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unleaded fuel in a65
April 1, 2013
5:31 pm
Sparky
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Hi all,

Not Bantam related at all.

Few weeks ago bought an a65 project bobber and have been on it 24/7 since.

Can anyone advise on using unleaded fuel as i think it may effect the top end rebuild ?

Thanks Sparky

April 1, 2013
8:43 pm
BASIL
Club Member 874 Hamstreet,Ashford. Kent Area Rep.
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Unleaded is ok if you put some lead addative in it failing that make sure it has some modern valve seats in it. Regards Basil.

April 2, 2013
9:19 am
Sparky
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Hi Basil,

Cheers

April 2, 2013
11:14 am
Scotnormbsa
Club Member 599 Blackridge West Lothian Scotland
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Hi Sparkytip-my-hat

 

I have several old BSA bikes which are two strokes and a four stroke. I was informed that It was prudent to use the higher octane fuel in my bikes instead of standard grade. It runs better when mixed with a lead fuel additive and protects the valve seats from burning.It also is better as the level of bio fuel is less – so I am informed. I have to agree as I have since started using my bantam and the tank had been coated previous to me purchasing it and that coating has now flaked off.You have an A65 which is a higher performance bike than a bantam so this may make good sense.

 

regards

 

scotnormbsahope-that-helps

D7 Trail Bantam; D10 with D14/4 Engine: D7 Basket Case and a BSA C15 Star
April 2, 2013
11:35 am
Jubilee
Club Member 1357 North Yorkshire
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Hello Sparky,

The higher grade petrol is better than standard for the reasons given by scotnormbsa. It has no more than 5% ethanol in it and some manufacturers do not put any ethanol in it at all. The minus side is that it is considerably more expensive if you use a lot.

I have read somewhere that this year all filling stations have to display the percentage of ethanol in their fuel so that will be a big help for old vehicle owners.

Regards

April 3, 2013
10:03 am
Cornish Rooster
Saltash Cornwall
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Don’t get over concerned about running an older engine on modern fuels especially with regards to valve seat recession, ok if you do really high mileages and at high speed on say Motorways etc then it could be an issue but even then maybe not.

I have been running my older four-strokes on modern fuels without any problems and my Moto Guzzi Single has been used on modern fuels for around 13 years now and has not suffered any valve seat problems judging by my infrequent valve clearance checks. This bike has done some long runs as well including covering 270 miles or so in about six hours, my 250 Starfire has also covered around 275 miles in a day and again no noticeable valve seat wear and both these bikes do NOT have modern valves and seats. 

The main issue seems to be that these modern fuels make the combustion hotter and the fuel has less calorific value (energy) so with a higher performance engine some carburation changes may be required. A good start is to use the “super” grades on these engines and dependant on where you are in the country it may or may not include an ethanol content.

My single carb A65 Thunderbolt was pinking quite badly under load under certain conditions, such as pulling up a hill in top gear, to overcome this I fitted a “3″ slide to replace the 3 1/2 original spec (slightly less air) and went up 10% or so on the main jet size going from the original spec 230 to a 250, and since then the pinking has gone. I fact I think the carburation must be just about spot on now, it pulls through the throttle range very well. These single carb A65′s have some real grunt and the way it picks up in top gear from say 50 mph to 70 mph is very impressive even by modern bike standards, plus on a run doing between 50 and 70 mph it will do around 70 mpg ! It will also quite happily sit at 70 mph all day, a very under rated engine these A65′s and surprisingly smooth if put together well, though mine does have a balanced crankshaft and pistons.

By all means use an additive if it makes you feel better, it can’t do any harm, I still have some in my garage though I haven’t actually used any for years.

Phil 

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

April 3, 2013
3:40 pm
Peterg
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I agree with Cornish Rooster. Your A65 has an alloy head with valve inserts. Being a specialist metal producer they tended to use higher spec metals than other manufacturers.The valve seats will have no problem coping with modern fuels. In most cases replacement valve seats (only the exhaust is needed) are a con. Unless you are racing or doing very high mileages your valve seats will out last you.

