Ticking or rattling .

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18/08/2009 at 18:55

I brought a cg125 in Coventry last week and we took it for a test ride and all was well.

I then rode it to London, Yes it took me three hours. I took it top top gear and pinned the throttle back and sat on the motorway all the way home.

Well now there is a rattle at the top end.

What could it be? Maybe being thrashed for three hours did not do it much good. But I got nearly 70mph out of it! well it was a steep hill!

 Do you think I might have bent a valve slightly? there seems to be no loss of power, I think any way? So the valves might be fine? maybe an adjustment would be nice.

BUt it rattles,  so I am thinking cam chain. Maybe the tensioner needs to be looked at? Does the cg125 have a cam chain tensioner? If so where is it?

Am I right in thinking that a 04 model, the one with electric start would still have tappets and not be shim under bucket. Are there any 125's with shim under bucket?

If it is the cam chain it would be easy to replace no? Just make sure I use new gaskets. But just check the tensioner first.

any advice is appreciated.

Thanks.

19/08/2009 at 22:16

CG125s don't have a cam chain - the cams are gear driven and sit below the cylinder, and actuate the valves vie push-rods and rocker arms. Mucho potential for some lash in that lot somewhere so by all means check the valve clearances (cold) but don't go looking for a cam chain tensioner .

If you have bent a valve then you might see extra valve clearance on the bent one (it'll not be shutting fully). With a bent valve you might not notice any performance loss at high engine speeds, but may find starting harder or low speed running is rough. If you're not getting either of those then it's probably not a bent valve.

Such a long ride might've cooked the oil a bit if its old or been sitting for a while and now would be an ideal time to change the engine oil (take it for a ride first to get the oil good and hot so it brings all the crap out with it).


arrrf.
20/08/2009 at 12:47

Wow no cam chain eh, gears sound like a much better idea when I think about it.

Bike starts fine, runs fine. I did find it a bit asthmatic when I went up some hills, speed went down to 45, which is scarey on the M1. Low speed it is fine but I will check the valves out any way and have a look at how the gear driven cams work.

The noise deffinatley comes from the top of the engine and I suppose with only the valves there it may be a bent one or not sitting properly.

Thanks for your advice Tappy

20/08/2009 at 14:23
My son thrashed his really hard and seized the engine. He had repeatedly failed to let me change the oil which is what killed the engine. Tappy's advice is excellent.

I don't suppose anyone cares.
24/08/2009 at 23:01

Scarily I think I woke up thinking about this a few days ago but have been away for a few days:

The other possibility may be a bent pushrod - so if one of the valve clearances is a mile wide, it could be that too.


arrrf.
25/08/2009 at 03:04
has the same engine as my xr 125 which just crapped out due to a "ticking".. assumed it was the tappets so just left it.. what actualy happned was the gudgin pin had came out and the piston was sliding around on the con rod. now the engine is stripped down and im waiting on funds for a rebore new piston con rod etc etc etc. so becareful wtih it. but i gotta admit. it did do a good 4k miles with the ticking sound

http://img31.imageshack.us/img31/274/1001189q.th.jpghttp://img24.imageshack.us/img24/2609/1001185m.th.jpg

xr125... BECAUSE ITS FUN

25/08/2009 at 22:16

Ooh nasty - that happened to mi dad's GT550 years ago.

In that case - check the tappets etc for valve clearances and if one of them is a mile wide, find the problem. If all are fine, sounds like you might do well to pop the head and barrel off...


arrrf.
15/04/2010 at 17:33

@ Bikerchef, did you diagnose exactly what the problem was? And was it easily fixable (and affordable!).

My CG125 has been 'rattling' for a good few months now (it started when I forgot to put oil in the engine for a few months or so and the bike ground to a halt whilst going up a hill). I'm thinking (and hoping) that the engine isn't discintergrated inside due to the lack of oil it had, but it has been working ok since, but only gets 50mph MAX on flat, and about 55 downhill (on big hills)!

The most annoying thing is that I need to do my practical test before september, and to get a Cat A licence my bike needs to do 62.1mph (which it can't!!).

