YICS Questioin

I'm getting close to finishing my Seca. Ready to re-install the carbs and start the sync/tuning process. I pulled the two YICS end plugs and cleaned the bore. I'm looking down the bore trying to find the 4 holes that exit the bore. I found the holes for 1 and 4 (they are right up against the ends of the plug threads), but I cannot see any holes for 2 and 3. I can tell where they should be by looking at the casting from the outside, but no visible holes in the bore. I tried a bent wire probe, but the bore was absolutely smooth where the holes should have been. Obviously, the holes for numbers 2 and 3 must be plugged solid.

My question is, if I am unable to clear these two holes, with 1 and 4 open, would I be better off stuffing the passage permanently basically disabling the system or leave it alone? I would think that with some of the holes open and some clogged, this would mess with the sync with some cylinders drawing on the passage and some not.

 

You sure they aren't on the "backside" or top or bottom of the bore? I can't fathom how they could be plugged solid.

I WOULDN'T "stuff" the system and disable it, you'll lose a good 15% of your power. If they are truly plugged, it will mess with sync, yes.

How about this (never tried it but never needed to either

What if you were to turn the motor over until one of the affected cylinders is on its intake stroke; then with the YICS caps removed, blow compressed air into the cylinder through the spark plug hole. With the exhaust valve open, the compressed air will want to go out the intake port and hopefully up the YICS passage too. Might end up having to do it with the carbs off and a rag stuffed into the port itself, so the only escape for the air would be the YICS passage... and just BLOW 'EM OUT?

Like I said, it's an untested theory...

 

Good thought Fitzs.
On a car we used to use a carb bong when the base plate on the carburetor got clogged.
Kind of the same thing.
It hooked to the large vacuume nipple on the front of the baseplate and sucked a chemical through that dissolved the gunk and then burned in the cylinder.
You could possiblly do the same thing introducing it at the vacuume nipple that's plugged off on all but #3, normally.
hmm that wouldn't work maybe introduce it right into the passage itself.
I've never done this on a bike.

I have a question though doesn't the YICS tool plug all the passages so you can do a synch?
I have a none YICS motor, haven't had to use one.

 

I can't believe they're that clogged. I would hope a blast of air would do it.

Yes, the YICS tool blocks off all the passages for sync purposes, but shutting off the YICS and leaving it off will rob the motor of power, remember the passages are still open from the valve side. Blocking them off is a temporary tuning tool; the only way to "do away" with them correctly would be to pull and disassemble the head, weld them up from the valve side and grind the port smooth again.

I assume we're trying to conjure up a solution that doesn't involve pulling the head.

 

I'd pull a vacumm on the end access for the YICS, leaving the other end bolt on. Should pull out what ever if anything is in any of the intake port holes.
Think about it, the way it works to pull vacumm from that port accessing the shared tube. If anything is plugging it, it would/should be on the shared tube side and should come out with a vacumm.

 

I like the idea of searching for the #2 & 3 YICS ports with a bent wire. They must be detectable, how could they be clogged so neatly that the bore was smooth?
Keep searching with your wire tool, try a heavy wire like coat hanger, with some aggressive bends that will put pressure on the tip, and pull some solvent soaked rags through the bore.
I got two YICS engines myself to do soon, so I will be testing my own 2¢ worth of advice.

 

I cleaned my passage with a rifle cleaning rod + cloth square + gun barrel solvent. It required about ten cloth squares to get the passage clean. There was some serious gunk in mine. My motor has 18k miles.

Never bothered to look inside and try to eyeball the openings.

 

Come to think of it vacuum (hook up your shop vac) might be better than compressed air.

 

that yics port blocking tool just blocks 1 and 4 then isolates 2 from 3, same thing i guess
when i used the tool i could see the impression the hole left in the rubber of the tool, 1/8 inch maybe
keep looking , you'll find it

 

Re: YICS Question

Thanks for the thoughts. Really, after the bore was cleaned, it looked just like a perfectly smooth rifle barrel. I would think the exit holes would leave from the top of the bore like 1 and 4 do. I tried to take a picture, but couldn't get the camera to focus inside tube.

I'm going to try a combination of suggestions. First, soak a sponge/rag in Liquid Wrench and push it tightly under where the hole should be,allowing it to draw up and soften the material blocking the hole. Then use Fitz's idea to place the cylinder on the intake stroke, remove the soaking rag, plug the intake boot and blow the material into the YICS tube with 50-60 pounds of air into the spark plug hole. Is there a way to identify the intake stroke by the position of the timing plate? That would save having to pull the cover. (I know, I'm lazy)

 

Yes. Remember why we call them 4-strokes. (1) intake <down> (2) compression <up> (3) power <down> (4) exhaust <up>

Stick your finger tightly in the spark plug hole and turn the motor over. You'll know when it comes up on compression. Then-- keep your wits about you-- the downstroke immediately after TDC (1/2 a crank rev) is the power stroke. The NEXT upstroke (the next 1/2 rev) would be the exhaust stroke. So your exhaust valve will be open on that stroke until exactly one crank rev after the compression stroke. It will be open while the piston is on the way up, so you won't want to go one FULL revolution from TDC on compression, go about 3/4 or a bit more. It closes as the piston approaches the top, so the intake valve can open.

Hopefully that made sense. If not I can go drink another Leinenkugel's and try it again?

 

Yes, that made perfect sense, but go ahead and drink another Leinenkugel anyway.

 

could just look in the intake port?

 

Shoulda had the next beer first. Yes, that was a VERY explicit way to tell if the EXHAUST valve is open; you want the intake valve open. Same procedure, just a different stroke.

You're going to want to be about 1/4 rev PAST TDC, on the downstroke FOLLOWING the exhaust upstroke I so carefully explained how to find.

[quote="turtlemann14:]could just look in the intake port?[/quote]

True; I was assuming the motor was fully together including carbs.

 

Well, make sure you have a few beers in ya before hooking up a shop vac to the YICS port- - because you WILL have an explosion !!

The pilot jets will transfer gas and air, the shop vac will fill with an almost perfect air/fuel mix, the spark from the electric motor is in the discharge airstream. . .