Modern ‘petrol’ is very different to the fuel your carb was tuned for. Generally unless you have over 9:1 compression you don’t need higher octane fuel. But because of the different burning characteristics your carb and ignition will need to be tuned to match the fuel you use.

I have a Gold Star with 9:1 compression and it runs worse on higher octane fuel. It would probably run better than on standard fuel if the carb was retuned and the timing was changed but I an happy enough with my current performance.

I also had a B31 with standard cast iron head (no valve inserts) and it has lasted about 160,000 miles with three recuts when the valves were replaced. so I don’t think you need to worry unless the seats actually need to be replaced due to recession.

Peter

April 3, 2013
7:51 pm
Sparky
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Hi Scotnormbsa and Jubilee,

Thanks for your advice on different octane fuel it was definately something i didn’t know.

When you say coated, with what and why has it come off ?

Thanks again Sparky

April 3, 2013
8:14 pm
Sparky
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Hi Cornish Rooster,

Thanks for your advice,

I was told by the seller the bike has high compression pistons

The bike has been fitted with new unused Mikuni VM twin carbs ( loosely bolted on ).

Any thoughts.

Sparky

April 3, 2013
8:20 pm
Sparky
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Hi Peterg and all

Thanks for help.

Bike has been fitted with high compression pistons i am told by seller but don’t know what this really means or how to tell if this is true.

Also fitted with Mikuni twin carbs.

Any advice would be appreciated.

Sparky

April 4, 2013
3:28 pm
Scotnormbsa
Club Member 599 Blackridge West Lothian Scotland
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Hi Sparkytip-my-hat

 

The petrol tank was coated with a film that protected it from rusting I assume, and was white in colour.

Just recently I filled the tank with petrol and the coating started to peel. I was told that ethanol is the culprit

and it is used at either 5% or 10% strength in modern petrol.

It can affect seals and tubing and fibreglass and causes failure of the component. You can however purchase

modern components that are resistant to the effects of ethanol. There are tank coatings on the market to deal

with the effects of Ethanol too. Apparently it can gum up the works within carburettors but I do not know if this has any foundation.

There was a great debate in the classic vehicle organisations and tests were carried out. The Government were

lobbied about the effects of Ethanol on vintage and classic vehicles.

The government are introducing 10% ethanol fuel as part of their green campaign to reach targets agreed with EU.

The lobbyists wanted provision for ethanol free fuel to be available at the pumps. If required the user can add lead free additives to combat the heat and pinking (weak mixture). As previously mentioned you can alter the settings and needles etc. to suit the fuel mix. I suppose the Amal Carburettor Company can advise you on these matters.

 

regards

 

scotnormbsahope-that-helps

D7 Trail Bantam; D10 with D14/4 Engine: D7 Basket Case and a BSA C15 Star
April 4, 2013
3:49 pm
Cornish Rooster
Saltash Cornwall
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It’s quite a common mod to fit the Mikuni’s to the twin carb A65′s so if you have a trawl around you should be able to find some info for a starting point at least with regards to the carb settings. The Yanks go in for these carbs on the A65′s so you may even find some info on the American sites that sell these, plus the numerous Forum’s of course, there is one called “Britcycle” if I remember correctly that has a lot of BSA info on it.

It should be a real flyer once you get it sorted, my standard single carb job cracks along well, infact the single carb versions may actually be quicker in the mid range due to the greater air velocity through the carb though the twin carb will give the engine more puff at the upper end of the rev range. Should not be impossible to sort it out one way or another but it may take some experiment to get it spot on carburation wise, fortunately Mikuni jets, needles etc seem to be fairly easily available.

Keep us posted on this one as it will be a real goer when sorted.

Phil

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

April 5, 2013
10:08 pm
Sparky
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February 29, 2012
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Hi Phil , Scotnormbsa  and all.

Still computing all this information.

Just finished rewiring bike, well helping to rewire with  auto eletrician freind.

The ignition system is a Boyer Bransden 12v with digital ignition coil.

Now have all lights,horn and SPARK working.

Any advice or thoughts appreciated.

Will update when try to start but double checking all before.

