Alpino camshafts, ignition timing and other mods

[corsaro]

Findings during alpino rebuilds.
Having rebuilt the 350 laverda alpino and the 500, the 350 started up straight away - although when strobing I did find that the ignition was retarded and had difficulty aligning any of the marks. I had to advance the pickups to their most advanced position, however the bike ran and does run quite well and ticks over with very low rpm indicating the retardation. on the 500 it was very reluctant to start , in fact I only got a couple of fires/backfires . So I changed the position of the machining using the info given by Ross many years ago - this resulted in the bike firing straight up and settling to a nice tickover
So I may carry out the improvement on the 350 as the machining on the rotor appears to be exactly the same.
The difference in the position is substantial at 30 degrees. My feeling is that the machinist/draughtsman has had a miscommunication in laverdas works and milled the timing position the wrong way from the trigger position - clockwise when it should have been anticlockwise........ an easy misreading of the drawing, having been an Engineering draughtsman many years ago I can understand how this can happen.

On the 500 when rebuilding I could not find an exhaust camshaft to replace my damaged one, but when measuring the inlet camshaft - which has the same casting number 14 the camshaft appears identical - so when reversed can become an exhaust camshaft - one just needs to block the tapping for the speedo drive which is now on the right.
This may be common knowledge, but could not find any references on the forum. The advantage is that inlet camshafts appear to be available from Thorne engineers and others whereas the exhaust camshafts are unavailable due to the propensity the Alpinos have for eating them........ especially on the offside.
While the engine was apart I also enlarged the oilway slightly to the offside exhaust camshaft as it is the last position in the flow of oil from the pump.
the other difference between the 350 and 500 is the throttle resistance - the 350 is light whereas the 500 - due to the pumper levers is quite stiff, as most classic bikes are treated somewhat more gently than when they were new the pumpers are maybe redundant for normal riding, I removed the operation from my 750 SF when I owned it and did not notice any difference in performance - apart from the heavy throttle suddenly becoming much lighter

The 500 is for sale if anyone has a hankering for one

Stu

 

[sfcpiet]

"14" is the designation for the stock 500 cam, not a casting mark. Other 500 cams are S/1 or S/2 for the Formula models.

piet

 

[Paul Marx]

500s don't have a propensity for eating exhaust cams. They'll happily eat both cams for breakfast.
Paul

 

[italmot25]

The camshafts in/ex oft he Laverda 500 are identical. The only difference between intake and exhaust is that the intake shaft has the M6 thread for the rev-counter drive.

As the cam profile is symmetric with respect to opening and closing the shafte worke in both rotating directions. So it makes no sense to produce a seperate exhaust cam shaft.

I think the eating up of cams is the result of a high sensitivity of the oil circuit to the fill level. If you run the engine at minimum oil level above 2800 rpm there is more air than oil in the circuit. (measured at 21°C with oil 10W40)

 

[Paul Marx]

The big problem with the cams is the bearings.
Then the heads being warped.

21°C. Is that the oil temperature?

Paul

 

[sfcpiet]

Wifeys' 500 has run flawlessly since I overhauled the engine in 1991. New guides and seats with Formula/Atlas valves over skimmed Formula pistons to make it more streetable. A Formula/Atlas pump was also installed. Cams run in alloy bushes without issues.

Running on 20W50 keeps it healthy.

piet

 

[italmot25]

Yes, I did the measurement at room temperature with an empty engine with the outer rings oft the inner main bearings mounted to have the correct oil flow to the crank shaft. I drove the oil pump with a drilling machine and measured the driving speed with a laser counter. I assume that if the oil is hot he critical rpm would even be lower.

I did all that because I wanted to mount a larger oil pump and install a better cooling oft he head and to have nozzles for aktive piston cooling.

 

[Paul Marx]

Yes, I did the measurement at room temperature with an empty engine with the outer rings oft the inner main bearings mounted to have the correct oil flow to the crank shaft. I drove the oil pump with a drilling machine and measured the driving speed with a laser counter. I assume that if the oil is hot he critical rpm would even be lower.

I did all that because I wanted to mount a larger oil pump and install a better cooling oft he head and to have nozzles for aktive piston cooling.

What motivated that weld in the crankcase?
Paul

 

[italmot25]

The drilling for the stud on the front right side is put to deep on all three 500 engines iI have had open up to now.
They tend to get cracks there after some life time. I think it also depends on how hard they have been reved.

 

[sfcpiet]

What motivated that weld in the crankcase?
Paul

They all do that, Sir!

It's where most hard-pushed 500s crack up. They were never intended to push out 60+ hp for any length of time.

piet

 

[Paul Marx]

They all do that, Sir!

It's where most hard-pushed 500s crack up. They were never intended to push out 60+ hp for any length of time.

piet

I have seen a couple, in fact.
They also split down the front, right hand side as well.
Paul

 

[sfcpiet]

Yes, I did the measurement at room temperature with an empty engine with the outer rings oft the inner main bearings mounted to have the correct oil flow to the crank shaft. I drove the oil pump with a drilling machine and measured the driving speed with a laser counter. I assume that if the oil is hot he critical rpm would even be lower.

I did all that because I wanted to mount a larger oil pump and install a better cooling oft he head and to have nozzles for aktive piston cooling.

I see you've also adopted the "oil cooling" for the exhaust valves as on the 668. Do you have any figures for real world temperature decrease with these mods?

The crank is the least dependant on a steady oil flow. Mains and big ends survive OK with a couple of drops every second lamp post...

piet

 

[italmot25]

No, I don t have any data about temperature decrease. And in fact for my style of driving motorcycles no modifications would be necessary....
Modifying engines is just fun to me - I am doing it allmost every day.......

 

[Otto]

Not my work. I bought a spare race engine of a German (Horst Scherer, Piet knows him?).
He build a special engine with Honda pistons and outside oil lines to the camshaft’s.
The right side was welded were ever it could. See next post.
It never had run and I had to make it ready.

The bronze bushing works well.

 

[Otto]

The same engine was welded everywhere at the front and right side.
Look at the ring with bolds mounted.

The first time I rode with this engine it ripped at the backside

 

[Robin Webster]

It’s been 10 years since I raced my 500 but I ran the larger capacity oil pump from the bigger engines which worked out well.
When my engine was first tuned the plain bearings were bored out and needle rollers inserted. Second race they collapsed and the head went off to someone else, a known tuner who had no preconceptions. The motor ran hard with 62bhp up until I sold it.

 

[Paul Marx]

The drilling for the stud on the front right side is put to deep on all three 500 engines iI have had open up to now.
They tend to get cracks there after some life time. I think it also depends on how hard they have been reved.

Many years ago, I chatted with Tim Parker and mention of the Ogier Daytona winning bike was made. It ended up with with two oil radiators because it was pulling the studs and that was put down to heat.
Maurice Ogier had some re-enforced cases made that were never used. I tried to buy his two bikes and the bits and bobs from him but he wanted more money than I was willing to offer for clapped out barn condition race bikes.

My TT2 which is an ex semi official machine built by Toni Cavazzin with Gianni Sperotto and Toni Rossato had preventive work on the cases.

Paul

 

[Vince]

A mod done on XT500 Yamahas to reduce heat involved running an extra oil line to the cam in a similar way.

 

[piranha-bro2]

Racing 500s sound a bit like hand grenades.

 

[Paul Marx]

Racing 500s sound a bit like hand grenades.

Keith Nairn describes 500s as time bombs if I remember correctly.
Paul