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2017 300xcw engine knock?

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Hey guys:

It seems my new bike has acquired an engine knock that comes and goes that just started today.  

It seems to be more predominant while under load climbing steeper trails that require slipping the clutch.

I did notice that I bent my pipe a bit so it's not sitting square in the exhaust port because of my lack of skill riding over larger logs, I'm just wondering if that might cause a knock because maybe it's not sealing properly?

 

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You need to address any header leaks especially on a 2t as on the intake stroke it can pull in dirt, it could be running lean from the leak too. look at your piston while the pipe is off.

Ps: Practice your log jumping skills.

 

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I have a Husky TX300 (same motor) and have the engine knock, as well as do many others.  Also, make sure it is not pipe bang, but since it happens under load, that is highly doubtful.

I have a whole thread in the Husky section and experimented with jetting to resolve this (went richer and leaner and changed clip positions) and it did not fix the problem.  I was running 93 octane and it was just not enough.  I tried Sunoco 260GT 100 octane race fuel and the pinging completely went away.  I experimented with a 50/50 mix of 93/100 octane gas and the results were still not sufficient.  There was still light pinging.  At $10 per gallon, it is not cheap, but not sure there is another choice.

It is disappointing to say the least that I have to run race fuel in my stock bike.

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Seems odd that it just started. Was it immediately after your pipe bash? Is the noise "mechanical" or "combustible" or just slap-bang? I know, hold your phone up to the bike so we can hear it! Anyway, if it started after your log splat, see if you can borrow somebody's pipe for 15 minutes and see if it goes away...

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It's weird because I was riding the other day with zero issues or no knock, but it was the first thing I noticed right off the start when the bike warmed up which was before the hard log splat.  Also I forgot to mention as well was the lean hanging idle started only after slipping the clutch up a long steep climb.  Other than that on normal flowing trails the bike preforms normally.

also Id like to mention that it's been extremely smokey due to forest fires and I'm wondering if that would play an effect on jetting

Basically my current set up is a stock 300 with a JD kit set at their recommended 0-4000' setting,

 

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It sounds very similar to this, just not as frequent and yes on deceleration.  

the hanging idle only happens after lugging  a really long climb, when the trail crests the bike has a high idle and takes a bit to settle down. It won't do it just putting around or ripping up and down logging roads.  Just on the steep climbs when the engine is really working and pulling.

im just wondering if this is normal with these bikes.

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I hear no detonation in this video, but I do hear mild pipe bang.  You would not hear detonation at idle but riding under load.

Pipe bang is a nuisance, but harmless.

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Jason,

If for some reason it is detonation, you could try a different thickness of the base gasket which lifts up the cylinder/cylinder head, reducing the compression ratio just a tad.  I think there are probably still three different thicknesses of base gaskets for KTM 2-strokes.   The thicknesses are likely to be .40mm, .50mm and .75mm.  So, the next time you have the cylinder off the bike, install the thickest base gasket (.75mm).  I have never tried it before, but if you choose, you could try this wild idea:  Usee the .75mm and .40mm together.  If you try putting two together, I would seal the two gaskets together with some extremely high temp resistant Permatex sealant.

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What the heck is "pipe bang"!?  never heard this before...

It's when you drop and break your crack pipe, and it goes bang.
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I have a 2017 300XC and I installed the JD kit after the first ride as it was running really rich. The JD kit for 0-4000 feet has you put a #30 pilot jet in. I immediately ran into detonation issues, hanging idle, and even some overheating. I went to the 32.5 and it ran great all the way up to 6000 feet last weekend without issue. The JD kit is too lean on pilot in my opinion.

Edited by Mickdady
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56 minutes ago, Mickdady said:

I have a 2017 300XC and I installed the JD kit after the first ride as it was running really rich. The JD kit for 0-4000 feet has you put a #30 pilot jet in. I immediately ran into detonation issues, hanging idle, and even some overheating. I went to the 32.5 and it ran great all the way up to 6000 feet last weekend without issue. The JD kit is too lean on pilot in my opinion.

I bet that is it, I pretty much experienced the same thing, knock on decel, hanging idle after a prolonged climb, over heated a bit. It didn't have those symptoms until the last day I went out.  It was muggy and humid that day.  I'm going to try a 32.5 pilot when I return home from work in 3 weeks.

for some reason I'm really nervous about seizing up, probably because I don't have a lot of experience with 2 strokes. 

Edited by Jason76

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14 hours ago, Mickdady said:

I have a 2017 300XC and I installed the JD kit after the first ride as it was running really rich. The JD kit for 0-4000 feet has you put a #30 pilot jet in. I immediately ran into detonation issues, hanging idle, and even some overheating. I went to the 32.5 and it ran great all the way up to 6000 feet last weekend without issue. The JD kit is too lean on pilot in my opinion.

I tried a 32.5 pliot on mine and it was too rich (very blubbery) and it still detonated.  I even ran the AS out like 3 and 3.5 turn and still a mess.

Very picky bike to jet.

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1 hour ago, 95jersey said:

I tried a 32.5 pliot on mine and it was too rich (very blubbery) and it still detonated.  I even ran the AS out like 3 and 3.5 turn and still a mess.

Very picky bike to jet.

Are you using the JD blue needle? What clip are you on? I agree it is a difficult bike to Jet and it appears no 2 bikes are the same. Now that I finally have mine where I like it I am very happy with the bike.

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3 minutes ago, Mickdady said:

Are you using the JD blue needle? What clip are you on? I agree it is a difficult bike to Jet and it appears no 2 bikes are the same. Now that I finally have mine where I like it I am very happy with the bike.

JD Blue, started on 3.5, but due to warm humid weather had to go to 3.  

30 pilot, 430 main, AS 2 out, 100f elevation.

I am happy with the performance, somewhat happy with the jetting, but not happy that I need to run race fuel.

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It looks like I was finally able to correct my issue that required me to run race fuel. After trying all kinds of jetting combinations, different head compression inserts, I called JD jetting to see if they had any insight, as I used their jet kit and was thinking it was carb related somehow. So after a lengthy discussion about my symptoms of pinging at steady throttle using anything but strait 110 octane race gas...they thought it sounded like an intake air leak after the carb. I did at one point install a Vforce4 reed cage (had one on my gas gas) as I heard the OEM cages had manufacturing issues. JD recommended to go back to the OEM reed cage and put in new gaskets and check the boot for holes or cracks and make sure it is sealed tight. We'll that made a dramatic difference. Bike ran cleaner, smoother and even stronger and was way less noisy than before. I put in 93 octane and took it for 30 min ride and all seems well. So I must have had an air leak somewhere in the reed cage or gaskets which caused a lean condition at part throttle causing detonation. I can't believe I didn't think about this sooner. 

If you have Vforce reed cage, dump it and go back to OEM and install new gaskets.  Cleared my issue up.

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