Electric Start Blues

Uncle Frank · Apr 17, 2023

The electric starter on my MK3 is having problems turning the engine over. When it does it fires straight away but it has been getting slowly worse the last couple of months. I have the "DynoDave" starter motor from Mapcycle, new cables, CNW engine sprocket, sprag and starter gear and an OEM starter solenoid. The battery is a Motobatt 16.5AH 210CCA. It tests up ok and can start my MT-01 Yamaha. All connections are clean and tight. This is doing my head in - help will be appreciated. Thanks in advance.

EstuaryBoy · Apr 17, 2023

Have you tried bypassing the solenoid, i.e: running a jump lead to the starter straight from the battery?

Not offered as a solution, but just seeing if the problem lies with wiring/solenoid.....

Uncle Frank · Apr 17, 2023

EstuaryBoy said:
Have you tried bypassing the solenoid, i.e: running a jump lead to the starter straight from the battery?

Not offered as a solution, but just seeing if the problem lies with wiring/solenoid.....

No I haven't. It was doing the same with another aftermarket solenoid which makes me think that isn't the problem - however I'll give it a go. Nothing to lose now.

concours · Apr 17, 2023

Connect jumper cables from a car, retest.
Report results back here.

Deets55 · Apr 17, 2023

If your bike is still positive earth please be aware of how you connect your jumper cables from the car, especially if going directly to the starter motor. Also make sure no part of the bike and car are in contact with each other.

possm · Apr 17, 2023

I am running a YTX16BS in my Mk3 which is a similar CCA but I feel the battery is just adequate, a YTX20CHBS {270 CCA] is the same dimensions as the YTX16 I have and I will try that next time, I am not a fan of motobatt I believe they are made in China, but as they leave the factory sealed you have no idea of how long they have been sitting on the shelf "activated".

Uncle Frank · Apr 17, 2023

concours said:
Connect jumper cables from a car, retest.
Report results back here.

I've tried that - no difference.

dobba99 · Apr 18, 2023

I doubt its the OEM solenoid, they either work or don't work, ive had 2 fail on me. Replaced with a lucas item and no problems since. I know of a local Mk3 to me, that has a dynodave/wosp starter fitted, that the last time i witnessed it starting, displayed symptoms similar to yours. Is your starter a genuine Dyno dave item? I ask because his starter has been copied by wosp and probably others.
Your problem mirrors one of the failure modes of the original prestolite starters. i.e. struggling to turn the engine over and slowly getting worse. This problem in the prestolite is caused by the starters rotor wearing itself into the drive end cap until the rotor windings contact the end cap and gradually short out as the rotors insulation is worn away. ive seen this in loads of prestolites sent to me in part ex against a new/overhauled starter.
Personally i would be internally inspecting the starter itself to check all is well in there. if so can you try your starter on another Mk3 to see if the problem follows the starter to the other bike

concours · Apr 18, 2023

Uncle Frank said:
I've tried that - no difference.

Next, put your voltmeter on the starter itself, monitor actual voltage while cranking.
Report back the value observed.

Uncle Frank · Apr 18, 2023

dobba99 said:
I doubt its the OEM solenoid, they either work or don't work, ive had 2 fail on me. Replaced with a lucas item and no problems since. I know of a local Mk3 to me, that has a dynodave/wosp starter fitted, that the last time i witnessed it starting, displayed symptoms similar to yours. Is your starter a genuine Dyno dave item? I ask because his starter has been copied by wosp and probably others.
Your problem mirrors one of the failure modes of the original prestolite starters. i.e. struggling to turn the engine over and slowly getting worse. This problem in the prestolite is caused by the starters rotor wearing itself into the drive end cap until the rotor windings contact the end cap and gradually short out as the rotors insulation is worn away. ive seen this in loads of prestolites sent to me in part ex against a new/overhauled starter.
Personally i would be internally inspecting the starter itself to check all is well in there. if so can you try your starter on another Mk3 to see if the problem follows the starter to the other bike

