Upgrades: Krauser 4-Valve Heads

The Krauser 4-valve heads were part of what made the MKM1000 great.

Krauser MKM frame

The unique Krauser frame exposed.

Photo by Ken Richardson

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Although exclusive, the MKM1000 wasn’t actually any faster than a stock BMW R100RS. “The whole thing about the MKM1000 is the frame,” collector Phil Rose says. “Then, it’s the fiberglass bodywork, and finally, the 4-valve heads.” Ah, the allure of the Krauser 4-valve heads.

According to Phil, Krauser developed a special performance 4-valve head kit to bump the 980cc BMW boxer’s horsepower from 70 to 82: He also increased compression from 8.2:1 to 10.2:1. “Krauser sold the 4-valve kits as race parts, and a lot of people made the mistake of thinking the heads were ready to go right out of the box — they really weren’t. They had to be massaged and finished,” Phil says. According to a 1982 article in BMW News, the 4-valve heads were being tested on MKM1000s with kits to be available by early 1983 priced at $1,100.

Included in the Krauser 4-valve head kit was a pair of Mahle pistons and rings. The pistons were machined with pockets to match the valve layout. There was no problem fitting the new pistons, but the heads required porting and polishing to clean them up. Also, there were short, hollow pushrods constructed of two parts — the rod and a small end cap. If left unattended, there was a distinct possibility the rods would take on oil. “If oil got into the short pushrods, it would change the weight of the valve train and stress the valve train,” Phil explains. A BMW cam should last some 100,000 miles without issue. A stressed cam, thanks to oil-filled Krauser push rods, could self-destruct in 30,000 miles. “They need to be welded together and machined and polished to seal them up,” Phil says.

One of the MKM1000s Phil purchased from the Long Island collection was a single saddle or Monoposto (no. 065) machine fitted with the special 4-valve heads. In exceptional original condition, the engine had been built by renowned Krauser specialist Perry Bushong of Fort Worth, Texas, employing all of his tricks learned racing Krauser-powered machines. MC

Read more about the Krauser MKM1000 in Krauser MKM1000: Holy Grail for BMW Collectors.