Ask about T6

[ManfrerdSt]

Hi Guys,
I have for my 1931er T6 new pistons. Now asks cylinder grinder how big the piston game should be.
Do you have experience in this?
In the past, I noticed that when the engine is turned off, 10 - 20 drops of gasoline still drip onto the hot exhaust. I guess that is related to the float level.
Is there a setting instruction here?
Thank you for your help
Regards
     Manfred

[ManfrerdSt]

had these problems no one else?
 

[Bert]

Manfred,
I sometimes have 3 - 4 drops from my T6 after it it stopped. It may be that the bike is not completely level but I think the amount from yours is excessive. Do you have any dripping while the bike is idling?
Have you checked whether the float is sealed.

[cardan]

Re piston fit: this varies depending on the pistons. On a number of occasions I've used JP pistons (made here in Adelaide) in vintage motors, and I've always specified the largest clearance they will supply, but of course this too varies depends on the bore. JP hate large clearances because the pistons might rattle a bit when cold; I hate small clearances because the motor will seize when it gets really hot.

Are your new pistons cam ground? (i.e. is the skirt larger perpendicular to the gudgeon pin than parallel to it?)

Did the pistons come with any recommended clearance?

I've never rebuilt a T6, but even with good alloy pistons I'd be surprised if the clearance wasn't at least 0.005" (0.125mm)?

Hopefully someone else might have a better idea.

Leon

[eddie]

For normal roadgoing machines, I have always understood that the bore should be 'size' - that is 68mm is exactly that - the running clearance is allowed for on the piston. Machines for competition use may need a little extra clearance, so the bores may be honed a thou or two larger (depending on the pistons used).
   Regarding the fuel leakage, this is probably due to wear of the float needle/seat - updraft Amals seem to be more sensitive to fuel level than the normal side draft units. Just a few thou adjustment will probably cure the problem. If you were to add the 20 drops of leakage to the fuel in the float chamber, you would hardly notice the difference in the level!!

  Regards,
                Eddie.

[ManfrerdSt]

Hello,
OK, I will give the piston 0.125mm clearance.
Eddie, my problem is not the loss of the drops, but the fear of fire because it drips onto the hot exhaust.
For standard carburetors, there is a manual for setting the gasoline level in the float chamber, for this type I can find nothing.
Regards
     Manfred

[eddie]

Manfred,
              I appreciate that you are trying to minimise the fire risk. The problem is that the Amal carb was originally intended to be mounted upright, so that all the jets are submerged in the fuel. Under these conditions, they work well and can be tuned to cope with varying fuel levels. However, when they are turned 90 degrees (as on the T6), they can be a little more temperamental as the main jet is now situated above the fuel level. To obtain clean carburration, the fuel level needs to be as high as possible without causing the carburettor to flood (or even drip). To this end, the adjustment of the fuel level needs to be more precise than is the case with a normally mounted carb - lowering the float just .1mm may be enough to stop the dripping!
  Regards,
                Eddie.

[ManfrerdSt]

Eddie,
I can not imagine that the oil pressure is regulated by the weight of the indicator bar. The bar already rises at 0.2 bar or with an air bubble up to the stop.
It could be that in the oil change, the first liter at this screw is filled, so that the oil level shown in the picture (for the lubrication of the cam gears) is present.
The area in the red frame I can not assign and the text not read. So I ask for a good copy of this page.

Regards
     Manfred

[Dewey]

Manfred,
The oil indicator is just that - an indication of available oil for the purpose of lubrication. There is no regulation of oil pressure. It's a constant flow primarily to the crankshaft & bearings and everything thrown off the spinning crank & gears lubricates the rest.

Dewey

[Doug]

NOTE

Manfred also asked about the oiling system in the following post. One of the replies has a better scan of the handbook illustration of the oiling system.

https://www.douglasmotorcycles.net/index.php?topic=6579.msg24699#msg24699

-Doug