Rebuilding a YICS question

[munkyfistfight]

I have a spare YICS that I tested to be leaking with the water method. I managed to get it open and want to fix it up new. Im going to make a gasket for it like I saw on Lucky's page. I was curious about what would happen were I to take it to a belt-sander and take both halves in a bit to create a smooth matting surface. Are the chamber set to a certain volume that can't be tampered with? It wouldn't be by much.

[YellowJacket!]

Supposedly the chambers are a specific volume but sanding off a little to make good contact shouldn't make a big difference.

The easier solution - the one I use - is to tape a piece of sandpaper to a flat surface and sand down the edges by holding the YICS face down and sanding in a swirling motion.  No belt sander required...

David

[Lucky]

if you look at the YICS where it seperates, you'll see it has a tongue & groove set up.  I would only sand down the groove side, & seal & clamp it with a good epoxy.  I just clean mine off with a brass brush on a Dremil. I made the mistake if bandsawing my first one apart, hence the gasket, but since then all the rest have been split apart using the BFH method, scary as it may be, and resealed with epoxy.  on my latest one, the center 'wall' was deteriorated out so a made a new one out of sheet metal.

i'm convinced a working YICS is a substantial improvement, but I know others disagree. that's fine...

[munkyfistfight]

In doing some research, I can definitely see how a YICS improves things.

When I took this one apart I broke part of the "tongue" side off. The rest is in good shape. So if I just give it a liberal epoxying, it should hold up?

[Cdnlouie]

I'm in the "keep the YICS" crowd  :angel: and we have some pretty good company. The rest are part of the Rebel Alliance  :P.  My first YICs was done with the hacksaw down the middle/sand off both sides and JB weld back. It did about 10000km and failed. I then went with Lucky's gasket method (a thick one, plus sealer) and it has worked really well (at least 20000km now).

Lucky: So elaborate on the BFH method you are now espousing. I like the idea, but before I give it a crack sometime tell us where you hit the bugger and how hard  :o?

[Rikugun]

All this talk of YICS had me curious enough to retrieve mine from the "Rebel" storage bin where it's been languishing. I noticed 2 of the 3 screws securing the chromed cover seem to have sealing washers. Is this normal? Are those holes in any way open to the 2 chambers? A quick water boarding seemed to show some bubbles coming from at least one of the 3 screw heads.

Interestingly, the mounting tab broke and a PO glued it back together effectively gluing the cover on in the process. Then they backed it up with a metal strip for added strength. The only problem is, they sheet metal screwed the strip to the back of the YICS so now there are 2 additional leaking points.  :( It appears the screws just miss the web separating the 2 chambers and are both in either the front or back chamber - I can't recall now. The whole thing looked pretty sorry so I tossed it back into storage. I guess I'll continue to be a Rebel for the time being.  ;)

[Lucky]

Someone, it could have been Rick Greville or Jason Morris, i dobn't remember discovered that if you stand the thing with a point (corner?) facing up & whack the corner with a hammer, do this on all sides, the original seam will give way. you have to work at it a bit, but it preserves the tounge & grove, at least for the most part.  i've done several this way.

i'd clean it out as best you can, pick, file, dremil, scrape or whatever method you prefer, as close to virgin plastic as you can get, then seal with whatever method you like.  I've fallen in love with Dirko since i've started doing 2-stroke work...

[Cdnlouie]

Very artistic ;D! Nice touch, I will have to give that a try when I find another victim to assault  :-X. Preserving the tongue and groove would certainly add strength to the repair.  Have you had any of your gasket jobs actually fail? They can certainly be a pesky repair and not for the faint of heart.

[NewVisionGuy]

Just curious,  does the YICS have to be a certain shape, or is it solely the volume of each chamber that affects how the bike runs?   Say you had two tubes capped off with the same volumes as the original YICS chambers, would that give the same result, or does the shape of the YICS matter?

[The Prophet of Doom]

A lot of the German guys are running round with YICS fabricated from stainless pipe of similar volume.  Seems to work for them.

