06 TRX 350 tapping noise

[Sha35297]

Hello, got this bike in to replace the jug and piston. Made the swap, crank looks good, no play in connecting rod. Put it all back together and then heard a rubbing noise in the rear crank case. Ordered a new timing chain and tensioner. Installed them and put it all back together. Fired it up and ran great on the work bench. Took it down and went for a ride and noticed the higher the rpms, the noisier it got. There was a tapping noise on the exhaust side of the valve cover. Removed valve cover. Checked valve clearances, all good. Checked the valve springs, the were a good bit out of tolerance. Installed brand new springs. Same noise. Decided to replace the whole cylinder head with one from a known good bike. Still the same noise. Decided to replace the camshaft with one from a known good bike. Still makes the noise. Replaced lift caps. No change. I’m at a loss on what could be causing this noise. It’s very loud and not normal by any means. Any suggestions would be appreciated. Video doesn’t really pick up the noise good, but it’s there. 
 

Thanks

[Mech]

Well... Did you ride it before taking it apart ? Could it have had the noise before you worked on it ? What was the original problem you were fixing ? So the timing chain stopped the rubbing noise, that's not the noise you have now ?

And.. does it make the noise when it starts up cold, does it get louder or quieter as it warms up ? Did you check the piston pin fit in the conrod ? And are you listening to the noise through a screwdriver to your ear when you say the noise is coming from the top end/valve cover, or is that just where it sounds like from a distance ?

[Mech]

I can't listen to your movie.. so does this noise happen at idle, or only with a few revs, and does it get louder if you put a load on it, or does it rattle worse when there's no load on it ? In neutral, if you just gently bring the revs up a little and then back down again, does the noise come in as the revs are building up, or as the revs top out and the load comes off it, or is it worse as it slows down again ? And would the noise be at the speed of the piston going up and down, or only every second stroke, so on the firing, or perhaps something in one valve ?

[Sha35297]

Hello Mech,

Thank your for responding. So, I did test ride before doing the repair and this particular sound was not there. The original noise was a rubbing sound on the rear crank case. After replacing timing chain that noise went away and this new sound appeared. Noise is not apparent at idle on cold start or when warmed up. It starts at about 1/4 throttle and speeds up and slows down with the rev of the engine. Seems to be at the speed of the piston, not speed of the valves. Piston Pin fit is good. I've tried using a screwdriver to pinpoint the location. Seems to be more prevalent on the exhaust side, but hard to tell if its crank case or top end. I bought a stethoscope to try to pinpoint the sound better. I'll update on that when I get back in the shop.

[Sha35297]

Ok, With the Stethoscope it seems like the noise is loudest in the valve cover. What is strange to me is that I have replaced the whole top end with another one from a bike that I know runs good with no issues. So what would cause the same noise to be in the valves on both cylinder heads? Also, after listening better to the timing of the sound. It is in sync with the exhaust not the piston.  I'm going to pull the crank case cover again and check the timing one more time and post pics of the inside to post.

[Sha35297]

Just removed the rear crank case cover again. These are the pics of inside. I used a screwdriver to verify piston was at TDC. All marks are lined up.

[davefrombc]

Have you checked to be sure it isn't an exhaust leak  right at the head? Maybe  a crack in the header pipe  or warp / nick in the flange  that  makes it sound as though coming  from the valve cover.

 

Edited January 28, 2021 by davefrombc

[Sha35297]

This is the header. I'm not seeing anything abnormal about it.

[davefrombc]

I see quite a difference in the contact pattern between the bottom left and top right  in that bottom photo. Is there an  exhaust gasket between that flange and the head possibly missing? I'm  not familiar with the motor  so  guessing , but I would think there should be a thin copper ring or high temperature gasket of some sort there .

 

[Sha35297]

Thank you for the input. It does have a copper gasket in it that I had replaced the first time I tore it down. I could try replacing it again to be sure its not the issue. While its running I cannot see or feel any combustion coming from around that area though. I've had exhaust leaks before that did not sound like this.  That's why it has me stumped so bad. I feel like I have tried all of the obvious things multiple times and have become sort of blind to being able to see past what I know I have already done. Was hoping a fresh set of eyes or thoughts on it would trigger something new.

 

I am attempting to upload the video again a different way. The one I have already uploaded plays on my computer, but will not play from my mobile device on the website.

[davefrombc]

Your video and audio  plays  instantly on my PC but with my  bad hearing I  cannot  separate  any  tapping or ticking noise over the regular exhaust note. An exhaust leak  is the only thing I could guess at  with all  you've done.  With the motor  cold and at idle or low rpm  there is minimum pressure  in the  exhaust system ,  and when  the system  is hot , components  expand  slightly which would  make the connection tighter  and seal  off  a leak  if it was at that gasket.  It's always "fun"  chasing down  intermittent problems and strange sounds .

[spock58]

Have you been able to verify that there is enough oil feed to the cylinder head?

[Mech]

Hi again. My problem with the movie is my crappy internet connection.  Yeah sometimes we can get blind once we've looked at a thing too long.. sometimes a new pair of eyes, or even just a break and when we come back it's obvious..

