classic motorcycle forum

Chaps

1966 Triumph T120 Bonneville is proving to be an occasional pain in the neck when changing gear - especially from 3rd to 4th. Here it basically does not engage into 4th and finds neutral instead. Compared the other bikes, the gearchange just does not seem positive in selection and seems over-light - for want of better words. The throw of the gearlever between changes is also very small, and finding neutral from 1st or 2nd is a very fine art. The delicate tap required at the (standard) gearlever to find neutral is almost imperceptible.     

Of course I realize this may be all perfectly normal and that I need to adapt my right foot to the circumstances, but it does seem a little "light"

Things I have done fairly recently

Fresh gearbox oil - to the spec as per the manual - filled with correct amount
Fresh engine oil - to spec
Various adjustments at clutch nut - the one concealed behind the chaincase
Various adjustments of the clutch cable at both the lever and at the gearbox ends
Cleaned up the clutch plates/basket
I change up at around 4000/4500 rpm with a slight whiff of throttle.

It may simply be an attribute of the gearbox - which I understand to be original - but all thoughts welcome, particularly from other T120 owners.   

Just managed to break a fin on the aluminium alloy barrel of the Velo. I was heating it trying to bend it back and then snap! Much profanity followed. Piece is around 40mm by 15mm.

Forget welding it for the moment - looks very difficult and besides I am rubbish at it and there are no welders round here in the immediate vicinity.

Thoughts therefore are

Epoxy putty/plastic metal, JB weld or Belzona or something.
Solder?

Comments welcome 

Gents

I have half an eye on an MSS. Looks to be a nice single, though being a Velo somewhat eccentric. Thoughts welcome as to riding and maintaining it. Condition is above average, allegedly decent mechanically, some cosmetic work to do.

Many thanks

 

I am uncertain of just how and when my Pressure release/relief (PRV) valve should operate and seek enlightenment!

The PRV on my old nail of a 55 G9 Matchless twin is located within the timing case and is essentially a plunger with a captive spring ostensibly pressing against the timing case cover and pushing the plunger mating face against the seat. This seat is at one end of a filter housing - the other end of which is a ball valve with a weak sping, which ostensibly allows pressure to build, releasing said ball valve and allowing oil to flow through the engine at pressure.  This ball valve seems to be in order, and I also cleaned out the PRV tunnel when the timing case was apart last.

However, you may recall I am having problems with the dynamo seal - very close by the PRV. Essentially I am pretty sure it is leaking oil despite a new cork seal and plenty of silicone. With the dynamo removed and on starting the bike, it is very clear the PRV is relieving and spraying masses of oil around the vicinity of the dymano seal, probably overloading it and causing the leak seen. I am not certain of how the PRV behaves when up to running temperatire

Oil is Castrol straight 50

Questions

Is the PRV supposed to relieve at start like this? I appreciate the oil is thick, but surely the weaker ball valve spring would be first to go to allow oil to circulate?

 Is the oil truly circulating through the engine at start, the PRV just relieving excess oil? Would there be any merit in extending the PRV spring to possibly increase the relief pressure/the point at which it relieves- thereby reducing the amounts of oil splurging into the timing case? 

Given the above observations, can I expect the PRV to close when up to running temperature. I guess I am in trouble if it does not! No obvious sign that it doesn't when out on the bike!


 

Chaps

Noticed quite an oil leak coming from the dynamo and the timing cover mating faces. The gasket is of an annular type and of thick cork, and although seemingly not too bad, I have ordered replacements. The sealing seems to be done on the inner edge of the cork gasket and the dynamo "stub" end, and perhaps the vertical face of the dynamo - where there is no gasket.

Possible solutions - O ring instead of cork gasket?
Make up thin gasket for the vertical face?
Apply blue Hylomar or similar - in addition to the above.

Thoughts welcome.

Must admit I still have not looked at the crankcase breather valve  - on the crankshaft on the other side - as it it under the pressed steel primary chaincase and I don't really want to disturb it. I understand  pressure may be build up in the timing cover and blow things if this valve is u/s   

Chaps

Oil flowing out of the top edge of the mating suface twixt timing cover and crankcase. Oily right boot and gearlever ensued. Bike (59 Matchless G9) is newly overhauled - not by me - so currently cautiously riding around to establish confidence.

To remedy the above, cover removed, mating surfaces flattened as much as feasibly possible, screw holes deburred, flexoid gasket made, mating surfaces painted with Wellseal, Monograde 50 to be used intead of the previous 20/50. All now ready for test ride.

Qs

The leak was close to the oil pressure relief valve - spring and piston affair in the crankcase. Would there be any preponderance for a leak in this area? I am guessing that the void under the cover should not be pressurized.

Any thoughts as to root cause - apart from dodgy mating surfaces.

Many thanks



   

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.......

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