My 1959 R69 has a LK cylinder on one side and a pre-LK "butterhead" on the other? Does it affect the performance of the bike or would you just ride it as is?
It does require that you use long reach spark plugs on one side and short reach plugs on the other which is kind of annoying.
I guess back in the days they would just replace the bad cylinder instead of replacing both
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Last edited by Starklint on Sat Dec 19, 2020 3:04 pm, edited 1 time in total.
Welcome to the forum! Pretty bike! The bike will run just fine as is...you will have different spark plugs though for the LK side...should be 3/4" reach whereas the other head is only 1/2" reach. So, don't switch the plugs!
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
Welcome to the forum! Pretty bike! The bike will run just fine as is...you will have different spark plugs though for the LK side...should be 3/4" reach whereas the other head is only 1/2" reach. So, don't switch the plugs!
Thanks Schrader. I have been reading in here (and on the old forum) for quite some years but thought it was now time to join. It's really nice to have such knowledgeable people around in a forum like this.
Yeah, that is the thing. Different reach on the spark plugs. It kind of bothers me, but well. It rides wonderful anyways
If I was to change the cylinder heads one day would you then opt for pre-LK (the correct one for the bike) or LK? And are the pre-LK even possible to find?
I would just keep my eyes open for a matching cylinder head. Then I would buy either type to make a set.
Just leave the sourced head on the shelf till your engine needs to be overhauled.
Then just ride and enjoy what you have knowing you have a long term solution when the time comes.
I would just keep my eyes open for a matching cylinder head. Then I would buy either type to make a set.
Just leave the sourced head on the shelf till your engine needs to be overhauled.
Then just ride and enjoy what you have knowing you have a long term solution when the time comes.
I like your approach Mal! I think that is what I'll do!
I would put an LK at the top of the list. BMW changed them for a reason...and to be honest if the other non-LK head is original to the bike, it technically is not a "butterhead". Butterheads was coined by Duane Ausherman I believe to describe the situation in the mid 60s when the aluminum processing resulted in a softer material than spec'd. The result was the pads for the towers of the rocker arms IIRC began to sink into the head. So in 1959, that wasn't an issue. Still, I'd prefer the LK just because...
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.
I would put an LK at the top of the list. BMW changed them for a reason...and to be honest if the other non-LK head is original to the bike, it technically is not a "butterhead". Butterheads was coined by Duane Ausherman I believe to describe the situation in the mid 60s when the aluminum processing resulted in a softer material than spec'd. The result was the pads for the towers of the rocker arms IIRC began to sink into the head. So in 1959, that wasn't an issue. Still, I'd prefer the LK just because...
I hear a lot of the older crowd about LK's but this is the reality: they are EXTREMELY hard to find. They only made them for 1 year. I've actually never really even found one for sale, and I was looking for years.
The heads are less about the so called issues they had and more about the person or shop doing the work to them. Find a solid head for not much money and invest in someone who can make it right. Hen's teeth and unicorns are nice stories.
I violated my own ideas and just bought new heads and then had problems. That doesn't work either, and the head is only as good as the person checking it for every possible dimension and tolerance they can find.
BMW should have made available the LK design heads much earlier than when they started to use them. They are an excellent design change and help the engine run more efficiently. The design of the R50/60 LK head the revised stanchion design is superior to the 1/2" reach plug type.
If you're that satisfied with how the machine performs, then searching for a matching LK head might not be in your plans. If having cylinder heads that don't match does bother you, it is worth the search for a matching LK head. Interesting that your machine has an LK head. It was obviously installed at least ~10 years after the motorcycle left the factory.
I've found there tends to be more LK heads available here in the States than elsewhere. Myself and several others have been stashing them for our own builds for years now. I sometimes will trade an LK head(s) for parts, yet rarely will sell one. Here in the States, I also find that there are more left heads available than right. Maybe that is from getting hit by vehicles on the right and from going off road to the rider's right. From discussing this topic with several BMW builders, where they ride/drive on the left, it seems like they have plenty of right heads and lack a source of right heads.
Describing just a certain year batch of 55-69 heads as possibly having inferior castings is misleading. I generally have several hundred BMW cylinder heads from 51-69. It is not uncommon to find a head casting from any year in that range that is burnt toast. The castings get destroyed from moisture, trashed oil, carbon, salt, etc.... I have examples from that year range where their combustion chambers have the 'brain rot' damage and recessed stanchions.
Checking dimensions and tolerances is just part of the task of 'managing' the cylinder heads. Having the proper equipment, using the equipment properly and quality parts is also important. The availability of parts today for the BMW pre-70 machines is amazing. Some of it is high quality. Yet, some of it is junk and just should not be sold.
I guess I was really lucky in finding LK heads for my R60/2. The right side came from Texas many years ago and about two years later I found the left side from Hucky's in Florida. I paid $50 for the first one and $300 for the second. They sat in my garage for a few years and five years ago I sent them to Dan Neiner (Cycle Works) for rebuild. I could never have been happier with the results. Yes, the LK heads were far superior in performance than the short reach heads.
