VROD Cylinder compression question

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Mar 20, 2010 | 03:16 AM

Harlen Vega

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VROD Cylinder compression question

Im popping my forum cherry on this one so I hope it hasn't been covered in 40 pages of data I entirely overlooked.

Heres my question:
Why is the rear cylinder compression so much higher then the front cylinder on the Vrod. Off the top of my head I believe its a difference of around 80-100psi. Front cylinder is approximately 113-135 and 205-245 for the rear. Again the specs are from memory and accuracy of the spec in this regard is not vital to me. The reason (if any) for the difference in compression, which I feel is pretty substantial between the two is the focus.

As a side note, It would seem to me that the higher compression cylinder should be in the front since it will create more heat than the lower compression cylinder regardless of the fact that this is a liquid cooled machine. Am I off my rocker on this one? Im hoping for an explanation of some engineering brilliance to align myself with here.

I look forward to finding out more of what this is all about.

Last edited by Harlen Vega; Mar 20, 2010 at 03:18 AM.

Mar 20, 2010 | 08:38 AM

Hillsidecycle.com

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I believe those have spring loaded compression release lobes on the heel of the cam at where it would normally be closed.
As the rpms increase the release is retracted via centrifigal force.

Scott

Mar 20, 2010 | 06:04 PM

Harlen Vega

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Quote:

Originally Posted by Hillsidecycle.com

I believe those have spring loaded compression release lobes on the heel of the cam at where it would normally be closed.
As the rpms increase the release is retracted via centrifigal force.

Scott

The ACR or automatic compression release was available on models from 2002-2007 if memory serves me right. I'm not too sure they have a spring load however. I'm fairly certain they are counter balanced and swing freely when no force is being applied. You are correct they do work off of centrifugal force.

I will rephrase my question.

Was the compression intentionally made higher in the rear cylinder... and why? What mechanical benefits does this attribute to if in fact it was intentionally engineered that way.

There's also the possibility I may be simply asking the wrong question as well.

Last edited by Harlen Vega; Mar 20, 2010 at 06:15 PM.

Mar 21, 2010 | 07:43 AM

Hillsidecycle.com

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What I was getting at was that the releases could be causing that varience.
Was anaware of the later models not having them.
Certainly sounds odd that both are not carring the same ccp.

Scott

Mar 21, 2010 | 02:34 PM

Harlen Vega

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Ah I see what your saying. Ill have to tear one down on Monday and take a closer look at what is going on there. I talked to a vrod instructor friend of mine and he said the question for some reason has never crossed his mind and admitted that he was a little confused on why he had never thought of it. Him and I are going to take a closer look into this on monday when we can get a motor in front of us.

Last edited by Harlen Vega; Mar 22, 2010 at 12:52 PM.

Mar 21, 2010 | 05:42 PM

Hillsidecycle.com

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Keep us posted on your findings if you would.
Scott

Mar 21, 2010 | 10:04 PM

06roadglide

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From: sw ohio

I remember when the V-rod was released I seen a cut-away of the engine and I put my finger on a part in the front head and asked the rep. what it was, sure enough, it was a cintrifugal compression release on the cam. I don't recall seeing it on the rear so that may be why I asked.