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Old 4 Weeks Ago
LAPPER's Avatar
LAPPER LAPPER is offline
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KTM 350 issues

Ok so Ive bought this 2014 350 exc . Possibly a big mistake

Had some issues where it let me down on my third ride and wouldnt start as fuel pump not operating .
Mechanic thought it was fixed but further to this he found that the cams are over 90 deg out of alignment .
When re-aligned the pressure test was still not good ( 75%) so he has pulled cylinder off and found that some issues with lean running . Piston looks like its been eaten approx 1mm away above the ring . Possibly reason for pressure issue.
It looks like it may have had a bigger issue previously and there are marks in cylinder head .
I asked previous owner about history and he said he had bent the spring on the auto decompression cam thing on the exhaust to disable it as he said it was causing starting issues ?
It looks like its not flicking back as it should .
It also looks like there may be a hairline crack in that cam .
I'm thinking maybe the decompression cam thing caused issue - exhaust cam to jump ?
What else could have happened? The chain semed tight. May replace the chain tensioner ?. He said he thinks valves are ok due to a leak test ?

To also clarify I think the bike was quite lean and is running an aftermarket Vortex CDI to suit a 390 kit .
I think there has been some issues with our fuel that may have caused piston issue in the past before he changed to the Vortex but I cant be sure if there aren't still issues with detonation . I m not sure if I want to keep running it as a 390 or get a 350 cylinder from somewhere.
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Old 4 Weeks Ago
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Pygmygod Pygmygod is offline
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That's unfortunate. Sounds like the previous owner had zero idea.

I thought the autodecompressor is meant to increase startability...not make it harder to start.

90degrees is a fair way, possible that the auto-decompressor is permanently 'on' and is never able to centrifugally open (stop pushing the exhaust valve) because the previous ninny messed around with the spring/mechanism?
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Old 4 Weeks Ago
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The spring was bent so that Cam wasn't really flicking back and in on position - it was more in the loose off state .
I think cam issue must be linked to the timing chain tensioner suddenly failing ? It could have been the inlet cam that slipped - I don't know .
The tensioner doesn't seem to operate that well. It was fine when running though . I know some people buy an aftermarket one.

Hard to tell if it is a crack in cam and if its deep . I guess I have to be on safe side and replace it . . $400 just for that
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Old 4 Weeks Ago
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Ive given what the mechanic thought is a crack a rub with wet and dry and its gone . That's a win !
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Old 4 Weeks Ago
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pollock pollock is offline
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Damn Ash, that sucks. The marks around the compression ring groove on the piston are pretty common for detonation, must have been running pretty lean.

I doubt the cam would be 90 degrees out, the bike wouldn't run, I'm not even sure it would turnover. Even with the cam out by 1 tooth, they run noticeably worse.

They usually don't pressure test well because of the auto-decomp. I've seen some people restraining the auto-decomp to compression test for a more realistic result. Maybe find someone else locally and compare the cams if you're not sure how good they look, or your mechanic should know.

I would toss the vortex or at least get it changed to suit an OEM setup.

Who's your mechanic? Tim Langton? if not maybe try him or Caloundra Motorcycle Centre, both are very good.
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Old 4 Weeks Ago
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I dont think the engine turns over for this type of pressure test - leak test.
So decomp will not come into it ?

The previous owner said he got the Vortex due to issues with original CDi so maybe the damage was done to piston a while back


The bike was running well - stopped after flogging it on a hard hill w
Then not running at all
It was way out of alignment according to old mate
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Old 4 Weeks Ago
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I might have to put it back together myself with my friend Mr YouTube
How hard can it be

Are these hard to get timing of cams and chain right - special tool needed ?

Is it possible to get a thicker base gasket to ensure no detonation problem ?
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Old 4 Weeks Ago
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pollock pollock is offline
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Quote:
Originally Posted by LAPPER View Post
I dont think the engine turns over for this type of pressure test - leak test.
So decomp will not come into it ?

The previous owner said he got the Vortex due to issues with original CDi so maybe the damage was done to piston a while back


The bike was running well - stopped after flogging it on a hard hill w
Then not running at all
It was way out of alignment according to old mate
They are easy to align, they can jump on restart if the tensioner is a bit worn or still compressed, make sure the tensioner is popped out. You need to lock the crank in at TDC using the tapered bolt, then the cams are aligned using the machined flat surface on the cam sprocket side of the closest lobes. Make sure you recheck positioning after tensioning the chain. The machined flats on both cams should run parallel with the cam bridge. No special tools needed.

The bike would not run if the cams were 90% out of alignment. Maybe the tensioner sh!t itself and that's why it stopped? Lucky the valves still seal if that's the case.
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Old 4 Weeks Ago
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Yes what what I think . Thanks
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  #10  
Old 4 Weeks Ago
brent j brent j is offline
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I had a problem when the tensioner in my Freeride 350 failed. online searches suggested it's a common problem with 350's.

I replaced the std unit with one from Dirt Tricks
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