Thanks again Sparky

April 5, 2013
10:21 pm
Timbo
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Hi all, just a thought about A65 valve seats, i seem to remember they are not pressed in but are actually cast into the the cylinder head material, so replacement is not so easy. I may be wrong though.

 

Timbo

1957 D3 Bantam, 1971 BSA Thunderbolt, 1981 Honda XL 185
April 26, 2013
8:34 pm
Sparky
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Hi Cornish Rooster,

Had a few set backs since i last posted which is why i have not been on site.

After i bought the bike  which i is still think is awesome and the quality of the conversion now i have mangaged to bolt most together  from  the box of bits is very proffesional.

I checked sump filter.

                                                                                                                                                           

outpoured half a pint of rusty water

So no choice but to strip engine.

Never stripped four strokes before, only  Suzuki GT250′S, Honda CR250′S  and Bantams. All twostrokes.

Anyway the bearing conversion to the timing side was pitted, rusted  and ruined as was the the drive side bearing.

The rusting had gone in to the bottom part of the barrels and these were not good anyway.

I am replacing bearings, seals and having rebore,

Any suggestions and ideas would be great.

Thanks Sparky

April 26, 2013
10:04 pm
area51
club member 1947 west yorkshire
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April 5, 2013
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I love the unit twins…theres a lot of rubbish spoken about un leaded fuel these days.

I manage a classic car dealership and its a question I get asked every day.

my standard reply is if the engines not been apart for years then the lead memory effect will be fine unless your doing motor way runs every day.[

 

failing that use Castrol valve master..the dearer one with the octane booster so you can run on the original timing settings without fear of grenading your engine.

I think the a65 was supposed to run on 4 star so valve master should be good for it in terms of octane rating and not getting pre ignition.

tip…halfrauds sell it and if you ask for a trade card you get mega discounts on nearly everything! 

most of a 1968 d14/4
April 27, 2013
10:17 am
Cornish Rooster
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Sparky,

Well seems as if you have a fair bit of work to do then, the positive thing is you now have a few options. One being to go back to more standard compression pistons for a start, that may give you an easier time in the long run, these A65′s crack along quite well in fairly standard trim.

I was out on my single carb A65 Thunderbolt yesterday and it aways surprises me how well it goes helped by the single carb, glitch free acceleration and real strong surging power, the single carb effect can only be felt around above 75/80 mph and with the twin carb version it would be pulling harder above those speeds.

There is nothing too special with these engines and as with anything you can go as far as you want, the primary drive belt conversion is a good mod as you can up the overall gearing as l aways think these bikes feel a little under geared ? AS said above don’t get too hung up over the valve seats, but if the head is to be overhauled it’s another option to get modern valves and seats.

I aways run my A65 on the “super” grades of petrol and once l sorted the carburation out everything runs well, the timing side conversion is a good mod but according to folk who know these engines is not actually needed if you keep the oil changes regular.

The Clymer manual is a good buy, got mine from an Ebay shop, they are laid out well and easy to follow and understand, probably a better bet than the Haynes jobbie.

Phil

http://i1125.photobucket.com/albums/l585/bsathunderbolt/BSAA65ClymerManual_zpsee26241c.jpeg

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

May 9, 2013
7:23 pm
Sparky
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Hi Phil,

Thanks for your reply

Took the head to local bike shop/garage in bristol (matts motorcycles) and spoke to matt who has owned a few a65s and was told the it has been highly polished as everything is completely smooth and it is in excellent condition as for racing but has not been used ? there have been accurate spacers fitted to replace the rocker spindle springs which i was told was alao a racing mod.

While i have been waiting for rebore and new bearings i have carried on with other parts of the restoration but have come up with a couple of problems the main one being the front brake system.

The bike is fitted with a taylor dow twin leading shoe brake (which i am told is a race mod) and have been told it is a goldie wheel and hub.

The whell rubs intermitantly  on the brake when turned by hand.

I have been trying to find an exploded view of the internals of this brake system before i take it apart to see what is causing it.

Any advice on the taylor dow tls would be great.

Thanks SPARKY

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