High fuel consumption solved!

A

Alan L

Joined
Apr 13, 2021
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Hi all,
Two days ago I put a post on ‘What did you do with your Norton today’ about an excellent ride I went on over the Snowy Mountains in Australia. In general the bike went beautifully although I did comment on higher than expected fuel consumption (40~45 mpg).
On return my wife commented on the petrol smell of my cloths (woman have a better sense of smell than men, as many a cheating man has found out to his detriment on returning home after a clandestine assignation).
I also noted that the bike was not quite a good a starter as it had been. Usually, like a Ronson Lighter (or anecdotally, a Sherman tank) a matter of pride that it lights up first time, every time
Anyway, this morning I decided to investigate. With timing light attached and kneeling down near the primary I gave the motor a rev, fuel seemed to squirt out everywhere.
It turned out I had lost a carburettor bowl screw and the bowl was quite loose.
Hopefully a new screw and a general tighten up will have it back to scratch. If only all problems were this easy to fix.
Alan
 
Alan L said:
Hi all,
Two days ago I put a post on ‘What did you do with your Norton today’ about an excellent ride I went on over the Snowy Mountains in Australia. In general the bike went beautifully although I did comment on higher than expected fuel consumption (40~45 mpg).
On return my wife commented on the petrol smell of my cloths (woman have a better sense of smell than men, as many a cheating man has found out to his detriment on returning home after a clandestine assignation).
I also noted that the bike was not quite a good a starter as it had been. Usually, like a Ronson Lighter (or anecdotally, a Sherman tank) a matter of pride that it lights up first time, every time
Anyway, this morning I decided to investigate. With timing light attached and kneeling down near the primary I gave the motor a rev, fuel seemed to squirt out everywhere.
It turned out I had lost a carburettor bowl screw and the bowl was quite loose.
Hopefully a new screw and a general tighten up will have it back to scratch. If only all problems were this easy to fix.
Alan
Click to expand...
I carry FOUR spare screws. Two to give away, and two to use.
 
concours said:
I carry FOUR spare screws. Two to give away, and two to use.
Click to expand...
Good idea. The carbies are the most violently shaken about part of the whole bike methinks. Driver not considered.
Last season on Northern Ontario trip back homewards I dropped a jet assembly , left side.
Talk about fuel consumption until getting to help 100 kms. later. Kept swapping plugs every 5 kms. on rich crap-out . That worked.. Pure bush on both sides of the Hwy. of high speed Trucks..
I bring a stubby shortened Phillips in the tool pouch for such an occurrence , since a stubby Posi-drive is a chore to find. But no new screws to replace one . I'm changing that now...also with 2 fresh plugs !
 
Make sure they have good spring washers as they lose their grip on the screws after time or how often they been removed, have never lost a carb screw in 46 years as I have a good spring washer collection in my workshop.
 
concours said:
I carry FOUR spare screws. Two to give away, and two to use.
Click to expand...
No good if you lose the bowl and if it still hanging on the fuel line I am sure the float needle and float as well gasket might not be so lucky, I always check things before any long rides planned and normally see seepages from the gasket is the first sign of lose screws.
 
Also, Loctite 222

High fuel consumption solved!
 
ashman said:
No good if you lose the bowl and if it still hanging on the fuel line I am sure the float needle and float as well gasket might not be so lucky, I always check things before any long rides planned and normally see seepages from the gasket is the first sign of lose screws.
Click to expand...
How can you lose a bowl ?
 
Torontonian said:
How can you lose a bowl ?
Click to expand...
Lose both screws and the bowl will drop off and hang by the fuel hose to me that's the same as losing a bowl, and if unlucky the gasket could go as well, but I have never lost a screw yet, have had then come loose and start to seep from the gasket.
 
Torontonian said:
Like the whole Norton. Lost my 73 one Sunday morning. Backfire , gas .
Click to expand...
Did it have an open intake? (bellmouth or velocity stack) I cringe when i see a bike with no air filter, a guaranteed way to start a fire if the engine backfires. Even a plain gauze filter will arrest a backfire flame, same way as the Davy lamp works. The Mk3 i bought last year had a history of catching fire. That had no air filters.
 
dobba99 said:
Did it have an open intake? (bellmouth or velocity stack) I cringe when i see a bike with no air filter, a guaranteed way to start a fire if the engine backfires. Even a plain gauze filter will arrest a backfire flame, same way as the Davy lamp works. The Mk3 i bought last year had a history of catching fire. That had no air filters.
Click to expand...
Traced back to a failing transistor pickup on the Boyer plate. Fired whenever.
 
Many years ago Triumph twins had a single carb with a float bowl which was held to one side by a casting, and attached to the bottom of the crab. I was out riding with one of my mates one night, when I felt my legs go warm. Luckily a guy in a car stopped and he had a towell with which we were able to fight the fire. The casting on the float bowl had broken.
 
acotrel said:
Many years ago Triumph twins had a single carb with a float bowl which was held to one side by a casting, and attached to the bottom of the crab. I was out riding with one of my mates one night, when I felt my legs go warm. Luckily a guy in a car stopped and he had a towell with which we were able to fight the fire. The casting on the float bowl had broken.
Click to expand...
Real stuff for sure. When mine went up in flames a quick observer said " Take off your shirt and smother it ". So I did and burnt my R. side palm.
 
I found out why the points were moved to the timing cover when fuel leaking from one carb was ignited by the points rather than by the plugs!
 
Alan L said:
...With timing light attached and kneeling down near the primary I gave the motor a rev, fuel seemed to squirt out everywhere.
It turned out I had lost a carburettor bowl screw and the bowl was quite loose.
Hopefully a new screw and a general tighten up will have it back to scratch. If only all problems were this easy to fix.
Click to expand...
Our daily prayer.
 

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