Wild Dog Adventure Riding

Technical Section => Make / Model Specific Discussions => KTM LC4 400/610/640 & 690 => Topic started by: cloudgazer on December 20, 2018, 05:02:04 pm

Title: KTM 640 not starting. Help required.
Post by: cloudgazer on December 20, 2018, 05:02:04 pm
I was on reserve fuel.
The bike started fine, but died after going one block.
I filled up on fuel, but the bike still doesn't start.

The battery is charged, and so it does turn over.
But won't start.
I drained the float chamber, but still no joy.

What can I try next?
Title: Re: KTM 640 not starting. Help required.
Post by: Tom van Brits on December 20, 2018, 05:07:44 pm
Running dry sometimes suck kark into the carb.
If it is not your side stand switch nor your 'start run switch' open carb and check jets.
That if you do not have an inline fuel filter. Otherwise just replace inline fuel filter
Title: Re: KTM 640 not starting. Help required.
Post by: Nigel X on December 20, 2018, 05:24:05 pm
Open the float bowl drain, then open the fuel tap to check fuel supply to the carb. It should flow out strongly from the float bowl drain.

If the fuel is feeding well to the carb, the bike should still start with the choke full on if the low speed jets are blocked.
You would need to open the throttle above a quarter to keep it running.
Title: Re: KTM 640 not starting. Help required.
Post by: cloudgazer on December 21, 2018, 03:07:32 pm
Open the float bowl drain, then open the fuel tap to check fuel supply to the carb. It should flow out strongly from the float bowl drain.

If the fuel is feeding well to the carb, the bike should still start with the choke full on if the low speed jets are blocked.
You would need to open the throttle above a quarter to keep it running.
Hi
I tried this.
Fuel does flow, but Iím not sure how strongly itís supposed to flow. Seems decent enough though.
What next?


Sent from my iPhone using Tapatalk
Title: Re: KTM 640 not starting. Help required.
Post by: Tom van Brits on December 21, 2018, 03:37:18 pm
Open the float bowl drain, then open the fuel tap to check fuel supply to the carb. It should flow out strongly from the float bowl drain.

If the fuel is feeding well to the carb, the bike should still start with the choke full on if the low speed jets are blocked.
You would need to open the throttle above a quarter to keep it running.
Hi
I tried this.
Fuel does flow, but Iím not sure how strongly itís supposed to flow. Seems decent enough though.
What next?


Sent from my iPhone using Tapatalk

If the bike ran dry and now refuse to start it should be the carb. Remove the carb and jets, remove jets one by one and clean them properly with carb cleaner and copper wire (the wire you find inside the electrical insulated cables) Make sure you get all the kak out, clean every jet and put it back. It should start if the everything is back together as it should.

on the fuel flow, not strong at all because it is gravity fed and not fuel pump

You should be able to find many youtube videos on how to clean a KTM640 carb, how to set the float level etc
Title: Re: KTM 640 not starting. Help required.
Post by: Casting from Turd on December 21, 2018, 03:43:20 pm
Lion Matches are also a good starter :peepwall:
Title: Re: KTM 640 not starting. Help required.
Post by: cloudgazer on December 21, 2018, 04:26:43 pm
Open the float bowl drain, then open the fuel tap to check fuel supply to the carb. It should flow out strongly from the float bowl drain.

If the fuel is feeding well to the carb, the bike should still start with the choke full on if the low speed jets are blocked.
You would need to open the throttle above a quarter to keep it running.
Hi
I tried this.
Fuel does flow, but Iím not sure how strongly itís supposed to flow. Seems decent enough though.
What next?


