VF1000FE Camshaft Bolts question

I have two F2 engines laying around in parts and I noticed that not only the camshafts are longer but they use different botls.

My bike is an early bike, is it wise to install the different style bolt instead of original one?

 

The bolt with a spiral flute is a Uniform Bearing Stress bolt. Very specialised and not used much, but Honda do use them obviously. Read all about them here.

http://books.google.com/books?id=_P...&q="Uniform Bearing Stress" UBS Bolts&f=false

Doesn't answer you question but at least you know what it is.

 

I remember something about these bolts are being specific to F2 and that they have bad impact on main bearings when installed on F1. Does not make sense to me, look like they can help with oiling issues of the camshafts

 

There is very little on the interweb about these bolts. I think the UBS designation applies to the design of the flange at the hex head. I think a better description of the fluted bolt is a special tension bolt. You can find a few very brief descriptions of these on the web but nothing definitive. I did think the role of the flutes was to reduce the cross sectional area of the flank of the bolt. This makes the bolt more elastic and more tolerant of large magnitude tensile stresses encountered in the cylinder head. However thinking about it a bit more, this doesn't make sense.
I think the fluted design as opposed to he more common waisted flank is probably due to reduced manufacturing cost. Those flutes can be rolled into the flanks. These bolts are installed on the VF500 engines too. They don't behave like normal bolts either when loosening and tightening.

 

The plastic region bolt is used in such areas as the cylinder head or bearing cap assembly to provide a steady bolt tension. Normally bolts are tightened to the elastic region. In this condition, the bolt is tightened to the specified tightening torque.

In the elastic region, the bolt tightening torque and bolt tension becomes greater proportionally. For tightening a bolt in the elastic region, some tolerance will be created through the bolt thread, flange or washer if the bolt tension is controlled at the tightening torque.

In the plastic region, there is almost no change in bolt tension from tightening torque. The plastic region tightening method uses the material properties so that the uneven bolt tension from fluctuations in tightening torque is reduced. Bolt tension is stabilized as bolt tension itself becomes greater.

So, Honda used the Plastic-Region Tightening Method to insure that force was uniformly applied across a flange, which is basically what an engine's head and its crankshaft bearing cap are.

 

Here it is again, still being used in the 5th Gen VFR800

In the 5th Gen Service Manual the Plastic-Region Angle Method of Tightening is:

1. Tighten the Main Journal 9mm (pre-coated) bolts in their numerical order by several steps to reach 20Nm, 14ft lb.
2. Then further tighten each Main Journal 9mm bolt by 90 degrees in their numerical order.

 

I understand how a bolt going plastic can result in a more even clamping force. However you don't need those flutes to do that. A reduced section flank will achieve the same result. If the bolts were going plastic on my VF500 they would permanently stretch and the manual would say not to reuse, but it doesn't and the torque value on the VF500 bolts is only 30-34Nm, which I would have thought was insufficient to induce enough tension to go plastic as they are chunky bolts. Fascinating stuff. I will investigate further and thanks for the VFR800 info.

To the OP, I would use the correct bolts to be safe!

 

Thank you for a lot of usefull information. I will keep the original bolts in place just to be safe.