cylinder head

[lostgmc]

I was wondering if someone out there could answer a question for me. I was wondering what the differance of the head was from a 78' to an 81' besides the part number. and if a head and cylinder section from a 81 would mount to a 78 motor?. The other question is I have a head and cam that have some gouges in the journal area and I was wondering if there is anything that can be done with them or are they scrap?

[DiverRay]

I believe the '81 has the Yamaha "induction system" built in. There is a tool that you need to sync the carbs, as the four ports are connected. The head should bolt up, so you could use it. You would need to sync and tune per the '81, not the '78/9.
The head and cam may be repairable, but the cam would cost as much to repair as a new aftermarket cam. The head would have to be heliarc welded and re-machined. I don't know if you have a shop nearby that can do the work, but there are shops that can and will, again for a price.

[lostgmc]

You said something about aftermarket cams. Where would a good place be to get those.

[TopCatGr58]

Hey LostGMC,

The 81 does NOT have the YICS system, it's essentially the same as the 80. Allegedly it may have smaller diameter valves, due to changes for emissions.

DiverRay, we would like to know where these "Aftermarket" cams can be found!?!?

Is the cam damaged, or just the head journals/bearing combos!? Aluminum can be welded, and so it possibly could be repaired, but you may be able to find a used head and cam combo from an otherwise dead engine that should be a straight bolt on! So...if you have an 81 head and cams, it should work just fine, but might cause a slight reduction in performance due to smaller valves.

Hopefully, Ken Talbot, Denny Z, or Ken Daniels(Ratbyk), will chime in here, GURU's with more engine knowledge than I! !

[DiverRay]

I didn't know when they started the YICS on the eleven. I've only had the '78 and '79 models. I know there was a thread on here about cams, and they did have a listing, as I went to the web page. As money is still tight, I have not bookmarked the page.

[DiverRay]

Here is a web page with a camshft listing!!

http://www.webcamshafts.com/yamaha-moto.html#16

[chevy45412001]

cams

as you can see diver ray and others,the cams ARE NOT AVAILEABLE. that list says regrind...n/a and new cam ...n/a. It looks like you send in your cam then they will hard weld it and make it so..

[lostgmc]

thanks for the replys the other part of the question I forgeot to include is can I us an 81 cyl. section( I have a buddy that has one with a 1179cc big bore kit and only about 200 mile on it) with a 78 head or will there be clearance problems? Thanks to this sight I might have been able to come up with a correct head.
and if I cant you the 81 cyl section does anybody know a good place I can get my cyl section bored to put in a 1179 big bore kit, preferably so where close to NE ohio(geauga county, yes the lovly snow belt area, so I have plenty of time before this white stuff is gone so I can ride again)

[Czekus21]

Talkin about the difference between heads, The XJ that I have has got a sparkplug hole that is stripped out severly. I have a head for a 79 sitting on the shelf. Does anyone know if the head will work on the XJ? I know that the XJ has the YICS. What exactlly is the YICS? I don't have an XJ manual yet and will not buy the manual on CD. ( I need a hard copy so I can refer to it in the shop. Not in the house. ) The XJ is pretty much complete. Next question. Will the XJ carbs work with an XS head?

[chevy45412001]

stripped plug hole

you could always use a heil coil to fix the threads,(see other post on that i believe jerry was thinking he got a bad valve from that fix) yics i'm not XSactly sure, emmmisions or cold start helper something like that. as far as carbs you can make anything work given enough time and money. But i personaly like the XJ carbs,(even though i have no XSperiance with the other years). The cd on rom would be a good investment (shamless plug ) you can print it out and take it to the garage,but i know what you mean i like to page through the mannuel myself. . Even though the XS man is for those years,i have been using it for my XJ even did the cam chain with it haven't yet found it not to help me ,besides we always have this wonderful site to help over the lumps....Ok Ok i'll shut up now.......

[Jerry]

The YICS (Yamaha Induction Control System) has 2 components not found on the XS.

There is a vacuum balance port cast into the cylinders just under the carb inlets. This port needs a special tool to block it off when synching the carbs, otherwise you are pulling vacuum from a shared source instead of each individual carb.

The other change is a small port cast into the head. This port leads from the carb inlet to just behind the inltake valve. The purpose of this port was to 'swirl' the incoming air/fuel mix, causing a more complete burn. (Bike could run leaner, create fewer emissions, and not loose to much power.)

Because of these modifications the XJ cylinders and head carry different part numbers than the XS counterparts. However, I do believe they are interchangeable. Ken Talbot's SO rides a bike (Purple Reign) that looks like it has XJ cylinders under and XS head, for example. There is a difference, cosmetic only, between the XJ and XS valve covers.

