My BMW tech friend, the guy who worked in Research prototyping the original K100 and K75 has a fertile mind. Some years ago he did some hard thinking on the limits of the K1100 and decided to try placing a two valve K100 head with 284 degree cams and Bosch L Jetronic on a K1100 block. This is not a simple or straightforward swap, so don't try this at home kids. The result was about a 15 horse [i]increase[/i] in power, a great reduction in heat and the elimination of some heat related Nikasil failures near the top of the bore on the exhaust valve side that are more common to K1100s than most owners of them realize. I just threw away a low mile K1100 engine I was intending to use in my own Frankenbike project for this exact reason (I have one more used K1100 engine left). Those engines run far too hot. Replacing the stock head with an old K100 two valve head with all that extra coolant, and replacing the stock 2 row radiator with a 3 row radiator from an eary K100 yields a very long lived motor, and a nice increase in output.

He had always wanted to see how a K1200 engine responded to L Jet but there isn't enough room to stack up the L-Jet plenum on the K12 throttle bodies in K100 frame. L Jet doesn't work at all on the stock K1200 chassis. Well, he found a way (yes, my lips are sealed) and the result is epic. This engine is mounted in a K100 frame with a K1100LT driveline and Paralever. It also uses a very early conventional GSX/R 1000 fork, triple clamps, front wheel and brakes.

If anyone ever says BMW K bikes are slow and boring, they need to ride this bike. Acceleration is explosive, as in Holy Sh1t! explosive, especially since this thing is a naked roadster and is a good 45 kg lighter than a K1200RS. The only criticism I have is it will buzz your fingernails off. There is a reason BMW put the 1200 cc iteration of the Flying Brick in a rubber mounted frame. Short conrods with a long stroke make for a buzzy powerplant. I wouldn't put it in a touring bike, it's too crude, but for a Sunday canyon scratcher, this thing with his chassis set up and the right set of new tires would humiliate a lot of supposedly superior sport bikes. My friend knows how to tune L-Jet to give a result superior to Motronic and this thing is an effin howler! And it looks so boring and innocent, heh, heh, heh.

are ya gunna let us see ? , photo's please

JR

Melbourne Australia

Don't have any photos unfortunately. He doesn't like people taking photos inside his shop. I hope in a week or two to be able to get it out for an extended test ride in some local hills. I only took it for a brief test run around some freeways and access roads in the Port of Long Beach, but the way that thing rocketed up the Gerald Desmond Bridge was astounding.
Besides, the interesting parts are well hidden from view. From the outside all you can see is an old naked K100 in a darker than stock metallic blue with 1984/85 seat base and battery covers, a K1100 drive line and footpegs, and a four valve engine. What four valve engine is tough to tell from the exterior. The beauty of the thing is that there is precious little on the outside that gives the game away. The bike is only interesting from the saddle when you crack the throttle.

If localised overheating is a worry then run with the lowest amount of anti-freeze that you dare year round or none at all if it doesn't freeze in your location, but either way add WaterWetter from Redline to help reduce micro-boiling around hot spots. http://www.redlineoil.com/product.aspx?pid=74&pcid=10

Given the combined oil/water pump it is probably worthwhile to give it a clean out first with the cooling system de-oiler from Mercedes Benz, it is quite reasonably priced and was designed to safely clean out the cooling system from all oil traces
Regards,
K-BIKE

This is really interesting.

Please share more as you can.

K-bike, the heat problem is due to lack of coolant in the head and cooling system and lean tuning. The problem can be overcome in part by using an early K100 three row radiator and the higher volume early K100/K75 coolant pump. With the sixteen valve bikes, BMW changed the coolant pump to pump less volume. 1990 and later K75s received this coolant pump too (along with a lighter piston and conrod combo). The limited amount of coolant in the head is inherent in the design however. Two valve heads have much more coolant in them and none of the heat related problems that show up in the sixteen valve bikes.
Richening the mixture helps too, and this is why my friend likes to use L-Jetronic instead of Motronic. BMW was using lean mixtures and high temps to achieve good mileage out of a porky bike while meeting emissions requirements. There are some mechanical adjustments in L-Jet than make it highly tunable, and being an analog system responds very much like a good CV carb with none of the gritty throttle response common to Alpha-N systems like Motronic. Sporty use of a performance tuned L-Jet bike can drop fuel mileages into the low 30s. Chose your poison. For me gas is cheaper than Nikasil.

