Ignition system woes - early M900. Help please?!?

Goofle · 06-09-2014, 07:35 PM

Hi,

My 93 m900 has an ignition problem. The coils seem to be working fine (a single spark when turning the key) but when the engine is being cranked there's none. The indications seem to indicate the two ignition modules (or whatever the little black boxes are called!) are fried.
I think the rectifier regulator packed up, allowing pure AC into the system and so wiped them out. The battery got boiled dry at the same time.
The other option in my opinion could be the crank position sensors not working for some reason, but a continuity check down the wires to them seems to indicate a fluctuation in resistance as the engine is turned over slowly by hand, albeit with a smaller change in resistance than I'd have expected - between about 95 to 120 ohms as the engine rotates.
Does anybody have any good ideas please?
Equally I don't suppose anyone has a pair of the ignition units they have no need for and would be willing to sell or lend me to test please? There's a few on eBay but for the pair I'd be looking at £140 or more - and there's I'm not 100% sure they're the problem!

Thanks all!

06-09-2014, 08:38 PM

The Haynes Manual covers the range of checks on these - your multimeter should be good enough to check them

Goofle · 06-09-2014, 08:50 PM

The Haynes manual doesn't seem to mention how to check either the igniter units or the crank sensors that I can see? Please correct me if I'm wrong though!

Murray Mint · 06-09-2014, 09:18 PM

Section 4.2 onwards show how to test the ignition components.

Murray Mint · 06-09-2014, 09:26 PM

Try these two pages.

http://murraybown.plus.com/monster/Haynes01.JPG/

http://murraybown.plus.com/monster/Haynes02.JPG/

Goofle · 06-09-2014, 09:29 PM

That's great thanks! I'll be back with the multimeter tomorrow!

06-09-2014, 07:35 PM	#1
Goofle Registered User Join Date: Feb 2014 Location: Powys Bike: M900 Posts: 334	Ignition system woes - early M900. Help please?!? Hi, My 93 m900 has an ignition problem. The coils seem to be working fine (a single spark when turning the key) but when the engine is being cranked there's none. The indications seem to indicate the two ignition modules (or whatever the little black boxes are called!) are fried. I think the rectifier regulator packed up, allowing pure AC into the system and so wiped them out. The battery got boiled dry at the same time. The other option in my opinion could be the crank position sensors not working for some reason, but a continuity check down the wires to them seems to indicate a fluctuation in resistance as the engine is turned over slowly by hand, albeit with a smaller change in resistance than I'd have expected - between about 95 to 120 ohms as the engine rotates. Does anybody have any good ideas please? Equally I don't suppose anyone has a pair of the ignition units they have no need for and would be willing to sell or lend me to test please? There's a few on eBay but for the pair I'd be looking at £140 or more - and there's I'm not 100% sure they're the problem! Thanks all!

06-09-2014, 09:26 PM	#5
Murray Mint Member Join Date: Jul 2009 Location: Crawley Bike: M900 Posts: 106	Try these two pages. http://murraybown.plus.com/monster/Haynes01.JPG/ http://murraybown.plus.com/monster/Haynes02.JPG/ Last edited by Murray Mint; 06-09-2014 at 09:29 PM..

06-09-2014, 08:38 PM	#2
DrD Guest Posts: n/a	The Haynes Manual covers the range of checks on these - your multimeter should be good enough to check them

06-09-2014, 08:50 PM	#3
Goofle Registered User Join Date: Feb 2014 Location: Powys Bike: M900 Posts: 334	The Haynes manual doesn't seem to mention how to check either the igniter units or the crank sensors that I can see? Please correct me if I'm wrong though!

06-09-2014, 09:18 PM	#4
Murray Mint Member Join Date: Jul 2009 Location: Crawley Bike: M900 Posts: 106	Section 4.2 onwards show how to test the ignition components.

06-09-2014, 09:29 PM	#6
Goofle Registered User Join Date: Feb 2014 Location: Powys Bike: M900 Posts: 334	That's great thanks! I'll be back with the multimeter tomorrow!