KTM 50sx not starting

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6/2/2018 10:57 PM

Hi all,

My son has a 2014 KTM 50sx that I bought from a dealer.
It started first go when I bought it but then after a few weeks it started playing up. Hard to start from cold but fine once hot.
Replaced spark plug and that help.
Then got worse and worse to the point where it never started again.
Took it to my local mechanics around the corner from work and he took the cars apart, gave it a clean and reassembled everything.
Started great for a day.
Took it back to him and a week later we were no closer to finding it out what was wrong.
Put new stator as apparently the readings where too low and a kickstart. (And $1300 down)
He also checked the compression and reckon I did not need a top end rebuilt.

Before I picked it up from the mechanic I rang him to see if it was all good and he told me that yes indeed the bike would start everything time even when cold.
Upon turning up to his garage I tried it and did not start.
He gave it a shot and struggled to start it, but he then quickly removed the air filter and spray some cold start spray ( called start ya bastard) and it fired up.
I took it and at the track it did not start straight away but after a few kicks it fired up.
Today, it simply refused to start. I will go and buy some of that cold start spray and if this does the trick, what do you guys reckon and where would I need to look into.
Top end? Will a top end stop a bike from starting?
Hope to read from you soon,

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6/3/2018 5:22 AM

If you havent done a compression check than yeah do that and make sure the motor is good.

You need 3 things to start it. Fuel, air, and spark. Sounds like youre not getting gas if you have to spray starting fluid in there.

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6/3/2018 5:52 AM

I know you said he cleaned the carby but check the vent hoses are clear. Check the coils and spark plug cap

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6/3/2018 1:56 PM

Thanks for replying guys.

The little 50 has also had the spark plug replaced.
I do get fuel to the plug as it s wet.

Will check the vent hose for sure.
Cheers

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6/4/2018 9:02 AM

I have the SAME exact problem Grrrrrrr

What I have found It starts great when you start it frequently, after sitting all winter or even for a weeks starts like a Bear. I pull the plug and it is wet so I heat dry it put it back in same thing grrrrr. I tried starting fluid against my better judgment on a 2 stroke, It fired up right up !!!! I think it needs MORE fuel and every time I heat dried the plug and removed all the fuel it pro longed the start?

I have also heard of bouncing them on the front tire when they won't start which maybe puts alot of fuel into the cylinder and allows it to start? I haven't tried this as it seems insane but then again kicking a right side kicker that is 2" long is pretty insane as well LOLOLOL

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6/4/2018 1:27 PM

526, you r spot on.
Those little things are a weapon when they work but when they don t they are frustrating.

I think the lifting may be true to be honest.

Once I tried a few things but never started.
I took it of the tray of the car and it landed roughly on the front wheel as I almost drop it.
The thing started first kick.

Next time I ll try lifting the rear up for a while to see.

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6/4/2018 3:51 PM

I have literally put 100's of hours on these bikes and I just dont have barely any problems, probably done 2 stators over 3 bikes and I heavily modify the bikes porting, high compression, pipes, race fuel etc.

My maintenance is good though change oil every ride measure the clutch and keep the air gap in check I do a top end every 30hrs and full rebuild every 90hrs at the end of every season strip it and grease and replace everything that looks half damaged or worn.

Jetting is really important to get it right!

I hear people have a lot of problems with them but I dunno maybe it is them but yeah I cant fault them.

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6/17/2018 2:41 AM

Just an update.
The bike has been starting without too much difficulties over the last 2 week ends.
Not forts kick but after may be 10 kicks.
I switch the file off when finish riding and start it again until it drains the carb completely. Seems to help a little..

Header. What do you mean by getting the jetting right.? Have you replaced needles or clip position from the factory settings...
Any advice will be greatly appreciated.

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6/17/2018 7:51 AM

For some reason these bikes don’t like to put fuel to the motor. Lift the back of the bike up onto the front wheel for a few seconds To get some fuel flowing. Should start. Can’t tell you how many times I’ve seen and done this at the gate.

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6/17/2018 3:10 PM

Froggy76 wrote:

Just an update.
The bike has been starting without too much difficulties over the last 2 week ends.
Not forts kick but after ...more

I found the pilot circuit way to lean, basic jetting checks will show this mate what main and idle jet are you running, also sometimes people put the baffle upside down under the main jet its worth checking that, also make sure you have throttle freeplay. There is so many things that can go wrong.

The baffle is number 24 the lip needs to face up to the atomizer and not down into the bowl.

Photo

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6/17/2018 3:12 PM

What is the clutch set to how many rpm is full lock up, having to lift the rear end and all that tells me something is wrong and needs to be addressed, I could walk out to my 50 now in the cold pull the choke and start it first kick, I'm not having a dig but often there are just little things wrong and dads curse these little bikes when really they are great and just need sorting... I really want to help and see this little bike singing for your young fella and then it will be more enjoyable for you to.

