classic motorcycle forum

Gents

Matchless G9 appears to be leaking lube oil from the pressed steel primary chain case. Not a great design, held in place with a steel band/turnbuckle arrangement around the circuference. All ideas much appreciated - apart from the ususal gasket sealant - in order to impove matters.......

Heating up the plug(s) beforehand sometimes works - plus spraying petrol directly into the carb just beore starting....

John K - all useful stuff - thanks. Apparently this one has just been rebuilt, and I have a degree of mechanical sympathy. Box is a Burman - I think....

I quite like the look of them - aesthetically pleasing, twin OHC, bit of charactor

Gents

Yes indeed - all good stuff. I appreciate the main jet reasoning. Amal recommendations for the 930 concentric 4 stroke mk1 premier - which I think I have - specify 200 for main jet - I have 220, so perhaps leave it alone. I will change out the needle jet for another .106 - in case it has worn.

I also noted that my needle has 3 rings - cannot see a number anywhere. I believe this is incorrect for the needle jet part 622/122B - it should have 2 rings - part no 622/124. This may contribute to the apparent rich running.

Agreed that balancing is a factor. Will be done after all the above tinkering.

Floats are the stay up (plastic?) things with a tipped needle.

He states that a .106 needle jet is .106” diameter which is the size of a number 36 drill, I can verify this having checked a new set bought last year from Amal. However not everyone has a set of number drills, so you if you’re in any doubt jets aren’t that expensive so why not replace them as a matter of course.

As far as valve clearances are concerned why bother setting them tight or slack when it’s just as easy  to set them correctly. I dunno if you’ve come across the tip for setting them by winding them down onto the valve tip by hand and then backing them off. You will have to determine what thread pitch the adjusters are, I would guess yours are CEI, then working out how much of a turn gives you 0.004. This is a particularly good way of setting valve clearances if the valve tips are worn

Yes - think I will replace the needle jets and the mains - to 200 as per various recommendations
VV clearance  - 40 deg from stop is the setting if doing it on the thread. The point about setting them slightly slack is that it avoids any risk of ex valve burning. I am not convinced it is at all easy to set them spot on, so I prefer slightly slack.   

Fettling the Triumph and in checking the exhaust valve clearances, I noted the LH side was too tight. re-checked and set to 4 thou. as per manual

A few things

Corresponding exhaust is coated far more with soot than the other. Could the tight valve be a factor, or is this purely a function of the associated carb?

Setting exhaust valve clearances on my old MG, received wisdom is too slack is better than too tight - valve burn out etc. Does similar apply. If anything, I have set both slightly more than 4 thou.

Needle jet is 220 on my 930 Amal concentric. Reading around it seems a tad high - try 200 perhaps?  This may also explain the rich mix perhaps.....

How on earth do you measure needle jets to check the orifice size?

Cheers

Mark 

 

Apart from Fleabay and carandclassic, does anyone know of other sites on the web that are useful for classic bike sales? I have come across one or two others in the past, but invariably they are way out of date.