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How much dammage can a cylinder head take?


don_k

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I don't know how I missed this checking over my bike as I started repairs but while putting the fairing back on I noticed several cooling fins broken off of the left cylinder head. So I am wondering if this is critical or if I can wait a bit before fixing it.

 

I know nobody could offer an opinion without seeing it and rather than eat up bandwidth on this site with large images I posted them to my personal site. I warn you they are somewhat large images and are both on the same page (I was rushed and didn't even try to make them or the page pretty.

 

You can see them at:

http://www.dkramber.com/Motorcycling/Repairs2006.htm

 

Do I dare ride the bike at all like this or must I replace the head RFN? Any opinions?

 

P.S. For anyone following my repairs, the ABS fault is due to a missalignment of at least the front sensor. I haven't decided if I'm going to buy a set of shims and try aligning it myself or have a dealer look at it.

 

Thanks in advance for any and all help.

Don Kramber

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Wish I could help but I will not offer an opinion on something I don't know. I'm sure someone here will be able to answer it. But I did want to wish you good luck on this project as I've been watching your progress and looking for you out on the roads. Good luck! thumbsup.gif

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ShovelStrokeEd

Well, right in proximity to the exhaust port like that is probably the worst place to lose cooling fins but, the primary cooling for that area comes from internal oil passages cast into the head through which coolant, in this case, oil is pumped.

 

I would venture that you can ride around with no problems, perhaps keeping a weather eye on oil temps. You may also wish to limit sustained full throttle operation.

 

Not being privy to how much the engine depends on radiant cooling as a supplement to the circulating oil makes this pure speculation on my part but, taking into account that exhaust gas temperature stays pretty low when operation is confined to moderate throttle openings, so long as it isn't leaking, your probably OK.

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As long as it is just the cooling fins you shouldn't have any problems at all, there are enough left to cool the engine.

 

btw, you can put a link to those images here, the bandwidth still comes off your site where they are hosted.

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One other thing to consider is to retorque the head. After a blow that broke fins you may find the the head gasket might be more prone to leak oil.

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Echoing "Paul De", I'd be more concerned about damage deeper from a blow like that, than the missing fins. The fins themselves I would say is no big deal. But what damage did the head incur elsewhere is the question. Any sign of head gasket or exhaust leakage? Does the cylinder run all right? Checking the torque on the head would give some indication if anything else was damaged.

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I have to ask...What did you hit, or think you hit to knock them off?? And no colateral damage to the belly pan or others?

Inquiring minds.

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No_Twilight

I like Ed's carefully worded response. I'll add that aluminum is an awesome conductor of heat so the fins nearby would help a lot in dissipating the heat. You could clean the area will make heat transfer to the air better.

 

If it were mine I would ride on and never give it another thought.

 

---Jerry

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Ride with missing fins without worry. Boxer heads in worse shape than yours will go 100,000 miles without a problem (ever watch the Boxercup?).

 

Also, measure the clearance you need for your ABS sensors, order appropriate sizes from the dealer (or online) and install them yourself. It is a simple repair.

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Echoing "Paul De", I'd be more concerned about damage deeper from a blow like that, than the missing fins. The fins themselves I would say is no big deal. But what damage did the head incur elsewhere is the question. Any sign of head gasket or exhaust leakage? Does the cylinder run all right? Checking the torque on the head would give some indication if anything else was damaged.

 

Checking the torque....what torque?

 

There is no torque spec for the head fasteners.

 

Ride the bike without worry.....don't bother trying to "check" anything....there's nothing to check.

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Echoing "Paul De", I'd be more concerned about damage deeper from a blow like that, than the missing fins. The fins themselves I would say is no big deal. But what damage did the head incur elsewhere is the question. Any sign of head gasket or exhaust leakage? Does the cylinder run all right? Checking the torque on the head would give some indication if anything else was damaged.

 

Checking the torque....what torque?

 

There is no torque spec for the head fasteners.

 

Ride the bike without worry.....don't bother trying to "check" anything....there's nothing to check.

