B33 exhaust and inlet valves

[Malc]

Hello again everyone.
The continuing saga of getting the bikes running their best goes on.
Having rebuilt the engine on my B33 I'm finding that the valves are pocketed and making adjustments of the valve clearances very difficult.
It has been suggested to me I could put valves that have heads that are a couple of millimetres wider, therefore can be ground in without pocketing.
The standard size valves are 96.3 mm long, stem 8.8mm, head 41.4mm diameter. So I'm guessing it will need to be the same dimensions except for the head which needs to be about 43mm.
If anyone can help me with this I would be very grateful,  or if anyone has any alternative suggestions,  that would also be great.
I thank you in advance.
Malc

[JulianS]

You could have new valve seats fitted or source a better used head?

If you used oversized valves they would need to have the cotter groove in the same place and exhaust would need to be made from an appropriate steel.

G and S valves have a downloadable catalogue for classic bike valves which lists valve sizes.

http://www.gsvalves.co.uk/

[Malc]

Thanks for the reply. 
I have to confess,  I didn't realise you could have new seats fitted so that's something to investigate.  As for a decent 2nd hand head, I've been looking for the past 3 years and they come up very rarely and those that so are usually damaged in some way.
I will download the valve catalogue and see what's available on that.
Many thanks again Julian for you assistance.
Kind regards
Malc

[scifi]

You will need at some time to recut the valve seats with a proper valve seat cutter.  You then might find that the original valves will give a good air-flow profile.   Also are your dimensions correct, I doubt metric was even invented when they were designed..  8.8mm might in fact be 11/32 inch.

[neil1964]

Although finding originals might be difficult using the part numbers to find replacements might help

Exhaust valve 65-1646 will fit from a '49-'53 ZB34 500 gold star (Head Dia 42,2 mm, total Length 97mm, Shaft .374 = 9,5mm)

Inlet 65-1239 also from a ZB34 similarly (Head 1.21/32 = 42mm, Stem .348 = 8,85mm, Length 97,62mm)

I think that they will work for you although you may need to ream the guides and certainly recut the seats.

[Steve.S]

I think the engine will still run OK with pocketed valve seats, you just won't get the best out of it. If it's not too badly pocketed, you may get away with relieving the outer diameter of the seat, to improve gas flow. But your best course of action would be to have valve seat inserts fitted.
If the pocketing is so bad that you can't get a tappet clearance, then you need inserts.

[scifi]

I just looked at the price of valve seat cutters...   Machine Mart do a nice set at £969.00, but if you want something cheaper, Ebay does a 20 piece set for £26.00.
However, with there being no Lead in petrol these days, maybe hardened valve seats need to be inserted by a local machine shop, which would stop the pocketing issue.

[Roy]

It's only exhaust that normally changed for lead free , you be far better taking head to specialist to cut /grind , that way the seat will ( should )run concentric to valve and seat properly and be correct angles , that's my opinion any way ,

[Mike Farmer]

 

I would uggest your best way forward is to have new seats. If so its a short step to new guides or guide inserts. T&E engineering Bedford has done a couple for me over the years. They'll grind the valves in for you at the same time.

There are of course several reputeable machinists across the country who will happily do the biz for you. I would further suggest that such may not ultimately be that much more expensive.

Mike

[Malc]

Thank you all for some great advice. I will look into new seat inserts and the GS valves and choose the best option. As for the imperial vs metric measurements,  I did it metric as in the 21st century even I can work out metric equivalents. Although I think my old girl actually has chains and furlongs to record  speed, so who knows.
Many thanks to all.
Malc