bike will spark, but starter motor will not turn

[mikey909]

i just want to check so that i dont purchase the wrong part. when i press the ignition, i get the click from the relay, i get a spark from the HT coil to the plug, but i get no response from the starter motor. initially i thought it was the starter that was the problem, but i found that after a few tries at the ignition, the battery would die and i would have to charge it again. now the battery has become really hot and has developed a swelling at the side. although when fully charged the battery reads 12.7v, i do believe that it doesent have enough power to drive the starter motor. alongside the battery, would i also have to replace the starter motor as well?

[_Iain_]

It's a little odd you're getting a spark from the thing without it spinning over.

Does the engine turn over & bump start? If not it may be seized. & the starter could be perfectly fine. Have you removed the starter motor itself & checked that it spins freely? Does the starter spin up if connected directly to a known good battery??

Either way sounds like you've just held the starter button in without it spinning over till the batterys boiled itself to death.
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[mikey909]

[_Iain_]

[mikey909]

[_Iain_]

Right,

Does it fire on the kickstart. You need to find out if the engine spins over or if its locked solid. Not the starter, the engine. You may have to pull a cover off and get a socket/spanner on the end of the crankshaft if there isnt a kickstart. The aim of the game isnt to start it, but to find out if the crankshaft will rotate without any problems. It will be very stiff unless the sparkplug is removed.

The more you press that button the more damage you are doing to the bike. If you replace the battery & starter & the engines locked up then you'll have another burnt out battery & starter within 30 seconds & have wasted £££ on a fucked engine.

The fact you've boiled a battery without realising makes me wonder if the "timing cog" you've altered was done correctly. If you've altered a cam chain & seized the engine, bolted it back together & held the starter till it burnt out wondering why it wouldnt start then its a whole new engine you need. But again, i've got no idea. When did the thing stop starting?? After you'd messed with it & had it running or before?


To the point,

Stop pressing the starter.

Find out if the crankshaft spins by hand without the plug in.

List up EVERYTHING you've touched on the engine & transmission.

I cant help with half the story.
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[Vincent]

If the battery is exploding, either the reg/reg has gone or you're using the wrong charger.
____________________
Space Is Deep

[_Iain_]

[Vincent]

[mikey909]

[mikey909]

right, ive tried turning the crankshaft. it will turn, then i'll hear a metal to metal clang, and i can no longer turn the crankshaft. im going to pull the engine apart anyway and see what i can find...

[tahrey]

[tahrey]

[_Iain_]

[mikey909]

much appreciation for you help guys ive removed the engine, taken the cover off the cam shaft, and removed the cam chain (spark plug has been removed also). ive found that when i hold the cam chain loose, i get that same clang sound, and the rotation stops. but when i hold the chain taught and rotate the engine, its perfect. i get the feeling that i probably messed up somewhere on the cam chain. yep i agree, its all a learning curve as the bike has been built from frame up...i'll just try not to burn the bike down this time

[tahrey]

^ This.

I've spent so much time amongst a world full of brushless AC motors and the like I forgot that yer typical cheap starter motor is likely to just be a simple brushed-DC affair.

Which is quite literally a free-to-rotate heating element surrounded by a strong magnetic field that, through the wonders of electromagnetism, means that all the energy being transported by the electrons gets converted into kinetic (movement) rather than internal (heat) energy in the material it's flowing through.

Stall one of those, it heats up in pretty short order, and as the battery forms the other end of the loop, it suffers a similar effect. The saving grace is that, although the resistance is quite low in order to get the most power going through the motor (power = current x voltage, and current = voltage divided by resistance), it's still a looong length of wire, so it's nowhere near as low as a spanner dropped across the terminals would be. You have to abuse it for quite a while before it actually gets to the battery-killing point.

[tahrey]

Oh ... chain not tensioned up somehow?

So, one presumes, if you've followed proper procedure and timed the engine up to TDC (so the valves are shut anyway), it's managed to turn the cam loosely at first, enough to open one or other of the valves enough to interfere with the piston, but then started slipping and left the valve open far too long?

[mikey909]

[Vincent]

[_Iain_]

If it's just valve springs compressing then you should be feeling two bits of stiffness to every one rotation of the camshaft.

Once for the exhaust valve, once for the inlet.

However - if one valve is bent up then that valve will get very stiff when it opens or shuts, and the other will operate smoothly.

If you only feel one bit bit of stiffness this could be potential bad news.

On the other hand you might just have left the sparkplug in and be feeling the compression stroke.
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[mikey909]

[tahrey]

If you find it difficult to line the cam up so it's in the dead centre of the "stiff" area (ie with the tallest bit of the lobe pushing the valve fully open) even with the plug out - because once you go a little past in either direction the spring pushes it round to the flatter bit - and it does it evenly for both valves, then that's probably a good sign.

(It's a right pain trying to line the cam up on my CG so I can do the clearances because of this ... it spins so far past the inlet valve opening point I have to backtrack to line it up on TDC )

Mikey, were you editing your post at the same time I was submitting mine? It seems we've ended up duplicating info "in our own words", sort of. I didn't see all the part surrounding the picture of the toaster elements before!

[mikey909]

right, ive fitted a new stater motor. when i pres the ignition, the motor will turn, but then will get stuck in the outer cog (i let go of the ignition this time). only once, i heard the crackshaft move when i pressed the ignition. i can move the crankshafe by hand though, so its not seized.

[tahrey]

What bike was it again?

Having just put my CG (mostly) back together, I found that the lower idler cog for the starter - the one that meshes onto the flywheel ring - will happily go in either way round despite being two slightly differently sized gears welded together on a common axle, and will spin just fine in seeming mesh with said ring.

However when you then pop the starter / stator assembly back on, and insert the upper idler gear (one large, small toothed gear welded on a small, large toothed one), it will jam solid unless you've put the lower one in the right way.

Guess which way I put it in... yep. Had to take all the bolts, wires and covers back off, unhitch the assembly, turn said cog around 180 degrees, and then put it all back together, at which point everything was just dandy.

And the brilliant thing is, thanks to the flywheel cog being on a freewheel mechanism, you can't even tell unless you either try the starter or attempt to turn the crank backwards a bit. You just assume it's in right because, of course, the lower gear wouldn't fit in place if it wasn't the right way round, and the upper one wouldn't fit inside it's own slot if the lower gear wasn't properly aligned ... right? Wrong.


By the way, have you any way of kick / bump / pull-starting the engine without the electric starter? Just to make sure it will actually go and there's nothing seriously dragging on it?

You have put oil in, right?
(Yeah, guess what else I didn't do before my first test-start ... luckily realising within a couple seconds and killing the ignition straight away. The top end and piston/barrel had been dosed, but the bottom end was reliant only on whatever residual was left in the bearings themselves...)

[mikey909]