Yes I shouldn't have said OEM - it's a Lucas item around one year old. I bought the starter from Mapcycle who are a reputable firm so it would be disappointing if they sold me a knock on. I'd like to try it in another Mk3 but the nearest one would be 500k from here - we live in a big country. If I can't get any joy I will strip it and see what I can find.

kommando · Apr 18, 2023

I test starters by mounting in a vice in some way and then replicating the solenoid and starter circuit together with a spare car battery. A dodgy solenoid or starter shows up quickly.

dobba99 · Apr 18, 2023

kommando said:
I test starters by mounting in a vice in some way and then replicating the solenoid and starter circuit together with a spare car battery. A dodgy solenoid or starter shows up quickly.

All that will do is prove the the starter system works or not. Its not a real world test with the starter turning the engine over. The OP problem is that the starter system works but its performance is degrading, indicating that the problem/fault is getting worse

Carl H · Apr 18, 2023

concours said:
Next, put your voltmeter on the starter itself, monitor actual voltage while cranking.
Report back the value observed.

With a new, YTX14 gel battery from Ebay =60.00$ maybe the best battery I have ever had in my MK3, with a freshly maintained OEM 2 brush starter, voltage at starter drops to a little below 10 volts when cranking. But fires right up.

My friend with a 4 brush conversion does the same below 10. Both had larger gauge battery wires.

This MK3 has 185 Lbs of compressions on a fresh hopped up CHR engine.

maaseyracer · Apr 18, 2023

The dyno dave starter solved my electric start issues and it is strong enough to turn over a 10.5:1 850 commando with ease and has been daily rider reliable for three years now.

marshg246 · Apr 18, 2023

Carl H said:
With a new, YTX14 gel battery from Ebay =60.00$ maybe the best battery I have ever had in my MK3, with a freshly maintained OEM 2 brush starter, voltage at starter drops to a little below 10 volts when cranking. But fires right up.

My friend with a 4 brush conversion does the same below 10. Both had larger gauge battery wires.

This MK3 has 185 Lbs of compressions on a fresh hopped up CHR engine.

What ignition system?

Uncle Frank · Apr 19, 2023

concours said:
Next, put your voltmeter on the starter itself, monitor actual voltage while cranking.
Report back the value observed.

Four volts. That obviously is not good - I measured resistance across the solenoid and got 0.1 ohms.

concours · Apr 19, 2023

Uncle Frank said:
Four volts. That obviously is not good - I measured resistance across the solenoid and got 0.1 ohms.

Now perform the same test with voltmeter at the battery. Then at the relay. (Both sides)
Report back the three data points.

Carl H · Apr 19, 2023

marshg246 said:
What ignition system?

I had a Boyer MK3 in for years , but now I have a Boyer MK4 to freshen up the old box. The OEM starters can work well, If you maintain them. I replaced the brushes once when the starter failed to work.

marshg246 · Apr 19, 2023

Uncle Frank said:
I measured resistance across the solenoid and got 0.1 ohms.

Please finish the tests concours gave you.

*IF* you disconnected everything from the big terminals on the solenoid, activated it, measured across the big terminals and got any reading other than 0 ohms, the solenoid is bad. An easier test is to connect your voltmeter leads across the big terminals with everything wired normally - when activated, if you read anything other than zero volts, the solenoid is bad.

L.A.B. · Apr 19, 2023

An easy test to identify a faulty solenoid is to bridge the two terminal studs with a screwdriver blade or similar but be prepared for a few sparks.

Electric Start Blues

Uncle Frank

EstuaryBoy

Uncle Frank

concours

Deets55

possm

Uncle Frank

dobba99

concours

Uncle Frank

kommando

dobba99

Carl H

maaseyracer

marshg246

Uncle Frank

concours

Carl H

marshg246

L.A.B.

Moderator

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