Exhaust valve sizes

N

Nick

Full member
Hi,

I need a new set of exhaust valves. The ones installed measure 35.1 x 85.5 which I think are standard size for an RGS. Searching the web it seems 34 or 35.5 are commonly available. Can anyone guide me to a supplier of 35.1's?

I'm having the seats cut but wonder if 35.1's are difficult could I get the seats ready for 35.5s (which might go some way to overcoming slight pocketing with the current settup. Is there any compatibility issues with standard RGS inlet valves?

Have a good new year and thanks in advance for comments.

Regards

Nick
 
While you're contemplating the above you need to be aware that valve stem diameters differ.
Assuming you're guide keeping your guides because they're unworn and parallel, you ideally need same or larger to hone the guides to match the valve stems, then cut the seats. 1 thou undersized and you have a new problem.

It's likely that an 0.008" increase in valve head radius will do you a favour and if it "was" oversize, a quick whiz on a valvemaster would correct that.
 
Last edited:
Nick said:
Hi,

I need a new set of exhaust valves. The ones installed measure 35.1 x 85.5 which I think are standard size for an RGS. Searching the web it seems 34 or 35.5 are commonly available. Can anyone guide me to a supplier of 35.1's?

I'm having the seats cut but wonder if 35.1's are difficult could I get the seats ready for 35.5s (which might go some way to overcoming slight pocketing with the current settup. Is there any compatibility issues with standard RGS inlet valves?

Have a good new year and thanks in advance for comments.

Regards

Nick
Click to expand...
The valves fitted would have suffered wear and the diameter reduced as a consequence. The Australian Laverda parts specialist, DAM Racing, gives the stock dimensions of 35.5MM x 85.5MM for the RGS Exhaust valve, with a 7mm stem diameter.
 
Thanks for the responses. 35.1 was the size Clem quoted on this site & the size Keith Nairn supplied. I'm not weird about originality just want a settup that'll work with what's available.

I have new 'customer guides to take the standard 7mm stems. The guides were both worn and not a particularly tight fit so had to be changed. At some point the seats were replaced and I'm advised slightly out of line - which can be sorted.

I looked at the DAM site but they report being out of stock of their 35.5s. I'll send a mail to double check.

Happy New Year.

Nick 🙂
 
Standard valve sizes for an RGS is 35.0mm Exhaust, 39.5mm Inlet

Laverda as do most motorcycle manufacturers build their valve stem clearance into the Valve guides so standard stem size for a Laverda triple is 7.00mm
Car manufacturers build their valve stem clearance into the Valve stem so their stem size is 6.970mm

If your Valve Guides have been changed out I can supply Exhaust valves 35.5mm head diameter with 6.975mm Stem size made by AV&V in Canada though their valves are actually made in Argentina

I am in Australia and have at least 60 new Exhaust valves in stock though that will change in the next few days as have 4 x cylinder heads to assemble that we have just installed new Valve seats and Guides to
 
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