125H runs for 5 minutes then dies

[YZ250H]

Hi dudes,

Finally got the 125H/J going.  It actually goes really well - lifts the front wheel  - for about 5 minutes  .  Then it just dies .  Plug seems to be a nice colour, so I think I've got the fuel reasonably close.  Installed a new needle and seat, cleaned carb, checked float levels etc. It is also very hard to start (need to tow).  Starts better with no throttle (ie load) and once above a certain rev level goes like a rocket (relatively speaking).
So I'm suspecting electrical or overheating.  There seems to be a whole lot of gurgling noises coming from the head area when the bike has stopped.  Is this a normal thing ?  I can't see a whole lot of circulation when I remove the radiator cap.  I thought the impellor looked pretty good.
The only other thing I can think of is a dodgy coil or something.  Hilly has advised me to check the stators and the coil and the kill switch.  The kill switch I can do, but I need guidance on the coils/stators.  I know we have been through this a hundred times, but I can't seem to find the thread that explains it.
One more time for the uneducated please .
TIA

[evo550]

How does it stop?
Rev it's head off then die..Start miss firing... or just plain stop dead in it's tracks?

[YZ250H]

Just stops dead in a progressive sort of way. As if you hit the kill switch then let it off.  Because it dies a bit more every time it eventually just stops.  A bit like it's running out of fuel, but it isn't (99.99% sure).  I know, I know - I will check the kill switch first , but it seems odd that it will go for almost the same length of time every time before dying - that's why i was thinking overheating or coil.  Also forgot to mention that when I first got it it started second kick after being left for many months.  Has gotten progressively harder to start.  Now it's harder to start than a second hand lawnmower 

Found how to test ignition coil and kill switch in the manual.  Just need help with stator coil testing.
Cheers

[DJRacing]

250H Check the flow of the fuel. If it keeps dying after the same length of time it sounds like not enough fuel is getting to the carb.(the filter could be blocked). Is the plug wet after it dies? If it is electrical the plug should be wet because you have lost spark but the fuel would still be coming in. Is the gurgling sound in the barrel/head or is it more in the exhaust pipe? Do it run (time wise) longer if you are just idling around than compaired with full throttle?
Do a fuel flow check. Remove the fuel hose at the tank and check the tap and then replace it and check the filter and then check going into the carb. The flow should be good and constant.
Is it using/losing coolant?
The coil, remove the spark plug cap (check the lead for good wire) and hold the lead about 6mm-8mm away from the engine and crank it over to see if you have a big fat spark.
When the stator fails (high speed coil) the bike just doesnt want to rev and has no power.

[YZ250H]

DJ,
OK - so stators are OK.  It is happy to rev once you get it going and has plenty of power for a 125.
I did the spark test with the plug still in the cap and earthed against the head.  The spark was not what I would call fat.  Small and weak would be a better description.
I'll try the fuel tests you suggest.  Fuel upside the filter is fine.  Haven't tried downside of filter, but shall do so.  should be OK filter only installed recently.  I'll give it another ride and see if the plug is wet.  Can't tell if it idles longer as I've never actually let it idle and the idle screw isn't long enough to reach the slide (it's the wrong one - still waiting for Mr Yamaha "on back order")

The gurgling sound is in the head/barrel - definitely water.  It does lose some fluid, but very slowly.  I keep an eye on it and top it up regularly.  How hot is the colling water supposed to get.  I knew I should have stuck with a G model  .  I will bypass the steering head with hoses.  This will resolve the problem of the leak.  I will get around to your fix solution soon.

So down to 4 things now - ingition coil, kill switch, fuel shortage or overheating (maybe).  3 of these I can now resolve thanks to your help.  I'm going to the farm tonight, so I'll have a look at it.

Cheers

[jimg1au]

HI
i had a e model tz250 that did the same thing and it turned out to be the plugs.try a new spark plug as you could have fouled a plug you said the spark is not a good fat one.
cheers
jimg

[evo550]

250,
Also check the breather on the fuel cap, this is often overlooked, if it is blocked as the tank empties it will cause a vacume and prevent fuel flowing, To test run it until it stops then pull the fuel line off see how much fuel is coming out of the line, then undo the fuel cap and see if the flow increases. Does the fuel tap have a reserve? if so have you had it apart and re-assembled wrong and the "On" position is now the "Reserve" position? On the plug side of things, get yourself two new ones, run one until it dies, then fit the new one straight away, and see if it fires. I once had a maico that would just chew through plugs with no visual signs of fouling, they would just stop firing, on average lasting about 9 or 10 laps of a race track.
Could not rectify it, just got used to it. 3 new plugs to every race meeting.........beats me why they are the "must have" item in VMX.

