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small bore and large bore rockers
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Author:  72clubman [ Thu Sep 03, 2009 9:15 pm ]
Post subject:  small bore and large bore rockers

will rockers off a small bore motor fit on a 1275 12g940 head i have a set of plain 1098 steel ones (top pic)and also a later type a+ ones (bottom pic)
the a+ rockers dont seem to line up in the middle of the top of the valve only some valves
Image

Author:  drmini in aust [ Thu Sep 03, 2009 9:21 pm ]
Post subject: 

They will all work on a 1275 if you fit a flat washer next to the exhaust valves ONLY.
Valve spacing on a 1275 head is different, as the valve heads are bigger.
The A+ rockers were used on 1275LS etc, with a washer as I said.
<edit> they still don't line up properly, but they work.

Those top ones look like 1275 not 1098, as the pads are oval.
1098, 998 and 850 had round pads.

Author:  72clubman [ Thu Sep 03, 2009 9:26 pm ]
Post subject: 

is it a special washer or just put a flat washer that lines it up

Author:  drmini in aust [ Thu Sep 03, 2009 9:28 pm ]
Post subject: 

Just a flat washer about 1.5mm thick will do it.
I use 12mm ones and bore them out. It's hard to find proper 9/16" ones these days. :wink:
14mm ones if you find any are usually too loose.

Valve lift and rocker ratio:
The top ones in your pic are best.
The bottom ones are 2nd best.
the S rockers in your middle pic are worst for lift, and vary quite a bit.

Note if using the A+ ones- check their bores are not worn oval. If they are OK I would fit with a new shaft. These crap design sintered rockers have no bush, so cannot be repaired.

Author:  mini_mad_matt [ Fri Sep 04, 2009 6:16 pm ]
Post subject: 

I had a sintered one break on me once, i had just turned into my street and went to drive the 30 metres to my driveway when it happened. Pretty lucky to break within pushing distance from the house :D Apparently they aren't very good for racing either.

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