Hi you all,

I'm wondering if any of you done port flowing and head flattening.

I could try to find a couple of busted cylinder heads and cut them in half to get an idea of the "flesh" between the ports and water but if anyone has done this before I can spare myself the trouble.
Also if any of you played with flattening the head, it would be nice to hear the ideal compression ratio increase.

I'm rebuilding my K100 with K1100 TB's, still have to adjust the AFS (Bike is in pieces right now…), K&N box filter, semi open exhaust and standard injectors (also have the K1100 injectors) and the ignition advancement of course.

Planning to attend Belgian classic TT races so I want to keep the tech as close to the early 80's as possible.

Any input is welcome!

P.s.: Read that some AFS's don't like the oil coming from aftermarket filters, anyone experience with this using the L-jet AFS?

I'll be following this post, as I'm interested to know more about this. I've considered decking the head of my '85rt as I have access to a machining shop, but when I ran it up the flagpole (in another forum) I was warned of timing chain issues, why-would-you-bother, etc. 

Seems there's room for it, though, and we all know the K100 engines are massively overbuilt.

marti
I got some pics of a cross section of an 8 valve head from the mini minor - bmw head conversion site
heres a sample  although I don't have the link to the site anymore





just wonder about going higher in compression , as that usually means that you need to run a higher octane fuel all the time unless you like the sound of pinging occurring ....which is not good ...having said that the k75 runs a higher compression (near 11 to 1 ) and their pistons is where the difference lies .....get 4 x  k75 pistons ?


depending on the year of manufacture (the early models are the best) you will find a lot of irregularities in the ports and flow curves on the short radius turns especially (where I have found some with nearly 80 degree direction changes with near sharp point on the radius )

the later ones looked to be honed through the valve seat to achieve minimum port sizing  with little regard to smooth curves
I have done a fair bit of reshaping on my test head

it will be going on soon

you can see some of those pics in my restoration thread  starts about page 12 I guess  https://www.k100-forum.com/t1833p550-85-rt-resto-my-attempt-hey-im-not-into-making-a-show-bike

would be good to see someone elses attempts at this

Hi Martiman.
Ever considered 'degreeing in' the camshafts?
Remember reading an article about it many years ago on tuning a Z1 Kawasaki.
Seems that you could alter the dwell angle(?) between the cams to increase power. Can't remember the details but I believe it was thought that the manufacturing tolerances on the valve timing made a difference between a bog  standard engine and the 'special' ones that would pop up now and again.
Think some off the manufacturers were accused of breathing on their launch models using this method at the time.
Was it DOHC Manx Nortons that had a vernier system using a system of pins on their cam drives to tweak the valve timing?
Might be worth the research.

a contributor did the camshaft degree measurements before cj  ..thinking he would be able to do the same ....he gave up after seeing the cam durations that we have ...(lots of over lap )

but there might be some advantage in vernering in the inlet camshaft  a little

Suppose 90bhp per litre output is pretty respectable for a relatively low revving engine.
Thinking about it, my K16 has a similar bhp/litre and rev ceiling to the 16v K100 engine. The cylinder head design is supposed to be very similar.
Might be worth degreeing in to the original timing figures. Something like blueprinting the engine, I suppose?
Interesting thread. Please keep us posted on your progress.
Makes a nice change from fuel pumps and spline lubes.

San Jose BMW/CC Products in Calithumpia had a ported and flowed 'bare' K100 8V head available on eBay a coupla several months ago (maybe a year now) which no one bought. It was only in the mid-US$200 range. Perhaps they still have it.

I considered it along with the K75 pistons (available from Motobins UK for cheap dollars) for a mild HP boost along with my K11 TB upgrade of several years ago. Then I went overseas and got stuck into another project which I'm hoping will produce a similar result; more power in the midrange and upper end but with no loss down below. Displacement & especially weight savings ought to produce what I seek.

charlie99 wrote:marti
I got some pics of a cross section of an 8 valve head from the mini minor - bmw head conversion site
heres a sample  although I don't have the link to the site anymore





just wonder about going higher in compression , as that usually means that you need to run a higher octane fuel all the time unless you like the sound of pinging occurring ....which is not good ...having said that the k75 runs a higher compression (near 11 to 1 ) and their pistons is where the difference lies .....get 4 x  k75 pistons ?


depending on the year of manufacture (the early models are the best) you will find a lot of irregularities in the ports and flow curves on the short radius turns especially (where I have found some with nearly 80 degree direction changes with near sharp point on the radius )

the later ones looked to be honed through the valve seat to achieve minimum port sizing  with little regard to smooth curves
I have done a fair bit of reshaping on my test head

it will be going on soon

you can see some of those pics in my restoration thread  starts about page 12 I guess  https://www.k100-forum.com/t1833p550-85-rt-resto-my-attempt-hey-im-not-into-making-a-show-bike

would be good to see someone elses attempts at this

Wow! Thnx Charlie! 

Very interesting post, sure can do a lot with that already!
Indeed the diameter of the rubber mounts that hold the TB's were one of my first worries too.
Going to shop for some grinding tools today!    

Grtz Martijn 
(Martyn in old English)

Comberjohn wrote:Hi Martiman.
Ever considered 'degreeing in' the camshafts?
Remember reading an article about it many years ago on tuning a Z1 Kawasaki.
Seems that you could alter the dwell angle(?) between the cams to increase power. Can't remember the details but I believe it was thought that the manufacturing tolerances on the valve timing made a difference between a bog  standard engine and the 'special' ones that would pop up now and again.
Think some off the manufacturers were accused of breathing on their launch models using this method at the time.
Was it DOHC Manx Nortons that had a vernier system using a system of pins on their cam drives to tweak the valve timing?
Might be worth the research.

