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Mully

350FM engine noise

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Hi again 

Got a Fortrax 350 it’s around a2001 bike I think  into the workshop for service and to investigate noise from engine.

it’s like a tapping noise, thinking valves?
Bike is starting fine and there is lots of oil in it.
looking for the best and easiest place to start. 
I hope to but up a video later. Thanks 

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2 minutes ago, Mully said:

Hi again 

Got a Fortrax 350 it’s around a2001 bike I think  into the workshop for service and to investigate noise from engine.

it’s like a tapping noise, thinking valves?
Bike is starting fine and there is lots of oil in it.
looking for the best and easiest place to start. 
I hope to but up a video later. Thanks 

early trx350 ranchers had a defective head in them. the valve seats would work loose, and slap the underside of the valves, unless they valves are not adjusted right ?, then this is the problem, or the cam chain, or worn rod causing piston slap ?.

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Adjust valves first.  If that doesn't work, then you'll have to look deeper into timing chain/piston slap/ loose valve seat.

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Ok, I adjusted valves and tapping remained.  But as I looked at valve adjustment 1seamed different from the other. I'm also confused: line up T in window and set valves, and if I turn crank 1 revolution ( T lined up in window again) cheak valves and they are tight. Another rev of crank and valves are where I set them. Piston is at the top both times.  How do I determine which stroke is the right one to set valves?

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Posted (edited)

Both intake and exhaust valves are closed on the compression stroke.

i rotate CCW until i see the intake valves open, as soon as the intake valves shut you’ll be on the compression stroke 

Edited by Goober

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Got ya!  Checked like you said and turns out I had them set right. Thanks Goober. Cam chain looks ok too , tensioner against it and very little movement in it. Is there any other cheaks I could do on cam chain?

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Just now, Mully said:

Got ya!  Checked like you said and turns out I had them set right. Thanks Goober. Cam chain looks ok too , tensioner against it and very little movement in it. Is there any other cheaks I could do on cam chain?

how can you say cam chain looks ok..when you can't even see the cam chain without removing rear cover ???...unless this atv is not a trx350 rancher ??.

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4 hours ago, Mully said:

I have removed rear  cover

16552304120389051536784514581520.jpg

ah..ok..did not know you even had the engine out ?!. 

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there used to be a sticky here made by me on how to EASILY check, adjust, set valves on all honda atv engines. i do it old school, no feeler gauges , no torque wrenches, just old school all the way. the way i do my valves: remove the rear pull starter ( i see you already have the rear cover off ), if you have the rear cover back on, but not the pull starter ?!..do this: look at the pull starter cage, on one of the tabs is a line in the middle of the tab, this line faces the raised arrow stamped on the stator cover, about 12 or 11 o'clock on the 350 ranchers ?. line up the line on the tab to the raised arrow, your piston is now on top dead center...IT MAY..OR MAY NOT BE TOP DEAD CENTER ON THE COMPRESSION STROKE THOUGH !. the way you find this out...is take a 17mm socket with a ratche. with rocker box removed so you can see the intake and exhaust valves, slowly rotate the starter cage counter clockwise ( go left ), as you are doing this turning, carefully watch the intake valve, it should start to go down as you are turning the starter cage ( crank ), if it does start to go down ?, slowly rotate the starter cage ( crank ) back clockwise ( go right ) until that line on the starter cage lines back up under the raised arrow on the stator cover. hold it in place, set the valves. if for some reason the intake valve DID/DOES not start to go down when you first started turning the crank counter clockwise from the get-go ?, this means you had the line on starter tab set on top dead center on the exhaust stroke, which is wrong. valves must be set on a cold engine, and on the compression stroke !. ok, now that you see that the piston was on exhaust stroke, and not compression stroke, with the line on the starter tab facing the raised arrow on the stator cover, rotate the crank clockwise ( to the right, as if you are pull starting it ), go 360 degree's, one full turn, all the way back around to line up the line on the starter cage tab, facing raised arrow on stator cover, get it lines up, no go back counter clockwise ( back to the left ) slowly, the intake valve should starter to go down now. once it does, rotate the crank back clockwise slowly, line the line on starter cage tab back under the raised arrow on stator cover, hold it there, adjust/set the valves, done..wrap it up, drink a cold one on me.

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Thanks I'll recheck the valves using your procedure . Any tip on confirming cam chain?  It seems fine to me tight and all?

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You're going to hate me for this, but check your rod on your crankshaft.  Pull straight up and down on it.  If ANY play at all, crank is shot.  A little side to side play in the rod and crank is normal, but up and down it's no good.

 

Next, and more likely, take the piston on, slide the wrist pin back into the rod end about 1/2 way, and try to wiggle the wrist pin around.  If you have any play there (and my guess is you will) your crank is shot.

 

You can take the crank out and send to Vince at Mr Crankshaft.  He'll build it back better than new for much less than a next factory crank will cost you.

 

I've rebuilt 3 350 Rancher engines.  Every one of them has been running when I started, and every one of them has had to have a new crank.

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