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 snow's engine

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Number of posts : 13
Age : 68
Localisation : bristol
Registration date : 2015-08-28

PostSubject: snow's engine   Tue Sep 01, 2015 5:12 am

Having read all 24 pages of the forum can someone please point me in the direction of the mythical "snow's engine build" article that's if it is for all to see and not top secret?
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Trevor Amos

Number of posts : 876
Registration date : 2010-08-13

PostSubject: Re: snow's engine   Tue Sep 01, 2015 6:15 am

No myths or secrets,Try page3?
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john bass


Number of posts : 1742
Age : 89
Localisation : Bensberg, Germany
Registration date : 2006-12-06

PostSubject: I wonder how many ....   Tue Sep 01, 2015 10:41 pm

I wonder how many of our members have missed the information that lies in the row of blue boxes to the left

Maybe because of their Box titles?

The other thing is that keying the box brings more boxes with titles that pop up to the right -- and one has to key those boxes to get more boxes ---

--- its those boxes further on that have some really good bits of information and probably by then the keyer-in has tired of it all,...

Back to the blue strip of boxes:- The third box along is Titled "BIKES" and it ought to have a better title because Alan Brown´s articles are there and And Moulden has included "Useful Tools" DIY... and since Alan  included a lot of photographs in his Articles it is well worth 40 minutes -- with your feet up and a pint or two of IPA or Cider -- of going through.
Tony Davis´s 175 building work -- is also there.

Next door is the box titled RACING -- which has GETTING STARTED  which then opens up a whole host of boxes which are worth reading than banging your knuckles in the shed. Mike Powell on gearboxes, Brian White on his barrels with good pics of ports, Peter Tibbitts with his technical ramblings, A.Mouldon  and  sevearl others (sorry) names not remembered.....

Short of time and the partner playing up about mowing the lawn ... etc ... etc... etc ...

Here´s how it´s done. Remind of the terrible state those country´s are in where Relief Aid is not enough.

Get the missus/lady-friend interseted in far away places and off  to Africa  -- or some such desolate place -- with a Do-Gooding Relief-Aid group -- even a group of Nuns -- and settle down to a good read. Could take to Xmas when you might want her back....

But rememeber most of it is out of date yet still a good read.

You might even get round to reading about the Wobbleyman -- that´s in the second box along -- my great Bantam  Intermediate rival and good friend -- who died far too young and  who even blew his ashes over Slick (my son) on their favourite golf course in the Island when rteading his eulogy...


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john bass


Number of posts : 1742
Age : 89
Localisation : Bensberg, Germany
Registration date : 2006-12-06

PostSubject: Back to your box of Dead Pistons   Wed Sep 02, 2015 6:46 pm

Hello Mikerwt!

So! back to your DEAD pistons. Are they standard BSA? If so Trevor will advise on what is best to use. One sticks a pin in Trevor and out oozes wonderfully informative advice on racing Bantams......

But why your "Dead Pistons" was ignored, on here,  beats me...
 All Bantam racers have suffered this dreadful disease albeit Icarus-1 less so because Derek Neil -- my blessed engine tuner -- had me doing a RUN-IN procedure at Brands Hatch (Practic Days)  with EVERY new piston he purchased,  such that in races I had reliability.  

Why no one on here has picked up on your "Dead Pistons" comment surprises me -- I guess they are all very busy with preparation  for Cadwell -- end of this  month. You ought to be there...!! ...??

So! Back to your box of DEAD pistons....? Questions you must answer-- or forever hold your piece...

(1) Have you measured the compression-ratio of your engine yet?

(2) Do you know what the first owner was using as fuel:   pump petrol or high octane fuel? Bantam race formula allows the use of Avgas (Aviation Gasoline) with a guaranteed over 101 octane .

(3) Do you know what a Plug-Chop-Test is?

(4) Do you have any information on how much the ignition was advanced - retarded against engine speed and load?

(5)  This is not a question -- PISTON SEIZURE IS FREQUENTLY BECAUSE THE FUEL-AIR MIXTURE IS TOO WEAK (Too LEAN) -- which is the case in Q2 where perhaps a 95octane petrol was replaced by a higher octane fuel -- say 105 octane without increasing the main jet size or the ignition timing was not changed to suit the new fuel
detonation and destruction are inevitable ..

Octane Rating is defined as KNOCKING RESISTANCE of a Fuel but there can be Inaudible Detonation (precombustion)
which happens extremely quickly and had most 60s´ to 80s´ 2-strk racers developing a nervous twitch of the left hand and wrist. I used to have two fingers on the clutch lever not only for piston seizure possibility but because I slipped the clutch a great amount when racing frenetically hard.

There were two Standard ways of determining the Octane Rating:  In 1993 One was called the Research (RON or ROZ) method and the other Motor (Mon or Moz) method. The former is used commercially but care should be taken to ensure  there is no confusion. That is because Premium petrol at 95RON is 85MON.and Super Plus (here in Germnany) is )98RON and 88MON....  

Because the Thermal Efficiency of an IC engine increases with Compressio Ratio increase,  many Tyro Tuners
bump up the compression ratio to be incompatable with the  octane rating of the fuel they are using and disaster follows in terms of overheating which brings on piston seizure  and  piston-crown destruction.

In the dark-days -- which I must not rrefer to,  too often, on here -- before the banning of lead***
in Filling Station petrol the Compression Ratio of normal road going cars was frequently up above  10:1 and after the ban - even when using petrol station´s  SUPER-PLUS ROZ (octane rating) of 98 the compression-ratios      were  brought down to around 8.5:1 for reliability.

The high octane  -- aircraft petrol -- was hard to come by in the 60´s to 70´s  and lcarus-1 was run on Premium petrol with a consequently lower compression-ratio than what we´d like, that was around 8.5.
Comparing that with my previous Grass Track Speedway JAP 500 engine with 16.5:1 comp-ratio using 2% TEL doped methanol and looking at the famous Australian (where doped ethyl alcohol fuels weres permitted)  Walsh Bantam with 16:1 C.R.  one can see that tuning to Petrol or Avgas are two different situations with the doped Ethyl Alcohol/Methanaol fueld being a third situation which never ocurrs in Bantam Rcaing.    .

I´ll close by mentioning the devastating expereince I had with Andy´s 250 ABS. It had a Gardner carburrettor and to my mind was running too rich. Andy organised the Gardner Rep to be at Brands on a practice day and together we did several Plug-Chops to eastablish the needle to use. The Plug-Chop is to get the bike under full-load max speed on a straight and whilst declutching the engine  switch off the ignition. A study of colour, sooty carbon and white scale tells whether the mix is rich or weak. Having installed a longer needle I went to Snetterton (my jinx course) on teh Sunday and in practice the ASBS was passing all the Japanese things out of the cornesr and  on the straights. Then about 3/4s along the old Norwich Straight it went ding! and the back wheel locked -- compulsively the fingers of my left hand contracted at graet speed.
   Now, why should the ABS seize and put a hole in the piston at Snetterton when at Brands I flogged it unmercifully  4 days  earlier when weather conditions were no different and the altitude of Snetterton above Brands  is not enough to effect the situation?  I can only think the periods (on Norwich Straight) of longer time on wide-open-throttle were the reason. The fact that the ABS was really quick was because it was right on the limit of a Lean mixture          
I hope this rabbit-rabbit has some use for you -- even if the Moderns on here say it is Out-of-Date it might have made a good read...!

*** TEL -- Tetra Ethyl Lead --

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