Krauser heads

(Slightly off topic) I was talking to a chap at the weekend who builds racing sidecars. He’s done some with 2 valve airheads which he dry sumps, takes them out to 1070, fits a hot cam and 40mm Dell Ortos (bored out to 41.5). This gives around 103 bhp at the back wheel!
 
Richie is reputed to get a reliable 130 HP , but I suspect he does a bit more than ChasF's mate.
There are guys who claim 110 HP with 32 mm carbs too - you only need to flow enough to overfill the cylinders by 15/30% and you dont need 41.5 mm carbs to do that!
But you do need a decent intake velocity to ram the charge in after the exhaust valve closes , and oversize carbs are not always a help here - remember that the Vincent Black shadow performed more than adequately with 1 1/8" or 28.6 mm non CV carbs, and for a road BMW 28 mm slide carbs would probably work fine too.
 
But a Funduro also has OHC, FI and proper electronics which enables it to run a high CR......

Nothing wrong with 4 valves per Se, (I also have a 1937 Rudge), but the Krauser version seems to me to have been a piece of underdeveloped aftermarket Bling.

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Funduro has carbs
2x33mm mikunis.
10.5 to 1 compression iirc
 
I have already built a motor with Krauser heads, and I paid $1400- for the kit.
They were $2300- new in Oz, or would have been if anyone had bought them
It had sat for years and had never been fitted to a running motor.
The are not a bolt on item, they were always sold for race use only, and it was assumed that the would be fitted by expert race mechanics who knew what they were doing.
Not a back yard bodger who posts a dyno chart on face book with no connection between the torque and horsepower curves------------.
Luckily both my local bike guys and riding mates are ex race mechanics who have worked on world championship motors and have the equipment and know how to make just about any thing work - air cooled 500cc push rod four valve motors were in common use in speedway almost 50 years ago so it is not cutting edge technology!

There is little point in fitting a 90 HP motor to a stock road bike, as the running gear on a stock bike struggles to cope with a well tuned stock motor and another 30 HP is a step too far.
My motor ended up in a MKM 1000 frame, which had also sat around unused for 30 years.
It did OK in local hill climbs and clubmans racing, and maybe half a dozen club runs / rallys in a year.
It was powerful and reliable enough for that.
Race motors are not usually built to cover huge mileages, so people claiming that they are junk because some wore out in less than 20,000 km are just showing how much the know about race motors.
 
130 horse from a airhead , hmmm I smell Shite. Is this with a blower.
 
At the crank maybebut they reckon with shaft drive a 18-20% loss.
 
The 130 hp bikes in question are sidecars racers and they are blowing everyone else away with their power and reliability.
And the guys they are blkowing away claim over 120 hp--------.
Like most real tuners the guy who builds them is reluctant to reveal exactly how he achieves it, but among other things he seems to be able to get them revving a fair bit higher than most.
If you want pony poo go to Scrimagers Facebook site - he has a dyno chart which claims 86 hp with a piece of simplistic schoolboy engineering, although the torque figures on the chart have relationship to the HP ones!
And yes, most real engine builders test their motors on a dyno, the various devices that measure the capacity to do work at the rear wheels can be adjusted to give you just about any figure you ask for, and some automatically add on a percentage for transmission losses to give their assessment of the output at the crankshaft.
 
Come on fellas don't let this thread die here!

This is the best thread for ages, reminds me of when I first joined the forum when all the talk was of pushrods, bean cans, Scrimager, Gus Kuhn, carb sizes, derri boots, craven panniers, Bob Heath visors, Millichap and tyre pumps in frame tubes rather than "I can't believe the Comfort pack's heated footpegs only have 6 settings..."

:beerjug:
 
This is the best thread for ages, reminds me of when I first joined the forum when all the talk was of pushrods, bean cans, Scrimager, Gus Kuhn, carb sizes, derri boots, craven panniers, Bob Heath visors, Millichap and tyre pumps in frame tubes rather than "I can't believe the Comfort pack's heated footpegs only have 6 settings..."


In one!
 
Just back from the Pyrenees on/off road trip. Nothing went wrong and didn’t have to update the software once. The ABS worked perfectly :D
 


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