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Discussion Starter #1
Good evening everybody

I have a ktm lc4 prestige model twin pipe 2006 640 grey engine

It will not start good compression good spark has had all carb parts (mikuni 40), float height set, everything cleaned checked. Fresh petrol new spark plug extra earth points put on the engine to chassis, sprayed easy start direct through the air box to see if it would fire still nothing have connected the wires up on the side stand and clutch switch to rule these out. Has big car battery on it so plenty of power for the battery , check decompression lever to make sure it’s all the way off still nothing any other ideas I could try driving me mad
 

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Hi.
Auto decompressor (on camshaft) notorious for failure - to check... remove spark plug and turn engine using kick start, do you hear a distinctive click (from the top of the engine) as the engine goes over top dead centre ? If no then you're screwed.
Have you ever had it running ??
How do you start it ? - I pull in the manual decompressor, press the start button, release the decompressor after half a spin (or so) and hold on to the start button till it fires (usually straight away).
My first engine required only half choke to start, the second engine requires full choke to start - from cold.
Have you tried using the kick start with the electric start ? - as you reach the bottom of the kick start stroke, press the lecky start.
Checked the tappet clearances ??

Good luck, don't give up and have fun !!!
 

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Discussion Starter #3
Hi.
Auto decompressor (on camshaft) notorious for failure - to check... remove spark plug and turn engine using kick start, do you hear a distinctive click (from the top of the engine) as the engine goes over top dead centre ? If no then you're screwed.
Have you ever had it running ??
How do you start it ? - I pull in the manual decompressor, press the start button, release the decompressor after half a spin (or so) and hold on to the start button till it fires (usually straight away).
My first engine required only half choke to start, the second engine requires full choke to start - from cold.
Have you tried using the kick start with the electric start ? - as you reach the bottom of the kick start stroke, press the lecky start.
Checked the tappet clearances ??

Good luck, don't give up and have fun !!!
thanks for reply

Yes I have the the click from auto decompressor Check

I have had the bike going in the past year or so has been stood a while but has always been hit or miss on the the electric start so I usually kick the big beast over with success in the past

my process To kick starting is similar To Yours

clearances have been checked all good .
Bike has done 7000 miles

I’ve tried putting petrol in the bore to see if it would fire still nothing.

scratching my head now
 

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hi,
does it actually have a spark?
is the blue/white connector still making proper contact with the HT coil?
have you checked the pulse coil distance to flywheel, is it within spec (0.5mm~0.7mm)?
is the CDI still ok i.e. swapping out with another one?

had similar symptoms after I put in a grey 2003 SuMo engine into my 1994 Duke 1 and accompanying CDI (which made a high pitch buzzing noise). car battery to and leech started it, but kicking no way.
turns out it was the CDI about to go and a body blue/white connector (that wasn't dodgy at the time so probably went when put the tank back on).

just a few points that spring to mind.
 

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Discussion Starter #5
hi,
does it actually have a spark?
is the blue/white connector still making proper contact with the HT coil?
have you checked the pulse coil distance to flywheel, is it within spec (0.5mm~0.7mm)?
is the CDI still ok i.e. swapping out with another one?

had similar symptoms after I put in a grey 2003 SuMo engine into my 1994 Duke 1 and accompanying CDI (which made a high pitch buzzing noise). car battery to and leech started it, but kicking no way.
turns out it was the CDI about to go and a body blue/white connector (that wasn't dodgy at the time so probably went when put the tank back on).

just a few points that spring to mind.
Yes has good spark

Blue white Coil wire all checked cleaned

pulsar coil is in spec there is no adjust on these Anyway do they just wear then you have to Fit new

no noises coming from the cdi haven’t Tryed a spare to try
 

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Weird that you get nothing after putting fuel in the bore. Fuel, air, spark, you should get something unless your timing chain is broken or the con rod is snapped.
 

