crankshaft balancer backlash adjustment

[Todd_K_imp]

Had a Honda civic that developed piston slap at 50k miles. On Cold mornings it sounded like a bearing was going. Never had any real problems up trough 205k when I sold it.

[the_undecider_imp]

Can one of you guys explain just what piston slap is and what it sounds like and any bad things it does? Thanks. I gots to know

I'd be happy to! The best example I know of it is in aluminum motors. Specifically GM aluminum motors. To be out simpky, the piston at any given moment is too small or the bore too large and the sides of the piston are knocking against the bore. Since the rings have room to expand, a compression loss is not experienced. Usually this occurs because the pistons and sleeve are made of different materials and these materials have different coefficients of thermal expansion. So, in the case of steel sleeved, aluminum motors, the bores will 'open up' when it's cold and as it warms up, the block will expand just enough to bring that gap closed enough to stop the slapping. Sounds awful, but typically doesn't do any damage.

Sent from my Z30 using Tapatalk

I'd be happy to! The best example I know of it is in aluminum motors. Specifically GM aluminum motors. To be out simpky, the piston at any given moment is too small or the bore too large and the sides of the piston are knocking against the bore. Since the rings have room to expand, a compression loss is not experienced. Usually this occurs because the pistons and sleeve are made of different materials and these materials have different coefficients of thermal expansion. So, in the case of steel sleeved, aluminum motors, the bores will 'open up' when it's cold and as it warms up, the block will expand just enough to bring that gap closed enough to stop the slapping. Sounds awful, but typically doesn't do any damage.

Sent from my Z30 using Tapatalk
The early GM 5.3 and 4.8 motors were bad about this. My 2000 Silverado 5.3 has it. On a cold morning, it'll clatter about 45 seconds and quiet down.

My 13 CB was clattering to my alarm, so I am glad I found this thread. I adjusted the backlash per the manual and she quieted down considerably.

[INTP_imp]

That really sounds to me like an exhaust leak. Is the cat split, or the O2 sensor loose?

[Firstfour_imp]

Can one of you guys explain just what piston slap is and what it sounds like and any bad things it does? Thanks. I gots to know

I'd be happy to! The best example I know of it is in aluminum motors. Specifically GM aluminum motors. To be out simpky, the piston at any given moment is too small or the bore too large and the sides of the piston are knocking against the bore. Since the rings have room to expand, a compression loss is not experienced. Usually this occurs because the pistons and sleeve are made of different materials and these materials have different coefficients of thermal expansion. So, in the case of steel sleeved, aluminum motors, the bores will 'open up' when it's cold and as it warms up, the block will expand just enough to bring that gap closed enough to stop the slapping. Sounds awful, but typically doesn't do any damage.

Sent from my Z30 using Tapatalk

I'd be happy to! The best example I know of it is in aluminum motors. Specifically GM aluminum motors. To be out simpky, the piston at any given moment is too small or the bore too large and the sides of the piston are knocking against the bore. Since the rings have room to expand, a compression loss is not experienced. Usually this occurs because the pistons and sleeve are made of different materials and these materials have different coefficients of thermal expansion. So, in the case of steel sleeved, aluminum motors, the bores will 'open up' when it's cold and as it warms up, the block will expand just enough to bring that gap closed enough to stop the slapping. Sounds awful, but typically doesn't do any damage.

Sent from my Z30 using Tapatalk
The early GM 5.3 and 4.8 motors were bad about this. My 2000 Silverado 5.3 has it. On a cold morning, it'll clatter about 45 seconds and quiet down.

My 13 CB was clattering to my alarm, so I am glad I found this thread. I adjusted the backlash per the manual and she quieted down considerably.

By "manual", do you mean shop manual? I checked my owners manual supplied with the bike, and can't find anything about this adjustment. Indeed no mention of the balancer at all, even in the maintenance schedule. That seems odd to me... I don't have any of the symptoms, but it would have been nice for Honda to tell owners how to do it should the need arise. I guess they expect it to be set right at the factory, and should never need service?

[Lord Popgun]

Yes, adjustment procedure is in the service manual. Also, it is posted in the How to section on the board here.