Carbs will interchange will small modifications. The XJ uses a handlebar-mounted cable operated choke system, where the XS uses a mechanical system mouted directly on the carbs. XJ Carb inlet size is 54mm, where the '78 - '79 models used a 52mm inlet. (The other '80 - '81 models also use the 54mm inlet.) So if you put late-model carbs on a '78 - '79 you will have a slight mis-match between the carbs and air box but not between the carbs and engine. The XJ carbs are jetter leaner than all the XS carbs, so you will probably have to re-jet if you use them on an XS.

In short, the XS head should fit the XJ, but you loose the 'swirl' port...which didn't seem to be very effective anyway. The XJ carbs will fit the XS head. You can use either the XS or XJ valve cover, differences are cosmetic. You will still need the special tool when synching the carbs (YICS blockoff tool.) Instructions for making your own are in the Tech Tips section. Exhaust stud mounts and gaskets are the same, no problems fitting the XJ exhaust to the XS head.

BTW, you can print out any/all pages of the service manual off the CD. I would go ahead and get it. I have both the shop manual and CD. I find myself printing off the few pages I need for any given procedure and taking them with me to my work area. If the pages get greasy just toss them and print out new ones, keeps the factory manual nice and clean, and the pages lie flat. And since the CD also has the parts microfiche, you can view/print out exploded views and parts list which are not in the manual.

Another good source for views and parts number is Yamaha's on-line parts catalog at:

http://parts.yamaha-motor.com/

HTH

[TopCatGr58]

Hey there LostGMC,

The only changes to the 78 vs 81 cylinders appears to be the little rubber camchain gasket that was eliminated in the latter years, and with the BIG BORE kit and gasket, it's not needed anyways.

The heads were changed with smaller diameter intake valves, and possibly modified the cams with different lifts, durations, again to reduce emissions in the latter years, but there won't be any clearance problems. And if you put both the 81 cylinders and 81 head on the 79 case, it's a no brainer.

BTW, with the 81cyl. big bore kit, you're getting a bigger "bang" compression ratio anyways...! The 79 states a 9.2:1.
Take stock max. compression 142 psi, divided by sea level pressure of 14.7, it's about 9.6...close!

After my big bore, I got 185psi compression! That came to about 10.5:1, so a nice boost even with the smaller valves and ?milder cams! I use premium gas due to the increased comps!
Have fun!

Jerry, thanks for info, I didn't realize the heads were ported as well, I thought it was just the jugs on the XJ.....very interesting!

[Jerry]

I have a .jpg of the specs page for the XJ here:

http://idisk.mac.com/jerryfields/Public/xjspec.jpg

It gives a brief description of the YICS system and mentions the head porting. File is large, about 1.7mb, so it may take a while to load. Page is from an original XJ sales brochure. Page includes other XJ specs for those who may be interested....no HP, only torque figures.

[Dan Hodges]

Originally posted by TopCatGr58
Hey LostGMC,

The 81 does NOT have the YICS system, it's essentially the same as the 80. Allegedly it may have smaller diameter valves, due to changes for emissions.

DiverRay, we would like to know where these "Aftermarket" cams can be found!?!?

Is the cam damaged, or just the head journals/bearing combos!? Aluminum can be welded, and so it possibly could be repaired, but you may be able to find a used head and cam combo from an otherwise dead engine that should be a straight bolt on! So...if you have an 81 head and cams, it should work just fine, but might cause a slight reduction in performance due to smaller valves.

Hopefully, Ken Talbot, Denny Z, or Ken Daniels(Ratbyk), will chime in here, GURU's with more engine knowledge than I! !

The 80& 81 have the big valve heads and so does the 82,but the 82 has the YICS.The late heads also have larger ports and bigger combustion chambers and will out flow the early heads (78-79) by ten percent.Web cams has a number of cams that work well,depending on what you want to do.The early cams,have 12 degrees more duration than the late ones,but the late ones have .020 more lift on the exhaust.One more time,late heads have 2 millimeter larger intake valves and 1 millimeter larger exhaust.The valve size is covered in the shop manual.

[xschop]

have to bring up old thread

Can some kind XS11 expert give advice on what is the absolute best combo of HEAD, CAMSHAFTS, and PORTING that can be done to STOCK parts. I am confused on the best Camshaft combo to use, duration-lift,early-late years. I have 3 or 4 spare Heads to work with and one is definetly an 80 model which someone posted had the best flow porting from factory. Thanks to T.C. for his help.