Replacement Valves for little Laverdas?

C

chris78jota

Senior member
Location
England
Afternoon,
I'm getting stuck into the Laverda 75cc engine rebuild at the moment.

The valves need replacing ideally, but I am struggling to find suitable replacements. (60mm length, 22 or 23mm head).  Even monkeybike/pit bike valves are too long.

Before I venture into a world of pain buying jap superbike valves and having them shortened etc etc etc,  has anyone come across a suitable off-the-shelf replacement?

Stem diameter isn't a problem (the skinnier the better) as I will be getting colisbro valve guides made up after I find the valves.

Many thanks, Chris
 
Chris,

Though not exactly plentiful, they do pop up at the big italian jumbles, just like pistons, gearbox bits and engines in various states of completeness.  Not even expensive!  Try "King of Pistons" on the web, he might have a source for the valves, has been very helpfull in the past.

piet
 
Hi Piet,
sounds like a damn good excuse for me to go to Italy and search the autojumbles  :)

I'll try the King of Piston site as you suggest, but leave the thread open if its okay, just in case someone has found that a 2003 Suzuki RGVXSR638RR uses a suitable valve  (hahaha)
 
Length and diameter sound very like Benelli 250 single valves which are the shortest i've come across.
There seems to be a fairly good parts supply for those anyway, may not have go to italy....

Edit - just pulled one out of the odds and sods box. Too long, 75mm overall. Inlet 32mm dia. Big collet cutaways so not really possible to shorten them either. Still the shortest bike valves I know of personally.
 
Chris,

If you do go to Italy in your search, take a magnet... at least for the Turismo models, both valves are the same size and indistinguishable from one another, except the inlet is magnetic, exhaust isn't. :D  Can use an exhaust valve for an inlet, but the factory probably used the more heat resistant exhaust valve for a reason.

piet
 
Chris,
I have both a 75cc and 100cc here in the workshop waiting for a space on a bike lifter so they can be restored.
Dare say I'll come up against the same issue one day.

What stem diameter do you actually want ?
I just buy blanks and make my own valves, went and bought a pair of Ferrea 6mm waisted stemmed valves yesterday actually for our next run of triple race heads we have started to build.
Is straightforward making valves for a triple but bit harder for say a 750 twin where you need to harden the tips due to direct action.
Figure the small engines would be the same.?
Not looked inside yet.

Did you ask Cor Dees ?

Good luck
 
Red, be very wary of Ferrea blanks. I've used them for race Aermacchi motors but stopped because what you get often isn't as labelled. Most of the stainless valve manufaturers do 3 qualities of valve. We with air cooled motors need the top quality ones to stand the heat, After losing the heads off two inlets - not exhausts, you note....We had what we were buying tested and they weren't as labelled. I simply go elsewhere now.
The weight saving with 6mm stems was attractive....but the ultimate cost too high. 8500rpm is easy in the pushrod macchis with 7mm stems.
 
redax5 said:
Is straightforward making valves for a triple but bit harder for say a 750 twin where you need to harden the tips due to direct action.
Click to expand...

Red, I've used Rotax (KTM) tappet adjusters for 30 years and have solved the prob of 750 valve tips pitting from the direct action. They are the same thread and pitch (M7?) and have a ball & socket arrangement so lateral movement on actuation is minimal. Requires a small amount of metal to be removed from the SF2/3 rockers (more if it's the chunky early 750 rockers) and cutting down the Rotax adjuster. overall weight would be same or less than stock.

Not sure it would allow non hardened tips but worth a try.
 
GregT said:
Red, be very wary of Ferrea blanks. I've used them for race Aermacchi motors but stopped because what you get often isn't as labelled. Most of the stainless valve manufaturers do 3 qualities of valve. We with air cooled motors need the top quality ones to stand the heat, After losing the heads off two inlets - not exhausts, you note....We had what we were buying tested and they weren't as labelled. I simply go elsewhere now.
The weight saving with 6mm stems was attractive....but the ultimate cost too high. 8500rpm is easy in the pushrod macchis with 7mm stems.
Click to expand...

we may not be using Ferrea at all yet, we needed a pair of 6mm blanks so we can start welding ports and spending time on the flowbench
Ferrea were available here in Brisbane and are also what my cylinder head man uses when he builds Nitro and Pro-Stock Harley engines
both the valves we bought yesterday were their 6000 series but when the time comes we may go titanium anyway, or go with Kibblewhite valves
 
Here is a bit on Ti valves used on Husky dirtbikes.The early models pre 2004 had serious issues,solved by using Del West Ti valves in the post 04 engines. Zero issues after the change.And they get the shit revved out of them.
 