[Andor_imp]

Today I removed the drain with a cold engine and with a video camera for inspection I watched the smoke filter, everything is ok then I tried changing the oil 15w40 with a 10w40 oil and filter, I warmed up the engine and then with a long screwdriver I tried if the filter vibrated ... but anything all ok, I finally made a trip of 100 miles but I did not hear more noise, Baker!!!!Maybe when I put the bike on the side stand the oil goes on the left and interior noise you hear more, and when I put the motorcycle on the Centre stand the oil suppresses noise!!!!!?!?!?!?


Angelo.

[Dakota_imp]

Can one of you guys explain just what piston slap is and what it sounds like and any bad things it does? Thanks. I gots to know

I had a 454 chevy with piston slap. Sounded like strong lifter clatter which decreased and went away as the engine warmed up (aluminum pistons expanded). Did not at all sound like a lower end knock. Low end noise gets worse as the engine warms up and oil thins out.

[Stary Motocyklista_imp]

Huh! You’re never too old to learn something. I never heard of bores getting smaller as the block heated up. I kinda still doubt it. As a block heats up it gets longer and wider. The cylinder bores get larger exactly proportionally. Aluminum expands more than steel or cast iron with the same increase in temperature. Typical hot rod lore includes the knowledge that forged aluminum pistons expand quite a bit and when given proper clearance, piston slap will happen until they heat up and take up proper clearance. Actually all engines have piston slap: The wrist pins are offset toward the thrust face so the piston (the largest and most critical bearing in the engine) rotate the skirt fully against the cylinder bore to take advantage of the full skirt for bearing area under the firing stroke. Conversely the pistons attempt to rock the opposite way on the intake stroke. This is very small movement and not heard on a good motor. Modern hypereutectic pistons have recipes in their casting materials, which minimize the difference between thermal expansion of the cylinder and pistons making piston slap loud enough to hear rare.

I believe motorcycle owners that aren’t gear heads worry overmuch about noises, especially in air-cooled motors. Large flat cast covers and fins have harmonics and can amplify noises. Honda is so aware of this I’m sure every cover, fin, every casting is engineered around this and many other parameters. They have done an amazing job and the casual rider has no concept of the depth of their research and knowledge over the years. There is violence going on inside these motors. Controlled explosions, valves opening and closing rapidly, pistons coming to the top only to be yanked back to the bottom at great rates. There will be noise, and we love all those noises. All motors have their signature noises. It is wonderful we can experience this. Try not to worry.

I haven’t got my shop manual from Helms yet but why are people calling the balancer an “engine and transmission balancer”? All inline fours vibrate in a vertical plain at twice the frequency of crankshaft rpm. Nothing in the transmission needs balancing.

[CBXBob_imp]

What about the possibility of some kind of throttle body sync issue ? Just a WAG. If you have ever heard a 4cyl or a CBX way out of sync , it sounds like the eng will come apart.

[Stary Motocyklista_imp]

I was a mechanic in a Honda, Yamaha, BMW, BSA and Greeves dealer when the CB750 came out. The first ones had cable splitters, the one throttle cable from the twist grip pulled the 4 separate carb cables out of this splitter. Carb syncing was tedious and lasted for a couple of high speed blasts. All the fours had vacuum ports to plug gauges into. All of the big four quickly changed to common throttle shafts which helped a lot. There is a couple of aspects to throttle synching. First, the idle mixture had to be adjusted so that all cylinders fired at idle. If the air mixture was off, the throttle adjustment could be right and the idle would still be terrible. At an idle everything is so close to being closed and off it is hard to get perfection. Also those bikes had two ignition systems. All fours fire 1,2,4, 3. 1 and 4 had a set of points and coil; 2 and 3 had a set of points and coil. Timing could easily be off between those two sets of cylinders. Also valve lash is an important component of a stable idle. I’ve always been a proponent of setting valve lash to minimum specs, seems to make sense, less room to bang components and maximizing valve lift. However a stable idle on all those old fours was best achieved with the middle of the lash specification or at the upper end of it. This was particularly true of the Kawasaki 900s/1000s. I have a great appreciation of My CB1100 as I stare at my dusty sync gauges hanging above my workbench. Hale, My Ural even has FI. The chance of your CB1100 being out of sync much is slim or none unless some busy fingers have been in there. After a while, I got to care less what my Kawasaki’s idle sounded like as long as all the throttle slides reached the top at the same time and under load it ran fine on all four cylinders. A heat gun is a good tool to see if all the TBs are working ok. When you first start it up, get the heat gun out and check each head pipe at the same distance from the head. They should be in the same ballpark.