Shim under bucket

[Maturecheese_imp]

Why did Honda feel the need to arrange the valve clearances the way they did, shim under bucket? What engineering/performance gain do we get from that? Surely it would have made more sense to go with the usual bucket and shim setup that is so much easier for the average bike owner to deal with, not necessitating the removal of the camshafts to adjust the valve clearances?

[Tev62]

The shim under bucket tend to be the smaller shims, ~7.5mm and shim over bucket the older ~25mm. Shim over bucket had to be the full size of the bucket for the cam lobe to act on. By sticking the shim under the bucket you can use a smaller diameter shim as it is now just a spacer and the bucket is directly acted on.

So now there is less weight reciprocating up and down in the valve mechanism and you can rev the engine higher (if required and dependent on any other restricting parameters). But I would have been very happy with shim over bucket as our engines are not particularly high revving.

Some alternative engine designs are well thought out. The Kawasaki W800 uses smaller shims which you can directly access by sliding the rocker arm on its shaft. A nice solution for another low revving engine.

The good news is our clearances seem to hold up very well according to this forum users' experiences.

[Maturecheese_imp]

The shim under bucket tend to be the smaller shims, ~7.5mm and shim over bucket the older ~25mm. Shim over bucket had to be the full size of the bucket for the cam lobe to act on. By sticking the shim under the bucket you can use a smaller diameter shim as it is now just a spacer and the bucket is directly acted on.

So now there is less weight reciprocating up and down in the valve mechanism and you can rev the engine higher (if required and dependent on any other restricting parameters). But I would have been very happy with shim over bucket as our engines are not particularly high revving.

Some alternative engine designs are well thought out. The Kawasaki W800 uses smaller shims which you can directly access by sliding the rocker arm on its shaft. A nice solution for another low revving engine.

The good news is our clearances seem to hold up very well according to this forum users' experiences.

Thank you for an informative answer. It still is a shame they chose this weight saving method when as you say our engines are not high revving, in fact I believe they are rev limited It just makes servicing the valve clearances either hard to do or expensive if you get the dealer to do it.

[PowerDubs_imp]

It all plays together- weight and size of the valves themselves, the spring size and tension, the 'bucket' size and weight, camshaft profile, and not least importantly- making it all fit inside the cyl head while still allowing for the shape and angles of the combustion chamber, inlet and exhaust ports, fuel injectors, spark plugs- and making it look pretty on the outside.

There is an awful lot going on inside a cylinder head.

Quite often changing one thing greatly affects something else- or negates it from even being possible.

Example- by having shim over bucket- they may have to make the springs stiffer to avoid float and throwing the shim- which may have required the springs being bigger - which might not fit the required space for diameter, or may have bound depending on lift. Stiffer springs would mean more wear and service interval, etc etc..

The variability at play are quite complex at that level.

[the Ferret]

Almost all of the manufacturers have adopted that system as the most dependable and trouble free Honda,Yamaha, Suzuki, Triumph etc

[Tev62]

Almost all of the manufacturers have adopted that system as the most dependable and trouble free Honda,Yamaha, Suzuki, Triumph etc

Yes, tis so. Particularly impressed with Harley's use of a zero-maintenance hydraulic self-adjusting lifters though. That 1250 engine has bags of character. A low 5,000-mile oil service interval but maybe that is there to give the hydraulics a fighting chance.

[Nachodaddy]

Almost all of the manufacturers have adopted that system as the most dependable and trouble free Honda,Yamaha, Suzuki, Triumph etc

Yes, tis so. Particularly impressed with Harley's use of a zero-maintenance hydraulic self-adjusting lifters though. That 1250 engine has bags of character. A low 5,000-mile oil service interval but maybe that is there to give the hydraulics a fighting chance.

Yes, tis so. Particularly impressed with Harley's use of a zero-maintenance hydraulic self-adjusting lifters though. That 1250 engine has bags of character. A low 5,000-mile oil service interval but maybe that is there to give the hydraulics a fighting chance. I like a 5K oil change schedule, since it is easier to remember to change the oil. Uneven (3,000, 7,500, etc.) numbers can get skipped if you are not paying close attention.

[PowerDubs_imp]

Almost all of the manufacturers have adopted that system as the most dependable and trouble free Honda,Yamaha, Suzuki, Triumph etc

Yes, tis so. Particularly impressed with Harley's use of a zero-maintenance hydraulic self-adjusting lifters though. That 1250 engine has bags of character. A low 5,000-mile oil service interval but maybe that is there to give the hydraulics a fighting chance.

I’m unfamiliar, but what is the rev limiter?

For someone like me that does not pay attention I put Harleys in the same category as the classic pushrod American cars that are perfectly happy for you to shift it 4000, 4500.

I know there are a few high-performance models of American cars that can compete with the Germans, etc. but that is a relatively recent and high cost option compared to the normal stuff.

Although I suppose for what Harley charges for the bikes they should compete and not be what they were when I was a kid.

But I would still guess with hydraulic lifters, their RPM limit is probably 7K, 75? Maybe 8K w/ a bikes smaller valves compared to cars- but I wouldn’t expect much past that.


Sent from my iPhone using Tapatalk

[GoldOxide_imp]

Almost all of the manufacturers have adopted that system as the most dependable and trouble free Honda,Yamaha, Suzuki, Triumph etc

Yes, tis so. Particularly impressed with Harley's use of a zero-maintenance hydraulic self-adjusting lifters though. That 1250 engine has bags of character. A low 5,000-mile oil service interval but maybe that is there to give the hydraulics a fighting chance.

Honda regularly used hydraulic lifters on their early-to-mid 80's DOHC 16-valve inline-4s, and I think (?) their V4s also. The inline-4s never seemed to have any maintenance issues.

[DrewNJ_imp]

Almost all of the manufacturers have adopted that system as the most dependable and trouble free Honda,Yamaha, Suzuki, Triumph etc

Yes, tis so. Particularly impressed with Harley's use of a zero-maintenance hydraulic self-adjusting lifters though. That 1250 engine has bags of character. A low 5,000-mile oil service interval but maybe that is there to give the hydraulics a fighting chance.

I’m unfamiliar, but what is the rev limiter?

For someone like me that does not pay attention I put Harleys in the same category as the classic pushrod American cars that are perfectly happy for you to shift it 4000, 4500.

I know there are a few high-performance models of American cars that can compete with the Germans, etc. but that is a relatively recent and high cost option compared to the normal stuff.

Although I suppose for what Harley charges for the bikes they should compete and not be what they were when I was a kid.

But I would still guess with hydraulic lifters, their RPM limit is probably 7K, 75? Maybe 8K w/ a bikes smaller valves compared to cars- but I wouldn’t expect much past that.


Sent from my iPhone using Tapatalk

I’m unfamiliar, but what is the rev limiter?

For someone like me that does not pay attention I put Harleys in the same category as the classic pushrod American cars that are perfectly happy for you to shift it 4000, 4500.

I know there are a few high-performance models of American cars that can compete with the Germans, etc. but that is a relatively recent and high cost option compared to the normal stuff.

Although I suppose for what Harley charges for the bikes they should compete and not be what they were when I was a kid.

But I would still guess with hydraulic lifters, their RPM limit is probably 7K, 75? Maybe 8K w/ a bikes smaller valves compared to cars- but I wouldn’t expect much past that.


Sent from my iPhone using Tapatalk
9500 It's a good sized bore but a short stroke. 105mm/72mm