Sent from my iPhone using Tapatalk

If the bike ran dry and now refuse to start it should be the carb. Remove the carb and jets, remove jets one by one and clean them properly with carb cleaner and copper wire (the wire you find inside the electrical insulated cables) Make sure you get all the kak out, clean every jet and put it back. It should start if the everything is back together as it should.

on the fuel flow, not strong at all because it is gravity fed and not fuel pump

You should be able to find many youtube videos on how to clean a KTM640 carb, how to set the float level etc
Remove carbs? Clean Jets?
It's like you're trying to communicate with me in a foreign language.
 ;D
Title: Re: KTM 640 not starting. Help required.
Post by: Sprocketbek on December 21, 2018, 07:54:52 pm
Remove the carb and jets,

Cough, cough...... ::)
Tom, you make it sound real easy.
On a 640, that's half a day's work..............the subframe needs to be loosened from the frame. And to do that, a LOT of other stuff have to be undone and put back.
Title: Re: KTM 640 not starting. Help required.
Post by: Dux on December 21, 2018, 08:35:41 pm
Remove the carb and jets,

Cough, cough...... ::)
Tom, you make it sound real easy.
On a 640, that's half a day's work..............the subframe needs to be loosened from the frame. And to do that, a LOT of other stuff have to be undone and put back.

No Nic , it's not so bad , I can think of many bikes that are far worse .
Title: Re: KTM 640 not starting. Help required.
Post by: cloudgazer on December 23, 2018, 02:40:37 pm
OK, I've doubled checked the fuel flow, and battery and that's all good.
Still not friggin starting though...

 don't have the time to take the bike apart and learn how to clean the carbs now... esp as that might not be the issue.

Definitely gonna need some help.
Title: Re: KTM 640 not starting. Help required.
Post by: Nigel X on December 23, 2018, 08:23:26 pm
You are right.

You should be able to establish what the problem is without taking much of the bike apart.

Rather get some help.

I for one, am most interested in the what the problem is.
Title: Re: KTM 640 not starting. Help required.
Post by: Mello on December 23, 2018, 10:29:23 pm
My 640 seems to get very grumpy if it has stood for some time.  The last time this happened I removed the air cleaner, took some quick start, sprayed it into the carb and she started fine and sat idling away.

It's worth a shot.


Sent from my iPad using Tapatalk
Title: Re: KTM 640 not starting. Help required.
Post by: the_BOBNOB on December 23, 2018, 10:33:04 pm
Before stripping down to remove the carbs etc. I prefer to do the following.

Remove the air filter.

Then open the throttle to open the butterfly valve in the carb.

Then while turning the motor with the starter spray so flammable spray into the air box.

You can use almost any flammable spray from Quick Start to deodorant to Doom  ;D

If you have spark it will start to run or sound as if it wants to run.

If it remains as dead as a doornail you know your problem is not fuel but spark related.

You first need to pin point the problematic system and then you start to tackle the problem. Just blindy stripping stuff is a sure fire way to waste alot of time.
Title: Re: KTM 640 not starting. Help required.
Post by: cloudgazer on December 24, 2018, 03:08:54 pm
thanks for the replies.

The bike sounds like it is firing (so not completely dead) but it just doesn't 'catch'.

will check the air filter option mentioned above.
Title: Re: KTM 640 not starting. Help required.
Post by: Sprocketbek on December 24, 2018, 05:52:36 pm
Could be something small.
Check that your decompressor cable is not snagged/tight.
Title: Re: KTM 640 not starting. Help required.
Post by: BuRP on December 25, 2018, 03:24:08 pm
My money's on a clogged idle jet........
Title: Re: KTM 640 not starting. Help required.
Post by: Operator on December 25, 2018, 04:15:31 pm
Before stripping down to remove the carbs etc. I prefer to do the following.

Remove the air filter.

Then open the throttle to open the butterfly valve in the carb.

Then while turning the motor with the starter spray so flammable spray into the air box.

You can use almost any flammable spray from Quick Start to deodorant to Doom  ;D

If you have spark it will start to run or sound as if it wants to run.

If it remains as dead as a doornail you know your problem is not fuel but spark related.

