Emma the 'M' model.

[teazer]

Chapter 2.....

OK so I rambled for so long I forgot to add a more important difference in exhaust design between 2 and 4 strokes and that's Overlap. On a 4 stroke there is a short time during which both inlet and exhaust valves are open at the same time. The negative pressure wave is designed to arrive back at the exhaust valve in time to help extract exhaust gas and to pull a new charge into the combustion chamber. There isn't enough time for a stuffing wave to do any useful work.

On our old 2 smokes, the exhaust and transfers are both open for a long time (relatively speaking) so a lot more fresh mixture makes its way into the exhaust pipe. And we have the relatively long period after the transfers close to stuff as much of that fresh mixture back into the combustion chamber just before the exhaust port closes for the night.

On a 3 into one that stuffing wave is diluted by trying to fill all three headers and also works against the exhaust flow from at least one other cylinder. The good news is that pressure waves can travel through each other. the bad news is that the stuffing wave is also pushing up against outflowing gas from other cylinders.

A two stroke twin has less of a pulse timing issue because when all that wave motion is going on from one cylinder, the other cylinder is approaching TDC and firing. They are not as good as twin pipes but can still make decent power especially on a sled where low and midrange are not an issue.

[Alan H]

I appreciate the comments and always welcome debate, but there's a 3-1 going on it whatever it runs like. I've ordered some earplugs too!
The engine has gone to the 'cleaners' today for the next stage. I'll post pics when they're sorted!

[750ynot]

I appreciate the comments and always welcome debate, but there's a 3-1 going on it whatever it runs like. I've ordered some earplugs too!
The engine has gone to the 'cleaners' today for the next stage. I'll post pics when they're sorted!

[teazer]

I personally prefer the sound of a 3 into 1 and hate popcorn popping sounds that some pipes make at idle, but nothing beats the sound of an actual race 250 twin or 500 4.

As for what pipe you fit, that's 100% up to you and wouldn't try to convince you otherwise. The post about 4 strokes got me thinking and that's not always a good thing for anyone else.

[Alan H]

Had a message from 'Uncle' Baz yesterday asking if I was popping down to Dudley yesterday, and as it was monsooning down, I thought 'why not'.
Of course I hadn't actually done anything with Emma since parking the heap of bits at home, and after dragging the engine out I had a good look at it.
Oh dear.
It's probably the worst one I've had yet and has been stood for 37 years with the heads & barrels off and most of the casings underwater, it seems. The clutch pressure plate is in two pieces (pics to follow) and the clutch is one lump of scrap, so I decided to use the percussion method of unmantling and got the hammer(s) out.
The 6 6mm pressure plate studs came out fairly easily - well, 5 did - part of number 6 is still in there. And after quite a lot of bashing, the clutch plates were ready for the bin. The centre nut came off easily and the centre followed the 'plates. After a bit of prising, the clutch outer (now without the 'fingers' that locate the friction plates) came out and on examination, the borg warner starter clutch parts - including the needle roller bearings and inner part that spins the clutch - were removed as they are in good condition. Motor remnants and carbs etc put in the car and off darn sarfwards.
Absolutely horrid weather with 50mph limit on the M1 - except for idiot bmw, audi & big volvo drivers of course, so a steady but safe journey for me.
I don't think Baz was impressed, but it's not as if he's doing owt else, is it?
The saga continues.......

[Alan H]

Before

Clutch off

[Alan H]

Clutch pics! Now mostly binned.

The other bit of the pressure plate fell off some years ago.

[Alan H]

Clutch plates now in the bin after being gently prised off the clutch outer & inner.

So Baz will have his work cut out with the cleaning bit, but at least the crank going in is a refurbed one!

[750ynot]

Crickey! looks like it was left in the sea for 20 years.

[Alan H]

In a cellar for 37 years, which is much worse. It will be saved though.