Hi Comberjohn,

I work at a sheet metal factory as a PLC / electrotechnical engineer where we have a conventional lathe and milling machine, which I also grew up with at home, so I have the biggest "hobby shed" I could ever wish for. Therefore I'm able to do mostly everything by myself, keeping the expenses low… Think degreeing the camshafts is a little bit out of my league lol    
But if I win the jackpot I'll keep it in mind!
Vernier system sounds interesting though, you got me curious!

Two Wheels Better wrote:San Jose BMW/CC Products in Calithumpia had a ported and flowed 'bare' K100 8V head available on eBay a coupla several months ago (maybe a year now) which no one bought. It was only in the mid-US$200 range. Perhaps they still have it.

I considered it along with the K75 pistons (available from Motobins UK for cheap dollars) for a mild HP boost along with my K11 TB upgrade of several years ago. Then I went overseas and got stuck into another project which I'm hoping will produce a similar result; more power in the midrange and upper end but with no loss down below. Displacement & especially weight savings ought to produce what I seek.

I was also thinking of shrinking the combustion chamber to get more compression.
Changing the K100 pistons to the 75'ers is an idea but I would make sure the weight is the same, you might end up in rebalancing your crankshaft or killing your crankshaft seats with everything else to follow…
Don't know if this is a "proven to work" mod of course  

should be ok ....just the pistons will be a little closer to the valves every time they go round ,,,these are definatly an interference motor.

maybe new springs (if it is an early motor) might be an wise thing   .. all springs tend to sag over time and use .

charlie99 wrote:should be ok ....just the pistons will be a little closer to the valves every time they go round ,,,these are definatly an interference motor.

maybe new springs (if it is an early motor) might be an wise thing   .. all springs tend to sag over time and use .

Correct me if I'm wrong but I think there is more piston around the sides of the valve but I sure hope they don't get closer  
Still have to check the spring length and tension but keeping in mind that she hasn't even ran 30.000 km's I'm not that worried 

Just found a German forum where someone put the K75 pistons in a 2V K100.
The piston weight increased from 266 to 268 grams. (less than 1%) 
Don't know if that's worth considering recalibrating your camshaft or take 2 gram out of the piston…

Felt like more power in the lower revs and engine sounded "rawer" in a good manner of speaking.
But overall not that much improvement after the dynotest as he hoped for… 
Sadly the link to the actual test graph is expired.

He had 87.5 BHP and 90 Nm so that's an increase of 4.2 Nm over the BMW specs so let's assume he lost 2.5 BHP because of age, the Nm increase could be a bit more. 

If someone dares themselves to try and read a German forum, here's the link   
Sure you also can have a good laugh with google translate…

http://archiv.flyingbrick.de/viewtopic.php?f=2&t=3314029

Overall if you'd have to take the block apart to install fresh bought K75 pistons I wouldn't spend the effort and money for the gain but if you have it apart anyway… 

Perhaps if I can find very cheap new ones. 
Don't like putting older, more deteriorated things in my K100 when she only has 30K on it. 
Doesn't feel right…

true ....but consider that those springs have been under tension for in excess of 25 years 

yes measure the lengths to start with ....compression measurement could be a complicated affair with mods planned ...I would prefer to discount any of those issues for the reasonable price of replacement .

K75 crankshaft 120 degree no vibes
K100 crankshaft 180 degree. Vibes. Piston weight and deviation to be watched or adjusted. 
It a good thread.

Olaf; even a 90-degree V-twin (Guzzi) benefits from balancing. I could never afford to dynamically balance the rotating mass but I always statically balanced it to around one gram. I know...

Charlie; I think it was you who commented on the port exit angles as being inconsistent. I had a K100LT in yesterday for an engine check and found that no.1 spark plug was way off centre. Couldn't get a standard plug socket on there at all and had to use a thin-wall box spanner in the end.

wow ...haven't seen that before dai

Dai

I was only suggesting getting piston weights equal, possibly same with con rod assembly for perfection. Any more not really worth expense or effort.

The K75 also has the benefit of a balance shaft. I believe BMW had to fit one as the engine harmonics caused it to self destruct after some bench testing.
Agree with Martyn. Not sure if the small gain would be worth the cost and potential problems that it could bring.
Motorcycle Sport(?) ran an article some years ago, when they still wrote articles for grown ups, about a privateer team who ran a K100 in endurance racing.
They had some modest success. Even went as far as using a frame to raise the engine for better ground clearance.
They said that their biggest problem in tuning the engine was that BMW wouldn't allow them access to information on the fuel injection mapping and settings. They had some modest gains in power but nothing like what they needed.
That would seem to indicate that the hard, shiny bits are pretty well designed to start with and may not allow much room for improvement.
Seem to remember that they did, eventually, get access to the info. But by that time things had moved on.
Wonder whose shed that endurance K100 sits in now? 
To put things into perspective, the first Z1 900 Kawasaki put out 82bhp and everyone was gob smacked. Even when they produced the Z1000(1015cc) with fuel injection it was still only 96bhp.
Enter the boring K100 which only put out a measly 90bhp and was designed for those equally boring BMW touring types. Still a well kept secret today.
Maybe lightening your brick is the way to go, Martyn. What do the regs allow?
I'm sure others on the forum found the same as me when they removed the fairing. You can really throw it about without as much weight.
Removing as much metal as possible, smaller battery, spoked alloy rims!

Remember Godier and Genoud and the Bol d'Or on the Kawasaki?

Sometimes its much more about how much of the power you can put on the road. Endurance, power delivery, range, long distance reliabilty and comfort.