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V65 SP 1984 valve/spring upgrade to avoid dropped valves

Julian Sudano

Julian Sudano

Tuned and Synch'ed
GT Contributor
Joined
Jul 25, 2021
Messages
61
Location
Los Angeles, CA
Looking for some guidance on the dreaded (potential) stretched valve issue on my V65...

My cylinder head gaskets have been weeping quite a lot of oil so it's time to replace them. Given the possibility of the dreaded "valve stretch" that can result in dropped valve heads and the subsequent damage that can create, I'm looking to future proof the cylinder heads during the gasket replacement process.

I have read that the valve springs on the V65 required too much tension to work which resulted in stretched valves which could eventually drop their heads creating damage. Supposedly a common upgrade was using the later Breva 750 single valve spring set up which alleviated the issues. Does anyone know the part numbers for the single spring set up?

Does anyone have any experience of this upgrade as I'd like to future-proof my bike whilst replacing the head gaskets.

Also, if I replace the existing valves with new ones, as a precaution assuming they are somewhat stretched, is it simply a matter of performing a lapping job to seat the new units, or does it require a valve seat cutting job to ensure correct seating?

Thanks in advance!
 
The 750 Breva parts manual is in the downloads. You can look up the parts yourself. If you have significant miles on the bike, having K-lines installed in the valve guides may be beneficial. This has to be done by a machine shop that has the equiment to install and ream the valve guide inserts. If you lap and you get a good gray band on the valve face you should be good to go. If not, then have an automotive machine shop do their thing to get a good valve seal.
 
I also have a leaking head gasket and in the process of opening the head.
I compared part numbers of the valves and springs of the V65 SP to the V65 Florida and my '91 V65GT.
Not surprisingly, they list the same numbers.
I don't think my engine was ever opened, so it probably has the stock springs and valves. I can see an inner spring and now I am tempted to replace them.
Then I ran across the V65PA, which has a slightly different combination. Inner spring the same as V65, outer spring is from the Breva.

Nominally the V65 outer spring seems just a whee-bit stronger than the Breva based on the weight and compression data in the diagrams. The V65 spring needs 18kg, while the Breva needs 17.5kg to get to 36mm. If we add the tolerances, I would say they are the same springs.

V65 springs and this info from the V65 manual
1688135437784 1688135674659

This is the Breva spring
1688135495035

However, the Breva spring is 3.1mm longer, so it should pull on the valve more then the V65 outer spring at the 37mm compression. But the data doesn't support that. 🤷‍♂️
The V65 outer spring is compressed to 37mm when the valve is closed, so the inner spring should not be pulling on the valve stem.
I don't understand how the Breva spring reduces stretching on the valve.
I guess I need to research what the inner spring does, other than help return the valve to the closed position. It doesn't keep it closed because of the 37mm note.

Fred, how do you check the valves for this? Shrinking tappet gap?
Are the stems brittle and snap instead of stretching?

Finally, does GTM carry the good valves, not the replicas?
I see wild prices online and I'm guessing the cheap ones are not OEM.

My brain hurts. Time to go for a ride.
 
Interesting to see these comments regarding the 2 valve V65 motor. I remember seeing over the years claims the valve springs were too strong on the 4Valve versions but not the 2 Valve. Are you sure the motor concerned didnt just have a valve fail from use and age? It can happen as they were a two piece valve , ie head of one material and stem of another pressed together in the factory as was common with many brands back in the early 80s.
 
Pescatore said:
I also have a leaking head gasket and in the process of opening the head.
I compared part numbers of the valves and springs of the V65 SP to the V65 Florida and my '91 V65GT.
Not surprisingly, they list the same numbers.
I don't think my engine was ever opened, so it probably has the stock springs and valves. I can see an inner spring and now I am tempted to replace them.
Then I ran across the V65PA, which has a slightly different combination. Inner spring the same as V65, outer spring is from the Breva.

Nominally the V65 outer spring seems just a whee-bit stronger than the Breva based on the weight and compression data in the diagrams. The V65 spring needs 18kg, while the Breva needs 17.5kg to get to 36mm. If we add the tolerances, I would say they are the same springs.

V65 springs and this info from the V65 manual
View attachment 30737 View attachment 30739

This is the Breva spring
View attachment 30738

However, the Breva spring is 3.1mm longer, so it should pull on the valve more then the V65 outer spring at the 37mm compression. But the data doesn't support that. 🤷‍♂️
The V65 outer spring is compressed to 37mm when the valve is closed, so the inner spring should not be pulling on the valve stem.
I don't understand how the Breva spring reduces stretching on the valve.
I guess I need to research what the inner spring does, other than help return the valve to the closed position. It doesn't keep it closed because of the 37mm note.

Fred, how do you check the valves for this? Shrinking tappet gap?
Are the stems brittle and snap instead of stretching?

Finally, does GTM carry the good valves, not the replicas?
I see wild prices online and I'm guessing the cheap ones are not OEM.

My brain hurts. Time to go for a ride.
Click to expand...
 
Wow - that is very interesting and very thorough! Maybe the answer is a V65 inner with a Breva outer?
I ordered as set of 4 Nevada (single spring set up & same part number as Breva) so I will measure the free length and see how it compares.

I'm curious to measure the valve lengths when I pull the heads, to see if there is any evidence of stretch.

Will let you know.
 
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