2012 RM-Z250 Engine Knocking Sound

[RMZ2Fifty]

This might be a retarded question can you start the bike with the valve cover off? I thought I saw someone do this once. Or is the lever that easy to remove? I think the cams have to come out first right?

[JohnnyB24]

You'll get oil slung all over the place from the cams and cam chain spinning

[xMUDKINGx]

This might be a retarded question can you start the bike with the valve cover off? I thought I saw someone do this once. Or is the lever that easy to remove? I think the cams have to come out first right?

so I just got to checking mine out and mine doesn't have nearly as much play as yours does. I'm not sure if you would have to take the cam out or not. But it doesn't appear you would have to. Yes you can start it without the valve cover on, but as stated you will sling oil all over the place

[RMZ2Fifty]

Does yours have any wear on the inside of the lever or where it snaps back to? Also can't find where those marks on the outside would have came from. Also I've been moving the cams by pushing down the kick start slightly. That lever doesn't seem to be actually opening the valve seems like the love does that by itself so what's the point of it or am I wrong? Bearing look fine in the cams from what I saw.

[RMZ2Fifty]

Another thing I noticed is at a certain point in the cam revolutions that the flat or round part that rides over the valve snaps back and forth rather than being spring loaded, what I'm trying to explain is that as the cams are constantly spinning and it reaches that point the valve will be moving the lever not vice versa which I thought was its purpose. May be I'm wrong I have it positioned as so right now and snapping the lever back and fourth isn't opening or closing the valve if it is suppose to.

[JohnnyB24]

I just had my head off my bike last week and now I wish I payed more attention to decomp lever on the cam so I could help you out. It's been a long time since I switched cams and I installed the oem auto decomp in the stage 2 Hot cam but you shouldn't have any wear marks on the outside of it where your did in that video. It shouldn't be making contact with anything other than where it mounts and stops on the cam. The spring on mine wasn't that strong but I never got any sound like that.

What is your idle speed set at? If you raise idle slightly does it go away? If the idle is lower than optimum you could be getting that knocking sound. Book calls for 2100 RPM.

Edited January 3, 2017 by JohnnyB24

[notoriousE-R-I-C]

Hot cams do wear faster than stock. I have a 10 rmz250f set of stock cams, I just went stage two but if you live in SoCal, theyre yours.

You can run Hot cams intake and stock exhaust or vice versa.

But I dont know if 10 cams are cool for 12 cams. You do the research!

MudKings a beast, Id trust his judgement

That knock to me sounds like spring tension. How it feels flicking with your fingers doesnt nearly compare to the force of a moving motor. I just think the discoloration is a result from something.

The spring is friggin piano wire. They make thousands. There are faulty ones

Edit; Ive used race gas, and Ive used pump gas in Tijuana...Im fine with both, no difference to me. It was basically like a warm drink, and then a drink with ice. Yeah better with ice, but the room temp beverage is fine with me. Ive used TJ gas in a few thumpers. Never one problem in Mexico. Just some club fights

Edited January 3, 2017 by notoriousE-R-I-C

[RMZ2Fifty]

@JohnnyB24

 

Yea, the weird thing is there are no scoring on valve cover, which when tapping sounded a little like the knock too. So I dont know what scored the outside of the lever but it has clearance so its truly a mystery to what caused the marks. The in and out play of the lever also can't be adjusted the bolt is fully tight. The only 2 things I could think causing it to have play there is the spring is worn so it is not forcing the lever to the outside, but as you said your spring wasn't very strong either I don't think they're suppose to be. The 2nd thing would be that the lever itself has been worn down so it has more play than it should. Other than these 2 things I might have to rule it out.

 

I don't quite know the RPMS but my idle point rule of thumb I use is 15 - 20 clicks back from full. I believe it has 40 clicks making my setting 20 - 25 on the higher side. While I will give this a shot I believe I have tried this, and also wouldn't giving throttle, adjust rpms in which the noise would have stopped because that has definitely been tried to no help.

 

My pops is questioning the valve springs whats everyones take on that?

[RMZ2Fifty]

@NotoriousE-R-I-C

 

Hey man your all helping a lot, yea xMUDKINGx seems to know his shit, props man! Funny you mention spring tension as my pops suggested valve springs. As for what you said about the spring being a piano wire, yea its a rinky dink little rat fink, but I think its designed that way, what do you think?

 

From what I'm gathering is that lever is suppose to swing back and fourth as acceleration increases and decreases, so a strong spring might interfere with that. And if it was a faulty one, I mean whats the fault? It springs or it doesn't which it does, what more is there to it? I agree a running motor would manipulate that spring a lot more than my finger. Do you think a stronger spring would still allow it to function the same? (MUDKING'S seemed about the same tension) but what kind of tension you really gonna get from a small spring like that? As for what I said about it not engaging, it did move the valve slight I noticed. The more I think about that part I feel its working fine.