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Discussion Starter #7
Yes has good spark

Blue white Coil wire all checked cleaned

pulsar coil is in spec there is no adjust on these Anyway do they just wear then you have to Fit new

no noises coming from the cdi haven’t Tryed a spare to try
T
Weird that you get nothing after putting fuel in the bore. Fuel, air, spark, you should get something unless your timing chain is broken or the con rod is snapped.
I know the bike has been stood a while but with spark and fuel straight in the bore something should happen surely loads of compression bike ran before this being stood
 

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have you tried brake cleaner instead of petrol? that should start right up provided you wet the spark plug.

snapped Conrad would mean no compression but above all a lot of noise. timing chain snapped would mean the camshaft doesn't turn and then you wouldn't hear the distinct clicking noise of the auto-decomp. and again, a lot of noise and probably a jammed crank...

cam timing can't just wander off, not if its been running before.

id try the brake cleaner. spray it into the carb with full open throttle and give it a good kick with ignition on.
 

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Discussion Starter #9
have you tried brake cleaner instead of petrol? that should start right up provided you wet the spark plug.

snapped Conrad would mean no compression but above all a lot of noise. timing chain snapped would mean the camshaft doesn't turn and then you wouldn't hear the distinct clicking noise of the auto-decomp. and again, a lot of noise and probably a jammed crank...

cam timing can't just wander off, not if its been running before.

id try the brake cleaner. spray it into the carb with full open throttle and give it a good kick with ignition on.
I haven’t tryed brake cleaner but I have been trying a wurth start rapid aerosol can and still nothing .

yes as you say everything turns over to nicely to be cconrod or timing issue bikes done 7k miles

still got spark but still no fire been checking wires today plugs cleaning with contact spray still no fire, I have found I couple of cut wires I I believe it’s the TPS and the bike use to run ok with this disabled

nearly scratched all of the hair off my head now !
 

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Discussion Starter #11
Unsure of this plug there is a black /yellow wire the go’s to nothing and no wire the other side of the plug but pretty sure this was all like this when the bike use to run ok
35012
 

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Discussion Starter #12
Does anybody have a cdi unit I could try ??? I don’t Think this is the problem but worth a try I suppose
 

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that plug is for the CDI to tell it if the bike is in 1st/2nd/3rd gear. somehow with the TPS it smoothens the power output in the lower gears in an attempt to minimise unwanted takeoffs with fast throttle openings?

wurth rapid starter is the same idea as break cleaner. its also a "dry" combustion, not sooty as petrol which can foul the plug.

is it sparking at the right moment, as in just before TDC on the compression stroke?
 

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Discussion Starter #14
that plug is for the CDI to tell it if the bike is in 1st/2nd/3rd gear. somehow with the TPS it smoothens the power output in the lower gears in an attempt to minimise unwanted takeoffs with fast throttle openings?

wurth rapid starter is the same idea as break cleaner. its also a "dry" combustion, not sooty as petrol which can foul the plug.

is it sparking at the right moment, as in just before TDC on the compression stroke?
Yes it seems to been sparking rite before the big compression stroke with the Plug out
 

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Discussion Starter #15
Check pulsar coil on multimeter 100ohms So within spec

same as the main coil all in spec

but as I have spark thought it would be ok

Damn thing ???
 

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have you got a spare plug?
take the cap off (keep the current one in), plug the spare one in and then see if you have a spark.
is it a blue spark?
 

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Discussion Starter #17
have you got a spare plug?
take the cap off (keep the current one in), plug the spare one in and then see if you have a spark.
is it a blue spark?
yes so new plug left in the head spare plug plugged into the cap which is being ground/ held against the cylinder head bolt , I get One small spark on the first Initial crank then It disappears so no spark when cranking so this seems to be the problem Good news

what would cause this pulsar coil even tho I’m getting 100ohms in the meter when testing ?? Thanks for your help appreciate it
 

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had similar when I put the 640 engine into my Duke with older cdi (requiring constant +12V from battery). kicking wouldn't start but long enough on the estart eventually did, didn't run smooth either. pulser coil was also in spec.
I would look into a spare CDI.

perhaps someone nearby with a running 640 could help you out with swapping just to try.
@Set had a donor bike before he traded it in for a 690:p
 
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