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DRZ400E: Engine producing a sharp miss at high revs

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Hi all,

My DRZ has been plagued with a problem for some time and continues to defy my best attempts at solving it. The stand cut off switch has been removed.

Symptoms:

At high revs the engine will 'miss' and sometimes backfire. The ' miss' is sharp and very short and can be every couple of cycles leading me to think it is an electrical issue. Also noticed that the speedo display will intermittently reset itself.

Attempts at diagnosis made:

- replaced battery : no change

- swapped out the CDI from a friends bike: no change

- replaced spark plug : no change

- replaced ignition coil and lead : no change

- checked stator output: good

- checked reg/rec: good

- checked connections to do with ignition etc.: no change

Is there anything that anyone can suggest I try?

I've read in a manual I bought that some issues can be caused by a 'faulty flywheel'. Has anyone had any experience with this?

Thanks for any suggestions!

Veefwoar

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If the clock is resetting itself, then its related to a power loss

If you have >12.6V at battery at rest and >14volts with engine running you are good

 

 

Have you tried bypassing the ignition switch?

You will see that they have no 'shutter' across the key entry slot, and water can & does get in and cause issues

 

As for 'faulty flywheel', unless its breaking up and the magnets are falling out then its not that, and it also wouldn't cause the clock to reset itself if it was faulty anyway

 

Also try bypassing the engine kill switch

Edited by GuyGraham

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I was beginning to think it could be the ignition switch. The was one instance where I lightly touched the key and the engine died. I'll give those a shot and report back with results.

Thanks!

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I wouldn't be so quick to rule out jetting or the carb as a possible issue...

 

I would verify jetting is correct for your elevation/setup and give the carb a good thorough cleaning.

Edited by Wisconsinite762

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Hi all,

My DRZ has been plagued with a problem for some time and continues to defy my best attempts at solving it. The stand cut off switch has been removed.

Symptoms:

At high revs the engine will 'miss' and sometimes backfire. The ' miss' is sharp and very short and can be every couple of cycles leading me to think it is an electrical issue. Also noticed that the speedo display will intermittently reset itself.

Attempts at diagnosis made:

- replaced battery : no change

- swapped out the CDI from a friends bike: no change

- replaced spark plug : no change

- replaced ignition coil and lead : no change

- checked stator output: good

- checked reg/rec: good

- checked connections to do with ignition etc.: no change

Is there anything that anyone can suggest I try?

I've read in a manual I bought that some issues can be caused by a 'faulty flywheel'. Has anyone had any experience with this?

Thanks for any suggestions!

Veefwoar

Check your stator bolts my guess is that they are loose.

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The DRZ has a source coil built into the stator, that's a possibility, its totally separate from checking your charging output.

I had a 2 stroke one time, that had high rpm break up, and pulled the flywheel and the crank seal was in there almost sideways, must have been intermittently sucking air at high rpm. replaced and issue gone.

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I've had mis-fire from source coil on stator breaking down, took me a while to find it as the stator checked out as good with the WSM resistance tests

Its the one thing the OP hasn't changed

 

Another possible is the pulser coil

 

If the OP has access to another DRZ, then its worth just swapping over the stator/cover complete to check the stator isn't breaking down under load

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Thanks all. You've given me plenty to track down. I don't have ready access to another DRZ (my friend with the CDI moved away). I will get cracking and post progress.

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I've pulled the side case covering the stator an checked all the bolts. I noticed a sensor mounted inside the top of the case and strips of metal on the outside of the flywheel. Can I assume this is a hall effect sensor used to detect the rotational position of the crank? Is there a way to check the operation of this?

Edited by veefwoar

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I put the stator cover back on and warmed the engine up. No change. This is what it sounds like (please turn your sound down!) : http://youtu.be/l8IWq6pIDAA. Sorry for the poor sound quality but you can hear what it is doing.

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Certainly seems electrical

 

sorry, cant offer anymore suggestions to those I've already posted above.

 

Electrical components can check out fine, and then cause problems when warm / under load of combustion chamber

The ignition system will produce a spark across an 8mm gap at atmospheric pressure, but subject it to the pressure of the combustion chamber and that drops to a bout 1mm, hence why you can get a good spark from the plug when testing it against the frame but a misfire when its put back in the engine

 

Try closing the plug gap down to about 0.2 / 0.3mm and see if it improves, as this will require less voltage to fire it

Edited by GuyGraham

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Problem solved. Replaced the stator and she's happy again! Thanks again to everyone who offered assistance!

  • Like 2

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Another Failed stator then

 

How many miles?

They seem to start failing at 15K+

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Another Failed stator then

 

How many miles?

They seem to start failing at 15K+

 

From my observations It seems there is no apparent trend to stator failure based on miles...It has more tendency to relate more to infrequent oil changes...

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The bike has about 12K km on the odo. I rode around Australia last year on it (around 11K km in 5.5 weeks) and only changed the oil once so Craig-o could well be right. Change your oil often kids! :) all things considered the bike did an amazing job. Did the whole trip with only a blown fuse due to a broken tail light shorting out after 16km of continuous woops in the sand about 3 times the regular size (check out the Finke desert race for an idea of what I'm talking about). I'm hugely impressed with my DRZ. :)

  • Like 1

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