Friend has a fuel with with a 250 Ninja

[berth]

Posting for a friend, I'll just quote it:

Got a maintenance quandary for y'all. Have a problem that's happened twice in about 3 years. Bike ('09 Ninja 250) doesn't start after being off for a couple of weeks (first time was 3 weeks, this time was 12 days). Both times the tank has been relatively empty but had gas. Engine turns. There is an occasional light backfire after attempting for a while, but no smell of gas as if my engine were flooded.

After the first time I have left the bike off for similar time periods with a full tank and not had the issue; I just forgot this time. Part of me feels that the level in the tank is me being superstitious, but that's could be just me not understanding what the cause could be.

Both times, to fix it I drained my carburetor bowls (second time I also had to recharge my battery but that was more due to draining it after trying to start so many times, so likely secondary), so the running theory is that there's some condensation/water getting in them.

41000 miles.

Wondering what the cognoscenti think. It's his daily commuter.

 

[motomania2007]

About a hundred different possibilities given that slight amount of data to go on.

Fuel in several different ways is certainly some of the possibilities.

 

[stangmx13]

ya, hes prob flooding the engine while trying to start.

the engine probably needs some maintenance to improve starting. that way the tiny amount of water that gets into fuel doesnt fully prevent it from firing.

 

[berth]

About a hundred different possibilities given that slight amount of data to go on.

What more data do you think would be useful?

ya, hes prob flooding the engine while trying to start.

the engine probably needs some maintenance to improve starting. that way the tiny amount of water that gets into fuel doesnt fully prevent it from firing.

Well he says he's not smelling gasoline, so that's why he doesn't think he's flooding it.

Do you think it needs some extended maintenance? over and above "routine" maintenance (for assorted values of "routine"). What maintenance do you think may be lacking?

Addenda, it has not had the valves adjusted in the past 20K, but they've been adjusted before, if that's any help.

 

[motomania2007]

Most likely possibilities:
weak battery
plugged fuel circuit(s) in the carbs
vacuum leak preventing the petcock from flowing fuel
out of speck valves causing hard starts
contaminated fuel

The first things I would check are the simple items:
1) How strong is the battery after a full recharge and load test.
2) Clean and tighten all 6 battery cable connections.
3) Make sure the spark plugs are recently replaced
4) Inspect all fuel lines and vacuum lines for cracks and leaks
5) Are the valve clearances in spec?
6) Once it is running, how stable is the idle? Does it idle with the choke turned off?


That gives a basic condition of all the parts involved and if all of that is very healthy then I would dig a little deeper and the next thing I would do is pull the carbs and clean the insides to make sure all the circuits and jets are clean and functional. I suspect one or both pilot circuits are plugged or partially plugged.

 

[berth]

Thanks, George. That list looks really helpful and I will pass it along.

 

[stangmx13]

Well he says he's not smelling gasoline, so that's why he doesn't think he's flooding it.

Do you think it needs some extended maintenance? over and above "routine" maintenance (for assorted values of "routine"). What maintenance do you think may be lacking?

Addenda, it has not had the valves adjusted in the past 20K, but they've been adjusted before, if that's any help.

draining the carb bowl is a trick I used to use on my dirt bikes after I had flooded it. im not sure why it worked.

pretty much +1 motomania. clean carbs and proper valve clearances make a bike a lot easier to start.

 

[Maddevill]

Ninja 250 has a history of valves tightening up. If you have tight valves, at start up you are losing compression due to valves hanging slightly open. On that bike, ANY loss of compression makes it harder to start. Usually it shows up when the motor is hot though. And tell your friend not to store the bike with an empty tank. Invites rust.

Mad

 

[berth]

He doesn't leave it parked for long.

Recent anecdote:

That's what happened last time this issue cropped up, which was after the holidays. Was parked with half a tank for the holiday week, started up okay did fine until I got off the freeway and then stalled as I was getting into work. Kept the choke on a little going back home, filled up the tank, did fine the next day. Didn't have to drain the bowls like I did years previously.

I find it interesting that it starts up fine, and then has problems later in the day.

Sitting for 5 days shouldn't be a real problem for anything.

 

[motomania2007]

He doesn't leave it parked for long.

...


I find it interesting that it starts up fine, and then has problems later in the day.

Sitting for 5 days shouldn't be a real problem for anything.

There are tons of possibilities still.

I suspect the carbs being partially plugged up and probably also a weak battery as these are the common culprits but valve clearances being wrong will also cause issues...

 

[295566]

There are tons of possibilities still.

I suspect the carbs being partially plugged up and probably also a weak battery as these are the common culprits but valve clearances being wrong will also cause issues...

x2

Sounds like your friend's bike can use some maintenance, it definitely won't hurt! Pull the carbs and thoroughly clean them, do a valve adjustment, and test the battery (or replace if it's been more than a few years since that has been done). Inspect all vacuum lines when reinstalling the carbs too. That should be a good start. :thumbup

 

[berth]

So, here's a follow up after a bit of work over the weekend.

new sparks and cleaned out the carb, no dice. Don't think this is my typical issue of days past. Still having a low idle and a loss of power. I do get occasional chugging where it feels like the power kicks in. Gonna check simple things like cleaning the air filter over the week and then probably take a look at valves next weekend when I have time.

Does this sound like a valve issue?

 

[mototireguy]

Possible gas tank breather not breathing.
Is there any whoosh sound when opening the gas cap?
Try starting/running bike with gas cap cracked open.

Vacuum operated petcock type bike?
Try running the petcock in Res/Prime position.

Possibly weak battery or charging system kaput.
What is the battery voltage key-off?
What is the battery voltage bike-running?

And valve clearance check, if within spec then easy task very much worth checking, not assuming/guessing.

 

[bobl]

Does the 250 Ninja use a fuel pump to deliver gas to the carbs? If the fuel tap is below the carbs, many bikes use a 2 to 4 psi pump for delivery. Sometimes if the tank level is well above the carbs, it will gravity feed to the carbs. Level gets low and it needs the pump. I don't know about the Ninja 250, but worth a look if it has a pump.

 

[Junkie]

I don't believe it uses one. I know the 1st gen and 2nd gen were gravity feed, I believe the 3rd gen is too.

 

[berth]

More updates:

voltages look good. 12.5V key off, 12 key on, 13.5-14 running, 10+ starting.

I'm sure that just one cylinder isn't firing though. Only one of my exhaust pipes are heating up.

Well, that can't be good!

 

[Maddevill]

First see if you have spark at both plugs. If so, you either have a really tight valve in the dead cylinder or a plugged carb on that side. Look into which it is.

Mad

 

[295566]

First see if you have spark at both plugs. If so, you either have a really tight valve in the dead cylinder or a plugged carb on that side. Look into which it is.

Mad

+1

Also check grounds, and wiring from coil/ignitor to the plugs.

 

[berth]

I passed this all along, thanks all!

 

[stangmx13]

theres little consistency in these "issue reports". first its a hard starting problem, now one cylinder isnt firing. I wonder if the owner working on the bike is causing more problems.