I have a 1995 TRX 300 fw that I bought when it was less than a year old. It has been well maintained and treated gently. It will start with a quick push of the button and has good power. Compression is 190 psi and when checking the cam chain there is 3/16" gap between the cylinder and the tensioner. It has an engine noise that has been getting worse over the last 4 years. When it is started cold it runs smooth and quiet at idle, but if you give it just a little gas (1/8" on throttle) it makes a loud clacking noise. If you give it more gas an rev it up it is smooth and quiet. It clacks even louder if you cold start it and try to ride it without warming the engine up. Sometimes the engine will sputter and miss when doing this. If you allow the engine to warm up for 2 -3 minutes at idle it will not make the noise or miss. Even with a stethoscope I cannot tell where it is coming from other than top end. When the engine is completely warmed up, there is a faint tap coming from the cylinder. This engine has never been torn into. I am thinking piston slap, but don't know how to verify this. What do the experts say and what would you do to it?
TRX 300fw clack noise when engine is cold
1 - 20 of 53 Posts
Joined
·
38,619 Posts
welllllllll..yes and no ?. let me explain
. loose valves for example, when cold ?, they are lose, when they heat up ?, they expand ( i'm sure you know this ? ), same goes for piston rings. it very well could be that because your cam chain is loose ?, your valves are not set or running right ?. sooooooo..after you get the new cam chain installed ?, check/adjust the valves, ON THE COMPRESSION STROKE !, then fire her up, and see what ya got ?. there is a great sticky in the repair section by me, that goes into great detail on how to set/adjust valves on all 4-stroke atv engines. the only difference you have from that sticky ?, is your crank is side to side, where the newer models today are front to back ?, all you would need to do is use the 17mm flywheel bolt on the left side, behind the center cap on the cover to rotate the crank clock wise and counter clock wise to set and adjust the valves. main thing when putting the cam back in ?, and timing marks set on cam sprocket ?..IS MAKE SURE THE CAM LOBES ARE FACING STRAIGHT DOWN !?, AND THE PISTON IS ON TOP DEAD CENTER ON THE COMPRESSION STROKE...NOT THE EXHAUST STROKE !?, and you will be fine. if ya get stuck ?, come back to this thread, and ask ! .
Joined
·
12,683 Posts
I just redone the top end and cam chain on my 95 300 , for right under $500 I got the cylinder bored , new piston , wrist pin , clips , rings , OEM cam chain , gaskets , filters , seals for side cover and decompression lever ---------this weekend I considered it broken in , changed the oil to some Amsoil , ( wow , that stuff really does quiet it down ) , I ran it hard , it sounds great and hope to get another 22 years out of it
Yeah, another 22 years is what I am shooting for too. It's strange how some engine noise can be so hard to figure out. I started out thinking cam chain may be the cause of the noise and misfire when cold, then it went away as things got oiled up and expanded from the heat. Piston slap made more sense to me but compression is still good. I don't know, maybe the piston skirt can wear and the rings and cylinder still be good? I forgot to mention the engine does not smoke - never has.
Joined
·
38,619 Posts
a worn connecting rod can make sounds too !..lol. they don't last for ever ?, and they have nothing to do with compression
.
Joined
·
38,619 Posts
22 years is about the average life span ( assuming it wasn't abused ? ) for most trx300 cranks
.
Joined
·
4,694 Posts
Fish........ How would you compaire gn4 to Amsoil besides the price, lol, i gather alot of guys here use n like Amsoil oil ?
Set her on TDC and pulled the rocker cover and found the front timing mark to be 1/8" below the gasket surface and the rear mark to be 1/8" above the gasket surface. Got a little stretch going on. I was suprised to see that the chain rides up on the sprocket enough to see daylight under it. Is this normal? The rocker slippers were smooth as glass and there was zero slack between the rockers and shafts. (other than side to side) Do I need to pull the rocker shafts and measure them anyway?
Joined
·
38,619 Posts
cam chain needs to be replaced, if you have 1/8 below and above ?, your at two teeth off, and this is asking for the chain to jump time, and damage your valves and piston. as for your valves adjusting, what your calling shafts ?, i'm guessing you mean cam lobes ?, is the cam lobes facing down when you have it set on top dead center ?, as this would be TDC on the compression stroke.
Joined
·
38,619 Posts
ah...rocker arm shafts, got-cha. nope, no need to remove them, they hardly ever go bad. my main concern is your cam chain
.
Joined
·
12,683 Posts
Jay ....I have never used GN4 , in fact this is the first time for the Amsoil for me , I will say right off the bat that the engine is much quieter with the Amsoil ----------
Thank you for confirming this as I know you just rebuilt your 300. There are posts on here that say you do and some say you don't. Since you have to go that far, I am considering pulling the cylinder and check the rod for slack. What are the chances that a standard bore cylinder this old would still be in spec? It is 22 years old, 190# compression and does not smoke. That is one tough little machine. I don't do a lot of trail riding but use it mainly for hunting 5 months a year.
Joined
·
12,683 Posts
I tried hard to get the chain out past the guide and couldn't do it , now if you were to cut a small section out of the guide you could do it , but I would think where it would have to be cut is a critical point right at the bottom gear ----so you are kinda where I was , if you are going to pull the head , why not do the extra step and refresh the rings and/or the piston or bore while you are right there
Joined
·
38,619 Posts
fish, if he has 190 psi ( which is very good for 22 years ! ), I see no reason to start replacing rings and boring ?, but I do agree he needs to check the rod for play at top and bottom ?, as this will determine if it has to be tore all the way down..lol.
Did not spend much time on the atv today. Shade and Fish, thank you for your input. I did get the exhaust off which was a pain since I have one of those silent mufflers on the end of the stock exhaust and I could not separate the two. I'll see what the head and jug look like when they come off. If they are not like new, I will probably send them to G&H.
1 - 20 of 53 Posts
Join the discussion
