DRZ250 has started conking out after running fine for several kms

[Meatlord]

Hi all, new member and I'm hoping someone with much more expertise can help me out with a problem I've just started to see with my new-to-me 2009 DRZ-250.  I bought it only a month and a bit ago and it has been going great, but there are two problems:

1. The battery isn't charging. It was flat when I got it so I bought a new one and charged it up which held for a while, but it doesn't appear to be charging up while riding.  Luckily it starts first kick when cold so this hasn't been a major issue, but I mention it here in case there might be a relation with the next problem
2. A few times recently after some longer runs it has been going along just fine but then when backing off the throttle a bit it sputters a bit then conks out completely.  Every time this has been after a decent run when it should be nice and warm.  After a short rest it starts and goes on as if nothing has happened.

The first time it happened was after a long run up some fire trails (maybe 20km but with a number of stops along the way) the other day and it just randomly stuttered a bit then conked out completely after a longer run on the way home in a thunderstorm.  After a few minutes of rest it started from the kick starter with choke out and then rode off as normal, before conking out again a few kms later not far from home.  Again I tried kicking it over a few times without success straight away before resting it maybe 5 minutes and then starting it up first kick and heading off again.  Both of these times my son was riding it.

Today I took it for a run about 10 kms up the road for a test and after running along flat out for most of that time, I eased off the throttle to go around some corners and it sputtered a bit then recovered, before conking out completely seconds later and coming to a stop.  No firing or sputtering during this phase, it's just like it had lost power, revving the throttle had no effect.  As before I tried to start it again quickly without success, then left it siting for 5 minutes or so and it started again no problem.  Exactly the same thing happened on my way home after giving it a rest for an hour or so in between.

So my question is has anyone seen this type of thing before and do you have any suggestions as to what I could check?  My first thought was dirty fuel, but I would have expected more sputtering and burping before and during conk out, when really it behaves just like the key has been turned off.  Could it be a heat thing? Are there sensors that could be being tripped perhaps that reset after it cools off a bit?   Apart from this it runs like a demon so I'm reluctant to start pulling it apart too drastically, but any ideas appreciated.

cheers!

 

[Meatlord]

No ideas from anyone?  That's a worry - thought someone here would have seen such things before or at least know what might cause it ?

[willie]

Sounds like fuel starvation. Could be a plugged gas tank vent or gas filter. 

[Meatlord]

1 hour ago, willie said:

Sounds like fuel starvation. Could be a plugged gas tank vent or gas filter. 

Hi Willie.  Would you expect it to go so far before that would become an issue?  When you say a gas vent do you mean the breather pipe on the fuel cap or the ones down near the carby?

[willie]

3 hours ago, Meatlord said:

Hi Willie.  Would you expect it to go so far before that would become an issue?  When you say a gas vent do you mean the breather pipe on the fuel cap or the ones down near the carby?

Yes, the breather pipe on the fuel cap. If this is plugged or restricted the bike will start fine and run for awhile until a slight vacuum is created in the tank and no more fuel will run into carb. Let it sit for awhile and fuel will trickle down and bike will start again and run until the fuel slows down. Same for fuel filter or restriction in petcock. Eliminate these first before moving on to the more involved stuff. I have also seen weak ignition coils break down and loose spark after warming up only work again after cool down or maybe even a bad sparkplug cap or a loose connection. Intermittent faults can be a real bitch!  

[Meatlord]

21 hours ago, willie said:

Yes, the breather pipe on the fuel cap. If this is plugged or restricted the bike will start fine and run for awhile until a slight vacuum is created in the tank and no more fuel will run into carb. Let it sit for awhile and fuel will trickle down and bike will start again and run until the fuel slows down. Same for fuel filter or restriction in petcock. Eliminate these first before moving on to the more involved stuff. I have also seen weak ignition coils break down and loose spark after warming up only work again after cool down or maybe even a bad sparkplug cap or a loose connection. Intermittent faults can be a real bitch!  

Cheers mate, thanks for giving me some good places to start!

[Meatlord]

On 5/2/2019 at 1:37 AM, willie said:

Yes, the breather pipe on the fuel cap. If this is plugged or restricted the bike will start fine and run for awhile until a slight vacuum is created in the tank and no more fuel will run into carb. Let it sit for awhile and fuel will trickle down and bike will start again and run until the fuel slows down. Same for fuel filter or restriction in petcock. Eliminate these first before moving on to the more involved stuff. I have also seen weak ignition coils break down and loose spark after warming up only work again after cool down or maybe even a bad sparkplug cap or a loose connection. Intermittent faults can be a real bitch!  

SO the breather pipe from the fuel cap goes up and into that strange clip on the handlebars, but doesn't have a hole in it - makes me wonder how it can be a breather.  Is there any reason I shouldn't drill a hole through that thing?

[willie]

2 hours ago, Meatlord said:

SO the breather pipe from the fuel cap goes up and into that strange clip on the handlebars, but doesn't have a hole in it - makes me wonder how it can be a breather.  Is there any reason I shouldn't drill a hole through that thing?

Try popping the breather hose off and see if you can blow through it. It only needs a very small hole to vent.

[Meatlord]

21 hours ago, willie said:

Try popping the breather hose off and see if you can blow through it. It only needs a very small hole to vent.

I drilled it out already - didn't appear to hurt it but need to take it on a long run to see if it made any difference