Any help would be gratefully recieved! Cheers...

12/09/2011 at 21:32

hey guys

i litterelly had the same prob with my cg today , i was doing 60mph then it dropped to 40mph like instantly and nose dived. my bike runs fine , a little trouble with starting only 5 kicks but thats generally normal, mine make a rattling noise from the top end , a little less power output on acceleration not alot tho....im not honestly sure what gone on , maybe valve clearances or push rods arent closing the valves properly? anyone got any ideas of what the rattling could be? i need to run it to college 4 days a week

13/09/2011 at 15:23
Hi there.

I too, am having the same issue. I've checked my valve clearances, and I've set them to 3 thou. Fired it up, and the tappet noise is horrendous. I've got little idea what it could be. I've had this tapping for a while, as well as when I go over 6krpm, it sounds as if the valves are smashing off each other. I'm also going to add, I've been quite neglectful in maintaining my oil, because of that; I'm going to get some now!

I'm a new user here, so hello all

Josh
13/09/2011 at 23:00

Well if you've neglected oil changes then there's a chance it's the little end, or a cracked piston or something.

Are you checking the valve clearances with the engine stone cold?


arrrf.
07/03/2013 at 21:59
27/05/2013 at 01:54

hi all. i have honda cg 125 which i brought 2 years ago. till now i never careless in changing oil and look after others parts. few weeks ago i notes rattling sound coming for engine head cover. i check clearance for 0.08mm on both tappets side (Exhaust and carburetor). i get confused every time i rotate the engine to recheck the clearance after properly adjustment,the values or changed. can any body tell me which feeler gauge may pass or which should not pass for clearance?? and what is the advantages and disadvantages for lose or tight clearance??? thanks

28/05/2013 at 00:52

If you need a 0,08mm clearance then a 0,08mm feeler gauge should be a nice sliding fit. The gauge should have just a tiny bit of resistance, and not be loose, but not be tight either.

If the readings are moving around then make sure that you're pushing the rockers hard onto the push-rods to make the gap between the rocker and valve a true reflection of the total free-play, then take the measurement and make any adjustments.

You do also presumably know that you have to turn the engine 720 degrees (two whole revolutions) to re-check the clearances?

Valves don't just suddenly wear however so unless the rattling has gone from a rustling, to a ticking, to a rattling over a few thousand miles then I'd suspect it's not the valve clearances.

Tight valve clearances give no space for the valve's thermal expansion so prevent the valve closing properly. This means a loss of compression - particularly at low engine speeds when hot, causing low power. It also means it can't cool down (most of its cooling is thru' the valve seat when closed) so the valve will "burn" - especially the exhaust valve. Ultimately that can cause the valve head to come off into the engine, causing huge mechanical damage.

Loose valve clearances increase valve train jerk & hammer, accelerating wear of valves, rockers, push-rods and cams. It also reduces the valve open "lift" and "duration" reducing engine power.

Very slightly loose valve clearances are preferable to tight valve clearances.


arrrf.
24/06/2013 at 23:12

Thanks Tappy, Late reply due to system error on my end. i made multipule attamps to get a perfect valve clearance as you mentioned , pushed the push-road, which provid a bit more free play at the time of clearance. I notes that pressing a push-road (Exhaust side ) provid move free play but on the 2nd rocker side (intake side) it also pressed down by the 2nd push-road. which also tightened the clearance gap on valve , Is it normal? or it need to use two feeler gauge separately at the same time to manage the .08mm clearance  on both ends.. yes i rechecked valve clearance after 2 complete rotation TDC to TDC again ( 720 Degree ). I tried both way ( two feelr gauge / one feeler gauge) to figure it out, noise is noticeable low now. but i m still confuse for which feeler gauge may pass or which should not pass for clearance..

Accidentally bike was tuned at unauthorized service center, after that facing ideal problem, mixture setting at its worse, NGK tip like burn, ideal at 1800-2000 RPM, bike stops at signals while its already worm up. back fire while running when closing the accelerator, . i dont have a bench mark at this stage. so my first target is valve clearance... i notes  lose ( a bit) bike run rich, tight make it lean..

