A forum for owners of Yamaha TTR250 trail and enduro bikes!

nads2475 · Newbie

starting problems

Cubber · Super Guru

It sounds to me as if your battery is packing up or isn't being charged enough, Paul. hmm

Do you know how old the battery is? confuse

Is it well connected, especially to earth? confuse

When the bike starts does the headlight brighten appreciably as you rev the engine - or is it just as bright/dull all the time?

If it brightens as the engine revs rise then it shows that your alternator/generator is working. If it doesn't then your alternator may need checkng out.

Martyn

yamalama · Veteran Member

Hi Nads, You might get more replies if you post this question in the 'Repairs & maintanance' section. Martyn's advice on checking that the battery is charging is worth while. Checking that the head light gets brighter when you rev the engine worked on older bikes but NOT on our TTRs. I was surprised that this didn't happen when I was checking my bike over before buying it, so I put a meter across the battery and was pleasantly surprised to see it was producing 14.4V at tick-over whereas older designs would have been at 12.5 ish and increases to 14-ish as revs increased, hence the headlight getting brighter. So you need a volt meter (or DMM on voltage setting) across a well charged battery to confirm that the battery is being charged properly by the bike. On these bikes you expect to se 14.4 (+/- 0.2-ish)at tick-over and staying steady as you increase engine revs. The regulators can fail in funny ways including stopping working at higher revs (voltage falls as revs rise). You can get very misleading test results if the battery isn't well charged and in good condition (Does it hold its charge over night once charged off the bike?) However, having said all that, I thought these bikes produced their ignition sparks from a CDI that didn't use the battery. If so, a flat battery would not cause the bike cut out once running, unless a safety relay is doing something odd at low battery voltage and disabbling the CDI. But I am new to this model and could be wrong about this. Hope this helps Lama

TTRfan · Super Guru

If the battery is OK then it sounds awfully like a faulty stator or rectifier/regulator.

Brian

TT-R250M · Super Guru

Here is a diagram of the ignition system

Oh Btw, the ignition coil does run off the battery so it suggests it's a bad earth/battery/rectifier/stator

-- Edited by TT-R250M on Friday 8th of February 2013 01:00:46 AM

TT-R250M · Super Guru

Check all wires have no cuts in them & are not grounding to the frame or crossing.

Then check your earth located at the resistor/rectifier.
Next thing is to check that you have a good open circuit reading from the magneto/stator coil. This will be higher than 12V & should be over 12V at 20 degrees celcius & can go up as high as 200V when the engine is cranked.

I have included a burnt out one from my old TT-R250. This should give you an idea on it. The main thing to note is that the broken wires were not visable until i took it apart & had a good look. You may not be able to find a burnt/broken wire but it does none the less look like it needs replacing.
Posted Image

The one in the pic above burnt out from wires cut from the chain. The previous owner had fitted the wires wrong & they got cut & earthed/crossed....End of stator. :rolleyes:

If you have spark there is obviously a circuit & assures me that it is your stator/magneto or resistor/rectifier or bad earth.

Just remember: Magneto's don't just burn out that easy & usually a grounded or crossed power wire is the cause.

If you have a curcuit (you do) i'd be blaming either the regulator/ressister or stator/magneto. The stator/magneto is highly likely though.
After checking the stator/magneto,check power at the fuse wire is not fluctuating after the regulator. This will give you a good idea whether it is bad or not. It should stay at a constant (or very close to) 11.8 V (closed curcuit).
I'd say it's your stator/magneto but finding out where the power wire is crossed or earthed may be the hard part.

Check for power at the fuse when engine is running. If you are getting power at the fuse then the rectifier/resistor or stator coil may be at fault .The three white DC wires from the stator/ressistor will be the power/charging wires. The other two will be your AC pick-up.

Maybe it has just got to the end of it's life & died. It's possible but in thoery i would expect there to be a cause for it blowing

TT-R250M · Super Guru

This is a simple test that you can do (i'll try to keep it simple)

Disconnect the battery
Ok....Unplug the three white wires coming out of the stator coil. Test these on Voltage setting while cranking the engine over. If you don't have a kickstarter put it in top gear & spin the back wheel. Let me know how many volts comes out from the white wires going to the stator coil.

Next....Unplug & check the two pulse wires (one green & one black) on AC setting while cranking the engine over.. Let me know how many Amps come out.

Now unplug the fuse & test on Voltage setting the harness side (not battery side) while cranking the engine over.Do this & let me know what voltage you get.

Once you have done this we can confirm that your stator coil needs replacing.

At a guess i'd say your stator is no good but i hope for your sake it isn't.

-- Edited by TT-R250M on Saturday 9th of February 2013 04:18:20 PM