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I just took the head off my 1971 T120R. The last time I rode it I got about 4 blocks away from home when it just cut out on me. So tonight i took the head off the engine and i found a lot of carbon build up, what looked like a blowout from the head gasket. I am wondering what i should be doing next with what i saw. Just wondering how bad this is. I can post more pics if needed.
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Hi Brad,

Welcome to the Forum. :)

I've moved your thread to the main Classic, Vintage & Veteran forum, where more people will read it ("Vintage Technical Tips & Tricks" where you posted originally is for posting 'em, not asking for 'em).

Regards,
 

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My T120r looks similar to that each time i have the head off. Looks like you do have a little oil burning and a bit rich mixture as the exhaust valves are usually a bit brown in colour. Hard to see why you have taken the head off just because the engine cut out. Not often a cylinder head problem causing a bike to suddenly stop running.
 

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Hi BradM, I've had some experience with blown head gaskets on Triumphs. Yours might be seeping or not even that. It doesn't look blown. Blown will generally show a decided burnt line where combustion gas is blown through. In most cases, bike will still run, but poorly depending on how bad & where gasket is blown.

It is unlikely head gasket caused bike to die. Regarding the oil crust/carbon on pistons I've seen this amount many times & bike still works decently or perfectly. How was bike running prior to the dying occasion, meaning in the past several rides? How much oil is motor burning. If it's not smoking bad, burning oil, & was running good, I would not address carbon on pistons at this time. We'll discuss this later after we get more info.

Did you test compression. Cold motor the compression is often low, especially low after repeated kicking. Even 80#. Slightly blown head gasket might be hard to diagnose.

What other diagnostic work did you do before teardown? Check for fuel to carbs by pressing ticklers? Check for spark?

What made you decide to take head off?

Could you have ran out of gas or go on reserve?

Most sudden shutting off is lack of spark. Next is fuel not getting to carbs. I've ran out of fuel a few times on Triumphs. It's like you turned off key. Same with going to reserve. Motor stops very suddenly. You'd think it'd lack power & stutter for a few moments, but I've not felt that. Just dies.

At this point I'd check for spark as you can kick motor over with head off. Be sure to squirt some oil around sides of pistons first. Slowly move pistons & wipe any loose carbon etc from cly walls. The oil will lift carbon from edge of piston/rings & deposit on walls. Also be sure to oil cly walls well before installing head. Dry rings will lower compression & make hard to start after assembly.

What ignition are you using? Points, Boyer etc? What is you battery voltage right now with key off?

We'll have to do the best we can on diagnosis with head off.
Don
 
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