25/06/2013 at 13:08
bilahm wrote (see)

fter that facing ideal problem, mixture setting at its worse, NGK tip like burn, ideal at 1800-2000 RPM, bike stops at signals while its already worm up. back fire while running when closing the accelerator, . i dont have a bench mark at this stage. so my first target is valve clearance... i notes  lose ( a bit) bike run rich, tight make it lean..

I appreciate that English is probably your second language, and good effort etc, but I don't understand much of your second paragraph - can you please write in full sentences explaining fully what you mean so that I don't misunderstand due to the language barrier - you describe several symptoms about mixture setting, spark plug burn, ideal - presumably "idle"? But you don't really say anything in a full sentence and I'm a bit lost.

What I can tell you is that loose valves clearances do not make an engine run rich, tight clearances do not necessarily make it run lean.

Regarding your stuff about the push-rods & valve clearances I'm not sure what you're saying. Yes, pushing the rocker hard onto the push rod will take out the free-play elsewhere and putting it all at the valve / tappet so your measurements are consistent. It sounds like that's what happened with the exhaust valve, rocker and push-rod.You then say "but on the 2nd rocker side it also pressed down by the second push rod". Well - yes, the 2nd push rod pushes the 2nd rocker which opens the 2nd valve. So what's the problem? Push the rocker hard against the push-rod so that all the free-play at the push-rod is taken out, and all the clearance is at the valve where you're measuring it... You should definitely NOT be trying to achieve 2 separate clearances at each end of the rocker arm.

When you're sure that all the free-play is at the valve end, and that no free-play is left elsewhere, then you should put in one feeler gauge after another until you find one that won't easily go in with a "sliding fit". Hold a feeler gauge gently between your thumb and forefinger and pull it out from between them - that's the sort of sliding resistance you're looking for.

If the largest feeler gauge that goes in is too big or too small then you need to adjust the tappets.

Did the idle (not "ideal") problem start at the same time as the ratting? Or did it start after it was tuned? Did you take it to be tuned before or after the ratting started?

If the engine is stopping when hot and back-firing on a closed throttle, then that suggests that the valves aren't closing properly in which case they're either badly adjusted or damaged. I could be many other things too, which is why I need to know when all these various problems started...


arrrf.
26/06/2013 at 13:00

Actually I was tied so trying to elaborate with short sentences, Ideal was absolutely typed instead of idle :P  Well I appreciate for your understanding J.

I do apologies for bad mechanical terminology as am new in this field and adopted it as a hobby now.

“Regarding your stuff about the push-rods & valve clearances I'm not sure what you're saying. Yes, pushing the rocker hard onto the push rod will take out the free-play elsewhere and putting it all at the valve / tappet so your measurements are consistent. It sounds like that's what happened with the exhaust valve, rocker and push-rod.You then say "but on the 2nd rocker side it also pressed down by the second push rod". Well - yes, the 2nd push rod pushes the 2nd rocker which opens the 2nd valve. So what's the problem? Push the rocker hard against the push-rod so that all the free-play at the push-rod is taken out, and all the clearance is at the valve where you're measuring it... You should definitely NOT be trying to achieve 2 separate clearances at each end of the rocker arm”

 Let me ask it again with differently, If engine is set at TDC then is it necessary the valve clearance should be remain 0.08mm for both valves at same time at every 720 rotation?? (Suppose we pushed rockers at push-rods and there is no more free play left) or we have to check the only one valve for clearance at a TDC

I have read some where on web that put a feeler gauge b/w a valve and rocker (for example Intake valve) and put another same gauged feeler in-between 2nd valve and rocker for valve clearance to set it .08mm..

 

“When you're sure that all the free-play is at the valve end, and that no free-play is left elsewhere, then you should put in one feeler gauge after another until you find one that won't easily go in with a "sliding fit". Hold a feeler gauge gently between your thumb and forefinger and pull it out from between them - that's the sort of sliding resistance you're looking for.”

