125 not starting

[dptilston]

morning all,

Sorry for yet another bike not starting post, but this one has got me puzzled. I took the bike for the first ride to work(about 40 miles) since owning it and had to get recovery to get me home , the recovery bloke said it was the ignition.

So i replace pick-up coil, coil pack, ht lead, cap and plug. I have a spark but the bike still doesn't start, I asked a local garage and they said it could have water in the fuel, so i drained out the tank clean it and filter plus carb, filled the tank up with new petrol. i let the float bowl fill up then i drained it again to check the fuel, which was ok but still nothing. i have done a compression test which tested 190psi, i squirted some oil in the cylinder still tested as 190psi, now im starting to think that it might be the starter gear , could someone point me in the right direction

any advice would be appreciated, thank you in advance

[Old Git Racing]

Can you bump start it? That would tell you if its the starter gear. Is the battery ok?

OGR
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2022 Tiger Sport 660 2019 Street Twin 2003 K3 gixxer 1000 1998 Srad 600 track hack

[dptilston]

tried to bump start it and it sounded like it wanted to go then died, brand new battery that i charged for 5hours before use.

[jeddy11]

What bike is it ? if you have a spark and you have fuel then it should start !! stating the obvious.

If after trying to start it have you taken out the plug to check if its wet ?? maybe you have a blockage in the carb you may fuel in the bowl and a blocked jet etc after checking and if the plug is dry try cleaning the carb jets and all...
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[Rogerborg]

What exactly is happening when you hit the starter? Does it spin over freely enough? Does it give any sign of wanting to start?

If it's a carb bike, is the choke on or off?

What condition was the old plug in?

Is the new plug correctly gapped? I know you said you're getting a spark, but it may not be a particularly strong one.

Are you confident that your sidestand switch isn't playing silly buggers? I'd give it a clean and try removing it to see if that changes the behaviour.
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[dptilston]

its a lexmoto xtr, yeah i know another chinese bike i only got the as a cheap runner before i got my full bike licence.

after trying to start it the plug wasn't too wet and smelt of petrol, i bypass the carb altogether, didn't want to start at all. the bike spins over fine, i took the plug out, had it in 2nd and spun the back wheel seems to be ok. iv tried it with choke on, half and off, little throttle, no throttle. the old spark plug was sooted up, the new spark is gaped using manual and old spark plug. The bike has no sidestand switch and iv bridged the killswitch.

Sorry for the long list this one has really puzzled me.

Thanks again

[Rogerborg]

That is a puzzler. It's a very simple system and there's not much to go wrong. Fuel + spark + compression = bang.

With the plug sooted up I'd guess you might be running mega-rich. Needle sitting loose, or jet dropped it? It happened to me.

https://4.bp.blogspot.com/__DYtEEjm5wE/S27qgGcHuaI/AAAAAAAAAI8/Q9DUZX-bJho/s320/float-bowl-jet.jpg
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[dptilston]

Ok thanks for the advice Rogerborg, I had someone have a look at the bike today, and they think it might be that the ecu is failing, could it really be as simple as that?

[Rogerborg]

As far as I know, the XTR has (or until recently had) a pushrod CG copy engine. There's a CDI that makes a spark at the appropriate time, and a carb that allows fuel into the air drawn in through the inlet valve. I can't think of anything in that system that could be described as an "ECU".

Did this "someone" point at the "ECU"?
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[dptilston]

Thanks for your reply, and yeah its a little red box sat above the cdi unit and in front of the coil pack with two pin connectors running into it, I looked at the wiring diagram in a haynes manual I got for this bike and its showing it has a ECU

[Rogerborg]

Crikey, you live and learn. I wonder what it's controlling.

Sorry, that's me baffled then.
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[stirlinggaz]

try bump starting it in 2nd gear?
cheers,
GAZ

[dptilston]

I know its got me stumped, on the diagram its showing that the ecu is connected to pretty much everything to do with the ignition. but whats throwing me that its got spark, air, fuel and compression

Thank you for the advice on the needle/jet.
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If nothing else works hit it, then hit it again

[P.]

