CBF125... STILL won't start...

[kal9001]

Okay, same old story...

Bike cut out on the GF on her way to work. She got it going again once, then it died again within a mile and won't start again.

It turns over, there is a minor rumble and sometimes it almost sounds like the engine is taking a little slack off the motor, but never actually starts.

The bike will bump start, but has notably poor power, and will die again as soon as you let the revs drop under about 4k or drop the throttle under about 1/3.

We have had the injector out and noticed the spray pattern looked a little heavy, so we replaced the pump. this has made a big difference and the injector now emits a fine mist and projects it much further. as I would expect.

We have checked the plug it seems in good order, with a strong spark.

Ive checked valve clearances but have no other means to check compression other than a finger, it's got some compression, but no was to know how much.

Any idea's what to check next? Its only done 1000 miles, though it was stood for a while its done 500 of those miles recently so its not like its got stale fuel or seized :-/

Getting pretty fed up of this bike now and really desperate for a solution, ferrying her to work in the car is expensive on fuel.
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Anyone stupid enough to think we will drag a load of wooden horses full of soldiers into our city is certanley stupid enough to drag all of ours into theirs!

[Copycat73]

[nowhere.elysium]

Have you checked the battery?
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'10 SV650SF, '83 GS650GT (it lives!), Questionable DIY dash project, 3D Printer project, Lasercutter project

[kal9001]

[jaffa90]

Is the exhaust system breathing/clear?

[Nobby the Bastard]

Ignore this, he's a fuckwit

[jaffa90]

Sounds like fuel starvation, which is rare. I'd normally say it'll be electrical.

However, take the fuel cap off, try and start it.

EDIT: Just noticed that you are getting a nice spray from an injector. Ignore the above. Look at timing of the cam chain and the pickups for ignition and injector.

Well that covers everything!

[kal9001]

Yea, with the old pump it looked like it was chucking fuel with a bucket. so we though it was that. Changed the pump, and in the process had to swap the fuel lines too as they felt like they were made of cheese and pretty much disintegrated :-/

So... I have no means to properly check the ignition timing, As for the valve timing, had the rocker cover off and checked valve clearances, again no feeler gauges but it feels like what you should expect (I've had experience building (and breaking) beetle engines) At the same time I can see and feel that the cams aren't doing anything bizarre, the rockers are working, the chain is still on, and turns freely without any noise, there is wet oil around the inside so it is feeding oil up into there.

If its an electronic issue then it has to be timing, the coil and plug do appear to work, though I will try swapping the plug as suggested anyway, but I can't check the actual ignition timing any way, but then how could that so off so badly it won't start, but then close enough it will bump start :-/

Compression is my other thought, if a valve or valve seat may be cracked, or a piston ring has annihilated itself O.o cross that bridge when we get to it.

As for the exhaust system... I could try running it with the pipe off, but I don't think thats the issue, there is noise coming from the tail end, and a small puff of air... oddly though, there doesn't seem to be a strong smell of fuel in what comes out. but fuel is defiantly going in...
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Anyone stupid enough to think we will drag a load of wooden horses full of soldiers into our city is certanley stupid enough to drag all of ours into theirs!

[Paulf]

I honestly would beg steal or borrow a compression tester. I did when I had similar turned out to be scored bore. I think last year I paid £12 quid of Amazon. With modern honda PGM engines if the lights not showing it a sign of mechanical problems in my experience of doing up a variety of modern abused honda PGM 125's. Or poor fuel in 45 years of cars and
motorbikes I only come across 1 case of crap fuel.
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Past bikes simsom mofa 1s, suzuki hustler 250 (£35 in 1973), suzuki ts125k, mz150, yamaha yb 100, honda pc50, honda vision 50, all 2 stroke - then cars - honda pcx 125 (sold) own honda fes 125 and Mrs 125 spares or repairs. Started 1972 all accidents walked away no insurAnce claims

[ZaphodBeeble]

Do the compression test. If it's low I recommend checking/adjusting the valve clearances as they will probably be tight.
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Current bike: VTR1000F Firestorm. Previous: Firestorm (written off) - XJ600 Divvy - NSR125 - DT125 and a load of offroaders.

[kal9001]

[ZaphodBeeble]