The first ('54) engine came with IDROK stainless (I think) valves fitted - there looked to be some galling on the stems from the cast iron guides and one guide had loosened (which I am told is not uncommon) which might be linked. Colisbro guides will be a fix for both issues. The inlet was 23mm so perhaps someone tried tuning it.

The second ('53) engine came with IVAM valves fitted which aren't stainless, although as you say Piet one valve isn't very magnetic. The valves look older and possibly more original. I haven't any originals to compare them with. I've emailed IVAM in Italy but I couldn't see Laverda 75's on their lists nowadays :LOL: so I doubt if they can help.

As I will need to get an 'unknown' machining genius (bribes of Laphroaig and shortcake being prepared as we speak) to make the valve guides from scratch, I could have any valve stem diameter (4,5 or 6mm) I suppose. Having looked down the inlet, all I can see is a bloody thick valve stem (6mm) and guide protruding into the inlet tract.

Whilst I'm not building the first engine as anything other than pretty standard, it seems sensible to try to help the poor little bugger if I can, so a 4 or 5mm stem would be an improvement without endangering reliability too much. I believe that people are still tuning them in the Breganze area, and 4mm stems are de rigueur. (apparently they can be taken out to 135cc!)

If I have to get a modern valve shortened, a number of options exist such as ZXR400 inlets and CBR600F3 exhausts - all 22mm. Red, you mentioned Kibblewhite - I understand they are very good quality and on the website they list 22 and 23mm CBR600 exhaust valves in stainless with 4mm stems. F*ck it, let's go for Titanium! Unfortunately they don't seem to import to the UK :(

I rang G&S Valves in the UK - very helpful and I will send them a valve just in case they can match it. They did say that wear will be a problem if you shorten a valve - the direct action on the tip. Stellite tips are added in the early stages of making a valve - they can't be added at the end due to machining issues. They advised using a valve lash cap (?) on the tip to prevent wear. Don't know if that would be ok or not.

When I solve the valve issue I'll move on to the rockers and then the pushrods.....

I'm beginning to think restoring a two stroke might be a lot easier!

Chris
 
Last edited:
Chris,

I was thinking of using a 500 valve before I stumbled over a couple NOS valves.  Not much room for caps on stock length valves, very little protrusion above the keeper.  You would need to lengthen the valve stem above the keeper, not much adjuster screw length to play with either.  Not much room in regard to springs, already very short.  Reckon flame hardening would have got me going for a while if I had continued with the 500 valves.  Actually used 500 valve guides as blanks for my engine, wasn't really looking for power, but I did clean up the ports a bit before I installed the guides.  Stock guides are peened into the head to keep them in place, I pressed/shrunk them in.  Stock seats are chamfered on the outside diameter and the alloy is peened over to keep them in place as well.  If you decide to replace the seats, you will find they almost touch, not much room for mistakes there.  I shrunk in the new seats, seems to be working OK, didn't fall out during the ultimate test, this years' Milano-Taranto :D.  Reckon there is a limit that the stem diameter can be reduced to due to the rocker action on the stem tip.  I took a different route.

I upped the compression a bit, the head I had overhauled had a rather wonky gasket surface, so that was seriously skimmed.  Guess the care I put into cutting the seat angles paid off a bit as well.  Bike ran terrific, was by far one of the quickest Laverda 100s in the event.  Managed to easily pass most others in the class going uphill while sitting bolt upright! :D  Lots of fun, the little bugger just kept on revving. 

Started work on the 1952 75 Turismo, much the same, all over again.

piet
 
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