787/800 rotary valve timing

[Ken62465]

While setting the RV on a 97 GSX I established my opening and closing marks from TDC, with dial indicator, and best closing timing I can get is 61 degrees, or flip the valve and get 68. Spec says 64 and +/- 5, which sounds like allot of allowable variation to me. Is 61 degrees close enough? Would you guys worry about 3 degrees with a new build? I could pull the shaft and jump a tooth but wish I could find out how many degrees doing this might yield...someone has had to have done it and know this answer.

Strange part is the factory scribe mark is 5 degrees off.

 

[Dr Honda]

Without seeing it up close, I would probably go with the lower timing, since it will have a little better torque.


BUT... I would think you would be able to get it closer to the proper mark. Is there any movement in the RV shaft?

 

[Ken62465]

>>Is there any movement in the RV shaft? <<

ohh forgot to mention that after I establish TDC I give the RV a simply clockwise turn to absorb/rid the backlash as that will be what will happen while it's running. Sure I can turn it just a tad and get 64 but that's not what will happen when running.

 

[griz400]

with these specs, shows you are good, Rotary valve timing Opening 146.5° ± 5 BTDC
Closing 64° ± 5 ATDC -- when i just put mine in with a degree wheel, i wanna say mine i set ay 147 deg. using the lower part of front intake passage at rv housing with degree wheel, making sure mag cyl is tdc, recheck your tdc, but, mine is an rfi eng, 99



just checked my specs and mine are 147 and 65 degrees, they are similar to yours, but not quit the same, still a 5 degree plus or minus though,

 

[Ken62465]

Were you able to land exactly at your opening and closing mark? Honestly I had WaterCraft Magic bore/hone the cylinders via Mel Miller and I inquired to him what he thinks and he's suggesting pulling the shaft to get it closer. To me I'm within 3 degrees, 61 vs. 64 on the closing so I'd think I'd be good but in an earlier email exchange Chris from WCM commented he likes to see no more than 1 degree variation. I might pull the shaft and spin it a tooth and see where it lands.

 

[griz400]

mine fell in place pretty nice, within a degree or so, but, mine was a new "reman" motor from sbt, but there is a new rotary shaft and gear in mine

 

[Ken62465]

well I pulled the shaft and three tries later finally got 63.5 and should be good. Wish someone made a better degree wheel. Man those things have to large an oversized center hole that it wiggles around enough to mess it up by 1-2°. Have to watch and make sure the hole is nicely centered about the splined end of shaft...drove me nuts but then again I'm one picky pain in the neck.

 

[Dr Honda]

I gave up on the plastic wheels. I actually use a paper one. I just print a fresh wheel every time I need one.