[BONEHEAD]

just a little concerned that you dont seem to have any coolant flow , you should be able to see flow in the radiator at idle,does the bike start after it dies or only when it cools down,it could be a partial nip up due to overheating,the only thing is it will get worse and eventually sieze, if it starts almost straight away after dying it is possibly a fuel concern (blocked fuel tap) or maybe something simple like float level not adjusted correctly (change of needle and seat),it is possible that its going like a rocket because its a tad lean,  then the next on the list is that the source coils are on there last legs and just cant handle the heat causing them to open cicuit, you may need to get the bike to that point of dying and check for spark straight away, use a screwdriver in the spark cap and find a good earth, kick the bastard and see if you have spark.also do yourself a favour and check your gearbox oil and make sure its not pumping coolant into the gearbox due to the seal leaking,the tell tale sign is it will be milky in colour, hope this helps in some way , let us know what you find.CHEERS   PS CHECK YOUR COIL LEAD IS SECURE IN THE COIL CAN IT BE REMOVED EASILY

[YZ250H]

Tried to test the ignition coil and the kill switch last night.  I found out the reason why the electrician left the multimeter at my place when he was doing a job there.  The f$%#&ing thing doesn't work properly   Thought I'd scored a multimeter, but instead scored a piece of crap !!  That's Karma for you !!

I'll buy one today and see how I go.  Lots of different things to look at now.  Thanks guys.  I'll check all these things one at a time over the week-end and let you know how I go.  Should just be a process of elimination.

Cheers
T.J.B.

[DJRacing]

250H it will be good to hear what is/was wrong with the 125H. Its always interesting to try to figure out a problem and get it corrected. Hope ya find the problem and let us(guessworkers) know what it was.

[YZ250H]

Hi Guys,

Tested the coil and kill switch with my new multimeter .  Kill switch seems fine with infinite resistance (open circuit) without the button pressed and bugger all rsisitance when the button is pressed, so that seems OK.  The ignition coil may be another story.  Clymer says 0.6 to 1 Ohm +-10% for primary coil and 5.6 to 6.2 K ohm +-20% for secondary (spark plug side).  My readings are primary - 1.4 Ohms and Secondary 6.27.  Primary according to Clymer NFG.  Clymer says chuck it and get a new one - what do you guys say ??
I imagine like cars someone make an aftermarket hot up coil for bikes ().  Otherwise there is one on Ebay.  The good news is the secondary on the 250 Coil doesn't come up to scratch either , so aftermarket would be good (maybe i can get discount for bulk buys  ).  Anybody know ??

I will continue to go through the other stuff on here as it may be a combination of things.

Cheers  

[Hoony]

YZ250H i would say your coil is fine !

0.4 Ohm Resistance extra is negligible. as a matter of interest did you Zero your multimeter before testing the primary ? this is done by holding the 2 multimeter leads together when on OHMS scale and using the adjustment Potentiometer (dial) till the meter reads zero, i would suspect that this is your0.4 ohm error. BTW, i am an Electrician !

[YZ250H]

No I didn't zero it .  That's why I'm a civil engineer not an electrician (or a mechanic) .
I'll give it a crack and get the coil out of the bin 

[Hoony]

as for any other electrical problems i can only summise that if the bike is getting hot and coils in the flywheel are getting hot it could possibly breaking down (coils shorting between turns) when hot , this can be a problem with bad insulation (enamel on the wiring) due to age.

also look for any plug in bad connections or worn insulation possibly touching the frame (earth shorting).

[YZ250H]

Cleaned the contact of the coil to the frame, cleaned the plug.  It push started quite easily with the choke on and stopped very shortlly after.  Then it kick started first kick .  It ran for the customary 5 mins then died true to form .  Checked fuel flow below filter - all good.  Drained carb from large plug in the bottom.  Plenty of fuel in there.  Fuel stopped flowing when I turned the fuel tap off and then flowed freely when I turned it back on.  To me this would indicate the needle and seat is opening().  On each stoppage the plug has been dry when the motor has stopped, but has been quite hot, so maybe the fuel evaporated .  I'll try and get a video of bike running then stopping to see if that helps you guys at all.

Anyone any the wiser???.  At the moment things seem to be pointing to the fuel side of things wouldn't you think?. Hoony was right about the multimeter.  Both readings in tolerance, so the coil is OK - thanks Hoony - saved me on that one.  I think I will pull the carb off and clean it again, check float levels etc.  I'll go over the wiring (which looks pretty dodgy) today as well.

As far as the gurgling sounds go - the transmission oil still looks good.  I put some new hoses on and bled the air out of the top of the head and it seems to have settled down nicely.  Still losing water from the steering head.  Nathan's got some hoses on the way, so I'll short circuit the steering head when thoose hoses get here.

I'll keep you posted.