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Petroil Mixes
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b175er
saltfleetby
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January 10, 2016 - 2:58 pm
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surely when our bikes were made - especially the early models - most people ran them on any kind of oil they could get. those bikes are still being used. I use low/moderately priced oil at 30 to one and it seems to work alright; though my longest single ride was only 120 miles. are we all wearing anoraks ? after all,  they're only bantams !

two B175s and a CB360

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mike p5xbx
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January 10, 2016 - 3:07 pm
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almost all of the seizures that people have posted on this forum have been using 32-1 and most all were using a mineral 2T oil

Stihl perhaps the largest manufacture of 2 stroke engines today recommend using 50-1 of their 2T oil
but 25-1 if using another make of oil, which really defies the theory that using more oil makes the engine run dangerously weak
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D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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HowD1
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January 10, 2016 - 7:22 pm
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I run two Bantams regularly on trips of various lengths.

The D1 is run on 25:1 semi-synthetic, from local trips into town to going up to Scotland, France etc 200 or so miles a day many times.

The B175 is run on 33:1 semi, and it does long trips trialling - long road sections with short, steep and greasy offroad bits at regular intervals. I did one yesterday, 250 miles in 20 hours with 13 sections and 2 timed speed tests.....

Basically the right amount of oil should just show as a light smoke. If you use a bike for short, low rev, low speed, trips then the oil will build up in the exhaust and create clouds when it reaches temperature - these engines need to be revved and made to work. If nothing else, the more revs will mean more oil. But they must be timed and mixture (fuel/air) correct. 

Look, if you want to run your engine at 16:1 or 50:1 it's up to you. But leaving a cloud of blue smoke in the middle of your local town or countryside won't endear you to the non-motorcyclists - and let's be fair there's a heap of people out there who want us off their roads; let's not give them an excuse to bash us yet again.

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Mags 1
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January 10, 2016 - 10:11 pm
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Well said Rick, some common sense quoted there.

Four now on the road and at least several in bits.

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Cornish Rooster
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January 11, 2016 - 12:45 pm
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As always read the various opinions and make your own mind up !

Just for the record my 150cc D1 in my ownership has covered around 8,500 miles now and managed to get around the most part of a 1500 mile "Around Britain Run" with one and a half piston rings (escapee piston circlip). I run a mix of 32/35 to 1 on fully synthetic, I'm not fussy on the exact mix, oddly or not when two-strokes seize (or general engine failure) one of the last reasons is what mix you are running, the usual culprits are overheating due to incorrect carb mixture, wrong spark plug grade, timing issues and what I think is a very common one too little piston clearance after a rebore.

Any good quality two-stroke oil is fine, mineral, semi-synth or fully synth, I only use fully as it's a nit more insurance to my mind, well put it this way it's quite amazing how my engine was still running reasonably ok for over a thousand miles with one and a half piston rings and didn't seize !!!

So make your own mind up.

Still ran reasonably ok with this:

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BSA Bantam D1 "150" in use regularly often as general purpose transport, quite a few other bikes as well. Cornwall Area Rep. 

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b175er
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January 11, 2016 - 3:37 pm
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thanks for some common sensical posts from the south west !!

two B175s and a CB360

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mike p5xbx
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January 11, 2016 - 4:14 pm
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Cornish Rooster said
oddly or not when two-strokes seize (or general engine failure) one of the last reasons is what mix you are running, the usual culprits are overheating due to incorrect carb mixture, wrong spark plug grade, timing issues and what I think is a very common one too little piston clearance after a rebore.

yes there are many reasons why a piston will seize but ultimately Piston seizures will Only occur when metal-to-metal contact occurs between piston and cylinder due to the breakdown of the oil film that should prevent this
the quality and quantity of oil used should be matched to the engine and it's type of use.
for instance the Yamaha RD Auotlube bikes use 120-1 ratio at idle up to 20 -1 ratio at full throttle
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As always read the various opinions and make your own mind up !

D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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Neil_EngUK
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June 25, 2016 - 10:13 am
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After running in, now gone down to 20:1. (50 ml of oil per litre of prime quality fuel).

(As recommended by BSA Bantam; BSA Bantam Racing Manual, BSA Bantam Workshop Manual & BSA Service Sheet 502)

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Mags 1
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June 25, 2016 - 11:43 am
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At the end of the day it's for each owner to make their own mind up, there's enough info out there and here to help anyone who's undecided.

Another common cause of piston seizure not yet mentioned, on this post I believe, is due to excessive piston/piston ring/bore wear.

Extremely hot gases bypassing the rings and bore destroy the vital oil film and maybe expand the piston too, not sure, all I do know is that engine will seize regularly until things are corrected.

I lost count of the times my worn bore and rings 'mini' seized, a couple of years ago on my red D7, I came to actually expect it on every long journey.

Four now on the road and at least several in bits.

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HowD1
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June 26, 2016 - 7:06 pm
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talking of causes of seizure....I couldn't fathom why my D3-barrelled D1 kept on seizing after careful running-in. It would run fine then nip-up after a hill or similar then after a few seconds coasting it would run fine again. There was never much in the way of marks on the piston......In the end I discovered one of the compression plates had come adrift and was jamming slightly - enough to seize the engine. After I fixed the plate back in position it never seized again.

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Neil_EngUK
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February 11, 2020 - 10:43 pm
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Just moved on to using a 25:1 mix.

40ml oil per litre of premium fuel.

 

(I might consider washing the Banty this year, but its only Feb - so perhaps a little early for rash decisions.)

