Plugging YICS ports

Many years ago I removed the YICS system and eliminated some tuning problems. If anything, my gas mileage went up and I did not detect any reduction in power. I would recommend all MK1 owners do this if they have not already done it.

The downside I had with this is over time with the caps I was using, that I got from the auto store, would deteriorate and bust the top off. To make it worse, it was always one of the two in the middle under the carbs.

While on a ride Monday in the mountains of NC in the middle of nowhere, as I was pulling out from an intersection, I heard the POP and the rough running and knew immediately what had happened. Now, this would not have been a big deal, even though difficult if it is one in the middle ones, as I always carry a spare in my tool bag, except I had left my tool bag at home. So, I really had no choice but to ride it the way it was with a storm coming.

I came up on a country store that was closed, but there was a lady that had a side door open doing something. I pulled in and asked if she had any hose, but what she had was either too small or too big. Just on a whim, I got a 1/4 20 bolt and with pushing a little and using a wrench, it started into the hole. This got me home with the bike running good. This morning, I found an Allen head bolt and with putting some sealer on the threads, I bottomed it out. Then I put the spare rubber cap over that. When I get time and some more Allan head bolts I am going to do them all.

I have included some pics and you can see where the first screw made threads in the tube. When I put the shorter Allan head screw in and it bottomed out, it was very tight.

The last picture is with the cap over the top of the Allan head bolt and as you can see, that cap is not in good shape..

RandyA

The YICS is a pain in the A$$. I know on my 83 Yamaha XJ750K the YICS has to be blocked off in order to do a carb tune/sync. this because you can not isolate the carbs from each other to sync the carbs. Many of the owners of the XJ's and Secas block them permanently and have not had any adverse effects.

Great job.... thanks for sharing it with everyone.

For the new (ignorant) owners, what is YICs?

For the new (ignorant) owners, what is YICs?

On the 83/85 Ventures, Yamaha added something to the induction system where it was ported to a box with four chambers that was over the front head. It was supposed to improve low end torque and help gas mileage. The problem is that with these bikes being about 30 years old, with the hoses and a plastic box, many create more problems than they are worth.

You don't have to worry about this because when your bike was made, it was discontinued.

RandyA

How long of a bolt did you use? Any special kind of sealant or just gasket sealer? On my bike I currently have hoses that are plugged since my caps would always come apart and I got tired of trying to replace them. Great fix. Maybe use chrome shc screws...

-Andrew

How long of a bolt did you use? Any special kind of sealant or just gasket sealer? On my bike I currently have hoses that are plugged since my caps would always come apart and I got tired of trying to replace them. Great fix. Maybe use chrome shc screws...

 

-Andrew

A 1/4-20 3/4 inch long worked perfect for me. You can get the Stainless Steel ones at Lowes or the standard steel ones. I just used Permatex gasket sealer as all you are trying to do is seal any possible leak around the threads. With as hard as the screw bottomed on the top of the port tube, I can not imagine it ever leaking any way.

I wish I had done this many years ago when I removed the YICS. This past event is the 3rd or 4th time I had a rubber cap fail and before it was one of the middle ones.

You don't have to use Allen head bolts, I just used them as I may put rubber caps over them.

RandyA

Many years ago I removed the YICS system and eliminated some tuning problems. If anything, my gas mileage went up and I did not detect any reduction in power. I would recommend all MK1 owners do this if they have not already done it.

The downside I had with this is over time with the caps I was using, that I got from the auto store, would deteriorate and bust the top off. To make it worse, it was always one of the two in the middle under the carbs.

While on a ride Monday in the mountains of NC in the middle of nowhere, as I was pulling out from an intersection, I heard the POP and the rough running and knew immediately what had happened. Now, this would not have been a big deal, even though difficult if it is one in the middle ones, as I always carry a spare in my tool bag, except I had left my tool bag at home. So, I really had no choice but to ride it the way it was with a storm coming.

I came up on a country store that was closed, but there was a lady that had a side door open doing something. I pulled in and asked if she had any hose, but what she had was either too small or too big. Just on a whim, I got a 1/4 20 bolt and with pushing a little and using a wrench, it started into the hole. This got me home with the bike running good. This morning, I found an Allen head bolt and with putting some sealer on the threads, I bottomed it out. Then I put the spare rubber cap over that. When I get time and some more Allan head bolts I am going to do them all.

I have included some pics and you can see where the first screw made threads in the tube. When I put the shorter Allan head screw in and it bottomed out, it was very tight.

The last picture is with the cap over the top of the Allan head bolt and as you can see, that cap is not in good shape..

RandyA

On my '07 VStar, I used 8mm bolts, covered with hi-temp RTV silicone and then capped it off with aluminum from a tin can and a clamp. Has lasted for over 20k miles. Just got a '99 RSV a couple weeks ago that the prior owner capped. I need to inspect and see what he used.

Looks like you now have a permanent fix on yours!

My grandson was out in the garage this morning and since I had replaced the one outside rubber cap with a 1/4 inch Allan head bolt, he touched the cap on the other outside port and the head of the cap came off easily on it too. So, I did the bolt replacement as I noted above and in a couple of minutes it was fixed. So, while sitting there looking at the bike and thinking about it, I decided to do the two inside ports.

I knew that it is very difficult to get to those two ports and I really did not want to completely remove the carbs because to me, the throttle linkage can be a PIA and that is with disassembling the throttle. I loosened all the carb boot clamps and removed the fuel hose and over flow hoses. I popped the carbs out of the boots and I was able to move the carbs from side to side and go between the carbs to get to the port caps. I just used long needle nose pliers to pop the tops off the caps and was able to use a small extension with a torque insert and start the Allan head bolt into the port tube after I put some sealer on the threads. Once it was started, I just cranked it down until it was tight. I then moved the carbs toward the other side and the slot aligned with the other port and I done the same thing. I did have to pull the funky hose that goes from the twinky to the box out of the way.

From that point, I lined up the carbs with the manifold boots and popped the carbs back in place and tightened the clamps. After hooking up the fuel line and over flow hoses, I started up the bike. Once everything looked good, I put the air box back on and tweaked the air/fuel screws a little and then synced the carbs.

Now I feel really good about this setup and will not have to worry about these YICS port caps coming off anymore.

RandyA

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