Joined: Oct 2017 Posts: 2 Threads: 1
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Location: Northern Ireland
Hi
I recently purchased a Big7 which is not driving at all well. She seems to be sucking air somewhere. She would tick over relatively good but wouldn't take the throttle. When I removed the air filter and fitted a cap over the carburettor she would take it but the power was badly reduced and she sounded like she was off cylinder 3. A lot of work has already been carried out to her namely coil, condenser, plugs and plug leads replaced. The carburettor has been refurbished and reset more than once. The tappets have been reset and a compression test carried out. The manifold has also been taken off and resealed.
Has anyone run across this problem before? if so please help as my 75 year old mechanic is at his wits end.
P J
Joined: Aug 2017 Posts: 121 Threads: 6
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Is the dizzy advancing?. I had similar symptoms on a seven of the engine refusing to rev. I coukd.make it rev by ritchening the mixture by blocking rhe intake with my hand but I was stumped. Eventually found the bob weights in the dizzy were stuck/tight.
Joined: Aug 2017 Posts: 882 Threads: 48
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Location: North Wiltshire
Car type: 1927 Chummy, 1938 Big Seven 1/2 a Trials Chummy
Sounds like a blocked jet or a blocked passage in the float bowl. Some float bowls give problems even though you take them apart and clean them - there must be hidden passages somewhere. If all else fails, try another float bowl. I think I have several spares if you want one.....
Joined: Aug 2017 Posts: 2,748 Threads: 31
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Location: Auckland, NZ
Anything is possible with unknown vehicles; these can be a challenge. Stale fuel can be very confusing. Valve timing can be approx checked using the crank. I have encountered distributors with reverse advance! There are many passageways in the carb and all are suspect in an old car. Carb and innards may be wrong.
Joined: Aug 2017 Posts: 41 Threads: 1
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How’s the battery? My 1929 Rover (running an SU and coil conversion rather than mag.) had been a nightmare, very similar symptoms in that would tick over, but as soon as you opened he throttle it was like it was flooding with a loud hissing sound as though it was sucking air. then as you closed the throttle would splutter and stop.
A new battery cured it instantly!
This was about a year ago. The cars not been used much during the year, and when it has they have been short journeys, the same symptoms have re-appeared! Need to charge the battery and get the mag back on the car!
Joined: Aug 2017 Posts: 532 Threads: 46
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Location: Oakley, Hants, UK
Car type: 1929 AD Tourer, 1930 Rosengart LR2, Rosengart LR4 Van 1938 APE Tourer (Opal)
(21-10-2017, 04:30 PM)PP J Wrote: (20-10-2017, 05:39 PM)Colin Swinbourne Wrote: How’s the battery? My 1929 Rover (running an SU and coil conversion rather than mag.) had been a nightmare, very similar symptoms in that would tick over, but as soon as you opened he throttle it was like it was flooding with a loud hissing sound as though it was sucking air. then as you closed the throttle would splutter and stop.
A new battery cured it instantly!
This was about a year ago. The cars not been used much during the year, and when it has they have been short journeys, the same symptoms have re-appeared! Need to charge the battery and get the mag back on the car!
Thanks guys for all the replies.
Colin the battery is running down but is fully charged and it makes no difference. It certainly seemed like a carb problem but it was refurbed before I got her and my mechanic has stripped it again and reset it. I will speak to him about the float. What is the "dizzy" I never heard that term before?
(20-10-2017, 08:15 AM)Hedd Jones Wrote: Is the dizzy advancing?. I had similar symptoms on a seven of the engine refusing to rev. I coukd.make it rev by ritchening the mixture by blocking rhe intake with my hand but I was stumped. Eventually found the bob weights in the dizzy were stuck/tight.
(20-10-2017, 08:18 AM)Parazine Wrote: Sounds like a blocked jet or a blocked passage in the float bowl. Some float bowls give problems even though you take them apart and clean them - there must be hidden passages somewhere. If all else fails, try another float bowl. I think I have several spares if you want one.....
Parazine thanks for your help. If you have a float I will buy one. Can you contact me directly on pjquinn24@icloud.com and we can agree cost and posting etc.
Dizzy, is a reference to the distributor
I am always interested in any information about Rosengart details or current owners.
Joined: Aug 2017 Posts: 381 Threads: 16
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Location: Port Elizabeth, Sunny South Africa
Car type: '26 Chummy, '28 Top Hat, '33 Type "65", single seaters
We had a similar situation with Dad's 1930 Triumph Super Seven, years ago we fitted a 1+1/8th SU to it as the old Zenith was badly worn at the butterfly shaft. Symptoms were just like spark breaking down - we rebuilt the magneto and the coil conversion twice each, to no avail. reset timing, checked compression, fuel delivery, swapped plugs etc, etc.
Turned out that the washer under the seat for the main jet had split and fuel was gushing out as soon as the needle lifted when trying to increase revs. This glut of fuel would wet the plugs and choke off the motor. Sometimes it's the simplest things that cause us the most headaches...
Cheers
Greig
Sunny South Africa