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NeilB
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February 12, 2020 - 8:31 am
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The stamped caps (2 measures per gallon, 3 for running in) equate to 32:1 mix (22:1 for running in). Don't forget, too much oil means too little petrol (lean and overheat), but also air and fuel mixture needs to be right.

BSA knew what they were doing with the oils they had, but modern synthetic oils change the game. If you're worried about the longevity, just buy the recommended castrol xxl and use that, it's what goes in your gearbox anyway and it's cheap. 

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AdrianS
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February 14, 2020 - 4:03 pm
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Another complication to the oil/petrol mix is how often the bike is used.

I find if the bike is standing for a considerable time ( a few weeks/months ) then the oil does separate from the petrol somewhat.

I often find starting very difficult because the bottom of the carb is oil rich and the engine doesn't like starting on oil rich fuel.

Eventually when the bike starts and runs, there is a lot of smoke for perhaps 5 miles or so until the oil remixes with the petrol and the carb and fuel lines have been washed through. A good enough reason for giving the bike a good shake to mix the fuel/oil if been standing a while.

I find even the modern high quality oils still separate a little when the bike has been standing.

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bantammad
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February 14, 2020 - 7:39 pm
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Hi bantammad ere sorry it’s like this bantams been around seventy plus years oil mix for me is 150m to 5ltr petrol that’s what I’ve used for my vintage motorcycles also oil type semi synthetic ask the trials lads forget what used to be with none pre mix that in the past regards Les

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Neil_EngUK
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February 15, 2020 - 5:17 am
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I think people are forgetting that when the bantam was introduced, the petrol recommended in many of the official sources (i quoted in my spreadsheet at the beginning of this thread) was pool petrol.

This would have had considerable effect on the machines, and inhibit any modern comparisons.

Unbranded, low octane unleaded rationed war time pool petol continued until about 1953.

Regular pool petrol was as low as 75 octane, whereas commercial grade was available (with a higher ration allowance). This was leaded and about 80 octane but dyed red in an attempt to prevent fraudulent use. The use of red pool petrol a serious offence in domestic vehicles, much like using red agricultural diesel in domestic cars these days.

Anyone know where i can buy authentic pool petrol, to recreate the original spec and performance of the BSA Bantam?

I know some wags will say "Tesco" 🙂

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NeilB
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February 15, 2020 - 9:24 am
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Petrol grade doesn't matter, you could run a bantam on 105 octane, the low octanes are just more prone to pinking so ignition timing has to be earlier than you can achieve with modern fuels.

The big problem of modern fuel is the ethanol content, and supermarket fuels are the worst for it (which is why they're cheaper), especially Tesco and Morrisons who have both received reprimands for not keeping within allowed limits.

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bantammad
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February 15, 2020 - 10:57 am
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Hi bantammad ere just had a flashback dad had a 250cc Rudge l remember him useing half paraffin half petrol well I think that’s what it was it would bang and splutter it weren’t happy if it meant going to work well when times were hard happy days Les 

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sunny
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February 15, 2020 - 2:54 pm
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any   engine  fited  with    a  brass  small  end  bush   rufly    road use   D1 ,3,5 &7      is  about    2  caps     is   16 to 1   ,, 3  caps  is  about  12 to 1 for  runin        for    engines  fited  with     small   end    needle   roler     bearings      the  oil raisho    is  about    16  to 1   for  runin    going  to  rufly  

  about   36  to  1      after    runin                 this  difers   with   m/cycle  mackes        lots     start    12  to  1    &   finish   up     at   42  to  1        new   oils    my  difer         you  are  serpos  to  let  any   engine     tickover   as long  as  posable   befor   pullaway       this  dosnot aply  to    any  kind of  race   engine   as   it will  have   a  diferant    oil   system  

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Neil_EngUK
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February 16, 2020 - 10:20 pm
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NeilB said
Petrol grade doesn't matter, you could run a bantam on 105 octane, the low octanes are just more prone to pinking so ignition timing has to be earlier than you can achieve with modern fuels.

The big problem of modern fuel is the ethanol content, and supermarket fuels are the worst for it (which is why they're cheaper), especially Tesco and Morrisons who have both received reprimands for not keeping within allowed limits.  

Surely pre ignition, causing  pinking and risking piston damage, definately effects performance? Just as much as deliberately retarding the engine. The original BSA sources were just as precise for timing, as they were for petoil mixes.

Or have we all wasted decades of our lives with dial guages, TDC tools, degree disks and a miriade of marked screwdrivers & feeler guages for nothing? Petrol grade has a huge effect upon performance.

Anyone know where i can buy authentic pool petrol, to recreate the original spec and performance of the BSA Bantam?

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NeilB
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February 17, 2020 - 9:26 am
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That was actually my point, higher octane fuel (also with fewer floaty bits) means less chance of pre-ignition, it's also why 90's Jap cars like the Mitsubishi FTO etc demanded 98 octane only. So, you could actually advance your ignition a touch and create a tiny bit more power / better running as has been discussed somewhere recently with people finding the D10 runs better at slightly closer to TDC than spec.

I believe it was the same 16.5° as the D14 model that was advised rather than the 19° specified. I'm not for a second suggesting that BSA were incorrect or not accurate in their specifications, they were just setting up their bikes for the lowest grade petrol likely to be run in the bike rather than what's available now.

You almost certainly won't be able to buy "poor petrol" in the UK as it doesn't meet modern specifications, but you could probably experiment with mixing in small amounts of something less refined like paraffin or diesel to lower the octane, but you'd be hurting performance and engine reliability rather than improving it. 

Hopefully that makes sense thumbs-up

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