A65 not running well

[Mike Farmer]

 

Hi help/advice please.

I have recently (finally) finished rebuild of 1964 A65T? Bog std 9.5 pistons +040 bore.

I have a bad running problem that I would like to discuss before I go into changing bits. New Electronic ignition, new battery, new alternator stator solid state rectifier. New concentric premier carb. It runs ok ish but rather like a bucket of something nasty. Its seriously lumpy as if its rich. It is jetted as per the book, the choke is completely open and there is currently no air filter. (this would normally result in a tendency to run weak???).

I know from previous posts that a couple of others have fitted the same carbs in the last year or so. So guys what is your jetting.

I know that there is a viable alternative that the timing might be a smidgen out, but I don't want to go down that line until I've had a good go at fuel. It wont make sense to be trying both angles at the same time.

So you advice or opinions please.

Mike
 

[Dean Southall]

How old is the fuel?

[DAVE BRADY]

Hi,

I recently fitted a new Premier Conc. and it is jetted as per the manual for a Thunderbolt.
Apart from setting the tick over and pilot adjustment the bike has run perfectly.
I did take the carb. apart prior to fitting to make sure it was clean as there is always the possibility of a bit of debris having been left inside.
Have you checked the plug to see if it is rich?  The lack of a filter will only have a small affect until running and like wise a smidgen out on the timing will have a minimal affect until on the road.
Although I have never had a problem with old fuel it is worth checking as mentioned by Dean.

Dave.

[LightningAndStarfire]

Could be float level set wrong or float shaft binding.

[Nanonevol]

With a new Premier it's likely something else.
Was it timed with a strobe timing light?
Valves?  Valve timing or setting?

[Mike Farmer]

 

Thanks for all your replies. Certainly a couple of points that I missed.

Mike

[JOHN KAY]

hi mike > try shifting the needle on the slide a groove to a slightly weaker position Regards johnboy .

[A65ROCKET]

Hi Mike,
check the ignition timing.
On early A65's, BSA specified 37 degrees BTDC, however this was later changed to 34, and sometimes 32 works well.
Andy

[Mike Farmer]

 

Had a bit of time to go through things with this problem. Went though the normals, got it running a bit smoother.
Then Oh deary deary me liquid(petrol) bubbling up alongside the cylinder head nuts .the ones either side of the plug. So I guess we have a head gasket problem. I know the gasket is the composite one. So I guess that its a quick tighten job and a few prayers(swears?) Then probably a solid copper gasket. Bu----r

Will let you all know

Mike

[DAVE BRADY]

Hi Mike,

This sounds like more than the head gasket.  Under normal circumstances would there be enough petrol in the combustion chamber to make its way up the studs?  Once through the carb the fuel should be mixed with air rather than a liquid.  Have you tried taking out the plugs and kicking the engine over with the fuel turned on and carb tickled?  If there is a lot of unmixed petrol getting in to the combustion chamber it will be visible as it blows out.

Dave.

[Mike Farmer]

 

I shall do as you suggested.
My thoughts are that if the head gasket is gone then the compression will force any fuel out through the weakest point.

We'll see.

Mike

[DAVE BRADY]

Hi,

If you have compression tester do a reading on each cylinder and see what the difference is.  A quick look at the head joint between the fins will also help with diagnosis. 

Dave. 

[Mike Farmer]

 

Dont have a tester but will look at the other point.

Big Fear-----cracked head?/

Mike

[Wessex100]

I had a new Concentric and had to strip and blow out drilling. Was causing poor cold starting. Also found this applies to new flat slide carbs.
Never assume a new carb is ready off the shelf.

[Mike Farmer]

 

Good point there. However I had to strip and re-jet mine so I think that aspect is OK

Mike