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Balancing shafts Yamaha Royal Star Vetrura and V-Max.


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Hi guys! Maybe someone knows the same or different balancing shafts at Yamaha Royal Star Vetrure and V-Max?

 

Yamaha used the same balance shaft in all balanced V-4's including the GEN 1 V-Max Boko.. There was a run of non-balanced V-4's in the Royal Star Classics from 96 till 99 (as I recall,, may be wrong on the years) with the smaller 26mm carbs that didnt sell well,, wayyy to putzy IMHO but other than those that did not have a balance shaft and the later GEN 2 1700cc V-Maxes,, the balance shafts from 83 up were the same according to parts fiche found here:

https://www.yamahapartshouse.com/oemparts/a/yam/500459d7f8700209bc793ba4/crankshaft-piston

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Thank. If anyone can answer, describe their feelings, please do so. Are the vibrations of Yamaha Royal Star without balancer shaft very different from the vibrations of Royal Star Ventura or V-Max with balancing shafts.

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Thank. If anyone can answer, describe their feelings, please do so. Are the vibrations of Yamaha Royal Star without balancer shaft very different from the vibrations of Royal Star Ventura or V-Max with balancing shafts.

 

IMHO, not really.. It's really not apples to apples though because the non-balanced 70 horse V-4 motor only spins up to 4750 rpms which doesn't even cross over the 5252 rpms line where it is performing in HP Heaven (what I call it).. The balanced V-4's are a capable of, and are designed to run well beyond that 5252 rpm line (due in big part because of the balance shaft) and they all develop wayyy more HP then the putzy/lazy unbalanced motor.. I have rode them both and, IMHO, the vibration comparison you are referring to may or may not be relevant as up to their perspective red lines (4750 for unbalanced,, 10500 for a balanced V-Max, 7500 for a balanced MK1) the vibes I felt, in a properly tuned/properly synced/similar tires/lubed drive shaft system was the same.. I have a hunch (and am fairly sure of this) that the balance shaft placed in the V-4 was placed there just as much,, and maybe more,, for engine longevity as it was for rider comfort..

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I have rode them both and, IMHO, the vibration comparison you are referring to may or may not be relevant as up to their perspective red lines (4750 for unbalanced,, 10500 for a balanced V-Max, 7500 for a balanced MK1) the vibes I felt, in a properly tuned/properly synced/similar tires/lubed drive shaft system was the same.. I have a hunch (and am fairly sure of this) that the balance shaft placed in the V-4 was placed there just as much,, and maybe more,, for engine longevity as it was for rider comfort..

 

In that case, what do you think? Does it make sense to install a balancing shaft in an unbalanced engine if it is supposed to increase the maximum speed to 6500 rpm.

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In that case, what do you think? Does it make sense to install a balancing shaft in an unbalanced engine if it is supposed to increase the maximum speed to 6500 rpm.

 

I highly doubt this would be financially or reasonably possible.. I have never been inside of one but I cant imagine Yamaha putting a crankshaft assembly with the gear on it needed to drive the balance shaft into a nonbalanced motor so a crank assembly would be needed too. I also doubt the case halves in the nonbalanced motor would be machined for the balance shaft so it would probably require some machining to accept the balance shafts.. Another thought to be aware of,, the balance shaft is not what increases or decreases the max RPM in and of itself.. That is all determined by piston speed designed into the original build.. A long rodded engine will have a lower rpm capability because for every 360 degree turn of the crank the piston has to travel farther so its speed is increased per revolution and as the rpm's increase - known destructive piston top speeds are reached sooner in the rpm range so the engine requires a lower red line.. Shorter stroked, multi cylinder engines (so piston mass is spread out) work opposite of that..

for kicks, lets get @Patch and @Flyinfool involved in this discussion... I know they both love to learn about this stuff :crackup::crackup:

(we go round and round and round with me trying to convince them that what I am talking about above is accurate)..

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Well it wouldn't be my choice for what that is worth.

 

For myself I first want to define my project goals.

 

What you have now is a cruiser and for other parts of the world it can be a descent touring ride where distances between countries are somewhat shorter.

 

As I eluded to in one of your calculation posts, rpm brings new challenges along with it.

Right now you have a torquey volume velocity combination breathing intake, that would need addressing as well, not just bigger carbs or you will slow its response.

 

The more rpm you add the more flows need to increase, the more that happens the more you fuel.

 

As far as stroke goes look at it as a line in diameter, the center rotates slower then its outer point tho the rpm is still benched, the one end has to speed up to keep up, that is time over distance traveled.

So the faster it travels the longer the distance it must travel relative to the center of rotation. That said then add those factors under combusted cycles, include friction and more listed below, duty cycles shorten.

 

Not sure why we are discussing the stroke but certainly a longer stroke will, if diameter is of equal bore of the shorter stroke, then volumes will increase as well. So in short verse long, long has more CC or more volume to displace. As a choice in rules one choose to lower the upper end of RPM.

Now there are reasons to this that are not so evident till you understand more around the physics like at TDC & BDC : in both cases the moving mass/inertia wants to keep moving in that one direction, where as the crank rotating will reverse the lever and at the same time it must absorb the effects of so! That goes for all connecting components as well involved in that case.

 

You must also look at the flow ports, valve sizing, seat angles, lifts and duration then you must consider ignition duration thru advance will you have enough at that new bench mark rpm? What is comparable between parts swapping from other higher output models to yours.

 

Likely I would look at a different engine swap, will likely save you time and money then effect your mods from and above that.

 

PS yes for vibrations

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I agree that there is a LOT more to setting red line than just adding a balance shaft. As puc mentioned I doubt that the internal features needed to add the balance shaft are even in your motor, the fact that there is no balance shaft now means that the balance weights on the crank are also different so even if you could add the shaft it would still be wrong and maybe even worse.

The biggest thing that makes the Vmax a 10,500 red line vs a ventures 7,500 red line is the cams, valves, and especially the valve springs used. The smaller springs in the MK1 and MK2 will allow the valves to float at around 8,000 rpm hence the 7500 red line.

 

ps.

Puc is talking silly again but then I am not a professional thread hijacker like SOME people are.:hijacked:

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