Head reread, part XVIII - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 29 (permalink) Old 05-26-2019, 04:16 PM Thread Starter
BMF
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Head reread, part XVIII

Hi folks,

Long story, had a few years trouble, head was leaking oil into the chamber, mixture lean. 1971 t120 motor.

Removed and reseated head with new head gasket and the proper large washer. Same story, sort of.


Redid it again over the winter real slow... checked head for straightness, etc etc... Had the seats machined flat where the large washes go...
Used new inner and outer head bolts as I found a little necking on one old one. Bolts were from TMS (recommended on this forum).

Torked head up, left for few days and torqued again, Ran it on a short ride for 15 minutes and torqued again. At this point most of the bolts had moved about 45 degrees from the very first torquing position (dab of white paint marking). Did tappets, etc.

I planned to retorque again after 250 miles.

But after I ran one tank of gas though (150 miles?) I heard a strange sound (like exhaust escaping) and so removed tank to inspect and retorque. I tried to loosen a quarter turn before torquing first bolt but realised there was no need as the bolts moved too easily.

I retorqued everything and found all bolts to be a little loose. The final position was now about 90 degrees for most of the bolts. I adjusted the tappets and found all to be tight, almost no clearance.

On top of that a close inspection shows that head gasket had blown and some gas was escaping from the side of the cylinder.





I'm starting to wonder if the head is not made of inferior material, or possibly was overheated and has weakened, I doubt it's the bolts as head has been problematic before.

I'm going to run after the retorque and see what happens. Either way I can probably not spend any more serious time on it until next winter so I've not got much choice but any ideas or advice greatly welcomed.

A bit depressed BMF....

Last edited by BMF; 05-26-2019 at 04:19 PM.
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post #2 of 29 (permalink) Old 05-26-2019, 04:46 PM
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Anneal gasket.
Torque and set valve gaps
Heat cycle
Torque and set valve gaps
100 miles torque and valve gaps
500 miles torque and valve gaps
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post #3 of 29 (permalink) Old 05-26-2019, 11:54 PM
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Using a copper head gasket?
Maybe in your case also spray the head gasket with coppercote?

tridentt150v,
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(Where women blow and men chunder).
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post #4 of 29 (permalink) Old 05-27-2019, 02:40 AM Thread Starter
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Hi Guys, its been a long story, I used the big gun merc sealant (similar to locktite 518 I think).

Gasket was old but annealed, I torqued the head (and adjusted tappets) a few times more than you suggest Dave.

Would the new bolts be stretching, even after the first three torques and a short runnning period (45 degrees more turn to get to torque).

Im stumped, what would you folks do next?
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post #5 of 29 (permalink) Old 05-27-2019, 02:58 AM
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Hi BMF, I'm very sorry, I didn't realize you reused the old head gasket.

I know some anneal & reuse, but I don't like to do that, especially if the old gasket had any signs of leakage at all. I'm very sorry I didn't make it perfectly clear to get new gasket. As I recall the old head gasket was leaking.

I know you flattened the head which was certainly needed.

I've never annealed a new gasket. Some do, but I never have & have never had a problem with new gaskets not annealing.

But at this point, nothing to loose in retorquing & another long road test. You might get lucky.

I know it's not wise to skim a head unless it's really needed, but dips & high spots in head sealing surface demand skimming. These defects cannot be cured by head straightening. Depending on how much skimming is needed, a thicker head gasket is required.
Don
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post #6 of 29 (permalink) Old 05-27-2019, 06:32 AM Thread Starter
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No worries Don. I only had 500 miles on the new then Morgo gasket, so did not think twice about using it again (I've got the Morgo kit on, came with the engine way back when )
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post #7 of 29 (permalink) Old 05-28-2019, 09:48 AM
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Are there any other changes from stock you havenít shared with us yet ?
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post #8 of 29 (permalink) Old 05-28-2019, 11:57 AM
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The leaks at the head/cylinder joint has been discussed many times on Brit Bike...On the OIF engines it can be oil leaking from the rocker boxes down the head stud and then onto the head gasket...Cylinder compression pushes the oil past the head gasket...A solution is to seal the washers with RTV or use "sealing washers"....
I have reused the head gasket on by 650 race bike at least 5 times, annealing it each time...It does not leak...

Second fastest Triumph..............land speed racing....dressed in animal skins clinging to oily vibrating machines propelled by fire..
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post #9 of 29 (permalink) Old 05-28-2019, 08:27 PM
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Many a head gasket seal failure is excessive thickness of push-rod tube seals, preventing full torque evenly applied across the head gasket.
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post #10 of 29 (permalink) Old 05-31-2019, 03:12 PM
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Quote:
Originally Posted by Freakmaster View Post
Many a head gasket seal failure is excessive thickness of push-rod tube seals, preventing full torque evenly applied across the head gasket.
Interesting observation, Freakmaster.

Said another way, insufficient 'crush'.

Bruce Miller (hermit47)
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www.hermit.cc/tmc
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