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[Dennis C]

Hi Norm and Tim if you can see this

Tim if you mean me, no you have not wound me up at all so don't worry about that, the information you have given is absolutely sound and very easy for anyone to follow and should be kept by forum users for future referal.

As I stated in my first post on this thread I normally keep well clear, but it is hard to keep quiet when bad advice is being given.

[Thack]

As I stated in my first post on this thread I normally keep well clear, but it is hard to keep quiet when bad advice is being given.



I find it hard to keep quiet when people resort to ad hominem attacks instead of supporting their own assertions with argument and evidence.



I think my advice was spot on:



1/ If you want to fit a BB system, find out from them whether it's for wasted-spark or twin-spark systems (1st post).



2/ Be aware that incorrect carburation can cause exactly the same symptoms (3rd post).



How is your advice looking, Dennis?

[Dennis C]

My advice, when in a hole stop digging,

You said "tap one of the plugs closed", good advice?. Poor guy does this and rides off into the SA sunset, What happens first?, bearing in mind the bike is now running retarded. the coil is overloaded and the guy is checking for a high speed misfire.

1/ the piston siezes. 2/ the exhast valve burns out. 3/ the overloaded coil fails.
br>This is my final reply to you Thack. Please have the good sense to drop it.

[Thack]

Yet another bloomer from an electronics "expert". The coil is not overloaded, it is underloaded.



And yes, I stand by that advice. We aren't talking about driving miles: just enough to see if the high speed misfire has gone. That won't cause any problems: there will be no burnt exhaust valves or seized pistons on that kind of test. I'd be happy to do that on my bike.



However, we will never know because the test won't be performed. Thus, from a debating stand point, it's a dead end.



Sadly, the ending doesn't look so good for you:



1/ You made a number of distinctly questionable statements which showed a lack of technical understanding.



2/ When challenged, you declined to either support or retract them, but instead resorted to a sulky, childish attack on me, including saying I was a liar.



Honestly, Dennis, you really can do much better than that.

[Thack]

THIS A BICKER-FREE POST



Actually, now that the bickering has ended, just one last thought for ChrisD:

"...it shows reversion at 1/3 throttle or more (charge spewing backwards from the carb throat..."



The more I think about this, the more I worry. I've never seen this except on really high-tuned engines with masses of valve overlap. Even then it's only near tickover. I've also seen it once on a Royal Enfield Crusader where the exhaust valve clearance was enormous, such that there was loads of pressurised exhaust gas still in the cylinder when the inlet valve opened, blowing the incoming charge out backwards.



ChrisD: to be honest something sounds seriously amiss with your valve timing or something, and I'd try to resolve that first before messing about with anything else. Indeed, sorting that out may well cure all the other mysterious misfires Dennis and I have been arguing about. I don't think it should be doing that - especially at medium to higher speeds.



By the way, is the exhaust system definitely clear? Not too much back-pressure from some kind of blockage?

[Tim NZ]

Chris: Even at worst the cam timing will not be any further astray from ideal than 9 degrees. So in all probability your reversion issue could easily be resolved by increasing the velocity of the exhaust gasses, by the simple step of fitting the 1 1/2" dia 350 header pipe.
I fit the same pipe to all my tuned 500's with noticeable improvement in mid range performance.
But first attempt to cure the 'misfire' issue, as your 'reversion' will also be effected by incomplete combustion.

Thack: I was mistaken, you are misinformed.
For someone who is unable to work out how a HT lead is attached to a coil, is not a good credential for someone debating HT electrical matters.

[Thack]

Hi Tim! At last we speak directly! Thank you for such an honest assessment.



This is a genuine and serious offer: provided we both agree to keep it civil, I am very keen to hear about the areas where I am misinformed. I genuinely do want to learn new stuff and "unlearn" any misconceptions I have.



I am totally committed to using the forum as a learning environment.

Very best wishes,
Thack

[Thack]

Oh, Tim, you are right to chastise me about the HT lead. One my UCE it is stuffed right up behind the steering head and very effectively shielded by the tank. I could just about get my fingers on it, and just about see it with a torch.



If I weren't so damn lazy I'd have whipped the tank off and looked at it properly and avoided the embarrassment of having to ask!