BMW R26 damaged cylinder head exhaust thread

Begonnen von Highland_Steve, 16 Dezember 2017, 15:49:08

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Highland_Steve

Hi everybody
I hope your all getting ready for Christmas.....
I would like to pick the brains of the forum members.
The thread on the cylinder head of my R26 is badly crushed and damaged.
I have seen lots of threads and information on the many fixing procedures but non of them state what the thread dimensions are.
Because my exhaust spigot is crushed Iam unable to get a thread diameter measurement.
Does anybody have the thread dimensions for the exhaust spigot?
Many thanks,
Steve

Highland_Steve


bwprice100

Hi Steve

My head is on the bench at the moment, I will measure it for you.

Brian

Sent by me using tapety talky


Kurt in S.A.

FYI...it's the same part number for the R24-R27.

Kurt
Kurt in S.A.

bwprice100

Steve, I've measured mine and it is M45x2.00 pitch.

Brian

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Highland_Steve

Hi Brian
Thats wonderful  :prost:
I'll get the new threaded collar machined tomorrow for fitting next week.
Are you doing a full re-build of the engine?
I have stripped mine down now and find the sealing face between the barrel and crankcase casting badly gouged.
Iam thinking of machining the face down by 0.5mm and adding an 0.5mm aluminium gasket from Ulis, do you have any experience with this issue?
Again thanks for a super quick response.
Steve

bwprice100

Zitat von: Highland_Steve am 16 Dezember 2017, 19:28:03
Hi Brian
Thats wonderful  :prost:
I'll get the new threaded collar machined tomorrow for fitting next week.
Are you doing a full re-build of the engine?
I have stripped mine down now and find the sealing face between the barrel and crankcase casting badly gouged.
Iam thinking of machining the face down by 0.5mm and adding an 0.5mm aluminium gasket from Ulis, do you have any experience with this issue?
Again thanks for a super quick response.
Steve

Hi Steve

The bottom part of the engine was fully rebuilt some time ago but a repair on the head failed (done by a previous mechanic).
https://photos.app.goo.gl/oOZhrhaAr6tu0dR83

I went for a refurbished head from Uli's and also a re-bore with a new piston.

I am currently rebuilding the gearbox on my R80TIC but plan to get Albert back on the road ready for the Spring. :)

With regard to the gouging on your bike, I have no experience of that but it sounds like a good solution. You could consider getting it TIG welded and then skim back to standard, perhaps.

Brian

Highland_Steve

Hi Brian,
Thanks for the reply.
My bike came with a new piston and rebored barrel so all good there.
I prefer your solution to the spacer shim it keeps the crankcase standard.
I'll get it welded and skim it back then get it vapour blasted.
I will hopefully do a better job of repairing the cylinder head by milling back to the thread root diameter and then build up with weld and thread milling to the dimensions you gave me.
Hopefully it won't distort the head as Iam having the valve seats re-machined and new valve guides as the originals are way off tolerance.
Steve

grahamjb

+1 to Brians suggestion of TIG welding the gouged area and then resurfacing.

TIG welding the damaged spark plug thread/hole shouldn't cause any head distortion

bwprice100

Zitat von: Highland_Steve am 17 Dezember 2017, 22:56:26

I will hopefully do a better job of repairing the cylinder head by milling back to the thread root diameter and then build up with weld and thread milling to the dimensions you gave me.


Although I am not an expert on this, welding the spigot seems to be the preferred method. I don't think there is enough meat in the head to press in a threaded boss like mine was.

Pederkr

Zitat von: Highland_Steve am 16 Dezember 2017, 19:28:03
Hi Brian
Thats wonderful  :prost:
I'll get the new threaded collar machined tomorrow for fitting next week.
Are you doing a full re-build of the engine?
I have stripped mine down now and find the sealing face between the barrel and crankcase casting badly gouged.
Iam thinking of machining the face down by 0.5mm and adding an 0.5mm aluminium gasket from Ulis, do you have any experience with this issue?
Again thanks for a super quick response.
Steve

I have made this modification, works very well.


cledrera

Du bist im Recht; nun sieh zu, wie du da wieder heraus kommst. (v. Chamisso)
Lieber Einzylinder als zwei Fallschirme (v. mir)

CowBoy

Probefahrt mit Helm, Stulpenhandschuhen - und Klompen  :respekt:

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