuel pulled out choke hit the starter and it immediately fired up. Turned off and tried another 3 times and all starts were immediate.
No heat from any cables and charging at 13.7 whilst running.

Hope this info may assist others if having the same issue and many thanks to all contributors.
 
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