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Author Topic: KTM 640 not starting. Help required.  (Read 935 times)

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Offline cloudgazer

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KTM 640 not starting. Help required.
« 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?
 

Offline Tom van Brits

Re: KTM 640 not starting. Help required.
« Reply #1 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
 

Offline Nigel X

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Re: KTM 640 not starting. Help required.
« Reply #2 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.
Quench my thirst with gasoline.
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Gimme Fire,
Gimme that which I desire
 

Offline cloudgazer

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Re: KTM 640 not starting. Help required.
« Reply #3 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?


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Offline Tom van Brits

Re: KTM 640 not starting. Help required.
« Reply #4 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?


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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
 

Offline Casting from Turd

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Re: KTM 640 not starting. Help required.
« Reply #5 on: December 21, 2018, 03:43:20 pm »
Lion Matches are also a good starter :peepwall:
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Offline cloudgazer

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Re: KTM 640 not starting. Help required.
« Reply #6 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
 

Offline Sprocketbek

Re: KTM 640 not starting. Help required.
« Reply #7 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.
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Offline Dux

Re: KTM 640 not starting. Help required.
« Reply #8 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 .
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Offline cloudgazer

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Re: KTM 640 not starting. Help required.
« Reply #9 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.
 

Offline Nigel X

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Re: KTM 640 not starting. Help required.
« Reply #10 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.
Quench my thirst with gasoline.
So Gimme Fuel,
Gimme Fire,
Gimme that which I desire
 

Offline Mello

Re: KTM 640 not starting. Help required.
« Reply #11 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.


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Offline the_BOBNOB

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Re: KTM 640 not starting. Help required.
« Reply #12 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.
 

Offline cloudgazer

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Re: KTM 640 not starting. Help required.
« Reply #13 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.
 

Offline Sprocketbek

Re: KTM 640 not starting. Help required.
« Reply #14 on: December 24, 2018, 05:52:36 pm »
Could be something small.
Check that your decompressor cable is not snagged/tight.
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Offline BuRP

Re: KTM 640 not starting. Help required.
« Reply #15 on: December 25, 2018, 03:24:08 pm »
My money's on a clogged idle jet........
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Re: KTM 640 not starting. Help required.
« Reply #16 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
 

Offline evansv

Re: KTM 640 not starting. Help required.
« Reply #17 on: December 27, 2018, 01:08:56 am »
 :sip:
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Offline elandsrider

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Re: KTM 640 not starting. Help required.
« Reply #18 on: December 27, 2018, 01:29:57 am »
Check gaskets that could create excessive air pull thru carb creating a misfire
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Offline trevo

Re: KTM 640 not starting. Help required.
« Reply #19 on: December 27, 2018, 06:59:23 am »
Might be valve clearances, depends on the km`s. 
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