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'19 350 EXC-F, de-smogged, uncorked, Vortex, Rekluse

Many say and have said that the OEM fully hydraulic (oil fed) cam chain tensioner on the 350 motors can be prone to collapsing in certain low oil pressure scenarios and allow catastrophic engine damage.   

Is all this just overhyped garbage being re-spewed on the internets?  (ie--maybe was an issue on older bikes but not in 2019)  Being a modern EFI 4t it has the tip over switch and will kill the engine after only 8 seconds of potential low oil feed. 

I know Nihilo, Rally Raid, and Dirt Tricks make tensioners that could be smarter or more fail-safe at preventing collapse than the OEM design.

Nihilo is a fully manual adjuster that also blocks off the oil feed port, sending oil that would feed the OEM tens'r up to the top end of the motor where it is more useful.  It would require periodic adjustment. 

Rally Raid is also fully manual.  But does not address the oil feed port.  Also requires periodic adjustment.  

Dirt Tricks is basically the same as the OEM design but adds an internal spring and ratchet teeth to prevent collapse.  It is self adjusting and is "set it and forget it"

--Regarding the Nihilo:  Not really wanting to tap and block off the port in my engine although fully confident in doing so.  I presume you could remove the plug and return the OEM tens'r without issue if ever desired?  It is ugly and basic looking and maybe bulky to get access for adjustments?

--Regarding the Rally Raid:  Very nice looking piece.  I had contacted them and got mixed answers about the oil feed.  Their design allows the oil that is normally fed to the tensioner to dribble its way back to the bottom end of the motor.  Blocking the oil feed port is not part of their design/install.  Has to be ordered from the UK.

--Regarding the Dirt Tricks:  I have concerns that the spring loaded/ratchet design could over tension the chain and lead to premature wear.  The self adjusting is attractive, but not vital to me.  And why bother being hydraulic if it is backed up with a spring and pawl design anyway?

--Regarding the OEM:  Hey---chill....obviously the guys at KTM know what is best for the engines they design, and would not be keen to warranty expensive motor parts if failures were frequently happening.

Lets hear some insights?  Lets talk oil pressure scenarios.  Lets hear from people who have first hand experience with any (or all) of the 4 tensioner designs.  Lets talk about engine safety, longevity, and wear with the different designs.  And of course.....lets hear what you would do on your $11k 2019 model bike that you throw around, drop, and abuse, yet still care for meticulously! 

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On my 2012 350 XCF-W I went 200 hours before I changed the OEM unit for a Dirt Tricks one.  The motivation for changing it was that the OEM unit appeared to be getting noisier over time....so I just thought it made sense to be proactive after 200 hours. My understanding is that the OEM units are well made and do a good job...but over time tend to wear internally....and, under certain conditions may not be putting proper tension on the cam chain at start up.

The Dirt Tricks unit has an excellent reputation and the spring provides for proper tension under low oil pressure situations....sounded perfect to me. The unit itself is a breeze to install...but on my bike its a real PIA because you have to remove the right side rad in order to have enough space to remove and re-install. Hopefully on the 2019 they have fixed that design flaw. This difficulty in access is also what swayed me to use the Dirt Tricks unit...it is self adjusting so no need for me to hassle with access in order for it to stay in spec.

And yes, I would agree that that there certainly is plenty of typical overblown internet BS surrounding the allegedly dangerous and catastrophic nature of running the OEM unit. It is not an imminent ticking time bomb...but it is something to be aware of and addressed as needed.

 

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The Dirt Tricks seems to be well liked, but you're not supposed to install it before 20 hours (according to them). I think the chain needs to stretch a bit, otherwise the DT tensioner puts a bit too much pressure on it. At least that's my guess for that requirement, but I don't actually know how much a cam chain stretches. 

The only data point I have is that the service lead at my dealer had his stock tensioner fail on his 250, but I don't know at how many hours. I plan to use the DT tensioner at the 30 hour valve check. 

Getting to the tensioner on my 2018 is a bit of a pain because the frame is in the way. I had to cut a hex key down so it would fit. And then you have to play around to actually get the cap off before the tensioner, or you can't get the angle to get them out at the same time. KTM engineering at its finest. 

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Dirt Tricks has always been the KTM solution to my way of thinking for this problem.  KTM largely resolved the problem on the 450/500s but has not with the 350s.  My 2011 350 uses the same lousy stk tensioner as the current 350s.  So yes...  get the Dirt Tricks Tensioner...  if you want my opinion.  

Wait 10 to 20 hours..  paperwork says 20 just to be safe.  But DT says 10 is generally OK. 

Edited by Jeff aka Bolt
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15 minutes ago, Jeff aka Bolt said:

Dirt Tricks has always been the KTM solution to my way of thinking for this problem.  KTM largely resolved the problem on the 450/500s but has not with the 350s.  My 2011 350 uses the same lousy stk tensioner as the current 350s.  So yes...  get the Dirt Tricks Tensioner...  if you want my opinion.  

Wait 10 to 20 hours..  paperwork says 20 just to be safe.  But DT says 10 is generally OK. 

I know about the 20 hour thing and can definitely take the proper measurement of the OEM tens'r to confirm that the DT one will go OK

 

How about this...  With the DT tens'r:  Does the spring actually press the cam chain all the time, or only when there is low enough oil pressure for the OEM tens'r to become collapsed?  (ie-under normal use the hydraulic portion does all the work----but failing that---the spring is there as a "backup".  --or--thinking of it this way:  DT spring active or passive)

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DT tensioner is just a little longer than the OEM. Hence the reason you wait for the chain to settle and stretch a smidge.

