Head Retorquing

[jackonz]

OK so since rebuilding the top ends on my R80/7 well over a year ago i have not ridden the bike much due to health issues, it's time to get it out again but need advise.

Having re fitted the heads and barrels with all new seals and gaskets do the heads need re tensioning on these airheads, I have read here that the studs can be pulled from the crankcase and I don't want to do that thank you, gaskets are not oem but came from Boxerworks in the UK.

[Kurt in S.A.]

It might be worth a check if it's been a while. So how many miles since the work was done? You're supposed to recheck the torque at certain mileage points after a top end or reseal.

I'd back off on the torque to be applied...only go to 26 ft-lb. Probably not an accepted practice, but I try and apply the 26 ft-lb for each nut...if it doesn't move, then I call it good. Technically, you're supposed to loosen the nut about 1/4 turn and then reapply the torque. I don't do that!!

Kurt

[Rob Frankham]

According to BMW, the head nuts should be loosened and re-tensioned at each full service. Have to confess I don't do it every time but fairly regularly.

There is certainly a lot of anecdotal evidence that cylinder stud threads can pull out. Not sure why this is... the threads are well within spec for the stated torque setting and load... but undoubtedly, it happens. The obvious conclusion is that they may have been overtorqued. Unfortunately, that could have happened sometime back in the past leading to a weakening of the thread and eventual failure, not necessarily at the time the failure occured. Some pundits recommend undertorquing the nuts and seem to get away with it. For my part I've always stuck to the factory settings and never had a problem.

To get back to your question... if the torques haven't been checked since the work was done, it should be done after about 500 miles... I don't think it really makes any difference if the bike has been standing for a year. After that, I would recommend that they are checked at the next service and then as often as you feel is wise.

Rob

[r67boxer]

According to BMW, the head nuts should be loosened and re-tensioned at each full service. Have to confess I don't do it every time but fairly regularly.

There is certainly a lot of anecdotal evidence that cylinder stud threads can pull out. Not sure why this is... the threads are well within spec for the stated torque setting and load... but undoubtedly, it happens. The obvious conclusion is that they may have been overtorqued. Unfortunately, that could have happened sometime back in the past leading to a weakening of the thread and eventual failure, not necessarily at the time the failure occured. Some pundits recommend undertorquing the nuts and seem to get away with it. For my part I've always stuck to the factory settings and never had a problem.

To get back to your question... if the torques haven't been checked since the work was done, it should be done after about 500 miles... I don't think it really makes any difference if the bike has been standing for a year. After that, I would recommend that they are checked at the next service and then as often as you feel is wise.

Rob

Great discussion. I might add that all of this is dependant on whether the torque wrench is calibrated correctly.

Kevin

[jackonz]

Thank you gentlemen for your expert advise. have done less than 120 miles on it since the rebuild so I will do a bit more before re tensioning the heads and adjusting the valve clearances.
As for my torque wrench it's spot on as we have calibration equipment at the Polytechnic where I work.

Would have been nice to be out on it today now we are in summertime but i was in work, from wednesday 7 days of rain

[Zombie Master]

I think a lot of stud pulling out problems is because folks don't understand that you have to loosen the nut you are check before re-torquing. They just eventually pull out.

[barryh]

I've only ever re-torqued the head once in 18 years and that was when I'd slackened them off to do the rocker arm clearance. They were checked again after 500 miles then left well alone. You hear stories of some engines having the studs pulled during manufacture at the factory and therefore supplied already Heli coiled from new which suggests a potential weakness.