Not sure which part of the forum to put this, but I need to cut and shut some motorbike cams

[minimutly]

Bit of a "want to have a go" project. I want to convert one of my Yam xj 8valve 4 cylinder engines to big bang - sort of farty twin.
The cams need a cut, rotate and reweld. They emit orange sparks when you grind them so expect they are cast iron of one sort of another. Allen Millyard shows how he did some Kawasaki ones, inserted a sleeve (gudgeon pin) and tigged them together. I don't know what filler he used though?
Now, as usual there will be the Harry Enfield cry of "you don't want to do that", but the only real option is to machine some new cams from billet, and right now that's a project too far. If Millyard can do it??

 

[cheb]

There was someone else on here doing that recently IIRC

 

[doubleboost]

If they e
were drilled and pinned they would TIG braze together .

 

[Robotstar5]

Calling @Cato

 

[minimutly]

If they e
were drilled and pinned they would TIG braze together .

Millyard tig welded them...

 

[Morrisman]

Apparently there’s a similar thing done to BMWs like mine, flat twin, set up to fire both cylinders at the same time, by changing cam timing. I’m not sure quite why, or what it would be like to ride….

 

[minimutly]

Apparently there’s a similar thing done to BMWs like mine, flat twin, set up to fire both cylinders at the same time, by changing cam timing. I’m not sure quite why, or what it would be like to ride….

A perfectly balanced single surely?

 

[minimutly]

I just fancy a 4 cylinder that gives the sound of a parallel twin - kind of unique?

 

[dobbslc]

Take one of the coils out...

 

[oldbikedavey]

Bit of a "want to have a go" project. I want to convert one of my Yam xj 8valve 4 cylinder engines to big bang - sort of farty twin.
The cams need a cut, rotate and reweld. They emit orange sparks when you grind them so expect they are cast iron of one sort of another. Allen Millyard shows how he did some Kawasaki ones, inserted a sleeve (gudgeon pin) and tigged them together. I don't know what filler he used though?
Now, as usual there will be the Harry Enfield cry of "you don't want to do that", but the only real option is to machine some new cams from billet, and right now that's a project too far. If Millyard can do it??

PM sent....

 

[Cato]

Pretty much as described already really. Cut the cams, rotate to suit, bore, slug, weld.

My personal approach was to get the spark erosion chap to cut them as it's a much thinner cut. Where I would diverge from Mr Milyard's approach is using gudgeon pins as my personal opinion is that it would be better to use something with a slightly rougher finish than ground and polished pins. So EN16 turned to interference fit but without a finish cut.

The other variation I made was to drill the cam pieces to be a slip fit over a 6mm rod. Put the cam pieces on to make a camshaft kebab, and then rotated the sections to their correct positions. They can then be marked for accurate alignment before welding.

I'm going for a long bang conversion rather than big bang BTW.

 

[addjunkie]

I likes the kebab version!

 

[minimutly]

Pretty much as described already really. Cut the cams, rotate to suit, bore, slug, weld.

My personal approach was to get the spark erosion chap to cut them as it's a much thinner cut. Where I would diverge from Mr Milyard's approach is using gudgeon pins as my personal opinion is that it would be better to use something with a slightly rougher finish than ground and polished pins. So EN16 turned to interference fit but without a finish cut.

The other variation I made was to drill the cam pieces to be a slip fit over a 6mm rod. Put the cam pieces on to make a camshaft kebab, and then rotated the sections to their correct positions. They can then be marked for accurate alignment before welding.

I'm going for a long bang conversion rather than big bang BTW.

View attachment 471203View attachment 471204View attachment 471205

The Yam cams are drilled already, and I only need one cut. Have enough cams to sacrifice a couple, so method of cutting not important. Method of welding is though - what process and which rod/filler?

 

[Matchless]

When Ivan Dutton (shed racing or Ivans shed) on youtube modified an Austin A35 crank and camshaft to fit the two cylinder A series block he spigotted the bits and silver soldered them.

 

[atomant48]

Wow. Craftsmanship like described here leaves me in awe.

 

[Seadog]

What an amazing chap. That's just cost me a couple of hours
I take it he's local, Pat?

 

[Morrisman]

A perfectly balanced single surely?

They call it the ‘twingle’ mod. It can be done very easily, just change cam timing, connected by chain, so no cutting required. It already has wasted spark, every revolution. Could be an interesting project but I’d think the double whammee of both cylinders firing simultaneously might not be too kind on the drive train.

 

[Cato]

The Yam cams are drilled already, and I only need one cut. Have enough cams to sacrifice a couple, so method of cutting not important. Method of welding is though - what process and which rod/filler?

Once everything's marked up, slugs made and they're pressed back together I'd be taking them to a grown up for that bit but it's worth noting that welding may not be needed as a suitably tight interference fit with pins may work just as well.

This pair are a proof of concept/prototype and once the engine has been run up and everything checked I can get a pair of cams ground from blanks with whatever tweaks (if any) were needed to profile and duration.

 

[minimutly]

Once everything's marked up, slugs made and they're pressed back together I'd be taking them to a grown up for that bit but it's worth noting that welding may not be needed as a suitably tight interference fit with pins may work just as well.

This pair are a proof of concept/prototype and once the engine has been run up and everything checked I can get a pair of cams ground from blanks with whatever tweaks (if any) were needed to profile and duration.

Erm, what's a long bang exactly?

 

[Cato]

Erm, what's a long bang exactly?

Staggered firing. The crank is a cross plane so instead of having two up and two down (180 pairs) you have the journals arranged at 0 - 90 - 180 - 270. If the firing order is set to 1 - 3 - 2 - 4 the firing pattern looks like this
X--X-XX-X--X-XX-X--X-XX-X--X-XX-X--X-XX- or in a descriptive way it goes bang pause, bang pause, bang bang pause and so on.

The end result is that it has an engine sound like no other, similar to a V8 but not quite. If you have a Google for the sound of an M1 Yamaha it's that.