From the pics below you can see @ TDC the pistons are about 2mm below top of Barrell.

Will this lower compression? or is this standard for T120r's???


Thanks in Advance.

I can't tell you anything about the piston height, but I like the engine stand! Did you make that? Can you post some pics of it?

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Hey, What's this oil on the floor?

That certainly doesn't look standard to me. I don't recall ever having that much "squish" in the cylinders.

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GrandPaulZ
Author of "Old Bikes"
Born Again Bikes
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Yeah i made the stand up.

Just some steel and a few welds.

I will take some more pics of it and post it up!

Hey Quaq,

Here are the pics of the stand that i made for the motor.
i have put in one of my bike which is waiting for its motor.
i cant get it in until i can work out whats going on with the barrel.

Ill make you up a stand or two for a 650 barrel??

Sound like a good deal??? hehehe

Any old 650 barrell?????? I'm sure I could find one, might only be usefull for a small anchor, but I could find one!

Actually if you want I can look at the swap meet in a few weeks.

Peter

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Hey, What's this oil on the floor?

I wonder if these are the right pistons.. The dome looks much higher than anything I remember. The old thunderbird pistons were flat and teh 8.5:1 had bit of a squish..

I supose you could assemble it and see what the actual compression ratio is without firing it up or installing the rockers... I would not try to start it unless you trust the valve clearance cutouts to be big enough ??

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A wise man learns from his mistakes..
A genius learns from other peoples mistakes.

Quag,

would be good if you could have a look for a 1971 t120r barrel for me!!!!! Preferably 40 thou or under!

I dont ask for much,......if you get one let me know and ill start up your stand and let you choose what colour you want!!

I'll have a look at the swap meet in two weeks.

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Hey, What's this oil on the floor?

VB,

Did you end up checking the 98.5mm depth between bottom of crankcase flange and top face? What was it on your barrels? What about the stroke - did that come to 82mm?

Occam's Razor - All things being equal, the simplest solution is usually the right one. If the barrel is a known standard Triumph barrel, the stroke is 82mm, and the pistons are non standard (which they look to be), then it's got to be the pistons.

What you could do from here:

Measure the height of the piston crown above the barrel top face.
Measure the depth of the combustion hollow in the head.
Check if the two will theoretically fit together - include the head gasket in calculation
Put the valves in the head without springs (wrap some tape around the stems so they don't fall through), and fit the head (gingerly - making sure you can get full crank rotation)
With pistons at TDC, check how far the valve stems will move before hitting the pistons. If this is shorter than the normal throw of the rockers (depends on cam), then you need to replace your pistons.

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Per Ardua Ad Astra
(Through difficulties to the stars)