DRZ400SM Engine cutting out after running at higher revs for extended period.

[AUS_Craig]

I just bought a 2006 DRZ400SM - the engine is regularly cutting out after sitting on freeway speed for a while. It runs great at lower revs. I can ride the same distance at lower speed and it's fine. Go at 100km/h for more than 10 minutes and it cuts out.

After pulling over and letting it sit for a minute, it comes good again and I can continue riding.

I've tried running with the Petcock on 'Bleed' as I've read that if it runs OK on Bleed, this could indicate a vapor lock. However it still cuts out with the Petcock on bleed. I also tried opening the tank cap after it cut out but no air rush could be heard, so I don't think it's vapor lock.

My hunch is it's electrical (perhaps stator getting hot and failing?), but would really appreciate some ideas if anyone else has had this happen.

I've read similar posts, but none seemed to have exactly the same symptoms.

Cheers!

[dad2u]

Hmm, my first guess would be that the tank is not venting air into the tank as the fuel is burned, and this eventually creates a vacuum in the tank. This would slow or even stop the fuel from flowing.  When you sit for a while, enough air gets into the tank to allow fuel to flow again, and so it starts back up. 
 

you should be able to check this without running the bike by pulling the fuel line off the carb, directing it into a container, and selecting PRI on the petcock. Watch and see if the fuel runs freely….for your ten minutes. If it slows or stops you will have proven it. 
 

if you do this and post your results, I can either cheer, or give you my next best guess!  Ha ha, good luck. 

[roleyrev]

Maybe you have a slight blockage somewhere in the fuel system. If so the fuel system may be delivering enough fuel for you to ride slowly but you use more fuel when going highway speed and eventually runout.  What happens when you do a little highway and then a bit of slower riding? 

[AUS_Craig]

So I've pulled the fuel line and run a whole tank through with Petcock on "PRI", and it seemed to run fine.

The problem seems to have gotten worse and happens sooner into the ride now.

I've also checked the Stator with a multimeter with engine cold and hot. Open circuit to ground on all three phases, so no issue there either.

Any further suggestions would be most welcome as I'm out of ideas!

[roleyrev]

1 hour ago, AUS_Craig said:

Open circuit to ground on all three phases, so no issue there either.

Any further suggestions would be most welcome as I'm out of ideas!

Open or closed on the phases are not going to stop your bike, they will stop the charging system.  You need to check the pickup (green and blue wires) and the signal generator (black and white), these are the parts of the stator that will stop the bike in it's tracks.  Spark coil also can have this effect.

 

[AUS_Craig]

1 hour ago, roleyrev said:

Open or closed on the phases are not going to stop your bike, they will stop the charging system.  You need to check the pickup (green and blue wires) and the signal generator (black and white), these are the parts of the stator that will stop the bike in it's tracks.  Spark coil also can have this effect.

 

Great info, thanks Roleyrev! Looks like I need to build a peak volt adaptor. I'll post my results. Cheers!

[Nor Cal cycle]

Maybe the cut off switch for the kickstand at high speeds? Possibly due to a weak spring or a series of hard bump or dips ?  Still learning the bike so hope this helps . 

[GuyGraham]

Possibly a blocked screen on the carb float needle seat restricting the fuel flow into the carb...I have had this and it drove me crazy trying to find it

Pull the carb out and pull the float needle seat out and make sure the gauze on the top of the seat is clean. Any debris here restricts fuel flow into the carb float bowl and will create your symptoms 

Edited February 7, 2022 by GuyGraham

[AUS_Craig]

On 2/7/2022 at 3:19 PM, roleyrev said:

Open or closed on the phases are not going to stop your bike, they will stop the charging system.  You need to check the pickup (green and blue wires) and the signal generator (black and white), these are the parts of the stator that will stop the bike in it's tracks.  Spark coil also can have this effect.

 

OK, so I've built a peak volt adaptor and measured the pickup and signal coil voltages.