With low coolant volume it becomes even more imperative to de-oil the cooling system and then treat with citric acid and finally after much flushing to re-fill with with the lowest concentration anti-freeze you can get away with plus WaterWetter in the mix. Liquid Tide for front loading washing machines (low foam) has been successful with many of my friend's engines at de-oiling them by running for an hour or so with the detergent mix followed by 3 good flushes and a citric acid solution run for an hour or so and then another 3 good flushes. Then refill with the coolant mix one has chosen.

That ensures that the liquid coolant gets to the metal and not an oil barrier or a deposited mineral barrier and that heat transfer is as good as it can be because water plus anti-freeze is not as good a heat transfer medium as water alone, if you are in a year round warm climate or the bike is kept indoors above freezing then pure water with corrosion inhibitors is best.

The WaterWetter apart from containing corrosion inhibitors helps reduce micro boiling which when it occurs forms an insulating layer between the metal wall and the heat transfer medium leading to localised overheating and kettling. When taken to the extreme that results in overheating and pre-ignition plus failure of the cylinder lining all not good. Many drag racers find using WaterWetter enables them to up the compression ratio without suffering detonation, whilst we are not upping the compression ratio getting all the heat out of the engine that we can is a good thing whilst of course maintaining an optimum running temperature via the thermostat.
Regards,
K-BIKE

[quote="K-BIKE"]With low coolant volume it becomes even more imperative to de-oil the cooling system and then treat with citric acid and finally after much flushing to re-fill with with the lowest concentration anti-freeze you can get away with plus WaterWetter in the mix. Liquid Tide for front loading washing machines (low foam) has been successful with many of my friend's engines at de-oiling them by running for an hour or so with the detergent mix followed by 3 good flushes and a citric acid solution run for an hour or so and then another 3 good flushes. Then refill with the coolant mix one has chosen.

That ensures that the liquid coolant gets to the metal and not an oil barrier or a deposited mineral barrier and that heat transfer is as good as it can be because water plus anti-freeze is not as good a heat transfer medium as water alone, if you are in a year round warm climate or the bike is kept indoors above freezing then pure water with corrosion inhibitors is best.

The WaterWetter apart from containing corrosion inhibitors helps reduce micro boiling which when it occurs forms an insulating layer between the metal wall and the heat transfer medium leading to localised overheating and kettling. When taken to the extreme that results in overheating and pre-ignition plus failure of the cylinder lining all not good. Many drag racers find using WaterWetter enables them to up the compression ratio without suffering detonation, whilst we are not upping the compression ratio getting all the heat out of the engine that we can is a good thing whilst of course maintaining an optimum running temperature via the thermostat.
Regards,
K-BIKE[/quote]

The only reason anyone uses a product like Water Wetter is because racing organizations ban coolant/antifreeze. If coolant/antifreeze gets on the track it is dangerously slippery and shuts the track down until it is cleaned up, just like an oil spiil. Racing organizations require plain water but some allow use of a product like WaterWetter. Using the proper coolant/antifreeze accomplishes the same thing.

The problem with the K1100 and K1200 is lack of coolant in the cylinder head, a small capacity radiator and lower volume coolant pump. BMW was seeking very high combustion chamber temperatures combined with lean mixtures to improve fuel mileage. It worked as expected, but an unexpected problem is heat damage to the cylinder bore on the exhaust valve side. Water wetter won't solve this problem.

Interesting discussion Guys. What is the effect of a Nikasil heat related failure as described and does the K100 16 valve suffer the same? I have not seen this described an issue (that's not to say it ain't one!). Is it actually rare and induced by sustained, really hard use? There are a fair number of K1100 and K100 16 valves out there with pretty big mileages and original engines?

Thanks
Dave

You have to just chuck out the block as the nikasil goes direct to the aluminium, probably just better to get a good used engine.

I have seen a few bores destroyed because of running low grade fuel and getting detonation which is deadly to the nikasil which is probably why the heat affects the bore.
I would say it is rare but well known problem and probably would not come about in a well maintained machine that is used for touring and commuting as are most Ks.

yep agree rick ....good fuel is a bonus to long life the higher the "ron" the better i recon

better than those cheepo mixes with little power and lots of preignition

the 16 valve models seem to have less realestate for the cooling fluids in the right areas i guess (as detailed before )

do the 16 valves run slightly higher compression as well ?

