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Discussion Starter #1
my, friends dad dropped of this Honda fourtrax. the engine is knocking. Below is a video i made so that someone may be able to help:
there is no smoke just that knocking sound. I do know idle needs adjusting, I can do that.
the other thing is that it jumps really bad when put in gear. they say that they had it tuned for the mountains and then had it brought back in to be tuned for lower elevation. not sure if that is the problem. i will be changing the oil for water. I will try to update this after I do that or anything else major happens.
 

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Welcome to the forums .....
Was that a 'cold start' in your video ?
The knock wasn't readily apparent to me ....
Hoping others will reply ...
 

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Welcome to the forums.

That seems like quite a loud knock, always hard to identify off a video but I think it sounds like little end bearing. If that's the case then your in need of a top end rebuild.
Wait around for a while, there are more knowledgeable guys than me when it comes to the 300's, I'm still in my first year of ownership.
 

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Talking of more knowledgeable guys.... @fishfiles you beat me to it lol.
 

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If it's tuned for high altitude the carb may have been rejetted. will have to remove the carb to check the jet size.
Look at the plug does it have carbon on it? It might be running lean.
Download the service manual that may help you; Could be behind on service and the valves need to be set.

Check everything like spark plug number; main/slow jet number; etc. specs in the front of the book.

Also a member had loud knocking noise and he found it to be an improperly set cam chain tensioner
 

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cam chain jumped timed, throwing rockers off a good bit ?, or wrist pin is shot ?, or bottom of crank bearing is shot ?. requires a full top end tear down to inspect.
 

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my, friends dad dropped of this Honda fourtrax. the engine is knocking....

....there is no smoke just that knocking sound. I do know idle needs adjusting, I can do that.
the other thing is that it jumps really bad when put in gear. they say that they had it tuned for the mountains and then had it brought back in to be tuned for lower elevation. not sure if that is the problem. i will be changing the oil for water. I will try to update this after I do that or anything else major happens.
I think that knocking is a lower rod bearing. Check the oil filter... see if it was put in backwards... it sounds to me like the cam & rockers are running with no oil too.

Videos are difficult to comprehend... let us know what you find out maybe we will learn something too.
 

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OUCH. yes, full tear down is needed. no point in wasting new oil for that.

sounds to me like they were running it low on oil, overheated it, possibly ruining rod bearings and cooked the cam journals.
 

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Discussion Starter #10
Wow, thank you for all of the help. Just drained the oil and we found metal shavings in it. I believe that eliminates valve timing. beings i have little to no clue what a rocker does, (I'm a dirt bike guy) I would assume it needs a new cam and timing chain if I am not mistaken.From all of your suggestions however, i should probably still do a tear down. If I am please correct me.
 

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Yes, you'll need to do a complete motor teardown to learn about everything that has been ruined and to find the cause.

If the cam has been without oil, not only the cam and rockers will have been ruined, but the head will be shot too. The head provides the camshaft journals... those journals are machined into the aluminum, so are non-replaceable...

Don't consider buying any parts until you have learned all there is to know. Many of the more serious motor damage cases (due to lack of oil) result in so many of the parts in the motor being too far gone, to be an economically rebuild-able motor. Whenever parts costs exceed replacement costs, its best to swap out the entire motor. The wallet usually makes that call...

Next task is to pull the oil filter to see if that was installed backwards. Then a complete teardown and cases splitting... including the oil pump. At some point the owner may decide it is not worth fixing. Maybe even before you do...

Wish you the best! Let us know how it goes if you can...
 

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you said " flakes in the oil eliminated a timing issue " ------------ the metal flakes could be from the cam sprocket
 
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