• Welcome to the website of the Vincent H.R.D. Owners Club.

    Should you have any questions relating to the Vincent H.R.D. Owners Club, or Vincent H.R.D. motorcycles in general, please contact Graham Smith, Hon. Editor and Webmaster by calling 07977 001 025 or please CLICK HERE.

    You are unrecognised, and therefore, only have VERY restricted access to the many features of this website.

    If you have previously registered to use this forum, you should log in now. CLICK HERE.

    If you have never registered to use this website before, please CLICK HERE.

Hello, 1951 Comet- and what are your suggestions for additives to the petrol ?

Philip Smith

Website User
VOC Member
For a 1951 Comet with BTH mag. what would you suggest as octane booster ? Where I am in Northern Ireland the petrol supply is limited to Octane 95, with ethanol at 5%- this will change to E10 in September. What brand of additive, and how much to add to the standard size of tank- 15 litres. To get 97 grade petrol is a 45- 50 mile round trip. Thank you.....
 

Mike 40M

Well Known and Active Website User
VOC Member
What octane is needed for a Comet? Given that it was made at a time when petrol was quite poor.
Read about a parliament question in Nov 1950 about raising octane rating from 70 to 80.
 

Alyson

Well Known and Active Website User
VOC Member
also an article not long ago somewhere here about extracting the ethanol from the gas. Was a quite easy thing to do after watching the video
 

LoneStar

Well Known and Active Website User
VOC Member
also an article not long ago somewhere here about extracting the ethanol from the gas. Was a quite easy thing to do after watching the video
Yes, you basically mix it with water, into which the ethanol dissolves, then discard the water. Not hard, but a nuisance, and the water may also have toxic chemicals in it. Also, the ethanol increases octane - so you reduce the fuel's octane when you remove it.

In the US we have ethanol-laced premium at 93 octane, which works well in all my old bikes including a Black Shadow. Not sure how that number compares, though, as we use the average of Research and Motor octane ratings and other locations don't.
 

vibrac

Well Known and Active Website User
VOC Member
Some small airfields sell premium petrol tax paid as well as avgas and I am amazed that in a Land where racing motorcycles abound there are not supply avenues for good juice
I read somewhere you shouldn't use Avgas for mechanical reasons, why I dont know
 

oexing

Well Known and Active Website User
VOC Member
Avgas leaves lead deposits on sparkplugs but otherwise no problems - if not for the price.
Changing engine oil more often is not a bad idea as well then.

Vic
 

ClassicBiker

Well Known and Active Website User
VOC Member
Some small airfields sell premium petrol tax paid as well as avgas and I am amazed that in a Land where racing motorcycles abound there are not supply avenues for good juice
I read somewhere you shouldn't use Avgas for mechanical reasons, why I dont know
Avgas still contains tetraethyl lead, which totally destroys the catalytic converters in modern vehicles by plugging up the small passages through which the exhaust gas flows. Here in the U.S. you haven't been able to purchase leaded fuel at filling station since 1 January, 1996. You can still buy leaded fuel at certain outlets for off road use only or avgas at a small airport. But you aren't supposed to use it on the road as it hasn't been taxed for that.
As far as 10% ethanol and 93 octane goes, I haven't had any issues with it since I started adding a little gas preservative to it when I fill up, Sta-Bil is the brand name. This considerably slows down the evaporation of the aromatics that make gas volatile and also prevents the ethanol from absorbing water from the air. It is some concoction of petroleum distillates.
There are a number of gas stations around here that sell pure gas with out ethanol, at a premium, and also sell unleaded higher octane pure gas, again at a premium.
To answer Philips' question. In my opinion as long as your fuel system components are not adversely affected by ethanol and you use a fuel stabilizer, you're going to be alright. As Mike 40M correctly points out when these bikes were produced the octane rating of fuels were much lower. My Shadow has 7.3:1 pistons in it that my father put in during the late 70s, early 80s. I have no idea what is in my 1950 Comet as it was running when I bought it. I've run 89 octane with 10% ethanol regularly in them with no issue. My 60s and 70s Triumphs have 9:1 pistons and 93 octane and 10% ethanol doesn't bother them. My 1995 Triumph which I'm sure is at least 9:1 has a minimum rating of 89 octane. As to amounts of fuel stabilizer to use, the brand I mentioned above recommends 1 ounce treats 2.5 gallons or if you prefer 30mL treats 9.5 litres. Occasionally I pour in a little carb and fuel injector cleaner for good measure. Just a splash, nothing measured. Everything seems fine.
Hope I've helped.
Steven
 

Mike 40M

Well Known and Active Website User
VOC Member
I think a more interesting question is if E10 needs slightly larger main and pilot jets due to less energy content. Also corrosion problems and effect on rubber and plastic parts. My main concern about ethanol containing fuel is it's short service life. Petrol suppliers here says E5 95 has to be used in six months.
The ethanol free alkylate fuel (95 octane) I use for chain saws, lawn movers and the old sidevalve Norton is still usable after 5 years. The race bikes are fed with 98 octane alkylate, except the Manx which drinks 102 octane alkylate. The road bikes gets alkylate last two fillings before winter hibernation to prevent tanks from rusting.
 

Latest Forum Threads

Can't Find What You Need?

Buyer Beware: Fake or Real?

The Mighty Garage Videos

List of Forum Categories

Top