 

Huh? We're talking the German's here. They have torque specs on every nut and bolt on the bike. I wouldn't be surprised if the BMW guys have published specs for the torque on the battery terminal bolts.

 

Are you confusing the valve cover fasteners with the head bolts? There very definitely is a torque spec for the head bolts. There are 4 nuts that compress the head to the top of the cylinder and at the same time the cylinder base to the engine case through the stud bolts anchored in the engine case. I think I have ever seen specs for using a degree wheel for the final torque setting.

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Juan_in_a_million
[Checking the torque....what torque?

 

There is no torque spec for the head fasteners.

 

Loosen up the 4 nuts holding the cyl head, tighten them up a little at a time on a criss cross pattern. Then apply, also in a criss cross pattern 20 Nm of torque. After that, always criss cross, tight them up 90 degrees and, finally, another 90 degrees.

 

Cheers!

JP

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Joe Frickin' Friday
Loosen up the 4 nuts holding the cyl head, tighten them up a little at a time on a criss cross pattern. Then apply, also in a criss cross pattern 20 Nm of torque. After that, always criss cross, tight them up 90 degrees and, finally, another 90 degrees.

 

Actually when retorquing them (as, for example, at 600 miles after replacing a head gasket), the book says to loosen-then-tighten each nut one at a time, leaving the other three at full-tight.

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Loosen up the 4 nuts holding the cyl head, tighten them up a little at a time on a criss cross pattern. Then apply, also in a criss cross pattern 20 Nm of torque. After that, always criss cross, tight them up 90 degrees and, finally, another 90 degrees.

 

Actually when retorquing them (as, for example, at 600 miles after replacing a head gasket), the book says to loosen-then-tighten each nut one at a time, leaving the other three at full-tight.

 

Correctomundo...and, no need to replace the head gasket....the original will take several re-tightenings.

 

 

Quit worrying about your cylinder head fins and torque....go ride!

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ShovelStrokeEd

Oh my, here we go again.

 

The cylinder head fastners do, in fact, have a torque specification. It is different from conventional fastners in that the nuts are torqued first to 20 lb/ft and then rotated 180 degrees which is the modern way to do things on critical fastners. This way a uniform stretch is acheived on the mounting studs.

 

Specs are available in any BMW servic manual.

 

I see no need, in this case, to retorque the heads and wouldn't bother unless there was evidence of a leak.

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Echoing "Paul De", I'd be more concerned about damage deeper from a blow like that, than the missing fins. The fins themselves I would say is no big deal. But what damage did the head incur elsewhere is the question. Any sign of head gasket or exhaust leakage? Does the cylinder run all right? Checking the torque on the head would give some indication if anything else was damaged.

 

Checking the torque....what torque?

 

There is no torque spec for the head fasteners.

 

Ride the bike without worry.....don't bother trying to "check" anything....there's nothing to check.

 

Huh? We're talking the German's here. They have torque specs on every nut and bolt on the bike. I wouldn't be surprised if the BMW guys have published specs for the torque on the battery terminal bolts.

 

Are you confusing the valve cover fasteners with the head bolts? There very definitely is a torque spec for the head bolts. There are 4 nuts that compress the head to the top of the cylinder and at the same time the cylinder base to the engine case through the stud bolts anchored in the engine case. I think I have ever seen specs for using a degree wheel for the final torque setting.

\\

 

Could you please provide those torque values for the boxer head nuts?

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Juan_in_a_million
Could you please provide those torque values for the boxer head nuts?

 

The values mentioned above are for the boxer (259) engine 4 cyl head nuts: 20Nm first setting, 90 degrees rotation the second setting and 90 degrees rotation the final setting.

Then, I believe, there is a 10mm bolt and, I'm not sure, 1 or two 6 mm bolts. After you're done with the nuts, you tighten the 10mm bolt to 40Nm and then the 6mm bolt/s to 10 Nm.

This is what I recall.

cheers!

Juan Antonio

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Juan_in_a_million
The values mentioned above are for the boxer (259) engine 4 cyl head nuts

 

I mean for the boxer (259) cylinder head nuts, which are 4 of them.

dopeslap.gif

Cheers!

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