M900 Carb issues... Need serious help!

[needtorque]

The grinding noise could be a starter solenoid beginning to go due to overheating from repeated starting.  The monsters have a very common issue with weak solenoids that cause the start to stick on even after the bike starts and that can make some noise.  Just a suggestion.

Didn't some of these older monsters also have issues with the stator/generator nut coming loose and causing some noisy/destructive problems?

[ducpainter]

Didn't some of these older monsters also have issues with the stator/generator nut coming loose and causing some noisy/destructive problems?

Yup.

[needtorque]

Yup.

Thought so.  This could also be causing the running problems you are having.  Might need to pull the side cover if your making lots of noise like that.  Try to turn the motor over my hand and see where the noise originates.  If that proves to difficult then pull the side cover, it is not that hard.  Stick with it.  Don't give up, once you find the problem and fix it you will feel very rewarded.

[the_Journeyman]

I hear autozone has an exact replacement for the carbie filter.

Yup, it should be the same as my 750's filter.  It's a 3047 from Auto Zone.

JM

[MonsterDave]

Thanks for the input guys! (journeyman thanks for the part number)

I'll see what I can come up with this week.

I'll keep you posted.

[MonsterDave]

OK!

I have changed the fuel filter (thanks for the info on that. It only cost $5 at AutoZone) and everything is back together.

When I start it, I still hear a grinding noise that sounds like it is coming from the back cylinder. Which, by the way, doesn't even get warm now. Telling me that it is not firing.

What could I have possibly done that would cause such a thing? 

I'll try anything so go ahead and suggest away.

Oh yeah, does anyone here work in commercial printing and looking for a Prepress Manager? I'll move where ever if I have to.

Thanks,

[bluemoco]

When I start it, I still hear a grinding noise that sounds like it is coming from the back cylinder. Which, by the way, doesn't even get warm now. Telling me that it is not firing.

What could I have possibly done that would cause such a thing? 

What do your spark plugs look like (especially the one in the rear cylinder)?  Have you replaced them lately?

I had a fouled plug in the rear cylinder of my Monster once, and the bike was surging and then occasionally firing on both cylinders.     

Replacements only cost a few $$, and it's one more thing you can check off the diagnostic list.

[needtorque]

List of possibles:
-something fell off into the cylinder like part of the plug
-Lean condition caused predetonation and a blown piston
-poor oil supply or simply a broken ring for whatever reason

No matter it sounds like you may be removing the cylinder to find out. 

Quick check method:
Pull the plug and take the cylinder to top dead center.  Get out a flashlight with a very narrow beam and look in the cylinder to see if there is something visibly wrong with the piston.

For sure method:
Get a compression gauge and do a compression test on the cylinder.  If you don't know how I can explain it but you are looking to pull 125 or higher on the test.  If there is catastrophic failure you probably wont pull anything on the test.  If a ring has failed you might get some compression but not as much like maybe 50-60.

[MonsterDave]

Well, I think I might be getting the hang of this 'repair' thing

After I made my last post I decided that I would start taking a look at everything I thought I could remove and replace without too much trouble. I removed the belt covers and wouldn't you know it... my rear belt was toast

So, after calling my local dealer (about 60 miles away) and finding out they have bunches of them in stock, I'll be taking a ride tomorrow  [moto] to get one. And it is only $30

When I return and get it installed, I'll let you know how it all turned out.

Thanks needtorque for the suggestions but I am very happy that it was not anything serious.

Until then...

[Ddan]

Well, I think I might be getting the hang of this 'repair' thing

After I made my last post I decided that I would start taking a look at everything I thought I could remove and replace without too much trouble. I removed the belt covers and wouldn't you know it... my rear belt was toast

So, after calling my local dealer (about 60 miles away) and finding out they have bunches of them in stock, I'll be taking a ride tomorrow  [moto] to get one. And it is only $30

When I return and get it installed, I'll let you know how it all turned out.

Thanks needtorque for the suggestions but I am very happy that it was not anything serious.

Until then...

Define "toast"

[greenmonster]

I'll be taking a ride tomorrow   to get one.

I`d replace both, they could`ve been fr a bad batch.

A pic of the toasted one would be educating!

When I start it, I still hear a grinding noise that sounds like it is coming from the back cylinder

Combining that w a bad belt, do you have compression?

[needtorque]

Sorry but you might not get off that easy.  If by toast you mean broken then you are in for a "treat".  You have an interference engine.  What that means is if the belt breaks or slips then valves hit pistons and parts break inside.  Like pistons and valves.  The grinding you heard is more than likely broken parts.

[MonsterDave]

Where to begin?

By "toast" I mean that the belt on the rear cylinder was split in the middle (narrow width of belt) and a few teeth were ground off. My guess is the grinding noise I heard was the belt slipping on the top gear.

I know, this could be REAL bad

What I have done is removed the belts and spark plugs in order to adjust the timing 'dots' where they need to be. Because of this problem, I have also removed the cover on the rear valve to see if everything moves correctly/properly. It does. I also looked into the cylinder to see if there were any broken parts or damage. There was not! (at least anything I could see) I also watched the front cylinder move (bike in gear, tire off the ground) to and past TDC. So, I think the front cylinder is OK.

My next step (tomorrow) will be to see if I can get the valve cover off the front without removing the air box and see how that looks.

Here are some things I noticed while doing this:

1. Both front and rear 'valve gears' (not sure what they are really called) move freely by hand. (I can spin them without any problems and they do have the resistance area where the springs must be doing their thing)

2. With the bike in gear (3rd or 4th) when I try to spin the wheel, it will move, but only about 8" - 12" (very rough guess) and then stop with a rather heavy clunk. I'm guessing this is really bad?

I have just downloaded a PDF M900 service manual to see if that will help me. It's not very... what's the word?...thorough! And everything I want to try needs some damn special tool

Thanks needtorque for the lighter "interference engine" phrase. That sounds better than saying I'm totally screwed.

I need BEER to think this over. I'll let you know tomorrow night how it's going.

Till then 

[needtorque]

Well.  With the belts off and timing marks lined up it is likely that all the valves are closed.  This will still make it difficult to turn the bike over while in gear.  Moving 8-12" before encountering resistance seems a bit far.  Like I said before.  Get the belts back on and get a compression tester.  Run a compression test on both cylinders and post results here if you don't understand them.  Or, if you need procedural help I can tell you how it is pretty simple really.

[MonsterDave]

After digging through everything I could, I pulled the head on the rear cylinder. What I discovered was quite impressive! Turns out there was some kind of nut or something resting on the cylinder head. Fortunately, the valves look to be fine. No scrapes or anything. The valve slots on the piston took a bit of a beating but appear in decent shape along with the bottom of the head where the valves are. (see photos)

Here's my question.

Is my piston and head toast? or can I grind them smooth? I'm not talking grinding a ton, just enough to smooth it down.

What does everyone think?

If someone would tell me how, I will post pictures. I can't figure it out. I'm probably being stupid.