I have a '73 750 Commando that came with a Combat head and a standard 1S camshaft.
Can I replace 1S cam with 2S or will I need to machine extra clearance on crankcases for the additional lob heights?
Any insight gratefully appreciated.
Peter
cam change
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Thanks David, I have a 2S…
Thanks David,
I have a 2S cam with scrolled journal and plain bushes which seems fine.
However an wondering what sort of shim replaces the Intake valve spring insulator when removed?
Also is there a specific valve spring seat for high lift of 2S cam?
Regards
Peter
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200000 combat breather series/ cam bushes?
Lucky to have the scrolled journal 2S cam plus a plain bush combinations is very lucky.
Insulation washer was omitted for all combat builds on intake. It is omitted to prevent coil bind due to high lift on intake.
In addition some valve spring seats were defective. They had a very flat profile that prevented them seating to the gentle curved in the head. It seems to have been only on early "C" heads.
The result was even with the insulator removed the spring seat did not "seat" to the bottom and was held up a little. A bit of examination and trial will find good profile spring seat that seats all the way.
I believe a factory service sheet exists on this topic. I added this topic to the INOA tech Digest
My original 2S cam was bent. The engine was a mess by 9500 miles when I bought it and needed a lot of work including a new Shenstone 2S cam in 1988?.
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200000 series cases should need NO additional work for a 2S cam
The original style bushes can destroy a 200000 engine.. upgrade is VERY wise
1. Strongly suggest you study and honor the cam journal/bushes oil scrolling issue.
2. remove the intake valve spring insulator to prevent coil bind.