YICS System TOTALLY underrated

While I've worked on my share of automobiles and their respective carburetors, this is my first experience working on motorcycles. I am hooked. I don't rip nearly as much skin off my knuckles and I don't hurt my back lifting enormous chunks of metal. But I am straying from my post's main point.

When I got my 1983 XJ750 Midnight Maxim back on the road, I started reading every single article and post I could about it. I can not express how incredibly awesome and informing this site, its moderators, and chacal have been. I read that the original specs indicated that my bike would get a whopping 50 mpg! Hell yeah! I was ready for that kind of fuel economy. Only problem was I found out that I was getting 15-18mpg. Damn. Something was seriously wrong. Bike was running fine. No power loss. No flat spots. Started decently in the cold. :? Hmmm...

I began fiddling - which usually tends to get me into trouble and create and all weekend undoing - and read all I could about how the YICS engines actually work. I read several posts saying that the YICS port was the key to Yamaha's fuel efficiency. So I FINALLY located it (sometimes I'm slow) and pulled both port bolts. Much to my shock and dismay, I discovered that the port was as clogged as a 400 lb man's arteries (who also suffers from high cholesterol and arteriosclerosis). 8O This poor bike was a stroke waiting to happen - pardon any implied puns.

Only problem was how to clean it out. I couldn't figure out how many gallons of carb cleaner I'd have to spray through it to get it clean. I honestly didn't want to have to buy a special part from chacal just to do this one job (no offense). So I set the brain cells to work. I finally thought, wait... :idea: this is just a gun barrel with an open breach. So I grabbed my shotgun cleaning kit and decided upon the 20 gauge wire brush. I assembled my rod (only 2 sections needed) and went out to the bike. I stood at the upper side and sprayed the hell out of the inside with carb cleaner. I shoved that wire brush through the port and holy mother of gods the gunk that came out of the other side was grotesque. I cleaned of the brush and continued a couple times until that port was back to metal. Unscrewed the brush and attached the cleaning patch tool and started to polish that puppy up. When it was beautiful and shiny I gave pause and realized that if it was that nasty, then NO WAY were the port holes clean.

I, again, didn't want to pay for a specialty part so I decided upon a piece of 12 gauge copper wire. I sanded the tip down to about the right diameter and then partially flattened one side to act as a chisel/drill bit. Grabbing my flat head long screw driver for leverage, I then cleaned out the holes. Sprayed carb cleaner up into them to make sure they were clean. Ran another cleaning patch through the bore and I was back to spec.

It just happened that I had my first ride the following morning. I fueled up and had an awesome time - albeit cold as HELL. We had traveled about 60 miles into the ride when I thought I'd better fill up my tank or I'd be in the middle of God's Country without a drop of fuel. I opened the tank to take a peek and there was... catch this, almost a full tank! HUH?!?! :roll:

I ended up getting 50 mpg going over the mountains from VA to WV. I continued the great efficiency throughout the ride. The following week (last week actually) I didn't go any great distances and mainly was limited to in-town riding. I knew I wouldn't get as good a mpg, but I ended up getting 35mpg. Amazing!

So here's the point of this rambling tale of self-discovery...

There's just not enough said about the importance of cleaning out the YICS port when it comes to fuel efficiency! But I guess now there is. Hopefully there are others out there without this knowledge that my post helps. I haven't been able to sync my carbs yet because I'm waiting until I yank apart the engine to replace a leaking head gasket to check my valve clearances - see? I DO listen to you guys. LOL

Who knows how great he'll run once I get everything returned to spec and begin tweaking the fine tuning. I'll keep you guys and gals posted though.

Thanks again for such an awesome site! Only down side is that I spend about 15-20 hours a week on this site reading every post I can. And I probably have read through chacal's entire catalog about 4 dozen times. 8)

 

I had no idea that it would make that much of a difference well its all appart anyway might as well take the plugs out and see whats in there tonight.
James

 

Makes ya think! I'm going to have to dig out my 20 gauge brush! Thanks for the tip

 

first, welcome
now motorcycle security, you should park your bike in a garage or off the street or at least under a street light because someone's been stealing your gas, dude

 

Welcome Loopa,
Q for U:
If the large port was that clogged, how could the thinner runners, that make 90* bends and are restricted to 2MM at the head gasket, possibly be free and clear?

I'm glad you're enjoying the bike- - I love the look of the Midnights !

 

I get 64/45 in my '82 XJ650J

My '86 Maxim X got 62/40

No they are not running lean, I just ride in the mountains at ~50mph

 

My Seca 550s get 52-56mpg all the time. Plus they run like rockets; they had a performance envelope the equal of most (not Yamaha) 750s in their day--- I don't know if it's YICS or not but the non-YICS 2010 FZ6R is rated at 43mpg.

I do believe that the YICS makes more of a difference in the smaller motors (400 twin, 500, 550) because of the size of the YICS passages and ports relative to the size of the intake port.

 

I'll definitely be checking mine tomorrow.

 

+1 to the "to-do" list on my '82 XJ 650 RJC YICS. Pulling the head tomorrow and starting the gasket kit deployment I got from Chacal!