The spring pushes it into place...  the oil drives it until it doesn't...  then the ratchet stops it from retreating. No amount of spring is going to stop the chain from slapping the oem tensioner back without oil pressure. It's the lack of ratchet that is the problem on 350s.  :cheers:

The manual tensioners stop the retreat but cannot adjust as chain stretches.  You have to re-adjust.  DT ratchet just clicks into a new forward thread as chain loosens over time.  

Edited by Jeff aka Bolt
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BTW - I am told the original ratchet tensioners came from KTM...  that DT just adopted the idea when developing theirs years ago...  and that new 450/500 oem tensions are ratcheting style.  Why KTM has not done this on the 350s is anyone's guess.

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2009 ktm 250, 2014 duke 690 and now a 2016 ktm 350. Never had a problem with the oem nor ever felt like it was a weak point. Thought about doing it on the 350 but the only way that i can see for it to fail is if you dont know how to reset it after install or youre one of those jackasses that revs their bike like crazy as soon as it starts. I always let my bike idle for a minute before even thinking about touching the throttle, oil pressure isnt instantaneous and you gotta give the oil a sec to thin out and get into everything properly (for the first start of the day). From what i mostly read is that people do it to get rid of the chain slap at idle which isnt a concern to me. Save your money for some bling or gas for your next ride.

 

 

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I like the idea of a hudraulic tensioner (KTM), it's just the perfect pressure and can accomodate some 'wobble' in and out (think if your sprockets werent perfectly round).  BUT that design does let the oil 'bleed down' if there's any extra clearance at all and the engine stops with pressure on the tensioner run of the chain.  

The Dirt tricks is just like the OEM, except it only can extend one way...  So no worries on that first start of the day, after the bike's been sitting for a month.

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I have seen two tensioners collapse on older XC4 engines, but not new bikes.

I do run a manual (DJH) on my 505 for two reasons: one was seeing the stocker fail on my friends 450 XCWR and two I liked blocking off the oil passage and sending more oil to the top end of the RF4.  IMO that engine should have as much oil heading up to the cams as possible at all times.  Yes, I did have to adjust the tensioner every now and then, but not a big deal to me.  Just part of normal maintenance to check it at every oil change.

I should note that the stock hydraulic tensioner from my 505 ended up in my friends 450 and was still working as it should years later...

I will probably put a manual tensioner in my 2018 simply because I can.  I don't expect the stock one to fail by any stretch of the imagination, but it can't fail hydraulically if it is a manually adjusted tensioner.  I do like the Dirt Tricks tensioner (I use DT sprockets on all of my bikes that they make them for), but if I am changing it out I like that the manual one is easier for me to determine if I am starting to get abnormal wear from the cam chain or sliders.

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I bought a dirt tricks one when my 08 250XCFW was brand new. I still haven't installed it, but the poor bike only has about 40 hours on it. Ill get around to it eventually.

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On 12/17/2018 at 5:59 AM, 87XR250R said:

I bought a dirt tricks one when my 08 250XCFW was brand new. I still haven't installed it, but the poor bike only has about 40 hours on it. Ill get around to it eventually.

DOOD!  ride more, haha!

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My bike has nearly 70 hours. Once the bike stays on the stand for 20 min and I start it, I hear the tensioner for the first few seconds.

Do I really have to replace it or it is still acceptable ?

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As a friend of mine found to his cost recently, a flappy hydraulic tensioner can be a symptom of a failing oil pump causing low oil pressure.

He didn't realise and fitted a manual tensioner. Meanwhile, his plastic oil pump drive cog failed and wrecked everything from the crank up. 2018 250 EXC-F with 35 hours on it.

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6 hours ago, Hubert Carpet said:

As a friend of mine found to his cost recently, a flappy hydraulic tensioner can be a symptom of a failing oil pump causing low oil pressure.

He didn't realise and fitted a manual tensioner. Meanwhile, his plastic oil pump drive cog failed and wrecked everything from the crank up. 2018 250 EXC-F with 35 hours on it.

That is possible. 

I believe that the tensioner was noisy when engine hot and not only right after the start? 

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My 350 got the Dirt Tricks unit and a new copper washer at about 15 hours.   Solved the loud noises on startup and never even thought about it since.  My 3 500s don't seem to need anything and they are all stock.

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13 hours ago, phatsmall said:

My bike has nearly 70 hours. Once the bike stays on the stand for 20 min and I start it, I hear the tensioner for the first few seconds.

Do I really have to replace it or it is still acceptable ?

I think it should be fine. I haven't seen a failed one in person so I can't comment.

The way I understand the stock tensioner operates is as follows: there is a small check valve in tip of the tensioner and this is the only part that I can see failing/wearing. If you try to reset the stock tensioner, a good tensioner takes a lot of force to reset (see youtube). I imagine that with a failed/failing tensioner, that force becomes less and less over time as the check valve will no longer keep the tensioner filled with oil. 

If you want to double-check, I would remove the stock tensioner and inspect it/reset it. Take pictures and notes so that you can see if there is any change over time. A little noise on startup is probably fine, in my humble opinion. 

Edited by Swappa

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