4 valve heads, back again.

[vanzen]

I aquired a set years ago but have been reluctant to install them based on comments at Luftmeister about the spring pressures and inertia forces flattening the cam lobes and then ruining the oil pump rotor surfaces. Still need rings and plugs for them. Any good sources for Krauser spares in the US?

These "problems" have been addressed by the "K4V Specific" cam profiles and a more robust front cam carrier.
The only source of remaining replacement parts that I know of
is in the Netherlands at de Hobbyist

Pistons were typically provided by Mahle (Artikel # 2K 31 657),
so that may be a possible source for rings –
Don't you got a plug to cross-reference ?

[DanielMc]

Just curious as I'm unlikely to ever be able to get a set, but what sort of performance increase would a pair of these give to a 1000cc engine assuming everything else was left standard?

[chasbmw]

I saw a cycle world review of Krausers on a early 80s R100. It included dyno charts and I seem to remember that the power recorded just about cracked 60 bhp at the rear wheel. Quite a good increase from a typical R100 of around 50 bhp.

However to put this into context you could get 60 bhp from the r100 with a tuning package that would be cheaper than the krausers and by many accounts be a bit more reliable.
Charles

[vanzen]

Cycle magazine, July 1983:

"The dyno explained it all. The kit adds an additional 18.5 percent horsepower.
But more significant, both for street performance and our roll-on tests,
is the Krauser's imposing torque spread.
The K(4V)-bike BMW has more torque between 3,000 and 6,500 rpm
than a stocker has at it's peak.
The engine's strongest torque lies between 3,500 and 5,500 rpm
where it remains above 52 pound feet, about 15 percent
on the average more than a stocker* ..."


* my emphasis, as this will be the more important gain, IMO.

Early K4V kits did have some teething problems.
Many of these were addressed by Krauser throughout the short course of production.
(BMW's introduction of the K-bike relegated the kit to history.)

The K4V kit's biggest fault might have been Luftmeister's nefarious advertising
which led the consumer to believe that these kits were a "plug-n-play" item.
They were not !
The "misunderstanding" made K4Vs unpopular in the states
even as they were used, raced, and further developed in Europe.

Disregarding the definite torque advantage,
I'm not convinced that 60 HP at the rear wheel
could be bought or built in 1983 for $1,500 –
the cost of the K4V kit at that time.

[Garnet]

"The K(4V)-bike BMW has more torque between 3,000 and 6,500 rpm
than a stocker has at it's peak.
The engine's strongest torque lies between 3,500 and 5,500 rpm
where it remains above 52 pound feet, about 15 percent
on the average more than a stocker* ..."


And that is realy what you feel on the "Butt Dyno".

It will be intersting to see if they sell, currently at $1300.

[vanzen]

And that is realy what you feel on the "Butt Dyno".

IMO, torque rules on the street – ASAP will be a more legitimate pursuit than top speed.

It will be intersting to see if they sell, currently at $1300.

Reserve not met. If it sells – my bet will be at @ 3-times the current.

[Major Softie]

Yeah, that is always the advantage of 4v heads: large valve area for good high rpm breathing without losing high charge velocity at lower rpm for low rpm power.

If you cammed those heads for less peak HP than stock, you'd still probably have significantly more power at 4000 rpm than stock. 4V's rock, but it is easy to see how the conversion kits would put a lot more strain on lifters, and solid lifters are even more susceptible to damage with current oils. I would think that oil choice would become VERY important with those kits, even with modified ramps.

[Duane Ausherman]

I had 4 vlave heads on a BMW motorcycle for a few years. It really had plenty of torque. I could put it in 4th gear, at idle and feather the clutch and pull away from a stop.

I think I remember that they were off of a 1964 1200 cc engine............. VW that is.

[Chuey]

[quote="Duane Ausherman"]I had 4 vlave heads on a BMW motorcycle for a few years. It really had plenty of torque. I could put it in 4th gear, at idle and feather the clutch and pull away from a stop.

I think I remember that they were off of a 1964 1200 cc engine............. VW that is.[/quote

I'll soon have my 1200cc VW back. In the car, that is. It will be all hopped up. Well, stock other than bigger jugs...1385cc. All freshened up and with its thermostat, etc.

Chuey

[sterob]

A mate of mine has two MKM's and he wants a rear axle for one...S.Meyer couldn't help. If nothing pop's up I suppose he can get one made.

Sterob