With a cold engine, they both are in spec according to the troubleshooting guide, however after taking the bike for a ride and it cutting out, the signal coil is only outputting 1.1 volts. This is probably obvious as the guide says OVER 1.4 Volts, but is this enough to be the cause of the problem?

Given the fault is intermittent, the reading could well be lower when the engine is actually cutting out, but that's going to be extremely difficult to measure.

[AUS_Craig]

On 2/7/2022 at 10:40 PM, GuyGraham said:

Possibly a blocked screen on the carb float needle seat restricting the fuel flow into the carb...I have had this and it drove me crazy trying to find it

Pull the carb out and pull the float needle seat out and make sure the gauze on the top of the seat is clean. Any debris here restricts fuel flow into the carb float bowl and will create your symptoms 

Thanks for your suggestion GuyGraham.

I feel like the way it's cutting out is too sudden to be fuel. It's quite abrupt when it happens. As mentioned earlier, the signal coil is only measuring 1.1V after taking the bike for a ride and it cutting out. I'm thinking this is the cause of the problem.

[roleyrev]

1 hour ago, AUS_Craig said:

Given the fault is intermittent, the reading could well be lower when the engine is actually cutting out, but that's going to be extremely difficult to measure.

If that's the clue, then have a physical check of the stator.   Lay the bike over on its clutch side (no need to remove oil), I use an old price of carpet to lay the bike on - contact points tend to be handlebars and foot pegs.  Remove the starter clutch cover (the three JIS screws) and the cover and starter clutch, being careful make sure the bushes and spacers are a accounted for (pop this aside in an appropriate container ) remove all bolts that hold the cover on and gently remove the cover.  The gasket is designed to be reused and is metal with a coating so be gentle with it and you can reuse it.  The stator is in the cover, place an old towel over that side of the bike and flip the cover over and inspect the stator for damage.  The magnetic force of the flywheel may make it difficult to maneuver the cover when it is close to the flywheel.  If all looks good reassemble and keep looking or replace the stator if it looks dubious.  Obvious things to look for are damaged windings due to debris or backed out stator bolts, blackened coils and poor connections.    

[bucket list]

4 hours ago, AUS_Craig said:

Thanks for your suggestion GuyGraham.

I feel like the way it's cutting out is too sudden to be fuel. It's quite abrupt when it happens. As mentioned earlier, the signal coil is only measuring 1.1V after taking the bike for a ride and it cutting out. I'm thinking this is the cause of the problem.

Don't be too quick to discount Guy Graham's suggestions, a buddy of mines has the exact symptoms as yours and the little screen on the float seat was partially plugged. When the fuel ran low in the float bowl, the bike bogged and cut out big time. A previous owner had siliconed the petcock at the tank and bits of silicone got into the screen.

A good visual of the stator is always good, but when it acts up it will sputter and fart at lower rpm's. 

[GuyGraham]

6 hours ago, AUS_Craig said:

Thanks for your suggestion GuyGraham.

I feel like the way it's cutting out is too sudden to be fuel. It's quite abrupt when it happens. As mentioned earlier, the signal coil is only measuring 1.1V after taking the bike for a ride and it cutting out. I'm thinking this is the cause of the problem.

I too thought electrical when mine did it but it was fuel when i was sure it was ignition

The fact yours starts again after a minute really does point to fuel flow issue

[AUS_Craig]

On 2/7/2022 at 3:19 PM, roleyrev said:

Open or closed on the phases are not going to stop your bike, they will stop the charging system.  You need to check the pickup (green and blue wires) and the signal generator (black and white), these are the parts of the stator that will stop the bike in it's tracks.  Spark coil also can have this effect.

 

 

On 2/10/2022 at 12:44 PM, roleyrev said:

If that's the clue, then have a physical check of the stator.   Lay the bike over on its clutch side (no need to remove oil), I use an old price of carpet to lay the bike on - contact points tend to be handlebars and foot pegs.  Remove the starter clutch cover (the three JIS screws) and the cover and starter clutch, being careful make sure the bushes and spacers are a accounted for (pop this aside in an appropriate container ) remove all bolts that hold the cover on and gently remove the cover.  The gasket is designed to be reused and is metal with a coating so be gentle with it and you can reuse it.  The stator is in the cover, place an old towel over that side of the bike and flip the cover over and inspect the stator for damage.  The magnetic force of the flywheel may make it difficult to maneuver the cover when it is close to the flywheel.  If all looks good reassemble and keep looking or replace the stator if it looks dubious.  Obvious things to look for are damaged windings due to debris or backed out stator bolts, blackened coils and poor connections.    