 

 

From this listing on eBay it seems like they do fit! Well I don't live in SOCAL, frequent to N. Cali Frisco area tho, but I would love those cams if your willing to spare. I won't be taking a road trip anytime soon but if I pay for a Shipping Label and email it to you would you mind puting it by your mailbox for you mailman to pick up? I'd also throw you a little something for your time, effort and kindness. Thanks!

[xMUDKINGx]

Another thing I noticed is at a certain point in the cam revolutions that the flat or round part that rides over the valve snaps back and forth rather than being spring loaded, what I'm trying to explain is that as the cams are constantly spinning and it reaches that point the valve will be moving the lever not vice versa which I thought was its purpose. May be I'm wrong I have it positioned as so right now and snapping the lever back and fourth isn't opening or closing the valve if it is suppose to.

the decomp lever spins outward which spins the smaller offset lobe inside the cam shaft when the bike is trying to be started, so you will not see it opening the valve unless you kick the motor over with enough force to start it. The centrifugal force of the cam sprocket spinning is what causes the decomp to work and it returns to the closed position when the bike is running, the idle speed would play a factor in this, but it would have to be set very low and from what you said that is not the case here. Your pops could be right, it very well could be a valve spring or valve retainer, but In my opinion, I don't think so, you would have some serious running problems(besides a knock) if there was a valve issue like a valve spring that has lost tension or a broken valve retainer.

[JohnnyB24]

That is just weird with the marks on the lever. Did you get the bike used? Maybe the previous owner had a problem with a cam chain that came off or just scuffed it up during disassembly somehow.

If you can get just the lever and spring to try out or even another OEM complete exhaust cam that could help rule it out

Your idle sounds normal in the video just wanted to see if it changed at speed.

I'm trying to think of a possibility where the springs would make an erratic knocking noise like that. Usually if there is a problem in the valve train with worn parts or out of adjustment the sounds do get louder but they are consistent/ repetitive. If you go as far as checking them it's just a measurement spec but you have to disassemble the head and need a valve spring compressing tool. I really don't see that being the issue though. Not for that sound. Weak springs can lead to other valve issues but usually at high rpm and they tend to be catastrophic.

You said you already checked the cam chain for wear and tensioner for wear/ proper function/installation right?

Was the cam chain replaced when you rebuilt the top end? When you remove the auto tensioner, how far out is the plunger extended?

[RMZ2Fifty]

@JohnnyB24

 

Yea I think I even turned the idle down for the video to expose the knock more (so the engine didn't over power it.) I have stalled it out by turning idle down too low and swear it was slowing down the knock til it stalled, not sure what that means.

 

Yea bike was bought used, I almost certain he rhode amateur MX (amateur plates, loads of upgraded parts, bike wasn't registered and well the bike has had some down time) I was afraid of buying a bike used for MX for this reason, but convinced myself that kind of owner would have maintained the bike better as he would rely on that, but I'm starting to think Bobby Brown owned this bike and beat her worst than Whitney.

 

Cam chain does look a little worn I have an over the top picture with the valve cover off you might be able to inspect it from. As far as tensioner, seems like propper amount of tension on chain, which would imply the auto tensioner is working correctly right? As suggested first in this forum I planned to mess with it but got a little scared when I heard the repercussions of screwing one up, also ran that by my mechanic and he said that wasn't my issue. As said there is tension, would you still advise playing with it? I also know the importance of TDC with adjusting the tensioner and how I could pottentialy off set the timing so I'd rather not play with it unless I felt my chain had slack.

 

I did not replace the cam chain, but if cheap am considering. As far as proper install the mechanic must of had to remove it in the process of rebuild which he re installed so i am sure it is installed fine.

 

The more I think of how my mechanic cracked the cases and thoroughly went through my engine I don't think it is something major like Valves and what not because there would be performance difference correct? And he would have seen scoring or saw something out of place. Which makes me think it is something stupid like this decomp lever as who the &%$#@! knows more about decomp levers than the more essential parts of an engine, making my problem get overlooked due to just lack of knowledge of whatever this little &%$#@!er is knocking on my engine like a Jehovas Witness.

[notoriousE-R-I-C]

I need nothing. It might do you no good. But Ive heard numerous times rmzs and kxfs hotcams knock. It might be nothing. Still not pleasing to the ear. Check your buckets. Valve springs can be tested.