 

Hi Loopawagon, welcome, so what you are saying is the pre-YICS motor will only return mileage figures similar to your pre-cleaned YICS motor, this Jock ain't swallowing that. Wiz.

 

C'mon wiz, he's just saying that his bike got dramatically better mileage when the YICS was thoroughly cleaned.

YICS and non-YICS (or pre-YICS, if you prefer) have other differences than the passage. Apples don't have very good orange color, do they.

Give him a minute here before you get him locked into the YICS, sync, oil, etc debates. I'm pretty sure we can all agree that a clean bike is a happy bike.

Except Polock, who out of principle disagrees with everything.

 

So, the money, time, and hassle of dealing with a YICS engine is costing me MPG? hmmm

This kind of steers us back to the actual YICS peformance debate.

With YICS = Better MPG
Without YICS = Worse MPG,,,,, same performance???

 

I don't think that's much of a debate. Correct me if I'm wrong, but isn't that the general consensus on what YICS does in our engines, if left stock, that is?

 

First off let me say this... I am not intending to start (or restart) any great debate regarding the wonders vs. BS of the YICS engines. I am not saying that your bike will have the same results. I am not saying that my engine is powered by magic squirrels who couldn't breathe, but now can. No aggressiveness needed. I'm simply letting others know what I experienced. That is all.

I have a locking gas cap. No one is stealing my fuel. If you knew my neighborhood, you would understand that what you are saying isn't true. My bike is directly in front of my house and my neurotic dog barks when a mouse farts three blocks over. My 2 nosy neighbors also report every Wal-Mart bag that floats down the street to me. Thanks for the concern though. LOL

Wizard... NO. I am not saying that at all. YOU are saying that. I am saying that I got better mpg after cleaning the port. That was all that I said. Period. The rest you created or perhaps you inferred it, but I did not imply it.

If what I wrote helps someone else, then great. If not, then sorry to waste your time. Some of you should think about what your comments say to people who write on here for the first time. Too damned much testosterone driving your blood downwards. Chill out, please.

A side note: I checked my YICS port today and found a good bit of carbon in it. Seems to me that it must be coming from the passages from the engine. Can't imagine it coming from the carb. Any prognostications on that? I'd honestly love to hear.

Thanks for the kind words from most.

 

loopawagon- i think what wizard is saying is that gunk shouldnt cause anything to your engine- because what that gunk is doing is essentially the same thing as the yics block off tool- that some people KEEP in their engine just so it's easy to tune and whatnot... but im glad you fixed your bike... i dont know how it worked, but im glad it did

 

Maybe its an intake valve that needs adjustment?
I'm gonna check my YICS port to see how clean it is,maybe if its plugged up it will cause the bike to run on the rich side,having partially blocked airflow.....?

 

Sorry if I have impinged on your veracity & credibillity, but "don't pick on me it's my first post", come on, your first post is not howdedo, it's a lengthy diatribe about the single most contentious issue on XJ BIKES, what's your second topic going to be, re-jetting for pods?
BTW welcome again. Wiz.

 

Loopwagon..how many miles between th clean out of th yics and th second inspection..just out of curiosity? And Welcome.
In my opinion if it's dirty again thats just th nature of th internal combustion engine, they are messy things......and it aint all flowers and smiles on here all th time, but don't worry about it.

 

I don't know much a out the YICS, but I would think that if it is clogging up again so soon, then something may be off. I had my head off this winter @ a out 124500mi, and only had a bit of residue to clean out of the passage.

I'm thing that you may have an excess of carbon buildup, maybe you enrichment circuit is off a bit, or your runnning rich under a load. Have you tried plug chopping.

Just a thought. Like I said, I don' really know much about it. Good post IMHO

 

Just out of curiosity, has anyone ever asked Yamaha what the normal service interval of the YICS port cleaning should be?

I understand what the OP is saying, but i have my doubts as well with a report of a ~40 mpg increase JUST from the YICS port being cleaned.

You may have seen this in practice, but i bet there's another underlying issue that has been the major factor to your mileage increase. So the YICS may have contributed some to your increase, but i don't think it's the sole reason.

 

Don't forget, he also tuned and synced the carbs.

 

There IS a condition where these bikes get ZERO MPG, and it happens when you are tuning the bike in the garage, spilling a little gas insalling the filter, checking float levels, sync and adjust carbs, warming the bike up.

Combine that with short runs around the block and some more cold starts, and you could see 18 MPG at first. (adding some fueling error too).

 

hay man don't mind me i'am just a disagreeable old s o b but someones got to do it or else everyone just goes walking down the happy road
after all "it must be true i saw it on the internet"
but come on now you tripled your mileage ? gimme a break

 

Hmmm wonder how to clean the YICS of a 400, I believe ours is 100% internal. We don't have the external port thet requires the YICS too for syncing...... guess I'll hit the manual for some reading.....

Not thinking it will triple the mileage, but damn well can't hurt

 

Yours is 100% internal. The only thing I could think of would be to pull the carbs and spark plugs, turn the motor over until an intake valve is fully open, and blow that cylinder full of compressed air; then spin the motor over until the other intake valve is open and repeat. Maybe even attach your shop vac to the intake boot on the cylinder you're blowing out.

Or pull the head.