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Hi, I have recently removed the head from a late model 1100 engine that said YICS on the top and had always wondered what exactly a YICS could be until I did this. I thought 'WOW' all it is is a balance tube between carburator intakes.
Then curiosity got the best of me & I wondered what good this would do to the running condition of my motorcycle. I had seen the balance tube before on my '73 Norton Commando (sweet bike but that's another story and site) but I didn't have a clue then either because it went away when I changed the carburators to the Mikuni brand.
So I hooked a piece of hose between each of the intake manifolds vacuum ports. My first impression was a great one - it cut vibration in half all over the rev range, the little flat spot between idle and go -- gone. The familiar noticeable vibration between 3-4,000 rpm -- gone; power seems to be very smooth and seamless after I did this. Life was good!
But THEN (you knew it was coming, didn't you?), I went for a top end blast to see what this new modification was like wide open and noticed how really lean the bike was up top. Couldn't get the bike to go over 95 mph and when I rolled back, it went a little faster for a second i.e. lean condition.
So my question is, (after this long a** explaination) has anyone else tried to make their own homemade YICS? If so, how was your experience and what modifications and jetting did you have to perform?
The bike that I performed this on is the '79 XS11 Special with stock exhaust, stock air box with K&N air filter and snorkle cut down to 1 1/2". 140 Main jets & the float levels are at 25.7 mm as per the book specs. Everything else is stock.
Gene
Then curiosity got the best of me & I wondered what good this would do to the running condition of my motorcycle. I had seen the balance tube before on my '73 Norton Commando (sweet bike but that's another story and site) but I didn't have a clue then either because it went away when I changed the carburators to the Mikuni brand.
So I hooked a piece of hose between each of the intake manifolds vacuum ports. My first impression was a great one - it cut vibration in half all over the rev range, the little flat spot between idle and go -- gone. The familiar noticeable vibration between 3-4,000 rpm -- gone; power seems to be very smooth and seamless after I did this. Life was good!
But THEN (you knew it was coming, didn't you?), I went for a top end blast to see what this new modification was like wide open and noticed how really lean the bike was up top. Couldn't get the bike to go over 95 mph and when I rolled back, it went a little faster for a second i.e. lean condition.
So my question is, (after this long a** explaination) has anyone else tried to make their own homemade YICS? If so, how was your experience and what modifications and jetting did you have to perform?
The bike that I performed this on is the '79 XS11 Special with stock exhaust, stock air box with K&N air filter and snorkle cut down to 1 1/2". 140 Main jets & the float levels are at 25.7 mm as per the book specs. Everything else is stock.
Gene
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