98 Monster 900 No Start

[daegrigg]

Thanks for the forum.

My son's 98 Monster (6512 miles) will not start.  It sat for about as year after it ran progressively worse and finally would not start. 

Bike cranks, has spark and compression but will not fire even with carb cleaner or starter fluid assistance. 

This is what I have done:

1.  Pulled the carbs, gave it immersion bath, pulled the jets (pilot and main), blew out every hole I could find with compressed air.  Reassembled checking the float level. Did not replace any jets - should at least start even with worn jets my thinking)

2.  Check vacuum pump to make sure it is delivery gas. 
3.  Drained tank and renewed fuel.
4.  Check for spark  - strong spark both plugs when grounded to engine while cranking
5. Check compression - cylinders at 150 psi plus/minus
6.  Checked the valve timing and all marks line up - exactly
7.  Recharged battery
8.  All fuses good

It is as if the spark is occurring at the wrong time in the power cycle.  When cranking, there is an intermittent "cough" back through the carbs.  When I use starter fluid, I get a muffled "whomp" with black smoke  out exhaust.

Well, that's it.  Hope is is enough to get some feedback.  I scratching my head by this great red machine won't run.

Thanks,

Don

[ducpainter]

could the plug wires have gotten crossed?

I know it's not easy, but like you say...

it has the 3 elements for internal combustion.

[daegrigg]

Great Catch!  The plug wires were reversed. 

Put them right and the bike ran for first time in a year - although briefly.

Now I have to solve a "regular" Monster puzzle. 

Will start and run for a few seconds, then try to catch again but no run.
Pull the plugs, dry them off ( they are not super wet but just enough to say it's flooded)
Put plugs back in, crank - tries to run but doesn't
Repeat the process again with the plugs.

Is fuel no being atomized enough to make up the right conditions for ignition?
Why do I have to clean plugs even though they don't look flooded?
Fiddled with the pilot jet on reassembly - was 3 turns/7turns originally and increased to more turns out - possibility?


Again,  Great catch ducpainter!

Don

[ducpainter]

How old is the fuel?

[daegrigg]

Drained tank.  New fuel.

[ducpainter]

Does fuel drip out of the overflows? Dirty float needles?

Try setting the air screws 4 turns out.

[daegrigg]

No drip from overflow. Will reset the air screws 4 turns tomorrow.

Thanks.

[671M900]

You set the pilot jet or the idle mix screw on the bottom of the carbs, accessible from the outside? Pilot jet should be screwed in all the way.

[koko64]

Stock carbs? Stock carbs areMikuni 38 mmCV carbs.

[daegrigg]

Update.

Yes, stock Mikuni carbs but not original set. 

Still no start with some firing after plugs are cleaned each time. 

After plug wires were corrected, bike started right up the first crank.  Ran a few seconds then to the plug cleaning cycle. 

Even with starter fluid, no firing.  (Using booster battery to make sure voltages are high enough)

Beginning to suspect ignition somehow.  Probably next step tonight is to switch the coil assembly from my 94 Monster (which runs perfectly) to son's  to eliminate that  factor.

Haven't ruled out carbs

By the way, tried air screws at 4 turns, 3 turns, 6 turns, no joy.

Thanks for all the responses.

[ducpainter]

Are you still getting spark?

[greenmonster]

Time f a new set of plugs just to rule that out, you still run the old ones, right?
2,5-3 turns is normal on screws.

[daegrigg]

Well she is running, albeit on one and half cylinders.

Catching up:

ducpainter was again psychic when he asked about spark.

Pulled plugs to check spark again and saw that vertical cylinder was sparking away.
Horizontal cylinder different story:  It would spark once or twice and then stop.
(Son switched out OEM for Dyna about year ago - so running on one oem and one Dyna)

Switched out one of my coils and to get repeating spark.

Now bike runs but seems only on vertical cylinder.  The horizontal cylinder is doing something, I can tell by exhaust and temp at head and muffler but is not hot like the vert.

Adjusted air screws 3,4,5 turns with no change.

So now I am focused on the front cylinder

So far you guys have figured out:

- Reversed plug wires
- No/bad spark

What's next -

Thanks

[ducpainter]

Is the plug for the horizontal cylinder wet?

still sparking? If not you may have a bad pick-up or ignitor. If you swap ignitors and the problem switches cylinders you found your problem

Check the vacuum line that runs to the manifold for fuel leaking into it from the vacuum fuel shut-off. You should ditch that pos anyway to avoid trouble if it isn't a source of it already.

[greenmonster]

Horizontal cylinder different story:  It would spark once or twice and then stop.

Does the hoz cyl spark when you switch plugs?

Just sayin, good to know you have fresh, working set of plugs to deal with,
they do give up sometimes.

Then it is time check ignitor boxes if coils are OK.