Boy these engines are picky about putting the piston rings back in. Glad you got things solid in that engine. You will get an error if you try to follow the old links from email notifications or ones that you might have saved. The new forum address contains "/forum" in the middle. Sorry for the hiccup. If you have an old link that you want to bring about just type in the following change:
Instead of: http://www.fourwheelforum.com/showthread.php?t=1099
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Can't get it started... some but little spark.
So, the latest:
Engine is closed, new plug installed (one had broken ceramic), timing adjusted. Bike started right up! No smoke, or a very little bit out of #2 cyl. which I can live with.
New problem though: there is an RPM related clack-clack noise in the head near the #2 cyl. The noise stays when revving up and disappears for a few second after the RPM goes back to idle.
I checked the valve/rocker gap twice, it's good, the timing chain/crankshaft/camshaft is also good, there are no issues with valves touching pistons as I previously thought.
Anyone has an idea of where that noise could come from?
Engine is closed, new plug installed (one had broken ceramic), timing adjusted. Bike started right up! No smoke, or a very little bit out of #2 cyl. which I can live with.
New problem though: there is an RPM related clack-clack noise in the head near the #2 cyl. The noise stays when revving up and disappears for a few second after the RPM goes back to idle.
I checked the valve/rocker gap twice, it's good, the timing chain/crankshaft/camshaft is also good, there are no issues with valves touching pistons as I previously thought.
Anyone has an idea of where that noise could come from?
A little test that you could make that don't take long and costs nothing.
Remove both plugs (cold motor) engage first gear and push the bike and listen. If it sounds metalic like a valve hiting a piston, It's probably piston slap caused by the rocking motion of the piston as it changes direction across top dead centre.
Sam.
Remove both plugs (cold motor) engage first gear and push the bike and listen. If it sounds metalic like a valve hiting a piston, It's probably piston slap caused by the rocking motion of the piston as it changes direction across top dead centre.
Sam.
Technically, yes. All piston driven internal combustion engines and compressors have some degree of piston slap. Usually,the loudest noise from piston slap is at startup. Piston slap is typically due to too much room between the piston and cylinder walls. Being that you hear this noise when revving the motor, my second theory is that you may not have replaced the rocker shaft and rockers back in their original positions when you reassembled the head. So what I am saying is that the noise is coming from the rockers assembly. I also would still consider a higher octane fuel with a replacement lead additive.
Well, I dont know what to do now. I know that the noise only happens with the engine under power.
I removed the plugs and used my drill with a socket on the nut at the left end of the crankshaft at the points I rotated the engine at 500, 1500 and 2500 rpms and no noise except the gentle clicking of the valve train.
I checked and adjusted the valve/rocker gaps again. I checked inside the chamber with a flashlight to make sure that no piston/valve contact existed, all is well.
Started the engine and the noise is still there. So I made a movie of it and I am seeking advice from the knowledge base on this forum as to what it could be.
The movie is here: http://www.youtube.com/watch?v=-e5_Sb0Eu2A
Thanks!
I removed the plugs and used my drill with a socket on the nut at the left end of the crankshaft at the points I rotated the engine at 500, 1500 and 2500 rpms and no noise except the gentle clicking of the valve train.
I checked and adjusted the valve/rocker gaps again. I checked inside the chamber with a flashlight to make sure that no piston/valve contact existed, all is well.
Started the engine and the noise is still there. So I made a movie of it and I am seeking advice from the knowledge base on this forum as to what it could be.
The movie is here: http://www.youtube.com/watch?v=-e5_Sb0Eu2A
Thanks!
Oh boy that is annoying. Very interesting. I would almost call it a ticking noise but being there in person it probably sounds more like a knock. I would get one of those stethoscope things (or a long screwdriver to your ear) and listen to see if the noise can be pinpointed to what side of the head.
The guides couldn't possibly be moving out of place when the engine heats up? Obviously I didn't' press them in myself so I can't tell how tight they seated. It definitely sounds valve related from what I hear in my opinion. And all the springs look to be in perfect condition? Did you replace the valve springs when you did the work? I would tighten the clearance on them a bit just to see if it makes a difference before I tore it apart again.
The guides couldn't possibly be moving out of place when the engine heats up? Obviously I didn't' press them in myself so I can't tell how tight they seated. It definitely sounds valve related from what I hear in my opinion. And all the springs look to be in perfect condition? Did you replace the valve springs when you did the work? I would tighten the clearance on them a bit just to see if it makes a difference before I tore it apart again.
Yes, it is more like a loud ping I would say. I have tried the stethoscope and it was difficult to figure out where the noise was. Just listening to it around the bike seems to point at the #2 cylinder.
I did not replace the springs when I rebuilt the head, they all looked fine (though I did not measure them). Keep in mind that this noise was not there while I ran the bike before rebuilding the head and had removed it twice before that.
I pressed the guides back in place where they came out of, down to the clip around them. I double checked them after that. The valves are seated nicely and I lapped them.
I will check the rockers by removing the rocker shaft since I dont have to take off the head for that. If it still does it, I'll have to remove the head again....
This project is dragging...
I did not replace the springs when I rebuilt the head, they all looked fine (though I did not measure them). Keep in mind that this noise was not there while I ran the bike before rebuilding the head and had removed it twice before that.
I pressed the guides back in place where they came out of, down to the clip around them. I double checked them after that. The valves are seated nicely and I lapped them.
I will check the rockers by removing the rocker shaft since I dont have to take off the head for that. If it still does it, I'll have to remove the head again....
This project is dragging...
What are the clearances right now? Here is a site showing a good "how-to" for Honda 90cc and 110cc bikes: http://ct90-ct110.com/Adjusting-Valves.html
I have been waiting to chime in after reading all of the responses. Thinking out of the box, could the rockers be worn? Here is my case. Engine oils once had a zinc additive that protected parts that rubbed, ie: rocker assembly's.
This zinc additive was removed with the introduction of the cayalytic converters arount the mid 1970's. It may be that this engine has been using "modern oils" all of these years and the cam side of the rockers are worn and sloppy.
The only oil I use in my rebuilds is diesel straight 30wt. as it the only oil available with the zinc additive to protect the contact to contact parts.
Worn rockers would give that "tap" except the "tap" is not at the valve stem, but rather at the cam shaft.
This zinc additive was removed with the introduction of the cayalytic converters arount the mid 1970's. It may be that this engine has been using "modern oils" all of these years and the cam side of the rockers are worn and sloppy.
The only oil I use in my rebuilds is diesel straight 30wt. as it the only oil available with the zinc additive to protect the contact to contact parts.
Worn rockers would give that "tap" except the "tap" is not at the valve stem, but rather at the cam shaft.