I have a connection with a Postal Annex, if you have a debit card you can handle shipping payment directly with the owner and I have nothing to do with your money. Just bring him the cams. But for years I hear, hotcams-knocking, put stock back in no knocking. Is there motor mods? If you saw valve move that might be working and this isnt even your problem. I wouldnt get rid of them if I rode this bike. But Im not satisfied with my 10 rmz250f. I want to sell it. Id keep these cams if I was to keep the bike. Believe it or not gentleman, my 04 rmz250f is waaaaay better than my 10!!! But thats had more money and attention. But I am a Honda employee so I dont get Suzi discounts. I get aftermarket distributor discounts I could get Suzi stuff from discounted. But access to tools, manuals, computer programs, specs, parts( new or used in a drawer of a completely different bike, but it works), then theres OGs who will hear that video and be like "this is your problem" and you open up and boom, hes right, theres my problem. Im honda all day, erry day. I just work on so many bikes, I like to keep learning.

But Im in Arizona right now. My boss flew me out for Christmas. I wont be back for a minute. So keep trying your skills and suggestions. And Ill holler when I get back. Theyre in my storage in downtown San Diego. PM me and Ill give you my #, cause no bs, I say this and people think Im just a stoner, but I have Diffuse Axonal Injury from a bike accident. Ran over by a Mexican. Im not racist, it was in Barrio Logan. Theres no blacks no whites no Asians, just thick in Mexicans. But I have bad memory loss short term. I could forget this in ten minutes. Probably not but I will forget by the time I leave AZ. And I didnt buy the ticket so I have no idea when Im leaving. But Ill holler when I do.

Do you have the stock cams? Put them back in and see if they knock. Or if knock is still there. Volume and lack of vibrations are our issue watching videos on cellphones. Go get a leakdown test. Entertain that. Valve seats?

And Ive pressed cam bearings with a vice and a socket the od of the inner race. Im ghetto but my bikes work. I cant afford the tools they have at Honda. But I can use them if I dont interrupt business.

Hit me up

[RMZ2Fifty]

As far as everyone leaning towards a spring issue, can you help my understand why the noise resembles a broken or so spring? If I had to describe how that knocking was happening I would envision a ceiling fan spinning you stick your hand through it every blade is going to hit your hand causing a constant knock until 1 or 2 or may be 3 blades brake then the sound would be less constant because it is clearing 3 times and then coming back and hitting the rest of the blades. I hope this makes sense. If my analogy is understood may be parts that behave like this could be the culprit. Just a thought

[RMZ2Fifty]

@NotoriousE-R-I-C

 

No, Bobby Brown the prevowner put the Hot Cams in. As for the leakdown test, lets just say a valve was leaking air, how would this be causing a knock? Wouldnt the bike show a performance difference due to this leak? Would this air leak be strong enough to lets say cause the decomp lever to flail about? Heres an interesting approach an RMZ owner took on the Decomp lever after doing a leak down test. Funny he has same Decals as my bike before he said 05 rmz I thought it was Bobby Brown the previous owner with my bike lol. Even looked like the garage too.

 

here the link check it out and tell me if I should try this approach first. He did say attempt at your own risk.....

 

[RMZ2Fifty]

Sorry for all the videos, but I thought this might be useful. This is a clip of it running when the knock first started. It seems to be knocking less times and less aggressive. I'm throttling because she was shutting off. I fixed it by I timing it to 20 second everytime and realized the tip sensor had came off its bracket.

Tell me what you think about how the knock has increased and what this may mean. This was before the engine rebuild.

https://youtu.be/pAUsATWQGd8

[notoriousE-R-I-C]

Valve seat bud. If its loose it would knock. But pretty much everything in the motor moves faster with rpms and more throttle. I would pop off the jug and look at the pin holding the piston in, then play with the rod. Put oil all over everything and hondabond on the gasket, torque spec. Ive put together many a bike with no new parts/machine work. If I could afford it I would, but if I dont nEEd it, I wont. Buying parts and building bikes is my drug addiction. I have a serious problem!

Wiggle the piston with jug off. Does it rattle?

Its just hard to hear with a speaker the size of a tic tac, but the knock sounds like thicker/bigger metal maybe not decomp. You gotta mechanics stethoscope? Get one at Autozzone. $15

[JohnnyB24]

As far as everyone leaning towards a spring issue, can you help my understand why the noise resembles a broken or so spring? If I had to describe how that knocking was happening I would envision a ceiling fan spinning you stick your hand through it every blade is going to hit your hand causing a constant knock until 1 or 2 or may be 3 blades brake then the sound would be less constant because it is clearing 3 times and then coming back and hitting the rest of the blades. I hope this makes sense. If my analogy is understood may be parts that behave like this could be the culprit. Just a thought

 

I think I get what you're saying. Thats what I heard when I watched the first video you posted. If you are still questioning the spring on the auto decompressor then maybe just take out the auto decompressor lever completely. It will be a pain to kick over but you'll know right away if it was the culprit. Using the wire to tie up the lever for a compression test I think is fine but I wouldn't try to run the engine like that just in case your metal tie flings loose and then you'll have another foreign metal piece clanging around your engine.

