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KTM 450 SX-F 2007 Won’t start ! Need Help!

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Hey guys. I really don’t have the money to get my bike to a shop to fix so I been trying to figure it out on my own with videos and talking to people but still no hope. Though i would try it on here.

 

So I bough think bike from a guy that has it sit for a couple of years. Only way he was able to get it started was by getting pulled by a truck and bump starting it. It only have electric start. No kick start!

 

I have checked all the electrical wiring for resistance and conductivity and it all checks out.

 

List of all new parts: lithium battery that has double the cranking amps

Starter

Flywheel/ stator

Spark plug

Valve adjustment.

 

All it does is turn over once and stops. Feels like it has too much resistance or something. If the spark plug is removed then it will turn over fine. Battery fully charged every time I try and noting. Just doesn’t want to fire.

 

Could this mean that the valves are bent? Or needs a top end rebuild? Or what. What happens usually when a bike stands for a while without being ridden.

 

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Sounds like the decompressor is worn ,it's a pin that opens the valve slightly relieve compression

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6 minutes ago, YoungBrosProductions said:


Where would that be located?

It is part of the exhaust cam.  Circled area in the picture below.  It lifts one of the exhaust valves slightly by engaging the finger follower to lower compression allowing it to start more easily.  Once the engine is at idle (operating rpm) the decompressor no long hits the finger follower and the valve operates with the follower and cam normally.

999808822_RF4decomp.JPG.2f7d31451dfcd444676614c380c6c0ae.JPG

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i had one in my shop-- same bike,same year, same problem ---at that time KTM says "NO PROBLEMS" with the cam -- but a few months later they said --oh yeah !! gotta replace the cam with one from an 09 -- this is after i "modified" the original which worked for a while -- after i finally convinced the owner to replace the cam --it is all cool now .. good luck

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i had one in my shop-- same bike,same year, same problem ---at that time KTM says "NO PROBLEMS" with the cam -- but a few months later they said --oh yeah !! gotta replace the cam with one from an 09 -- this is after i "modified" the original which worked for a while -- after i finally convinced the owner to replace the cam --it is all cool now .. good luck

Well I do appreciate it so much for this help. What did it sound when it was trying to crank? Did the electric start work? Did it seem like it had a lot of compression?

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had the same issue you are having -- would not turn over -- came up against compression and STOP.. it did have a snapping noise when i turned it over by hand (with the flywheel nut) -- turns out that the decompressor was simply not working correctly and was allowing the valve to snap closed prematurely

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i had one in my shop-- same bike,same year, same problem ---at that time KTM says "NO PROBLEMS" with the cam -- but a few months later they said --oh yeah !! gotta replace the cam with one from an 09 -- this is after i "modified" the original which worked for a while -- after i finally convinced the owner to replace the cam --it is all cool now .. good luck

So let me get this correct. You ordered a 2009 ktm 450sxf cam and it fits perfect? They are idle same same for size and everything ??

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You have to replace the cam and the valve follower. They wear and you can't spin the motor fast enough to start. you will think you have a bad battery.

CR

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The circled part of the pic is the decompressor.  It is part of the exhaust camshaft assembly.  It cannot be purchased separately.

The follower is the lever that sits between the top of the valve and the camshaft.

You have an RF4 series engine (DOHC 450/505) that was used from 2007 to 2012.  If you need to replace the exhaust camshaft, you can get a cam from any of those bikes and it will drop right in.  Same thing with follower.

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yes-- in fact i do not think you can even get the original 07 cam --it has been superceded to the newest one -- get the rocker arm also --i think KTM calls it a valve lever --also the cam gear has to be pressed off the old cam and you will need the KTM special tool (i made my own) to hold the cams in place (and in time) while you torque the retainer bolt --it is TIGHT because the gear is a simple taper fit -- no spline , no key --only a taper

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You have to replace the cam and the valve follower. They wear and you can't spin the motor fast enough to start. you will think you have a bad battery.
CR

Where would be a place to buy a good cam with a good price. I looked on eBay and couldn’t find one.

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You aren't going to do this on a "deal." A dealer or online OEM parts supplier is going to be the only option. Expect to spend around $200-250 depending on where you get it.

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You aren't going to do this on a "deal." A dealer or online OEM parts supplier is going to be the only option. Expect to spend around $200-250 depending on where you get it.

Do I need to hold the clutch in while trying to start it in neutral? If I don’t would it effect it trying to start??

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2 minutes ago, YoungBrosProductions said:


Do I need to hold the clutch in while trying to start it in neutral? If I don’t would it effect it trying to start??

No.

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