 Nicely conveyed

 

” Did the idle (not "ideal") problem start at the same time as the ratting? Or did it start after it was tuned? Did you take it to be tuned before or after the ratting started?”

 

Rattling started first, during rattling idle way quit ok hasn’t prominent to be notice. Then bike was being tuned (serviced) at unauthorized service center few days after my first post. After that it started Backfire at gear shifting, braking and during throttle closing. I installed a new NGK DP8EA 9, after 10-15 km city ride at 40-50km/h I checked the plug which showed a tip burn and very light brown deposits on white ceramic. Previous plug was black from round edges and tip and dark brown color on white ceramic. Bike some time hesitated on run at 4k to 5k RPM above 5k it didn’t hesitate but started backfires as soon as throttle was closed.

 

One more thing I bring it back to road after it was stored for 7 months due to an accident, I put one tablespoon oil (a little thicker oil I dnt have any idea about the no of it) in combustion chamber and refitted the plug as directed in user manual to store a bike. Engine wasn’t touched in accident, only the new exhaust (muffler) fitted and some body work done. No fuel mixture or jet setting was being disturbed. Only did valve clearance at that time. Previous exhaust was light brown head to tail, mileage was awesome 48 Km/L in city, 50-54 Km/L on long run. New exhaust’s tail is black and I can check the carbon at tail end with my finger. The mileage is

Edited: 26/06/2013 at 13:36
26/06/2013 at 13:39

The mileage is 32-35 Km/L. or less. The exhaust brought from Honda parts store, and I also verified its genuine or not by some other people.

 

For current situation Rattling is nearly gone and Backfires in...

.”if the engine is stopping when hot and back-firing on a closed throttle, then that suggests that the valves aren't closing properly in which case they're either badly adjusted or damaged. I could be many other things too, which is why I need to know when all these various problems started..”

 

 If the valve clearance and valves are fine then what next I should check for backfire problem..?

The fuel mixture screw is set at 2 and 3/4 turn out.. Turning fuel mixture screw IN is making mixture lean and turning fuel mixture screw OUT is making mixture rich!!!! Am I wrong??

Edited: 26/06/2013 at 13:43
27/06/2013 at 16:50

I have checked every thing but rattle has come again, backfire is on as well, especially when throttle close above 30-40km/h speed. i found some oil type substance in intake area and on plug that can easily wipe out with finger tip. . Last time i used Hi Octan... im going to disassemble it to check it thoroughly.  o_O

Edited: 27/06/2013 at 16:51
27/06/2013 at 19:54

Yes - single cylinder engine so both valves are shut at TDC on the compression / firing stroke. At this point both valve clearances should be set to the clearance specified in the service manual. If that's 0,08mm then that's what they should be. And they shouldn't change - each time you turn the engine 720 degrees and re-measure they should be the same. If one of them keeps changing then either you're not measuring them very well (seems unlikely given how many times we've been round this) or the valve isn't closing properly - possibly due to a bent valve.

If the valve clearance are OK then clearly the rattle is something else. Is it a consistent "rat-ta-ta-ta-ta" or does it buzz and get louder and quieter? Does it sound like it's once per engine revolution (engine speed) or at half engine speed? Does it happen with the bike in neutral and not moving, or only when riding?

Again, if the valve clearances are OK and it has good compression then something else is causing the misfiring and poor running. It could be ignition or fuelling. As it's doing it on the over-run then it's more likely to be fuelling. If the bike was stored for some time then the fuel in the carburettor may have gummed up, restricting fuel flow and causing poor running and idling. Water or rust in the petrol tank may have slowly settled and found its way into the carburretor, causing similar proplems.

A crack in the exhaust header might also cause the problems you describe - tapping noises, mis-firing on the over-run, poor running, burned spark plug. Check the system very carefully from the cylinder head through to the silencer. Maybe it received a heavy knock in the accident?

If the ignition uses mechanical contact breaker points then they could be set incorrectly. If the ignition used transistorised timing then check if it's adjustable - if so, then that might've been adjusted incorrectly, but putting it back to the correct timing will require a timing strobe.

 


arrrf.
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