 

I was asking about the cam chain only because they are a wear item and its usually a good idea to replace them when you change pistons. Last one I got was an OEM one for $26 and the aftermarket ones are under $40 usually. They stretch just like a drive chain does and it can affect timing slightly. The plunger on the auto tensioner can be a good indicator of how much the chain has stretched. If you pull it out and its maxed out extended then you know the chains probably worn out. Another thing that is quick to look at is the tensioner can be installed upside down. I've never done it so I don't know if this makes any weird sounds while running but the manual makes a point of showing that the flat line portion under the spring bolt faces down so it probably matters.

If you do mess with taking out the auto tensioner and cams just be sure you follow the procedure in the manual and you won't mess anything up. Its pretty easy. Align the timing mark on the magneto/ rotor with the marks on the inspection hole, confirm cam lobe positions are pointed away from each other and slightly up (also confirm with timing marks on cams at the 12 o'clock are up, and the 9 o'clock dot on exhaust and 3 o'clock dot on intake are aligned with the cylinder head surface). Also count the number of cam chain pins between the 12 o clock dots (should be 13)(matters for re installing). Then you can take out the tensioner before removing the cam caps. 

[J-Biv]

Valve seat bud. If its loose it would knock. But pretty much everything in the motor moves faster with rpms and more throttle. I would pop off the jug and look at the pin holding the piston in, then play with the rod. Put oil all over everything and hondabond on the gasket, torque spec. Ive put together many a bike with no new parts/machine work. If I could afford it I would, but if I dont nEEd it, I wont. Buying parts and building bikes is my drug addiction. I have a serious problem!

Wiggle the piston with jug off. Does it rattle?

Its just hard to hear with a speaker the size of a tic tac, but the knock sounds like thicker/bigger metal maybe not decomp. You gotta mechanics stethoscope? Get one at Autozzone. $15

RMZ2Fifty did you ever get this sorted? I wouldn't waste my time with the decomp spring, if it was weaker than normal the bike would be real hard to start cause it would swing open too fast. I agree with the above to get a stethoscope. Did you check your water impeller? Something could have broken off and got in there or a tooth on the back side could have broken off. Also since your mechanic thought it may be a broken clutch gear or whatever he said than it wouldn't hurt to pull the whole right side engine cover off and take a look. Besides the impeller gear there's a bunch of other gears behind there that could be broken causing that noise so eliminating that area is important and easy to do so if not done already than it should be looked into it. just start taking sections apart looking for things that are broken don't waste time replacing parts on a hunch unless you've looked over the entire engine and can't find anything. Just my .02. Good luck!

[RMZ2Fifty]

@J-Biv

Still haven't, had to take a little break. Yea I think the decomp lever and cams are good. Water impeller as water pump, correct? I'll take a look. As for stethoscope while I haven't completely removed the engine yet, it seems like the knocking has only increased so I'd rather not start her anymore but is a great tool to have around I'll have to grab one. He says it's the "Primary Gear" attached to the clutch basket that has a chipped tooth. While I did see a chipped off piece of metal that looked like a chewed up musket ball. I haven't actually seen the location of this missing piece, but any missing metal in a operating engine certainly isn't good. So I'm forced to replace that whether it's causing the knock or not. I guess what's really pissing me off is replacing top and bottom when they were perfectly fine, making me doubt my mechanic, but I would never have known about the chipped tooth unless. I should have had him check everything before addressing the T&B End. As for seeing the actual damage which I'd like to see before turning the engine over to him again. I took off right side and did the clutch plates and thought I was looking at the clutch basket I thought i saw some damage, but I've never seen a brand new clutch basket assembly. I have a picture of what I thought was some damage, but that's not what he's talking about. He's saying its the "Main Drive" behind the clutch basket and that the whole engine needs to come out. Is this so? I've done a fair share of removing and reassembling parts on my bike there is just some things I'd rather not mess with, such as the engine core components like T&B End. I have the tools, but what I did in a couple days he could do in a couple hours.

So my question is from what I "quoted" are those parts likely to be causing the knock and do I have to remove the whole engine from the bike to address this problem to at least inspect the worn part. I don't mind gutting the engine down to location, if I see any damaged part in the process I'll more than likely have him replace and reassemble if it's out of my league. I'm looking at either a wiseco or Hinson clutch basket as a replacement from what I found unless there's another option. I was told there is a Hinson in there currently, I thought they were suppose to be pretty rugged, no? And for the knock increase I asked him about it with the response of may be more teeth got chipped, if I find no more chipped teeth can I be certain this isn't causing the knock?