lack of YICS

[4runnerpilot]

my 82 vision (free) came with no YICS components. The box is gone, and the fittings at the manifolds are capped. The bike seems to run pretty well now (lots of cleaning and tuning later).
The question is whether or not this is a real performance loss or not. It seems (from my wholly uneducated viewpoint) that any improvements would be small. Is it worth tracking down the parts and replacing them, or just leaving it alone?
Thanks.
Brian

[bikeseamus]

Brian  Good question. My bike is in pieces for the next month, so I can't answer, plus it's about 0 outside. I was reading an old ROV newsletter, and a guy said his bike ran better after he removed his YICS system, but maybe his plemum (that triangular thing you don't have) was leaking. Yamaha invented YICS to get rid of a slight stumble constant velocity (CV) carbs had when you snapped the throttle open. The vision carbs are downdraft butterfly carbs, with accellorator pumps,so we have a different kettle of fish here. After reading of all the possible problems with the system, I've been considering eliminating mine, too. Maybe some visionary out there in warm weatherland could run a back to back comparison for us. Nipple it off and ride it, and let us know. It shouldn't change the mixture, so there shouldn't be any harm in it. AS for this infernal valve tool mystery, I'm gonna cut to the chase and lean on K&L today for some simple answers. Stand by for further developments. I hate to think of our Canadian Friends running around with incorrect valves.

[bikeseamus]

 Brian  I was just reading a discovery by the old ROV Carb Guru fifteen years ago, and he reported horsepower increases when he trashed the YICS Plenum and ran a vacuum line from front cylinder to rear, using the existing Yics nipples. Maybe someone can confirm this for us after a back to back ride. If it gets good reviews I'll do it myself. All that exposed intake plumbing seems to cause problems. Being able to gain steam and dependability sounds like a winning ticket to me. Let's wait for the feedback on this. Real world results are worth a ton of speculation.

[Rick G]

HI Bike , This was dicussed on the old forum and the concensus was to agree to disagree. Several people tried it both ways and disagreed on the results. You may have to wait for warmer weather and try it for your self.

[Lucky]

Rick is correct saying we couldn't agree, but i'll give my opinion anyway.

I have found that a V with a YICS in proper working order and good hoses, starts easier, runs slightly cooler out the exhaust, and has SLIGHTLY better fuel milage.  I do see quicker throttle response as well. I think Jason has dyno tested his 83 both ways as well.
Having said this, I want to point out that if you want to test this theory, you MUST be sure the rest of the bike is in tune.

Last thought, I disagree with joining the 2 fittings together with a straight hose.  the theroy behind the YICS is to use valve opening & piston position to cause vacume & pressure in the YICS box in order to "inject" fuel mixture into the cyl causing a swirl effect, promoting a more efficent burn.

Hooking a hose up between the two intakes (which is what you are doing running an straight hose between the two fittings) will cause vacume & pressure pulses between the 2 cylinders while they are trying to fill. This causes a disruption in fuel flow, the exact opposite of what the YICS is trying to accomplish.  my guess is that those who like the results of this were compairing it to the way the bike ran with a leaking YICS.
--nuf said ?
--Lucky

[4runnerpilot]

Thanks for the input. As I don't have any of the YICS stuff, I will just tune the bike as well as possible without it and call it good. It seems to run well now anyway, so...
nuf said, I spose.

[bikeseamus]

 Lucky   OK, now it's starting to fall together. I remember in the old days, the way to hop up your intake system was to polish it to a mirror finish. It sure did make a big improvement in quarter mile times, but the bike (and cars) ran real rough and unevenly at anything less than full tilt boogie. Norton, of all the bikes I'm aware of started experimenting with swirl in the combustion chambers to help fuel atomization and more complete combustion. In other words, if it aint mixed with air it wont burn. Let the fuel molecules pool up and they wont bang. Throw a match on a bucket of gasoline, and you have a torch. Aint no horsepower in a torch. Gotta have a bang. I've studied the intake cam timing on the vision enough ( I think) to  begin to understand that the Yics system improves what is known as "streetability". All the good stuff you just mentioned, in other words. I personally don't dragrace my vision. Sounds like a case where everybody is right, depending how they use their bikes. I'm having fun with mine, and this forum is part of it. Ride on.