[Jegs87trx350]

Ooohhhhh I'm so disappointed guys! My "new" 87 trx 350 foreman has, I think, rod knock. I used a long screwdriver to my ear and it's definitely coming from the connecting rod area. I can't tell if it's where it connects to the piston or crank but I think its where it connects to the crank. I took it down the street to a guy that has worked on these and other ol Hondas for all his life and he thinks it's rod knock too.
Could it be something else perhaps? Something less serious? It's most noticeable once she's good n warmed up.
On a cold start it's quiet as a mouse and it's not until it gets warm that it starts knocking. My other 87 trx 350 also has that same knock but it's only when it's idling low and if you goose it real quick you can hear it but it immediately goes away and only makes the noise when you blurb the throttle from that low rpm.
The foreman makes the noise just while idling and also once you get on the throttle but it does seem to go away once the revs come up enough.
I've heard tell of some motors just being noisy. Could that be the case? Has anyone had this lower end knock on their machine? As far as I know this has never been sunk and never run low on oil either. If there was a cause I think it would have to be the old fella I bought it from cranking the revs through the roof RIGHT after starting it. He'd get frustrated and just nail it once it finally started.
Any thoughts would be much appreciated. I'm so bummed because the rest of this bike including the top end is in such great shape! It's a pretty major task for me to pull the motor but I will.
I should add that the knock is merely present. It's there but it's not horribly loud or anything. When sitting on the bike you can't hear it over the rest of the noises except right after a gear change and you're bringing the revs back up. But if you get off and are eye level with the crank you can definitely hear something isn't right in there. Thanks again!

 

[retro]

The crank and rod in the old TRX350 motors are awfully tough to kill. I'd suspect something else is making that noise. Since the previous owner used to rev the snot out of it when it was dead cold, I'd be thinking busted/cracked skirt or a busted ring land on the piston first. But you should rule some of the other possibilities out before tearing it down since the knock isn't a serious one.

Try blipping the throttle by slapping it with your finger real quick so that the motor momentarily loads then unloads before it can rev off idle. Sometimes you can detect a lower end rod or main bearing that way.

Check the decomp lever cable for slack. Then feel/pull the chain tensioner to check chain wear and rule out the cam chain, chain guides & sprocket, then readjust the valves... to provide you with an excuse to snoop in on the cam lobes and rocker faces with a flashlight & mirror. This is routine checking... quick and easy to do.

 

[shadetree]

if it were mine ? ( we all know what I would do ! )..lol. pull the top end off before you pull the motor, check the piston at the top on the wrist pin, check for any play with the rod by pushing and pulling on it. they do go bad over the years ?, but most times it's the wrist pin at the piston.

 

[machinecrook]

The ATV Gods have spoken! Good advice guys, I enjoy reading your input even though i don't have a 350 yet.

Jegs, that's too bad man but if you gotta do it; you gotta do it! Fun project!!

 

[Jegs87trx350]

The atv gods! Hahaha I'm still laughing...
Okay okay I'll get my hands dirty this weekend! Lol. It's not that I even mind I just get nervous that I'll screw something up. It is fun though!
I will check all the things you both listed, twice. I especially want to do it because the top end on this thing is ultra quiet. Not TOO quiet because I have the valves adjusted correctly but there are just no superfluous noises. So I really am going to take care of this one. Never going through any water deeper than the the wheel bearings! Not even to the wheel bearings!
I did want to add that blipping, or slapping the throttle really quick is one of the things I've been doing to make the noise. Thats when it's loudest when i do that. It's a pretty good knock(or series of knocks rather)when I do that. I'm really hoping it's the wrist pin. I don't have to pull the motor to fix that, do i?
Last evening I ordered a d.i.d cam chain and a right side engine cover gasket. So hopefully I'll have the other one up and running within the month.
I still have to do a compression test on this. Geez I bought this wheeler to have one to ride while I was fixing my other one! Crap, now ive got two broken ones, twice the work and twice the amount of parts to buy! Lord help me were gonna either starve or freeze this winter but hey, I'll have a couple nice hondas!! Thanks again so very much. I'll post back��

 

[retro]

Great attitude man!!! Love it...!

You will have to split cases & change the crankshaft out if the little end of the rod is shot... think positive thoughts though. Sometimes just changing your hat changes your luck! LOL

You might have found it blipping the throttle but I'm holding on for something else... stuck tensioner maybe... busted off chain guide.... chain climbing the cam sprocket and slapping the rocker cover roof where the oil supply galley is... something simple.

 

[retro]

See where the cam chain climbed the sprocket and rubbed on the roof of my rocker cover in this pic?

I didn't hear that chain slapping the cover until the motor was fully warmed up. Even then it was just a faint intermittent tick only heard when I slowed down the idle speed. While I was holding my screwdriver inside the chain tensioner on the retractor screw I could feel that chain pulsing hard as it climbed the sprocket and got pulled back. The faint tick that it would make occasionally could be felt at the same time in my fingers! Ya gotta try that trick sometime... or often... its really cool. You feel everything! Which seems to improve your hearing too...

 

[retro]

I just re-read your other thread and noticed that you said you found a worn out cam chain on this motor too..?
Before you take this one apart to check for a worn wrist pin or rod bearing I'd recommend spending some more time snooping. I'm more confident now that you'll find your noise is caused by a worn out chain and related valvetrain parts issue. Haste makes waste...

 

[shadetree]

I just re-read your other thread and noticed that you said you found a worn out cam chain on this motor too..?
Before you take this one apart to check for a worn wrist pin or rod bearing I'd recommend spending some more time snooping. I'm more confident now that you'll find your noise is caused by a worn out chain and related valvetrain parts issue. Haste makes waste...

big difference between a knock and tap bro. cam chains don't knock, they tick or slap ?, but not knock. wrist pins and rods knock.

