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Has anyone ever used early 748 heads, (same 29 exh - 33 intk), as the 916 valves. Obviously smaller combustion pocket diameter, with bore difference of 88mm versus 94mm. The depth of 748 combustion pocket is 1.4mm shallower than the 916.

The stud spacing is the same as the barrels on the 748 are hugely thick to make up the difference in bore size, but I'm NOT going to use the pistons or barrels, only the HEADS. The valve sizes are the same, the cams are the same.

The basic reasoning for this question is: I broke an intake opening rocker arm under power and speed which jammed everything else, broke the tops of both valves, now bent an jammed in the head and nicked & flat spotted the V2 stage II camshaft, & obviously broke the belt. The hard weld and regrind of the cam alone is going to take a month - so I'm told. The valves will need to be cut out of the head along with new guides - more time than probably worth.

So a short term possible fix is using the 748 heads and open up the combustion pocket on the sides a little so it's not too much compression increase as I'm running BUCCI hi-comp pistons.

Any thoughts - pros & cons for this idea? Any help is appreciated

I've had this motor apart 3 times for various issues, so I do know how to work on it, installed the pistons & cams all balanced and degreed, and owned it for the last 19 years. It's like an old friend I can't get rid of.....

Thanks, 916duc/Terry
 

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Works just fine on 853's
 

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Ddont 748 headds have smaller valvess.
 

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Have a set of 748 heads and the intakes valves are 33mm
 

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from memory the 916 chamber is 33cc and the 748 is 27cc. that will give you a change from 11.3:1 to 13:1. i take the sides of the chamber out when i make them 853 as per the pics in this report - BikeBoy.org - 748 with 853 Kit which will take some comp out of it. nothing wrong with 13 though.

seems to me the 748 ports work pretty well at 853cc. not sure another 63cc will start to show them up.
 
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