I bit the bullet and bought a new (after-market) stator as I had the bike booked in for a road-worthy check today.

After installing the new Stator, I took the bike for a decent run (longer than was needed to induce the fault previously) and it ran fine. I'll take it for another run when I pick it up from the roadworthy check, but I reckon the signal coil on the stator was the cause in this instance. 

Thanks to all you legends for your tips and suggestions!

[AUS_Craig]

On 2/11/2022 at 2:38 PM, AUS_Craig said:

 

I bit the bullet and bought a new (after-market) stator as I had the bike booked in for a road-worthy check today.

After installing the new Stator, I took the bike for a decent run (longer than was needed to induce the fault previously) and it ran fine. I'll take it for another run when I pick it up from the roadworthy check, but I reckon the signal coil on the stator was the cause in this instance. 

Thanks to all you legends for your tips and suggestions!

Well, I thought I had it licked... Turns out the problem still exists! I guess I'll be pulling the carby down tomorrow.

[GuyGraham]

2 hours ago, AUS_Craig said:

Well, I thought I had it licked... Turns out the problem still exists! I guess I'll be pulling the carby down tomorrow.

You might want to replace the oring on the needle seat to ensure it seals correctly after you reassemble, as disturbing it may cause it to leak

They tend to go hard and brittle over time and yours may still be the original one

The size is in the faq section of this forum...I think its 7.75 id x 1.5 dia in nitrile or better still viton if you can find it

 

 

Edited February 12, 2022 by GuyGraham

[AUS_Craig]

On 2/10/2022 at 5:40 PM, GuyGraham said:

I too thought electrical when mine did it but it was fuel when i was sure it was ignition

The fact yours starts again after a minute really does point to fuel flow issue

GuyGraham, you nailed it I reckon... I pulled the carby out today (no easy job I might add). The Seat mesh filter was completely clogged with gunk! I haven't taken the bike for a run yet, but 100% that has to be the issue.

See before and after pics below. The fuel inlet gallery was completely full of gunk - I'm surprised the thing ran at all!

It's disappointing I spent $375 on a stator I didn't need, but I guess I can get a bit back for the old one now I know it's ok and I won't have to worry about the Stator for years to come.

Thanks again legends!

 

[bumtarder]

It was suggested by Roley in post #2 to investigate for fuel blockage.

[GuyGraham]

21 hours ago, AUS_Craig said:

GuyGraham, you nailed it I reckon... I pulled the carby out today (no easy job I might add). The Seat mesh filter was completely clogged with gunk! I haven't taken the bike for a run yet, but 100% that has to be the issue.

See before and after pics below. The fuel inlet gallery was completely full of gunk - I'm surprised the thing ran at all!

It's disappointing I spent $375 on a stator I didn't need, but I guess I can get a bit back for the old one now I know it's ok and I won't have to worry about the Stator for years to come.

Thanks again legends!

 

Is the gauze on top of needle seat clean?

 

Best way to get carb in and out is from the rear......undo rear subframe bottom bolts and pivot subframe up.....carb can then be removed from the rear, past the shock...much easier than struggling to get it out from the side

Edited February 14, 2022 by GuyGraham

[AUS_Craig]

3 hours ago, GuyGraham said:

Is the gauze on top of needle seat clean?

 

Best way to get carb in and out is from the rear......undo rear subframe bottom bolts and pivot subframe up.....card can then be removed from the rear, past the shock...much easier than struggling to get in out from the side

The gauze was filthy... Clean now. Great info on taking carb out through the back of the frame. Next time I'll try that for sure.

Cheers!