 

[retro]

Worn out concave rockers can knock louder than a wristpin. Loose sprocket bolts can knock as loudly as a sloppy rod at low RPMs. Any moving rigid part that comes into contact with any other rigid part can knock loudly... and thats why cam chains can't knock. They aren't rigid.

 

[retro]

shadetree lemme guess... you been speed-reading the forums again tonight nearly exhausted... while putting in several days of non-stop intense labor in your kitchen...?!

I lucked out and got a short rain day... I don't know how you do it man! I was whooped after only 3 days of steady work and you're still going at it nonstop!

 

[Jegs87trx350]

I'm really hopeful that it isn't the connecting rod. My gut really tells me it is but any amount of snooping and trying to find other causes is preferable to pulling the engine. I'm really not looking forward to that...

 

[Jegs87trx350]

That's crazy how the chain made contact with the cover like that! I just went and double checked mine and it doesn't have that spot. I'm relieved to see the exact same scratches in the journals on yours too. Normal. I'm really at my wits end about the cv on my trx 350 though. I've read through some of the posts here on the topic. I really think I'm going to have to remove the diff! Thanks again for all of your input. Any and all advice/tips are MOST welcome!

 

[shadetree]

That's crazy how the chain made contact with the cover like that! I just went and double checked mine and it doesn't have that spot. I'm relieved to see the exact same scratches in the journals on yours too. Normal. I'm really at my wits end about the cv on my trx 350 though. I've read through some of the posts here on the topic. I really think I'm going to have to remove the diff! Thanks again for all of your input. Any and all advice/tips are MOST welcome!

you don't have to pull the motor in order to check the connecting rod !. as for this cv ?, front cv joint at the knuckle ?. you don't have to remove the front differential either to pull the axles ?, you do have to remove the front knuckles though in order to yank the drive axles out. if your cv joints are clanking ?, spec when your turning ? ( very common for these old girls ), unless you have a pair of NOS axles on hand ?, your really going to have a VERY hard time finding a new set !!!. DON'T BELIEVE WHAT YOU SEE ON EBAY !!!!, been there, done that, they don't make them, or sell them....THAT FIT PERFECT !!!!. used front drive axles is the only way you can go here.

 

[Jegs87trx350]

So last year when I was trying to figure out the clanking and horrible sounds in my front end I switched the original CV shaft with an aftermarket one. I had trouble getting it in all the way, it was about an 1/8th of an inch from being seated enough and I tapped it in with a rubber mallet to get it in there.
The rubber boot broke recently right before I started tearing into the motor so I figured while I'm waiting for the cam chain I'd reinstall the original (which has new grease and a new, high quality boot). The old one will not come out! I've tried everything and yes, I started gently pushing and pulling and gradually I got more and more forceful until the articulating part, broken boot and all came right off. So now all I have to grab on to is the straight part that's sticking out of the diff! And lemme tell you what, it does not want to come outta there! I don't know what I did by tapping it in but it's not good. I've just taken the inside part of the knuckle off too thinking that might help me somehow but it's not. I guess i am going to drill a hole through the shaft, put a bolt through it and attach a cable to it and the other end to my sledge hammer with about two feet of slack. Then I'm gonna swing for the fences! I should video tape it! "How not to remove a CV shaft". That's the only thing I can come up with because I don't have any bearing pullers or anything of that sort that I could try. I did buy a spare diff so I may just remove the right CV shaft and switch diffs for now? Thanks for your input. I see you posted on the other one too, I'll go check that one out!

 

[Jegs87trx350]

Am I just being paranoid?? My other 350 would make this same knock when you brapped the throttle from idle. And my Kodiak 450 I bought for my girlfriend does the same thing. My buddy's wheelers also have a knock when tapping the throttle off idle. Can you 350 owners listen to yours and tell me if you hear a knock from your lower end too? I'm thinking some of this noise may be normal. Maybe all of it. Please let me know what you hear from your machines! Thank you guys so much yet again!

 

[misterclean59]

Listen in the area around the clutch. As the clutch basket wears the slots from the tabs of the plates it can make a knocking sound.

 

[retro]

Like misterclean59 said ^^^ Clutch.... Put the trans in gear then flick the throttle.... any change?

 

[Jegs87trx350]

sorry it took me so long to post back. I did try it in gear and it makes the same sound. I swear though that the more I hear it, even though with the stethoscope the sound is loudest near the crank shaft, the less I think the problem is on the crank itself. I bet it's a wrist pin. I'm just gonna ride it easy for the next day or so until I get my other one up and running again. Then I'll start tearing this one apart.
Do you guys reuse the staked nuts that hold the clutches on? I've been trying to find replacements but no luck so far... I was pretty careful when I "un-staked" them and I think I can reuse them this once.
I see that I'm up against some strong competition this month in the atv o' the month contest! There's some really great looking machines there! I can always enter again if I lose this time! Have a good one guys!

 

[shadetree]

sorry it took me so long to post back. I did try it in gear and it makes the same sound. I swear though that the more I hear it, even though with the stethoscope the sound is loudest near the crank shaft, the less I think the problem is on the crank itself. I bet it's a wrist pin. I'm just gonna ride it easy for the next day or so until I get my other one up and running again. Then I'll start tearing this one apart.
Do you guys reuse the staked nuts that hold the clutches on? I've been trying to find replacements but no luck so far... I was pretty careful when I "un-staked" them and I think I can reuse them this once.
I see that I'm up against some strong competition this month in the atv o' the month contest! There's some really great looking machines there! I can always enter again if I lose this time! Have a good one guys!

I always just zip the nuts off, I never bother unstaking the nuts, waste of time. I re-use them.