How to check a CDI and Stator on a Mountain Max

M.M. 700 · Sep 23, 2009

Buddies got an 01 700 Mountain Max. It is having trouble, it acts like it runs rich, or drops a cylinder. We can lean it way out with the Vari-Flo then it acts better. But is way leaner than were it should be.

Have checked floats/carb set up. Changed needle and floats.

I am wanting to check the stator/CDI, how do you check them?

SRXSRULE · Sep 23, 2009

Never seen an ignition problem change with a forced AIR/FUEL change. I would start with the basics, check compression and make sure all is good. Put 3 new plugs in it. Make sure the exhaust isnt plugged (mouse nest). Then make sure nothing is sticking in the carb rack. The choke plunger can get stuck in the the bore and cause problems.
The pilot jet circut is very small in those carbs and can cause hard starting and idle problems, but that doesnt sound like the issue you are having.

If the sled starts and runs, Its ~almost~ never a CDI/stator issue on these sleds. Good luck. Eric

M.M. 700 · Sep 23, 2009

I was just thinking of a weak spark.

Compression is good, have tried new plugs. Have cleaned carbs. Exhaust is not plugged. Have bypassed the TORS.

When talking the choke plunger. You mean to check to see if the choke rod (not sure on correct lingo) is not sticking? I have pulled/released the choke and watched the rod move out and then it returns.

The only other thing I can think of would be the reeds. I have pulled the carbs and looked into the reed cages, and everything looked fine. But might pull them out and check/replace them. The sled has around 5000 miles on it.

I have pinned the throttle it started acting up, I grabbed the choke lever and pulled just a little bit and it fell right on its face. Running rich, right?

snowdad4 · Sep 23, 2009

not aware of a check for the cdi, but the stator has stats for troubleshooting. my book is out right now, but if you have a good relationship with your dealer, he should give them to you. if i have a cdi that i think is questionable, i usually just swap out with a known good one. did have a viper a few years back that the connections had came loose and offered up all kinds of running issues. start there. takes alot for a cdi to crap oiut. wait a bit, i am sure the allknowing arfarce has some answers for you.

SRXSRULE · Sep 23, 2009

One more thing just came to mind. Check and make sure the fuel pump isnt leaking fuel into the crank case through the pulse line. That would make it run overly rich.

As for the choke, the choke cable moves the rod and the rod move each plunger on the carb. Just make sure the plungers are moving free. Eric

M.M. 700 · Sep 23, 2009

Thanks guys. :beer;

kozmo · Sep 23, 2009

you might also want to check the plug caps, they can cause the motor to run funny

kingofthemountain · Sep 23, 2009

I spent this entire trying summer to figure out what was wrong with my mountain max, and it ended up being the stator all along. It started out last season when i started having problems with loss of power and tough starting. I would replace the plugs and all would be fine for a while at least. This cycle went on until the last ride of the season, when i started it up to get it out of the trailer, shut it off, then couldn't get it started again. No spark whatsoever. I checked/tested everything connection there was to check, bypassed tors, and pretty much tore it apart. Finally i replaced the stator with a used one off ebay and it is as good as new. So it is possible that the stator is causing your problems, but hopefully not for your sake. Because the little phillips screws that held mine together were a b1t<h to get off

snowdad4 · Sep 24, 2009

trick for them little phillips screws is some pb blast, a little shot with a mini butane torch, and a high dollar snapon impact driver. dont know whats so special about that impact, but it sure works. and the little blue flame thats so directable to the area you point it is amazing as well. tricks from experience.

arfrce · Sep 24, 2009

As ^^ HE stated before, I do have a couple of things you can try.
As for the CDI box it is integrated, As in circuit board. There are usually 5 wires coming out of the CDI box.
1) Power
2) Ground
3) Pulse Sensor
4) Exciter Coil (Flywheel) The Magnets hardly ever go bad.
5) Engine Kill Switch.
To check it grab your multimeter and check the wires. To check if the ground is good just do a ohm check, it should beep at you. And for the flywheel use A/C current. Have someone pull the rip cord while you hold the wire to the connector (BE CAREFULE 200~VOLTS From the FLYWHEEL)
The rest will be DC current

But I can tell you if the CDI box goes bad the motor usually will not start at all.
Things I would check:
1) Check the ground wire. Make sure it has a good solid. Ohm check with Multi meter it will beep if the ground is good.
2) current from your CDI box to the COILS
3) COILS to your Spark plugs.
4) Spark plug wires (cracks, a cut in one of the wires)
5) gap on your Spark plugs If the gap is too large or too small it will run bad.
6) Check your reeds if you have a cracked reed it will run poorly.
That is what I would check. Not saying anyone of those things are it. But that is just me.

I hope this helps.

snowdad4 · Sep 24, 2009

actually, as i stated above, yamaha has specs for checking the stator. its a real simple testing procedure, you simply disconnect the feed from the cdi to the stator, take your testing multimeter, and check each phase, as directed per yamaha tech, specific colored wire to specific colored wire= spec ohms, + or-, at specified temp. if not within tolerances, unit would be faulty. not sure why someone would disconnect something and have someone else pull the cord at risk of personal shock, or a greater expense of smoking the cdi. direct short to ground kills more cdi's than anything. the little capacitors dont like shooting voltage into any circuit not designed to accept it. think twice before trying the above post's backfeeding voltage methods. you can also ohm the coils and the plug caps, all without fear of harming your highly sensitive ignition system.

arfrce · Sep 24, 2009

Oh Sorry I can see how someone might think I said to unhook the wires. Leave the wires hooked up while testing with your multi meter.

Well we know you are getting power since it is starting. What we DON'T KNOW is how much voltage is getting to the cylinders.
I stand by what I said above. Do a voltage check on the wires from the CDI to the coils, and from the coils to the spark plugs.
An ohm check will let you know you don't have a break in the line. BUt it won't tell you that you are low on current.

Blaine · Oct 12, 2009

M.M. 700 said:
Buddies got an 01 700 Mountain Max. It is having trouble, it acts like it runs rich, or drops a cylinder. We can lean it way out with the Vari-Flo then it acts better. But is way leaner than were it should be.

Have checked floats/carb set up. Changed needle and floats.

I am wanting to check the stator/CDI, how do you check them?

As long as the plugs are getting spark, more than likely your cdi box is ok.

Stator testing out of a sled
http://www.youtube.com/watch?v=rCqojU5wHos

Stator testing in a sled:
http://www.youtube.com/watch?v=Uzz2NZiw3fk

Stator removal:
http://www.youtube.com/watch?v=eGSsyRRiIDI

Stator reinstall:
http://www.youtube.com/watch?v=qGiXzdF_IaU

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How to check a CDI and Stator on a Mountain Max

M.M. 700

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SRXSRULE

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M.M. 700

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snowdad4

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SRXSRULE

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M.M. 700

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kozmo

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kingofthemountain

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snowdad4

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arfrce

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