Oddball engines and prototypes

[Grumph]

Yes oddball indeed, 4 overhead exhaust valves, reed crankcase inlet. It started life as a McCulloch mac 101 123cc two stroke engine.

Brings back memories - my first tuning success in karts was when a mate asked me to have a go at his mac 101....He was a pretty good pedaller too, which helped a lot.

[WilDun]

Yes oddball indeed, 4 overhead exhaust valves, reed crankcase inlet. It started life as a McCulloch mac 101 123cc two stroke engine.

http://www.vintagekartscollection.co...ulloch-miracle

My guess is that it's a uniflow two stroke. In which case the exhaust cams are set so only 2 valves open for each exhaust activity.

Here's a pic that TZ posted on ESE in 2011

Yes it was a uniflow two stroke with overhead poppet exhaust valves - obviously it wasn't competitive or we would have been more familiar with it.
I did mention it way back somewhere on this thread, but couldn't find all the info I had on it (in a kart engine book) at the time - I remember seeing drawings of the internals with dimensions, I'll have another try at finding it.

About the same time (early nineteen seventies I guess) when I was interested in this type of engine, I remember a guy having converted a Triumph Speed Twin (or was it a Bonneville) to a uniflow two stroke! - from memory he retained the pushrod operation too along with the half crankshaft speed of the camshaft and alternative opening of the exhaust valves (ie one open valve at the end of each power stroke) but I haven't checked all this, - it obviously would had modified cam shape etc.!
This was also probably the case with the IMI engine, with of course two valves opening (4 valve head) at the end of each power stroke - A camshaft rotating at crankshaft speed is liable to cause some valve bounce problems!

[WilDun]

BTW Grumph I just found some John Clarke pics - thought you might like to see......

[Grumph]

BTW Grumph I just found some John Clarke pics - thought you might like to see......

thankee Will - that'll edumacate the non Kiwis here.

[WilDun]

thankee Will - that'll edumacate the non Kiwis here.

Well, can't say I'm a Kiwi born and bred, but after 51 years I feel that I belong and they are my people. (They liked bikes too - well, a lot did)
JC had a good grasp of Kiwi culture and taught us all how to laugh at ourselves - (like Billy T and the Topp Twins did.) Then he went on to edumacate the Aussies (where he was equally successful).

[guyhockley]

I thought that was Flettner modelling the latest safety gear.

[WilDun]

I thought that was Flettner modelling the latest safety gear.

Not unlike my foundry safety gear either (except that I wear an old style welding helmet) and I'm saving up for a pair of leather gumboots to replace my rubber ones which can be quite smokey and smelly and have burnt through in places! ..... they all have the benefit of safety features like flying off quickly if you swing or shake your leg vigourously enough - they sometimes fly for bloody miles!

[guyhockley]

Yes it was a uniflow two stroke with overhead poppet exhaust valves - obviously it wasn't competitive or we would have been more familiar with it.
I did mention it way back somewhere on this thread, but couldn't find all the info I had on it (in a kart engine book) at the time - I remember seeing drawings of the internals with dimensions, I'll have another try at finding it.

About the same time (early nineteen seventies I guess) when I was interested in this type of engine, I remember a guy having converted a Triumph Speed Twin (or was it a Bonneville) to a uniflow two stroke! - from memory he retained the pushrod operation too along with the half crankshaft speed of the camshaft and alternative opening of the exhaust valves (ie one open valve at the end of each power stroke) but I haven't checked all this, - it obviously would had modified cam shape etc.!
This was also probably the case with the IMI engine, with of course two valves opening (4 valve head) at the end of each power stroke - A camshaft rotating at crankshaft speed is liable to cause some valve bounce problems!

There was this one that was quite well known and I'm sure I saw one done the other way back in the 70s at Blackbushe airfield/dragstrip. Blown through the valves and exhausts cut into the bottom of the cylinders.

[WilDun]

That could have been the one I was thinking of (exhausts up top), except that I'm not so sure that those big valves would have reacted favourably to crankshaft speed operation!

[husaberg]

Yes it was a uniflow two stroke with overhead poppet exhaust valves - obviously it wasn't competitive or we would have been more familiar with it.
I did mention it way back somewhere on this thread, but couldn't find all the info I had on it (in a kart engine book) at the time - I remember seeing drawings of the internals with dimensions, I'll have another try at finding it.

About the same time (early nineteen seventies I guess) when I was interested in this type of engine, I remember a guy having converted a Triumph Speed Twin (or was it a Bonneville) to a uniflow two stroke! - from memory he retained the pushrod operation too along with the half crankshaft speed of the camshaft and alternative opening of the exhaust valves (ie one open valve at the end of each power stroke) but I haven't checked all this, - it obviously would had modified cam shape etc.!
This was also probably the case with the IMI engine, with of course two valves opening (4 valve head) at the end of each power stroke - A camshaft rotating at crankshaft speed is liable to cause some valve bounce problems!

There was this one that was quite well known and I'm sure I saw one done the other way back in the 70s at Blackbushe airfield/dragstrip. Blown through the valves and exhausts cut into the bottom of the cylinders.

https://www.kiwibiker.co.nz/forums/s...post1130983660

[tjbw]

https://www.kiwibiker.co.nz/forums/s...post1130983660

Thanks for the link Husa. I heard that Rob Collett also built a sleeve valve two stroke engine, do you have any information about it?

[Grumph]

Thanks for the link Husa. I heard that Rob Collett also built a sleeve valve two stroke engine, do you have any information about it?

I certainly don't - and in the pics of the blown Triumph, he doesn't look a well man.

[husaberg]

Thanks for the link Husa. I heard that Rob Collett also built a sleeve valve two stroke engine, do you have any information about it?

I certainly don't - and in the pics of the blown Triumph, he doesn't look a well man.

That came from you Greg didn't it? that mag and the others are sitting in the drawer under the computer.

[guyhockley]

Presumably the same Rob Collet (good engineer's name!). He did 4 and 2 stroke sleeve valve engines.

[guyhockley]

Brian Woolley article. Think I've actually driven one of the Daimlers he mentions round a mate's field. They had 2, one was supposed to be unique as it was a pick up! Done by the factory for their own use, so the story went. Don't remember anything special about the engines, it was the pre-select gearbox that took most of my attention.