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[Presto]

For example the exhaust valve on a Bullet 500 closes 60 degrees ATDC - that means when the piston is well down its induction stroke.

I'd long suspected 'someone' on this thread is giving a heap of false and inaccurate information. Sounding impressive but mostly meaningless and misleading.

Thanks BW for your patient and knowledgeable comments.

[Bullet Whisperer]

For example the exhaust valve on a Bullet 500 closes 60 degrees ATDC - that means when the piston is well down its induction stroke.

I'd long suspected 'someone' on this thread is giving a heap of false and inaccurate information. Sounding impressive but mostly meaningless and misleading.

Thanks BW for your patient and knowledgeable comments.

Thanks for that, Presto, I think some people just like to stir for the sake of it, there are plenty more nonsensical remarks and replies on a couple of my you tube videos from the same source, who seems to hate Hitchcocks for some reason. I can remove remarks and block those who leave unpleasant or irrelevant remarks there if I wish, but occasionally I like to let people show themselves for what they really are.
Anyway, back to some logical stuff which shouldn't hurt anyone ... In addition to the exhaust valve still being open at the start of the induction stroke - and the outgoing charge providing some suction for the incoming charge, the inlet valve having long started to open by then, of course, the exhaust valve in all 4 stroke engines I can think of will be quite well open before BDC on the firing stroke, in many cases an exhaust valve will be opening not far after midway down the firing stroke.
As for exhaust pipes and systems, there is some very good information 'out there' about those, but I have seen very little in this thread!
B.W.

[Rushour]

BW - I think you should let your race results speak for themselves here and ignore the negative comments, those in the know are quite well aware of your reputation when it comes to tuning Royal Enfields.

[Wheaters]

For example the exhaust valve on a Bullet 500 closes 60 degrees ATDC - that means when the piston is well down its induction stroke.

I'd long suspected 'someone' on this thread is giving a heap of false and inaccurate information. Sounding impressive but mostly meaningless and misleading.

Thanks BW for your patient and knowledgeable comments.

I’d come to a similar conclusion. I’ve seen a few recent examples of “a little knowledge being a dangerous thing”.

[Cranky]

Oh thats a shame --why cant we carry on. I was going to ask why you don't increase compression ratio or bore out to 88mm with a Honda piston with better rings like I did.

OK, Mr Troll, I had my suspicions and for your information, the exhaust valves will be open in most four stroke engines for anything up to nearly half of the down stroke, after firing. Get your facts right, or wind your neck in. Oh, and I will ride in whatever the weather is doing, if I have to. Look out for another fast 535 CGT coming soon, whether you like it or not.
B.W.

Are you insane. did you say what ever the weather is doing!!! I dont care what bike you ride or what weather,-- be it a 535 or not. Are you confusing me with your wife.

You also said that you have no idea what the length of the down pipe has to do with reversion,--really.

Im not here to teach you --you have obviously no idea what reversion is.

[trophyvase]

Reversion is exactly as Presto described.
In other words:

Reversion is simply the flow of exhaust gasses back into the combustion chamber when the downward movement of the piston creates a vacuum in the cylinder. This event occurs when the camshaft is on the overlap, i.e. the exhaust valve is still open as the intake stroke begins.

But as that is off the internet it's probably wrong!!!!
Except it isn't!!!!!

[Bullet Whisperer]

Oh thats a shame --why cant we carry on. I was going to ask why you don't increase compression ratio or bore out to 88mm with a Honda piston with better rings like I did.

OK, Mr Troll, I had my suspicions and for your information, the exhaust valves will be open in most four stroke engines for anything up to nearly half of the down stroke, after firing. Get your facts right, or wind your neck in. Oh, and I will ride in whatever the weather is doing, if I have to. Look out for another fast 535 CGT coming soon, whether you like it or not.
B.W.

Are you insane.

You also said that you have no idea what the length of the down pipe has to do with reversion,--really.

You are insane and a liar to boot - I never said anything about exhaust pipe lengths or reversion. Don't put words in my mouth, not that I think anyone here is swallowing your crap any more in any case.

[Cranky]

. Nor do I understand how the length of the exhaust pipe would alleviate this problem.

But anyway...

BW you are correct. I guess from the pack of dogs type attack I was confused with who said what.

It was Presto said that.

You have very little wriggle room to tell me I am a liar I did not say you should not ride in bad weather or what bike to ride. That is just ridiculous.

Reversion is shock. It has nothing to do with valve timing in its origin . However the shock returning back up the pipe which is on the outer edge of the pipe will travel right across the combustion chamber and out of the carburetor if the VALVE TIMING will allow. I don't know where you are looking at all but spend a bit longer than 30 seconds.

If the down pipe is long it will be later, if it is short it will be early. Exhaust gases need to travel at 300ft per second for scavenging but again that is not thermal or sonic shock(reversion). A good long system will bring it so late as not to be a problem the 500 UCE is very long, beginning to sound like something is going on???

Have you ever seen fuel in the mouth of the carb and wondered how that got there, well now you know.

You are correct on the overlap and exhaust open but not half way down the stroke. what you mean is the exhaust will open half way down the POWER stroke ,--not BE OPEN half way down the stroke.

I have things to do and I will not be taking this any further until there is a proper conversation at least by some one that knows what the subject is.

[Bullet Whisperer]

I have things to do and I will not be taking this any further until there is a proper conversation at least by some one that knows what the subject is.
[/quote]
Oh, I think I can just about live with that ...

[Presto]

Both inlet and exhaust valves are closed on the compression stroke and the power stroke. On a 500 Bullet (for instance) the exhaust valve does not begin to open until 75 degrees BTDC on the EXHAUST stroke [the upward stroke AFTER the power stroke]. The exhaust valve closes 60 degrees ATDC on the INDUCTION stroke.

The exhaust valve is still open as the piston descends on the induction stroke and this is when reversion occurs – as the partial vacuum in the cylinder draws gases through both induction and exhaust ports. This is an inevitable primary tendency – as ‘nature abhors a vacuum’ – to which any ‘shock’ wave, exhaust pipe length or design is secondary.

As the man said –
Reversion is simply the flow of exhaust gasses back into the combustion chamber when the downward movement of the piston creates a vacuum in the cylinder. This event occurs when the camshaft is on the overlap, i.e. the exhaust valve is still open as the intake stroke begins.

And so, M’lud, I rest my case.