If the owner cleans out the cooling system then the owner has done everything that an ordinary rider can do without making significant physical changes to the head or coolant pump.

The bottom line is if you have one of these bikes with low coolant volume in the head you either do nothing and hope it goes OK or you check carefully to ensure the mixture is right and try to dissipate as much heat as you can by having a clean cooling system and WaterWetter inside with as little antifreeze as you can get away with. Last choice is to change the head and or increase the speed of circulation of the pump.

The issue about slipperiness of antifreeze is a totally separate issue, what is under consideration is keeping a given engine with a low water content head as cool as possible under the same external circumstances. If the engine has an oil layer and a layer of deposited salts from hard water that will compromise the ability of the heat transfer medium to do its job of getting the heat away from the engine and into the radiator and then the radiator shedding it to the air. It will also increase the risk of boiling taking place under load with consequent risk of failure.

When we add to that the problem that for antifreeze mixtures with water the ability of the antifreeze mixture to carry away the heat from the engine gets worse as the antifreeze percentage goes up and that water without antifreeze is better at transferring heat we have a delicate balance to achieve.

WaterWetter is not a replacement for anti-freeze it is both a micro-boiling suppressant and a corrosion suppressant. Anti freeze also contains corrosion suppressant because without it the cooling system would suffer corrosion, if you do not use antifreeze then one needs to use a corrosion suppressant.

Antifreeze mixtures exhibit the characteristic of elevation of boiling point and depression of freezing point as the percentage of antifreeze goes up.

The specific heat capacity of ethylene glycol based water solutions are less than the specific heat capacity of clean water. For a heat transfer system with ethylene glycol to achieve the same specific heat capacity the circulated volume must be increased compared to a system with clean water.

In designing a cooling system if a 50% antifreeze water solution is used with external operational temperatures above freezing the specific heat capacity is decreased by approximately 20%, the reduced heat capacity must be compensated for by circulating more fluid if you cannot change the coolant volume.

So in a nutshell those of us with 4 valve heads should keep the system clean, use the least amount of antifreeze which gives a safety margin against freezing and I believe adding WaterWetter is beneficial. It all comes down to as an owner "you pays your money and you takes your choices" as they say in the North of England.
Regards,
K-BIKE

charlie99 wrote:yep agree rick ....good fuel is a bonus to long life the higher the "ron" the better i recon

better than those cheepo mixes with little power and lots of preignition

the 16 valve models seem to have less realestate for the cooling fluids in the right areas i guess (as detailed before )

do the 16 valves run slightly higher compression as well ?

Yeah 11.0 - 1 as against 10.2 - 1 for the K100. The K75 is 11.0 - 1.
The extra heat build up is far more likely to cause detonation which will make the nicasil fail even quicker.

K-Bike recites Red Line marketing, always suspect.

The cooling problem is between the exhaust valve where there is no coolant in the head. The problem is due to the combination of insufficient cooling, lean mixture, aggressive spark advance and a deliberate choice by BMW to run a very high combustion chamber temperature to maximize fuel mileage and minimize emissions. The solution lies in either using a two valve head from a K100 and/or switching to L-Jetronic so you can run a richer and thus cooler mixture. A three row radiator from and early K100 and the early high volume coolant pump also helps.

Most Nikasil problems related to fuel are really related to riders using big throttle openings at low rpm. Spin the engine between 4500 and 7500 and detonation isn't a problem. You won't hurt a K100 or K1100 by spinning it up, but lugging them is deadly.

I don't believe the problem is as bad as you suggest because if it were we would be seeing a high failure rate with 4 valve K's and therefore a lot of traffic on the various sites relating to that, but I cannot say I have seen that, most problems seem to revolve around the basic things we see on this site. The other point is the K in both two and four valve variety was not a very high power engine even for its day as it was deliberately targeted at a modest 100BHP.

There is no marketing spin on the facts of physics and chemistry, an engine either has optimum heat transfer from the hot bits into the coolant or it does not. In a given engine if the engine coolant system is oily and or has deposits in it due to hard water or corrosion then the heat transfer by conduction from the hot engine metal to the circulating coolant will be compromised, that's basic physics of heat transfer by conduction.