 So does the sound get louder with load ?  Which would sort of point to the bottom end, even though you are sure the bottom end looked and felt ok, and the noise sounds like the top.. but.. If it gets louder with a heavier load ? When you checked the conrod for play, did you make sure you were testing it at the crank position where the play would be on the crank pin ? If there's going to be play in the bottom end bearing it would show up a bit after top dead center, where the heavy load comes on. And did you check the play by trying to move the rod up and down, or by seeing if it would rock from side to side  which is the more accurate test. When you had the head off the second time, did you look for any sign of the piston hitting the head ? Was the piston genuine and did you use the genuine gasket at the bottom of the barrel ?

You say you can listen to it with the stethoscope, so I'm guessing this is stationary ? And you are sure the piston was a proper fit in the bore ?, though I'd expect that to be noisier when it was cold if it was loose, and then quieten a bit as the piston expanded.

Spark plug is the right sort ?  Couldn't be detonation caused by a too hot plug ?

Some of these things I'm suspecting should have been there before you pulled it apart, which would sort of have to mean the new noise is something you've replaced..  Piston slap or if the barrel was second hand, a ridge at the top of the bore ? It was a new piston and barrel ?

Running out of ideas now but perhaps something will prompt a new thought.. Keep us posted..

 

[Sha35297]

Hello,

So I decided to remove the new cylinder and piston to swap back out with one I had from another bike. I noticed excess wear on the skirt of the piston and inside of the cylinder. Both were purchased from Niche as a kit. They have less than an hour of running time on them. Swapped with the jug and piston from the other bike and the noise is gone. My customer is going to attempt to return the kit he purchased from Niche and purchase a new OEM from factory. Hopefully the next one works right. Thank you everyone for the help. It is greatly appreciated. Hopefully this thread can help someone else in the future.

[Mech]

Yeah, that isn't a good look for a new piston alright..  Good onya finding it.

[Scott Stevens]

Very good must be china made parts I try to never use them much anymore as the inspection process is terrible its all money money money to them it seems. I know you no this but copper ring heat them up with a propane torch before reinstalling that makes them  good as new heating them.

I share this more towards V8 but has worked on friends quads when servicing was not done much but sure worked well on some chevys too.

The dealer has a oil additive called EOS  stands for engine oil supplement noisy values clear it right up as well as engine getting tired if I recall but save peoples asses back in the day as I worked for a GM dealer learning a trade & a old guy shared this stuff to me as I drove a old 1965 Malibu 283 & was so bad noisy fixed it right up just add to oil go for a drive for 1.2 hour noises were gone and improved power as well for me.

The smaller engines so had to find issues it working on that fixes them the best so ask people in the trade.

[gillies_robert]

So it was piston slap you were hearing? Too much clearance right outta the box, you did check it before installing? 

[Sha35297]

Well this was a kit brought to me by the customer made by Niche. I did not measure before installing. Guess in the future I will though. First time I’ve had an issue like this. The customer decided to take the original cylinder and send to a machine shop to be bored. Guess I’ll see how it turns out when I get it back. 

[MarkinAR]

Ah, didn't know the rebuild was Niche products.  That would have been the first thing I looked at because they are complete trash.  Niche makes a few disposable parts that aren't bad but never never use their piston or cylinder. 

[sgtcj]

Good to know since I am about to order piston set for Honda trx.

[MarkinAR]

The best cylinder and piston kits for Honda are from G&H supply. Quality OEM and Wiseco products. 

[sgtcj]

 

great.   Thanks for that.  It will surely save me a lot of time in research.

[MarkinAR]

You can save a couple bucks sending your cylinder to G&H for boring. They bore match to a new piston. Super high quality work. 

[Sha35297]

Just a final update. Customer had the old cylinder bored oversized and used a Namura piston. Got it all put together a couple days ago. All is good now. Customer is happy. Thanks for the help everyone. 

[MarkinAR]

Not a big fan of Namura, but they usually do ok in lower CC utility machines.  I've seen them blow to pieces in the 400EX.  Much better than the Niche from the first try though!

Glad you got it ironed out.  I'd bet for what the customer spent on a couple pistons, sets of rings, gasket kits and labor, they could have just got a quality rebuild kit and been done with it the first time.

[Dion Braud]

DO NOT BUY CHINESE PARTS FOR JAPANESE BIKES! I own and operate a Dirtbike/Quad engine machine shop(Cycletech Performance) and have MANY stories about that crap and not many are good! All those Niche cylinder kits are TRASH. Just have the OEM stuff Reconditioned by Myself or someone else. Unfortunately You lost your shirt on this job because some BS Chinese Company made Some money.  

[SashaGraves21]

Wow what great information! I think my exhaust looks sketchy too and sometimes burns off random liquid lol. I can only fix one thing per day or I will literally keel over. I was going to replace the rubber goods and the bearings next but one of the springs on the exhaust system is laughably loose and half of my engine block was covered in soot🥴