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I have a 748 motor which i don't know the history of. Doing valve adjustments, and so far, the Intake Opener clearances are within spec. The closer is riducolously tight. I'm getting down to 0 clearance when i subtract the unloaded from the loaded gap.
My question is, what would lead to such a tight clearance? I figure it would be looser, not so tight.
My procedure for measuring the valves:
Remove belts
Rotate cam so there is no load on the opener rocker- take measurement
Use flat head and push down on the closing rocker - take measurement again at the same spot
Then do subtraction to attain the closer clearance.

If my procedure is incorrect any, please advice.
Well, these are the closer clearances i've gotten for the intake side - .001" and .000"

I have the desmo times manual, and the closing clearnace listed .004"-.008" for exhaust, and .006-.010" for intake.
I've since done all the vlaves and the highest i've gotten on closers is .004" on one of the exhaust. All the other closers are .000" and .001".
I've gotten .003" in all intake openers, except one which was .004". And for the exhaust openers i've gotten .007"-.009".
So i guess i'll order shims to attain the .004 opener clearance on the exhaust side, and leave the intake opener clearance at .003". What do you think?
My concern though is for the closers. If it's okay to run the motor at the tight clearances that i got, then i'll leave them alone.
 

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The duc engines with the closers--if you run them tight. They burn out the rockers and camshafts. get the right shims and get the right clearances! ( you can 'sand down" the closer shims about .001" on some #400 grit wet sand paper if need be)
If they were truly at less than 0 clearance already--you may well already have cam and rocker damage. Inspect them carefully!!!!
I dont work on ducs anymore (not since about 96) but the closers used to run at 0 clearance and that was an extremely fine line to adjust to. Glad to see they finally changed the design so it can run some clearance.
I would think running the closers at the bottom end of spec should be fine--just check them often---but I dont have a 748 or similar service manual to look at for you. Good luck
 
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