vaccuum to advance

[Wild Hair]

have two 1200 voy,set the carbs,850 rpms,vaccuum on the 94 is 10-13 on the 92 is 3-5",gas milage 92 is at least 15% less than the 94,checked the vaccuum at the #1 carb,200 ml ride same road,92 used,4.7 gal,94,used 3.7 gal,55mph gps cruse set
what do you thank
lowell

[Steve in Sunny Fla]

Wow an actual gearhead question - cool! first off, I assume you've checked for any vacuum leaks from the manifold to the igniter? Have you checked the carb sync, if the sync is off the vacuum reading can be lower than the others because the throttle blade is set further open. If that's not the issue, have you checkted to see if the vac advance is actually working? If not, that can also lower the vacuum readings, assuming it advances at idle and doesn't hook to ported or timed vacuum. Otherwise, I'd be looking at retarded cam timing.
My responses are general because I haven't played with that system yet. i have an 87 that I'm rehabbing, anf fuel / ignition is next up, so I haven't traced the vacuum routing for the igniter. Still, I have 30 + years experience building autos and motorcycles, so I do know the generalities of the system. Steve

[Wild Hair]

did all that,vaccum,at the sycn port is the 10-13" range,on both bikes,thank that the port must be partly stopped,vaccuum advance is working,on both bikes,used the oral test,so now i have mod the vac advance,over to the sync ports to the #1 & #4,sync ports,seams to work,will give it a test,on my next trip,mod the air filter,also,used an auto air filter,only time will tell

[Steve in Sunny Fla]

then the only thing it could be is that inline vacuum filter/antibackfire diaphram. Steve

[Wild Hair]

then the only thing it could be is that inline vacuum filter/antibackfire diaphram. Steve

seams to be ok,can't find a carb break down,not going to pull the carb,unless,it gets worce. lowell

have you had any trouble with the ring gear,whining,the 94,whined 72-78mph,replaced it,now the 92 is starting to whine,72-74,what do you thank

[Wild Hair]

just did a 7000 ml ride,in 22 days,the mod did not make any differants,32 to 49 mpg,depending on speed and wind,from new hampton ia to spearfish sd, all big road 32 to 42 mpg,cruse set at 80 mph,680 mls,back to the drawing board
lowell

did all that,vaccum,at the sycn port is the 10-13" range,on both bikes,thank that the port must be partly stopped,vaccuum advance is working,on both bikes,used the oral test,so now i have mod the vac advance,over to the sync ports to the #1 & #4,sync ports,seams to work,will give it a test,on my next trip,mod the air filter,also,used an auto air filter,only time will tell