My M900 is hard to start, not sure where to begin troubleshooting

Started by Hella-M900, April 20, 2016, 04:16:22 PM

Previous topic - Next topic

Hella-M900

Hey everybody,

     first time poster here with a question about a 1994 M900 I recently acquired. I took this wonderful machine in trade for a Camaro I had right around Christmas time. The previous owner told me that if I left the bike off the trickle charger for more than a day "it might be hard to start". That being said I kept the battery in my warm garage during the winter months, hooking it up to my smart charger every other week or so.

     Flash forward to about a month ago when I finally got plates on the bike and started using it. Right from the first time I tried to start it I noticed the bike took an unusually long time to start and would back fire (through the cans) every few revolutions (while cranking) and then would usually start and run like a top. The battery itself is a 16Ah battery and it will crank the motor for a mighty long time before giving up. The bike never stalls, never stumbles, runs very strong and gives me no other problems except it is a royal pain in the ass to start unless its been charging for a while. I want to be able to take this bike on long trips and right now that simply isnt an option.

     This past weekend I took the bike on a wonderful 4 hour ride through Connecticut and then parked it. I was away from home so I didn't have a place to hook up my trickle charger. I figured that the battery would be ready to go since I put so many hours on it that day. Nope. When I tried to start the bike the battery seemed very weak from the get go and only cranked a few times before giving out. It did get very cold that night (mid 30's) but even still, I have a little Hyosung GT650 that starts after sitting for WEEKS with out ANY issues.

    What I want to know is where I should start in my quest for an easy to start M900. Its embarrassing to have such a magnificent machine that may or may not start when I need it. Electrical mods include, high output coils and upgraded halogen headlight, there may be more but I don't know. Also, how bad is it that the bike backfires LOUDLY while cranking? I am pretty sure my nieghbors hate my new toy because of the "gunshots" going off at 6am, haha. I thought the backfire could be a valve or timing issue but the bike runs so well otherwise that I find that hard to believe. Thanks in advance y'all. Here's a pic of my baby...


ducpainter

Have you checked to see if it is charging?

Get the bike started and check voltage at the battery at ~3000 rpm. You should see ~13.5-14.5 volts on the voltmeter.

If not it's most likely a bad R/R, but there are tests we can point you to so you can determine the problem. It could also be a bad battery, but you need to see if it's charging.
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."



Hella-M900

My bike doesn't have a tach but from a cold start, with the choke fully open, I'm getting ~13.5v at the battery and with light application of throttle I'm seeing ~14.5v... Seems like the regulator is functioning properly

ducpainter

What type of battery is in the bike, and how old is it? Have the battery load tested.

Is there any accessory equipment that might be drawing the battery down overnight?
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."



Hella-M900

I think it's an "Interstate" battery rated at 16Ah...I should be able to load test the battery in the next few days, I'll report back with my findings... As far as I know there is nothing on the bike that could be draining. PO installed a 12v socket for accessories but I don't think that itself would pull a load while off.

ducpainter

Flooded lead acid or AGM type?

An unuseed accessory outlet 'shouldn't' drain a battery.
"Once you accept that a child on the autistic spectrum experiences the world in
 a completely different way than you, you will be open to understand how that
 perspective
    is even more amazing than yours."
    To realize the value of nine  months:
    Ask a mother who gave birth to a stillborn.
"Don't piss off old people The older we get, the less 'Life in Prison' is a deterrent."



koko64

I know of some bikes with oem carbs that like less than full choke unless its very cold. Have you tried 1/2 & 1/3 choke?
2015 Scrambler 800

koko64

If the bike hasn't had a good tune for years then that could be your issue if the battery is fine.
Besides a valve adjustment there is a good carb tune and service, especially if the bike has sat for a long time with fuel deteriorating in the tank and carb bowls.
2015 Scrambler 800

Howie

Battery needs to be load tested so you know it is good.  You also might be using too much or too little choke.  New old bike?  Looks great by the way.  Off topic; Last service was done when?  P How old are the timing belts?  They need to be changed every 12K or 2 years, whichever comes first.  Tires should not be more than 5 years old and brake fluid changed yearly.  No records?  IMO, not a bad idea to start with a fresh service.

Some spam:
   
Since you are riding around in Connecticut you might want to join DESMO  http://www.desmoducati.org
Just click on "yahoo Groups" and you are in.  No dues.  Usually 5 group rides, BBQ, Holiday Party, Track Day and oil spill (work on your bike day at one of the best shops around.