Mikuni jetting question

[Silky_Johnson]

Yeah, right after I rebuilt the bottom end, I was fowling plugs like crazy.  Turns out the jets had worked themselves loose.  They're tight now.  I also diagnosed the outer venturi was loose in the No. 1 cylinder a couple months back.  I went through and tightened them all up after that.  It helped the air flow problem, but No. 1 is still lacking.  Good call though.

[Silky_Johnson]

Here's an update on my tuning for the edification of Ratsun:

 

I bought a new throttle rod and butterfly valves for my front carb.  That fix more or less evened out my vacuum on the first two venturis.  Whereas the #1 plug was generally leaner than the others, now they're all even.  Good.

 

On my compression ratio, I just swapped out my closed A87 shaved head for an open unshaved (Unshaven?  Scruffy?) U67.  I can now run 12 degrees of advance without any detonation.  My next project is going to be pulling the oil pump, adjusting it back a tooth to 11:28.  It runs fine now, but I don't have any adjustment left for more advance.

 

I just posted this on another thread, but I installed stock valve train components, including a stock cam, into the fresh U67.  Other than an exhaust leak, I now have no more engine noise.  It's great!  Sealik came up with a theory that my retainers were too high, and now I agree with him.

 

After I get my exhaust leak taken care of, I plan on putting one of my now two extra cams back in.  The first is my original mystery cam with .480 lift and unknown duration.  The second is a .490 lift regrind of a 210 casting cam.  This one also has unknown duration, but I suspect it has less duration than the .480?  The .480 has super fatty cam lobes, whereas the .490's lobes look narrower.  Both cams have matching rockers and lash pads, but both cams have issues with the retainers.  The .490 came with two stock retainers and the rest aftermarket, and the intake retainer on the 4th cylinder is all blown out -- literally.  The .480 appears to have retainers that are too tall.  Looks like I'm shopping for retainers...  I need a full set of retainers for .220 lash pads, and another full set for .160 lash pads.

 

Here's another question.  Can i not just file or grind down the tops of the oversize retainers?  Good idea?  Bad idea?  I'm guessing someone would want to buy them as is rather than grind 'em down.