1940s matchless

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Re: 1940s matchless

Postby g80csp11 » Thu May 09, 2019 6:39 pm

ive never updated any of mine , and even my 46 G80L has done Westwood Ho a 700mile round trip
Personally I would not use additive

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Re: 1940s matchless

Postby Duncan » Thu May 09, 2019 9:12 pm

Some light reading: https://fbhvc.co.uk/fuels

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Re: 1940s matchless

Postby Andy51 » Fri May 10, 2019 3:35 pm

I wrote a piece on this in Jampot a while ago, based on info from UN (lots of old vehicles out there globally that will be around for years to come long after leaded is gone) and their research shows that unless you regularly drive at 4,000+ rpm you will not get any significant wear, ally or iron heads. Your '40s bike will be low compression and I would suggest you will be keeping the revs below this level most of the time! Therefore no additives needed. My '54 18S runs scrambles cams and 8.5 to 1 compression, and is perfectly happy on 95 octane petrol, although I normally use 97 as it has less ethanol (less chance of rusty tank). In 3,000+ miles, often at high speeds, I have not had to adjust the tappets once - thus no seat recession, the supposed problem with unleaded. This was a scare that proved wrong, and the only reason for new valve seats is if the old ones are too worn or pitted. Cheers, Andy

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Re: 1940s matchless

Postby 56G80S » Fri May 10, 2019 8:22 pm


Thanks, an interesting read.

Only ever very occasionally used Redex.

Johnny B

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Re: 1940s matchless

Postby Plugsnpoints » Fri May 10, 2019 9:35 pm

For many years I ran my ancient (not as ancient as my Ajays admittedly!)Guzzi 1000 on unleaded with no problems, even though I was concerned at first. I assumed that as they were sold in the US, and they'd hadn't had leaded petrol since about 1974 it would be ok. Every time I when out on it I took it well over 4000 rpm even though it was a bit of a tractor! I don't ever recall having a tappet close up.

This thread is fascinating to me, as I recall it was one of the first questions I asked Tony after I'd won the M30. I doubt if I'll ever do the mileages I used to but it's put my mind at rest. I run both my bikes and car on super unleaded these days.

One thing I do insist on is using branded fuels. When I was doing 500 odd miles a week in my van I proved it several times that it did about 10% more to the gallon than running on supermarket diesel.

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Re: 1940s matchless

Postby r wheat » Sat May 18, 2019 7:48 pm

Hi lads thanks for the answers. I will not bother getting any, the story of the diesel in the fuel, I used to add diesel at a rate of 3 galls of petrol to 1 galls of diesel in my 1940 Bedford as the war time fuel was pool petrol with low octane, smoked a bit. I tried using paraffin mixed with fuel but any one following believes you have a primus stove not an engine and was told this could harm the bores, whether this is correct I have no idea. many thanks Richard


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