You first need to pin point the problematic system and then you start to tackle the problem. Just blindy stripping stuff is a sure fire way to waste alot of time.

Quick start is a good option
Title: Re: KTM 640 not starting. Help required.
Post by: evansv on December 27, 2018, 01:08:56 am
 :sip:
Title: Re: KTM 640 not starting. Help required.
Post by: elandsrider on December 27, 2018, 01:29:57 am
Check gaskets that could create excessive air pull thru carb creating a misfire
Title: Re: KTM 640 not starting. Help required.
Post by: trevo on December 27, 2018, 06:59:23 am
Might be valve clearances, depends on the km`s. 
Title: Re: KTM 640 not starting. Help required.
Post by: GreggB on December 28, 2018, 04:03:58 pm
thanks for the replies.

The bike sounds like it is firing (so not completely dead) but it just doesn't 'catch'.

will check the air filter option mentioned above.

Mate of mine had a similar problem. It turned out to be a pinhole in the fuel pump diaphragm that wasn't allowing the pump to deliver enough fuel to get it started keep it running. The pump works on vacuum so not much was happening with the hole.
Title: Re: KTM 640 not starting. Help required.
Post by: cloudgazer on January 07, 2019, 10:04:32 am
Hi

My nephew took a look at the bike while I was away.
He claims it is ignition related. No spark at all.
he tried multiple plugs with no luck. Also checked the wiring looms, but all seemed good.

Possible faults could be stator or CDI.

what do you all think?
Title: Re: KTM 640 not starting. Help required.
Post by: the_BOBNOB on January 07, 2019, 10:50:11 am
Hi

My nephew took a look at the bike while I was away.
He claims it is ignition related. No spark at all.
he tried multiple plugs with no luck. Also checked the wiring looms, but all seemed good.

Possible faults could be stator or CDI.

what do you all think?

Test the stator - that is easy and quick with a multi-meter.

If it is the stator they are quick and easy to fix/rebuild vs a CDI that might be a very expensive replacement.
Title: Re: KTM 640 not starting. Help required.
Post by: the_BOBNOB on January 07, 2019, 10:53:24 am
Looking at the stator on photos from Google I do not see any exciter coil - just standard stator coils.

So I would guess that the CDI is a DC type CDI and not AC fired - so you should see spark no matter what as the spark would come from the battery and not the stator - the stator will just recharge the battery and run the lights etc.
Title: Re: KTM 640 not starting. Help required.
Post by: AntonW on January 15, 2019, 04:00:00 pm

can you kick start bike?

possible problems

check side stand and clutch safety
starter clutch
decompression "stepped washer"
stater motor brushes, replace with Honda, i think from CX 500
Title: Re: KTM 640 not starting. Help required.
Post by: cloudgazer on January 21, 2019, 09:55:54 am
quick update.

The bike is at KTM in CT, the issue is something to do with the stator. needs to be replaced.
Waiting on the part.
Hopefully get it this week.
Title: Re: KTM 640 not starting. Help required.
Post by: onderbroek on July 12, 2019, 01:01:06 pm
Bike Starting yet?
 :sip:
Title: Re: KTM 640 not starting. Help required.
Post by: cloudgazer on July 16, 2019, 02:25:10 pm
Bike Starting yet?
 :sip:

yeah.
It sat at KTM for almost 2 months while they waited for the part.
Running like a dream now.
Title: Re: KTM 640 not starting. Help required.
Post by: evansv on July 17, 2019, 11:44:41 am
What was the problem in the end?
Title: Re: KTM 640 not starting. Help required.
Post by: cloudgazer on July 17, 2019, 03:59:07 pm
What was the problem in the end?

something to do with the stator not firing - or something like that.
Not a major part, R900 or so - just a very long wait to get it.
Title: Re: KTM 640 not starting. Help required.
Post by: Dux on July 18, 2019, 06:01:18 am
For that price it must be the pickup coil