1953 BSA B31 top speed and Timing

[briancairns]

I can only reach a top speed of around 55mph.
Bike only starts on fully advanced . If I retard bike even the slightest it will not start.
Bike starts 1st time and pulls very well.
I have timing set to 7/16 ( 37 degree) BTDC. ( timing set when filly advanced)
Everything has been checked.

If I set timing to 40-41 degree BTDC, will this increase my top spead?

Thanks in advance

Brian

[idie]

No. It might put a hole in your piston. It sounds as if the valve icing is out by a tooth.

[WayneBergman]

What are the symptoms when under power at full speed or up into your revs if you manually retard your timming? Just to rule out any confusion of the slack/tight wire posablilites of how your manual advance works?

[Ian C]

Apologies if you're already aware of this Brian, but is your mag a slack or tight wire advance?

[JulianS]

Starting on full advance would probably result in kickback through the kickstart are you sure the timing is set correctly.

If it will not start with any retard setting could mean your mag has a weak spark.

[briancairns]

What are the symptoms when under power at full speed or up into your revs if you manually retard your timming? Just to rule out any confusion of the slack/tight wire posablilites of how your manual advance works?

Hi Cams checked and all ok.

Cheers

Brian

[briancairns]

What are the symptoms when under power at full speed or up into your revs if you manually retard your timming? Just to rule out any confusion of the slack/tight wire posablilites of how your manual advance works?

hi

Bike is tight advance, no kick back when kicking over. When at highest speed bike runs fine and runs fine when getting to my top speed

[briancairns]

Apologies if you're already aware of this Brian, but is your mag a slack or tight wire advance?

Bike is defintely tight wire advance.

Cheers

Brian

[briancairns]

Starting on full advance would probably result in kickback through the kickstart are you sure the timing is set correctly.

If it will not start with any retard setting could mean your mag has a weak spark.

No kick back on full advance, which makes me think that I could advnace timing a little more?
When bike warmed up I can retard whilst sitting at traffic lights etc. , however not by much.
Bike always started well when I got bike but top speed was even lower ( 45mph) and would not pull me up a hill etc.
I checked timing and it was set at 47 degrees BTDC. Under furher investiagtion, it had wrong carb and the slide was very obviously badly tampered with.
I bought correct carb from AMAL which came preset and seems to be working fine. I also put new points in and spark plug.
Top speed now 55mph set at 37 degree BTDC. Bike always starts and seems to be a new mag.

Cheers

Brian

[Derek996]

My B32 will only do  55 mph max in top gear despite the engine being in very good condition, the timing accurately set and the carburation good. I understood why a couple of months ago when I was looking at the specs for the various BSA pre-unit singles and realised that my bike has a 19 tooth engine sprocket fitted by a previous owner but should have a 17t. It has been pulling B33 gearing. No wonder it wouldn't go any faster. I have a new 17t ready to fit over the winter.

[briancairns]

My B32 will only do  55 mph max in top gear despite the engine being in very good condition, the timing accurately set and the carburation good. I understood why a couple of months ago when I was looking at the specs for the various BSA pre-unit singles and realised that my bike has a 19 tooth engine sprocket fitted by a previous owner but should have a 17t. It has been pulling B33 gearing. No wonder it wouldn't go any faster. I have a new 17t ready to fit over the winter.

My bike is a 1953 BSA B31 S, it also has a 19T engine sprocket but I'm nearly sure that is the correct one. The rear break hub sprocket is 42T
Cheers
Brian

[briancairns]

My B32 will only do  55 mph max in top gear despite the engine being in very good condition, the timing accurately set and the carburation good. I understood why a couple of months ago when I was looking at the specs for the various BSA pre-unit singles and realised that my bike has a 19 tooth engine sprocket fitted by a previous owner but should have a 17t. It has been pulling B33 gearing. No wonder it wouldn't go any faster. I have a new 17t ready to fit over the winter.

My bike is a 1953 BSA B31 S, it also has a 19T engine sprocket but I'm nearly sure that is the correct one. The rear break hub sprocket is 42T
Cheers

Apologies, engine sprocket is 17T and gear box sprocket is 19T
Brian

[Derek996]

My B32 will only do  55 mph max in top gear despite the engine being in very good condition, the timing accurately set and the carburation good. I understood why a couple of months ago when I was looking at the specs for the various BSA pre-unit singles and realised that my bike has a 19 tooth engine sprocket fitted by a previous owner but should have a 17t. It has been pulling B33 gearing. No wonder it wouldn't go any faster. I have a new 17t ready to fit over the winter.

My bike is a 1953 BSA B31 S, it also has a 19T engine sprocket but I'm nearly sure that is the correct one. The rear break hub sprocket is 42T
Cheers

Apologies, engine sprocket is 17T and gear box sprocket is 19T
Brian

Well since the gearing is correct it must be down on power for some reason. Since the timing would appear to be correct a compression check might be in order. One other thing: Are any of the brakes binding? Although you'd probably notice that just pushing the bike around.

[briancairns]

My B32 will only do  55 mph max in top gear despite the engine being in very good condition, the timing accurately set and the carburation good. I understood why a couple of months ago when I was looking at the specs for the various BSA pre-unit singles and realised that my bike has a 19 tooth engine sprocket fitted by a previous owner but should have a 17t. It has been pulling B33 gearing. No wonder it wouldn't go any faster. I have a new 17t ready to fit over the winter.

My bike is a 1953 BSA B31 S, it also has a 19T engine sprocket but I'm nearly sure that is the correct one. The rear break hub sprocket is 42T
Cheers

Apologies, engine sprocket is 17T and gear box sprocket is 19T
Brian

Well since the gearing is correct it must be down on power for some reason. Since the timing would appear to be correct a compression check might be in order. One other thing: Are any of the brakes binding? Although you'd probably notice that just pushing the bike around.

Hi brakes not binding , so will try compression check.
Thanks for your help
Brian

[cdsdorset]

Have ypu checked for free play in the cable of the valve lifter.
Does the mag advance the same amout by hand with the cable disconnected?