Engine knocking need help identifing

[dan filipi]

Hate to say it but I guess time to open her up.

 

[esker]

Yes that ratchety sound.... still keeps me thinking what can cause that type of sound? I know that whatever we hear that was recorded by the camera will probably not be quite the same sound as heard by standing beside the bike. My digital camera pick out the valve train sounds on my BSA when it is 100 feet away. Sounds terrible on camera but normal in real life.
Valdarez, when you say that the sound appears to be coming from the exhaust valve area. are you able to pinpoint the area that is causing the sound using your stethoscope? Without burning your hands, are you able to feel for the shock of that tapping noise (engine cold of course)? Try running with the left exhaust pipes off the head and listen for the tapping noise (if you can hear it over the exhaust noise). Just trying to eliminate all possibilities before you pull the engine. I was having visions of the exhaust pipe sealing ring moving up and down but somehow I wouldn't think so. But that ratcheting sound..... just like shaking a rattle can of spray paint.

 

[slabghost]

Cycle of piston- SUCK (intake which creates vacuum)
Compress - pressurizes aforementioned intake
Bang- ignites aforementioned compressed intake
Blow - ejects burnt gases through the exhaust
Is it so hard to believe that in this cycle a loosely held valve cannot make noise?

 

[esker]

Yes I was wondering about that too. And on both heads?? With different valve springs being used ?? I looked at the video with the rockers removed on piston # 2 and really didn't see very much movement of the intake valve. Did you see the valve compress the spring and move the valve? Somehow I missed that. The exhaust valve was not showing in the video so I can't really say what is going on there. Would there be enough mixture drawn in past the intake valve for the piston to compress and ignite? What is the effect of compressing the burnt mixture when the exhaust valve is not opened because the rocker has been removed?
So what you are saying is that the vacuum developed by the piston will overcome the spring forces and open the intake valve , then after compression the spark ignites the mixture after which the piston on its way back up pushes the gases past the exhaust valve which was opened by the vacuum of the piston?
I'm still stuck at the fact that the same problem was occuring on two different cylinder heads.

 

[toytender01]

Just an observation: In diet bikes with kickstart, with the engine running and the kickstarter engaged you would hear that type of ratchiting sound ???????? :ahem: :ahem: :whistling:

 

[slabghost]

I figure if a vacuum cleaner can pick up a bowling ball. The vacuum created by the cylinders certainly could pull valves open slightly. Yes if you held the kicker after starting bikes made a similar sound but they actually did have a ratchet mechanism.

 

[dan filipi]

I'm curious, does this sound change with temperature or when cold starting before the oil pressure comes up. Any difference?

 

[Jalvarez]

Dan : no difference cold or warm

 

[dan filipi]

Don't know where your at on this, maybe the engine is already out but if not how about doing a running compression check. Wouldn't that maybe identify a valve problem?

 

[Jalvarez]

Dan: I am waiting for the new springs to arrive. I plan on replacing and if that noise continues I will reluctently take the engine out to check the piston pin and rod bearings.

thanks

 

[wilf]

I haven't read this thread thro all the way but if you where to play that audio to me in a blindfold test no info at all about what kinda engine or anything My reaction would be broken exhaust manafold. that is exactly what it sounds to me like. Hve you swaped out the lsft side manifold. may be a crack somewhere near where 2 and 4 join. Did you hit any potholes or other nasty stuff before this started
Wilf

 

[mwbill37841]

just a idea.. any tools or little bolts maybe in the exhost pipe.rattleing?

 

[wilf]

Idont think there is something in the just a crack
wilf

 

[Jalvarez]

thanks for the tip. will remove exhuast and check

 

[wilf]

if it's still all togther id fire it up on the sidestand and get under it with your stethescope and see if you can tack it down. Some of the ford v8s made that sound from broken manifolds but where hard to see.
wilf

 

[Jalvarez]

Well i finally got around to breaking the engine down and no surprise



All that guessed right

ROD BEARING resulytiing in piston knocking

Thanks to all for you suggestions and help


Any ideas fopr getting bearing as Honda does not make them any more

Cross referemce or kits would be greatly appreciated

Thanks again to all

 

[joedrum]

hmmmmm ...we need to find a bearing suppy somewhere ....dont throw anything away yet ...i bet there is something that will work if found ...there was a place in UK that had a supply ...old fogey from NGW forum i think may be the one im thinking had access to..

 

[mcgovern61]

Well i finally got around to breaking the engine down and no surprise All that guessed right
ROD BEARING resulytiing in piston knocking
Any ideas fopr getting bearing as Honda does not make them any more
Thanks again to all

Rebuilding would be expensive (IMHO). If the rod bearings are bad, everything else is most likely equally worn.

My'81 engine went through the same. I swapped it out with a lower mileage '83 engine and couldn't be happier with the result. I found the engine on ebay for under $200. Total was $376 with shipping from out of State. The ebay ad had videos of the engine running before pulling so it wasn't too big of a risk!

 

[Jalvarez]

O:K everybody the knocking problem was a main Bearing

Thanks to all that responded

 

[Steve83]

Are you going to rebuild? What's the plan?