It probably isn't an ECU.

It is chinese, so its likely some shitty relay.

If you have spark and the plug is dry when you try to start it, check the carb.

If the plug is wet, dripping, check the carb to see if the jet has vibrated loose.

If there is no spark, check the wires going to the coil.

[A100man]

Did you try a teaspoon amount of fuel down the plug hole ?

If it runs for a few seconds after that then it eliminates ignition problems..

J

[dptilston]

I'm getting a good spark, when trying to start the bike the plug isn't getting to wet and you can smell petrol from the cylinder. I'll have another look at the carb later. But it didn't seem to want to start when manually pumping the acceleration pump on the carb

[craisin]

Does it have a vacumn operated fuel tap???

[dptilston]

Tried patrol in the cylinder nothing happened, tried spraying carb cleaner through it and around both manifolds on the carb and you guessed it nothing happened.

[Rogerborg]

Weird. I'm strangely invested in this one now.

I know it's subjective, but does it look like a good strong spark?

Also, has the bike been modified in any way? Aftermarket exhaust? Tried sticking your hand over the tailpipe to give some more backpressure?

The only other thing I can think of is that the timing is off, although I wouldn't like to take a guess at how you'd check that.

Do you know which engine it's got in it? OHV pushrod, OHC? Any markings on it? 156FMI, K156FMI, anything different?
____________________
Biking is 1/20th as dangerous as horse riding.
GONE: HN125-8, LF-250B, GPz 305, GPZ 500S, Burgman 400 // RIDING: F650GS (800 twin), Royal Enfield Bullet Electra 500 AVL, Ninja 250R because racebike

[craisin]

is it a sheared woodruff key and the spark no longer happens at TDC?

[dptilston]

Yeah it's got an vacuum fuel tap, I cleaned that out with wd40 and blow through it when I cleaned the tank out, I've tested the air line by taking it off the tank and holding a sandwich bag tight over it and sucked the air out of the bag ok, I can see the patrol pumping into the inline filter

Thanks for all advice please keep then coming, I can't stand being stuck in traffic on the m25 no more lol

[dptilston]

I dont think its subjective, but yeah the spark looks strong enough.

Still got stock exhaust on it and don't think its got any mods, sorry to sound stupid but what would more back pressure do? Its a OHC and the engine is 156FMI.

Sorry craisin but I don't know what you mean by a shared woodruff key

thanks again for all advice

[stirlinggaz]

hi,
the 156 lump is a fairly old generic copy of an old honda engine & tbh, its usually fairly reliable, so its probably not a sheared woodruff key....
op : woodruff key looks like half a pound coin & slots into a "key-hole" on the crank. to see if its still in its key hole have a look at the crank taper & you might be able to see it.
i have had woodruff keys snap/shear before, though usually on 2 strokes which are putting out silly amounts of torque.
if you really want to investigate the woodruff key, you will need to remove the flywheel, which needs a special tool, funnily enough called a fly-wheel tool,lol.
like i said these engines, although old technology, are fairly reliable, its usually the other important parts that let these bikes down, like the sh*tty chinese carb, take it off, clean it thoroughly & re-install it. (or preferably replace it with a genuine mikuni)
stick a new spark plug in it (its not still got the oem plug in it, has it?)
then make sure you have a fully charged battery, its essential you have OVER 12v.
my moneys on the carb.....(it doesnt have that silly pump on the carb thats "supposed to" squirt extra fuel out at wot does it? the way to check - look & see how many cables go to the carb)
that or the dodgy ch*nky wiring....

cheers,
GAZ

[dptilston]

Thank you for explaining woodruff key, Ill have another look at the carb today, yes it has the "silly pump" on it. Theres three cables that go to it, you got choke and the throttle cable which goes to the needle and throttle. Got the new plug in and the battery is good.
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If nothing else works hit it, then hit it again

[dptilston]

Back to basics, carb is off stripped and left in carb cleaner