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6/18/2018 11:26 AM

Froggy76 wrote:

Just an update.
The bike has been starting without too much difficulties over the last 2 week ends.
Not forts kick but after ...more

Helder wrote:

I found the pilot circuit way to lean, basic jetting checks will show this mate what main and idle jet are you running, also ...more

Very common mistake indeed.

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6/23/2018 3:27 AM

How did you go froggy?

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6/23/2018 5:27 AM

It's going to be bad reeds or the float needle is leaking and the bike is filling up with gas. once these little bikes get flooded you'll kick them to your blue in the face , the easiest thing to do is take the spark plug out and turn the bike upside down and pump it to get all the fuel out of the bottom of the engine.

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6/26/2018 2:26 AM

Sorry guys, got totally side track.
Here in Australia, it s our financial year result in less than a week so been just smashed at work.

Bike was good last week end. Started fairly quickly. Not first kick but did not have to be out of breath before I started it.
It was really well tuned to, no smoke at all, running like a dream and everybody was commenting on how my little man was handling the bike.
Out of 12 riders in the junior track he was the only one a 50, the rest had 65 or 110 4 strokes. Only where in front lgpf him and the rest of the guys simply could not catch up. Of course, we are not talking serious racers here, but good to see him beat older kids on more powerful bikes.
Considering he s on,y been riding since December 17 he s come a long way. Incredible what confidence to you.
He feels so confortable on the bike that he really brakes late and carries good momentum in the corners.
Wish I was as confident ?

If the weather holds we will hit the track again this week end and see how the b8ke behaves.
That is what annoys me the most with it though, is that some weeks it s running well and some weeks not at all. So intermittent.
Clutch is set to 11 clicks so nothing extreme.
Out of curiosity if I have the clutch any higher does that wear it out faster or the opposite?
Thanks again for everybody chipping in. I really appreciate the help.

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6/26/2018 2:35 AM

Cool mate yep I'm hearing you with EOFY.

Further you wind it in the more slip you will have it will engage at a higher RPM technically it may wear more but yeah I dont think it matters they just wear, I run carbon fiber clutch plates.

Where in aussie are you?

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6/26/2018 2:59 AM

Hi helder

Thanks for the reply.
I am in Brisbane.
What about you?

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6/26/2018 3:00 AM

Mackay mate.

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6/27/2018 3:39 AM

How s the mx scene in mackay mate.
I already struggle in the middle of summer with the heat but can t imagine where you are.
Went to Townsville a few times for work, and gosh that was hot compared to Brisbane.
I thought I was used to hot sticky weather having lived almost 20years in New Caledonia but that was a different league..

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6/27/2018 3:55 AM
Edited Date/Time: 6/27/2018 3:56 AM

Yeah mate MX is getting bigger, a lot of people are over MA and all the BS when I was here in 06 it was massive but getting there again I dont race that much now just the young fella I probably race 5 or 6 races a year.

Working isn't to bad I do a lot of my work around moranbah, Mackay isn't really much like Townsville, townsville is hectic with humidity I did a bit of work in New Cal at Goro Nickle and agree Townsville is worse!!

I grew up in Longreach and worked in Newman in Western Australia for about 8 years it gets hot out there hahaha then up at Port Hedland that's like Cairns and Townsville its horriable!!!

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10/26/2018 12:42 AM

bf884 wrote:

For some reason these bikes don’t like to put fuel to the motor. Lift the back of the bike up onto the front wheel for a few ...more

This works for me! But why? 3 months ago this wasn’t an issue. Today it is. The plug is dry and tipping the bike up primed the intake & it starts. What can cause this?

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7/24/2020 1:48 PM

bf884 wrote:

For some reason these bikes don’t like to put fuel to the motor. Lift the back of the bike up onto the front wheel for a few ...more

Brian_Trudeau wrote:

This works for me! But why? 3 months ago this wasn’t an issue. Today it is. The plug is dry and tipping the bike up primed the ...more

turn the idle air mixture screw all the way in and then out 3 full turns, kick it.

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7/24/2020 3:08 PM

bf884 wrote:

For some reason these bikes don’t like to put fuel to the motor. Lift the back of the bike up onto the front wheel for a few ...more

Brian_Trudeau wrote:

This works for me! But why? 3 months ago this wasn’t an issue. Today it is. The plug is dry and tipping the bike up primed the ...more

meporter wrote:

turn the idle air mixture screw all the way in and then out 3 full turns, kick it.

This thread is two years old, I would think they have it fixed or have even moved up to 65's by now.

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2018 KX450F
2005 KX250
2003 KDX 220
1984 KX 80
1982 RM 80
1980 RM 80
1977 XR 75
1969 Honda Mini 50

7/24/2020 5:53 PM

Might be useful for someone else...

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