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'99 M900 running too rich

Started by mojo, May 20, 2009, 06:05:55 PM

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mojo

May 20, 2009, 06:05:55 PM Last Edit: July 28, 2009, 09:21:13 AM by mojo
I bought a '99 M900 last fall and after a few hundred miles, it became harder and harder to start until it just refused to start.  I pulled the plugs and grounded them on the engine head, and, no spark.  Replaced the NGK DCPR8E plugs with two more of the same, and it fired right up and ran great. A few hundred miles later, exact same thing happened.  It was getting cold here in Wisconsin, so I just parked it in the basement for the winter.  Today I put in two more NGK's, and it fired right up.  The plugs don't look bad, maybe just a hair dark (not black)indicating it's running rich.  That wouldn't make the plugs go bad every few hundred miles, would it? 

Is there anything I can check and could it be a quick and easy fix?  I did get a one year warranty with the bike, but the closest dealer is over an hour away.  I did make an appointment for May 30 to drop it off, but if there is something cheap to fix it, I would rather do that than haul it to the dealer and back.
Some people are like slinky's.  They serve absolutely no purpose, but they always bring a smile to your face when you push them down the stairs.

ducrider98900

#1
June 01, 2009, 07:31:29 PM
Quote from: mojo on May 20, 2009, 06:05:55 PM
I bought a '99 M900 last fall and after a few hundred miles, it became harder and harder to start until it just refused to start.  I pulled the plugs and grounded them on the engine head, and, no spark.  Replaced the NGK DCPR8E plugs with two more of the same, and it fired right up and ran great. A few hundred miles later, exact same thing happened.  It was getting cold here in Wisconsin, so I just parked it in the basement for the winter.  Today I put in two more NGK's, and it fired right up.  The plugs don't look bad, maybe just a hair dark (not black)indicating it's running rich.  That wouldn't make the plugs go bad every few hundred miles, would it? 

Is there anything I can check and could it be a quick and easy fix?  I did get a one year warranty with the bike, but the closest dealer is over an hour away.  I did make an appointment for May 30 to drop it off, but if there is something cheap to fix it, I would rather do that than haul it to the dealer and back.

I had the same problem, I found out that the emoltion tubes or neddle jets that the needles slide in get out of round and wore.  The tubes are about $33 bucks and really not hard to change if your not afraid to get into the carbs.  My 98 900 was fouling plugs and was very "cranky" on the start.

mojo

#2
July 26, 2009, 06:26:39 PM
Took my bike to the dealer last month.  They said the needle jets were badly worn and replaced them and the plugs.  Picked up the bike and it ran great!  It was a ton of fun to ride and I thought it was fixed.  Fuel mileage was a lot better.  Before, I was getting about 95-100 miles before the low fuel light came on, and now I'm getting 130!

Then, about 400 miles go by, and one day I went to leave work for lunch, and it wouldn't start.  Pulled the plugs the dealer put in (NGK DPR7EA-9) and they were fouled.  Bought two new DCPR8E's and it fired right up.  50 miles later, it started backfiring(in the carbs and exhaust), sputtering and bucking with small throttle openings.  Open the throttle about half way and it would clear up and run a bit better.  It was just unrideable.  I limped it home and parked it in the garage.

Last night I pulled the carbs, disassembled them, soaked them in carb cleaner, blew them out and put them back in.  Started it up today, and it still runs the same.  Here is the weird part.  It will run (very poorly) with fouled out DCPR8E's with almost no visible spark, but it will not start at all with the DPR7EA's that I cleaned up and put in that show a nice bright blue spark.  That has me just puzzled. 

When I had the carbs apart, I notice that the main jet size was a 170, and my Haynes manual says it should be a 140!  (Wondering if this might be my problem)

Anyway, tomorrow I'm gonna buy two more DCPR8E's and I'm sure the bike will run perfectly fine for a few hundred miles, then I'll be right where I am now.

Is the main jet wrong, or the Haynes manual?  If not, what else might it be? 

The clip on the needle jet is on the 4th notch from the top, the pilot screw is out 3 or 3 1/2 turns (can't remember for sure).  Do these need to be adjusted?

I mainly ride my bike to commute back and fourth to work (about a 5 minute ride) with occasional longer rides.  Is my bike fouling plugs because I let it warm up with the choke on for a couple minutes, then only ride it about 5 more to get to work?

I am not a mechanic, but am very mechanically inclined.  I am not taking it back to the dealer after spendig $280 to get it fixed the first time, and getting marginal improvement.  They are two hours away, and driving through Milwaukee is a PITA.  Tried doing a search on here, but most problems involved FI bikes, so I'm getting nowhere fast.

Any help/advise you all could give is very appreciated.
Some people are like slinky's.  They serve absolutely no purpose, but they always bring a smile to your face when you push them down the stairs.

Howie

#3
July 26, 2009, 07:03:38 PM
Unless you did some wild ass modifications on your bike those mains are huge, stock is 140.  You might want to look at all the jet sizes and post them.  Also, do you have an open air box or any other modifications? 

mojo

#4
July 26, 2009, 07:15:46 PM
Not sure about the other jet sizes.  I'll have to open up the carbs again and post them later.  The only mods that I know of are a K&N filter, stock airbox lid, and Wiley ti slipons.
Some people are like slinky's.  They serve absolutely no purpose, but they always bring a smile to your face when you push them down the stairs.

Popeye the Sailor

#5
July 26, 2009, 08:44:14 PM
Quote from: mojo on July 26, 2009, 07:15:46 PM
Not sure about the other jet sizes.  I'll have to open up the carbs again and post them later.  The only mods that I know of are a K&N filter, stock airbox lid, and Wiley ti slipons.

Then you should still be running the stock jets. The oversized main is probably why you're fouling plugs.
If the state had not cut funding for the mental institutions, this project could never have happened.

mojo

#6
July 27, 2009, 09:30:15 AM
Thanks for the replies.  Looks like I found the problem (main jet).  I see ca-cycleworks sells the Factory Pro Titianium kit.  Is this a good kit, or should I look for a Dyno Jet kit, or something else?
Some people are like slinky's.  They serve absolutely no purpose, but they always bring a smile to your face when you push them down the stairs.

mojo

#7
July 28, 2009, 06:00:22 PM
Bought a new set of plugs and the bike started right up but occasionally backfired through the left side carb.  After looking down the carb with a flashlight, I found that there was a little gas seeping from around the needle jet and the piston guide.  I pulled that carb apart again and found a very small hairline crack in the piston guide, and I'm thinking the crack isn't letting the needle jet seal up tight to it. This is the carb I found that was backfiring from the start, and yes I was careful not to overtighten the jet carrier bolt.
While I had the carb apart I looked at the jet sizes and here they are.  Stock sizes are in ( )...
Main jet-175 (140)
Needle jet- Y-2 (Y-2)
Pilot jet- 42.5 (40)
Looks like the previous owner put a jet kit in it and got it way too rich. 
Also, does anyone know where to buy a new piston guide?
Some people are like slinky's.  They serve absolutely no purpose, but they always bring a smile to your face when you push them down the stairs.
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