Not to get bogged down with chemistry. suffice it to say if there has been hard water in the engine with what is called temporary hardness due to calcium bicarbonate the deposits will be thickest at the hot spots that's just basic chemistry.

The amount of heat the coolant can carry away is affected by the percentage of antifreeze that is circulating in the coolant that is a physical fact. Therefore internally clean engine cooling systems with the optimum coolant mix are much more efficient at shedding heat. If you then add something to reduce micro boiling that is a plus.

Most owners don't have the opportunity or desire to change the head and or to increase the coolant flow and or change the radiator they just want to optimise what they have. It may well be the four valve head could be a problem for competition durability but on the road I doubt that.

On my 4 valve I don't get detonation on wide open throttle from low revs, even going up hills and I have tested and listened very carefully for the sound of detonation after a discussions on line a few years ago, however I do run premium grade fuel. If any owner is experiencing detonation then it may point to a need to adjust the timing or to fuel quality issues, anyone experiencing detonation could try using "top tier" gas as an experiment. If any owner is experiencing sustained detonation in their engine it will not matter what head they have, the engine is at risk.

Having ensured detonation is not occurring then coolant heat transfer overload problems will manifest under high load at high revs not at high load at low revs because each combustion cycle puts out a pulse of heat which has to be carried away by the coolant medium, if those pulses are occurring very rapidly there is a lot more heat to carry away per second than if the frequency of heat pulses is low.
Regards,
K-BIKE

I have seen the damage to Nikasil bores on K bikes from detonation. When I built a K100 two valve engine I went through four low mile (under 25K miles) used blocks to find one with perfect Nikasil (ok, the first engine I dissassembled had perfect Nikasil but the number 4 bearing had spun, another infrequent but known failure mode of these engines, the thrust bearing should have been on number 5). The blocks I had to throw away all had pitting at the top of the bore.

In the current case, the engine comes from a 50K mile K1100LT from Alaska that was parted out because the owner somehow managed to short the Motronic computer, and then broke the lower triple clamp crating it to send back to Alaska. Those two parts are so expensive new he decided to part the bike out. I ended up with the frame and complete drive line. My tech friend showed me some other damaged four valve blocks he has. It is not so uncommon in the southwest with our hot temps and ugly traffic.

BMW made a deliberate choice to use very high combustion temperatures, lean mixtures and aggresive ingition advance to maximize fuel mileage and reduce pollution. This is the crux of the problem. With the K1200 BMW pushed the compression and ignition advance even more trying to extract maximum power from that engine. They will experience high rpm detonation under very hard high rpm use while retaining the same cooling problems common to other four valve bikes. The cure is increased cooling, reduced compression and a richer mixture. The heat problem won't be solved by water wetter, and if you live someplace with winter riding conditions that are often below freezing (morning commutes in the teens farenheit), you must run anti-freeze.

Btw, if you lug a K bike engine below 3000-4000 rpm as matter of routine, and some old fuds I know do, the resultant detonation will pit the top of the bore above the top ring at TDC. It is a different sort of detonation than what you get at high rpm, but it damages Nikasil.

Well that sure is some chat on the 1100's heat issues, needles to say the bigger the core the better and the more you can push through the head the better, fully aware of the pitting issue from both the low fuel ron and the low rpm but heat well I never knew that one, so taa for the update, in cars you can get 4 and 5 core rodiators and an electric water pump and a matched variable thermo fan all three used in cohoots to make everything cooler in the engine than was ever possible for the origional car, Wonder if that is possible for our bikes?????? what about a lower radiator under the cam set and infront of the pump that might help. I''ll wait for a pic of this scoot when ya can get one taa

All you have to do is richen the mixture and you eliminate the heat problem. BMW runs a very lean mixture combined with an aggressive ignition advance. It was done to maximize fuel mileage but it is a recipe for Nikasil problems too. This is why my tech friend like to use L-Jetronic rather than Motronic on bikes.

I found a 17K mile engine from a wreck with perfect Nikasil, so the project is back on track. Whew.

https://youtu.be/K2k1iRD2f-c

I know my place....!

So how are things going now?

jdaley wrote:So how are things going now?

Themason is long gone.