[Rikugun]

does the YICS have to be a certain shape, or is it solely the volume of each chamber that affects how the bike runs?

I've wondered the same.  I was unaware of the stainless steel variety but think I've seen a picture of one made from capped copper tubing.

In addition to the volume, is there anything to the rigidity of the material used? I recall someone making the claim/theorizing that the flexing of the YICS chamber in use was integral to it's effectiveness. Or was it simply an ease of manufacturing/weight/cost choice?  Maybe the flexing is an unwanted byproduct of the pressure pulses realized and the source of it's demise.

[Lucky]

it's a theory of mine that some flex in the YICS unit helps 'shoot' the mixture back into the cylinder...

[Rikugun]

If that's true, I wonder if the effect is negated with the use of rubber lines?

[Cdnlouie]

Lucky, care to comment to how you have used the Dirko gasket maker? A new product to me, and I am always interested in a better one. I noticed they rate it as usable for head gaskets, which is pretty impressive.  What is it most similar to?  Yamabond products? or RTV products? or something else?

Then of course...where is this product usually found?  Thanks for introducing the idea  :).

[The Prophet of Doom]

I can't imagine the YICS flex is very important.  The air that is in there will compress far more than the box will flex.  As soon as the pressure is released the compressed air will expand like a spring for shooting it all out again.

I Used Yamabond - Failed in a few weeks.  Gasket paper and Red RTV still working after a year.

[Rikugun]

I could see the flexing chamber walls acting to store and release energy like an accumulator if they were flexing in the right "direction" at the right time. This combined with the pressure differential between the chamber and the port when the valve opens would enhance it's "push".

Whether or not it does in practice work this way is beyond me and trying to figure how the charge is going in and out of the same chamber at different times of the intake stroke makes my brain hurt.  :(

[Extent]

If the case is flexing at all under the measly 14psi that's applied to it at peak it's such a miniscule amount, you're more likely to be effected by the volume that the black gunk that builds up on the inside of the chambers takes up.  If the Yam designers were looking to get flex you would see a rubber diaphragm like the one on the inside of the fuel pump, and they certainly would have picked a hose stiffer than the rubber to prevent it from choking off the charge, if the amount of flex that you get in a plastic case that rigid has that great of an effect on it. 

[Lucky]

Don't overthink the YICS, its simple & it works (my opinion), the hoses are not supposed to kink.

does it or doesnt it flex? does it matter? how importaint is volume? material (heat), would a rebound diaphram help or hurt? these are questions for the R & D guys.

I get Dirko from my Stihl distributor. it is the OEM sealer for all their 2 stroke equipment. it's a german product, & it's expensive but i get it at cost plus 10% (or the "end" of the tube :D )
its fuel proof, (2 stroke, gas, E-10 & E-85) will easily hold crankcase pressure makes an excellent gasket, sealer & adhesive.  A quick google search found it ava here: http://www.frsport.com/Elring-Dirko-RTV-Silicone-Gasket-Maker-Compound_p_1287.html

[Cdnlouie]

That's great! I will keep my eye open as it sounds terrific.

I agree not to overthink the YICS.  It is a simple apparatus and anything close to it is going to pretty much work. The use of plastic is no doubt related to cost and weight.  The V configuration is probably style, so the volume is most likely the signficant factor, just enough to do the job of swirling the fuel mixture for better combustion.  It just seems the easiest to fix the old YICS as the very best solution.  I like taking the easy route, but I understand that others prefer to do it the hard way and feel a great deal of satisfaction doing so  :).

[Rikugun]

Regarding the Dirko sealant - Elring must market at least 2 of the Dirko sealers. The one Lucky linked is good for 180C but there is another labeled "HT" that's good for 250C.

http://www.corradoparts.com/Gaskets-Dirko_High_Temperature_High_Performance_Sealer.html

I've seen the Dirko referenced in several chainsaw forums and a few automotive as well. I thought I remember a claim that Audi or BMW replacement head gaskets were shipped with a small tube of Dirko?