Headcover fit from new models? Update!
 

Do the headcover from 1998mod fit my 93mod, what changes was made on the next engine? Is it any point changing only headcover or is it best changing cylinder/headcover in one unit for best fit?

The Rocker box and head should be replaced as a matched pair. I know some on eBay sell them separate, but this is not good. The cam bearing function is the combination of the two and should be matching to assure a proper clearance. You "MIGHT" be able to get by, but do you want to take a chance?

My opinion, I am sure others will jump in...

I do not know if the 89 head will fit the later model.

Yep what Steve said , the head and cover go together unless you remachine the bores together like I had to on one of mine. I'm sure quite a few can be swapped around, depending on how Yamaha original located the parts when machining them, but it would be a crap shoot.

Still have the oil leak huh? Maybe it's the head itself that has a flaw.

Ok i understand, yep leaking never stop. The strange thing is that i have located it to be beetween front and rear screw left side at the plug cap. I really dont see how only this small area can be uneven, stupid me came just now came up with the idea of measure if there is a gap when cover is on without sealent. How much can the sealent fill up?

I don't have a solution short of replacing the head and rockerbox as a pair but I had a similar problem with an 82 HONDA XL500. I understand this is quite common with that model as they do not have enough bolts to evenly hold the rocker box in place. I tried several times using different sealer, letting it sit for days to dry and NOTHING solved it. I later sold it on and next owner replaced the head and rocker box to solve it....

Steve

Sort of sounding like maybe the faces are not flat or at some point in past its had something jammed in to lever it off maybe?
If you can find someone clever they maybe able to machine the mating faces of the head and camhousing flat then take the bore then bolt both together and remachine the hole the camshaft runs in to the correct size..
Alternatively the machinist may say 'what are you sodding around with bloody old rubbish for?'....trouble is some of this bloody old rubbish tends to keep working long after some newer stuff has deceased..
I'd say your options are machining or another head and cam housing..

Never have been any problem with leak before, bike has 35000km and the only reason i did the seal because of the O ring leaked on the side of cover. I had an idea, what if i just put minimum of sealent around the cover and add some more where the leak problem is? Just thinking adding even around gives no help in a problem area, does it sound way out? Or maybe iam wrong and there problem is a high spot that makes the seal go away in that area, next time i will put the cover back and try to get feeler gauge in there and check clearance.

A feeler gauge should let you know what your dealing with. It's just weird that one of the sealants didn't fix it, the oil isn't pressurized up there so it is just flung or running past that area. Nothing should be forcing it out.:confused1:

Ok, have been out for hours and testing, checking every 15min around the engine with paper all around. And i think i have found the reason, the oil never came out on idle, i think i found a crack. Its strange that oil can come out in the top like that, but i guess in high speed it get sucked out. Oil was coming down to the sealent at the same spot every time when riding down hill, so i have fooled myself thinking its the sealent..

My big question now is, can i clean up this and use dremel to grind a little. Then use the alu stick over the area? please dont tell me i have to take cover off for welding? Iam just happy now for finding the leak:D:D

http://s18.postimg.org/dwosdkr21/DSC_0006.jpg
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http://s7.postimg.org/qx26thl2j/DSC_0008.jpg
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Take the mount plate off to gain good access to the area and grind a "V" groove the length of the crack on fill it all with JB Weld.

A true TIG aluminum welded fix would be best(take the cover offdoh), but the JB may just work.

I would have thought a leak from that area would show up in the back side of the cap not up by the front, sure there isn't more of a crack on the other side of that area?

Yeah the TIG was my fear hehe. I have the alustick so i think i give it a try, i have grinded i little as you see in pict just to check if its deeper. First it looked like just crack in top surface, isnt it strange that so mch oil can come out in the top of the cover after 2hours riding?

Is this possible to do on the cover?
https://www.youtube.com/watch?v=hHvrE1Cd5Eg

That is a stress point, the engine mount is flexing the crack, more so at speed. This means that you will have to have it professionally welded, hopefully it will not warp. If this were not a stressed area, you could seal it with JB weld. Expect the worst. Hope for the best. I expect a good heli arc welder can "fix" it. He may grind out a "V" as well, It would be best if you can soak the cover in solvent to get as much oil out as you can. If not, oil will try and seep out of the crack during welding, not good.

Steve

So you dont think that the alu stick can fix this? When we talk about heat, what is best for this, heat up to 350degrees for alustick or do TIG? Dont want anything else to get damaged, iam thinking its best doing this job with cover on engine so it wont bend heating.

This is the Alustick

http://www.ebay.com/sch/i.html?_sop=...ardweld&_frs=1

And how thick is alu at the point i want to fix? Seems strange if its only my engine that its happend to, hope someone else have done the repair.

Since this is a stress point, NOTHING short of a full aluminum weld will be strong enough. Engine torque will keep breaking the glue or weak weld. I don't think you can weld it on the engine due to the heat involved and the oil. You will most likely have to completely dismantle the rocker box, remove all the parts and seals as it will get very hot from the welding. Hopefully if the welder is good, he will preheat the whole piece then weld it and let it cool naturally, hopefully it will not warp.

Ok i understand, but what you mean by stresspoint? I think i will try with the wizard weld, this i can do with nothing removed. The temp on a TIG weld is extreme and iam more scared to damage the cover than not getting sealed. This engine monting is only for stability, its not like the engine is hanging after this monting. I was out riding now and had one hand on the engine on different rpm, cant even feel vibration.

Why would it have cracked in the first place if not a stress point... Remove the bolts, see if the leak is less.

Good question why it has happend, never heard of it before and havent had that experience with older xt with twice mileage. Just tried to understand what you mean with word stress point, i quess you mean that its alot of movement on the monting, I recon if there is so much weight on that monting they would have done it with more strength. I will call it just my luck and seal up and ride for as long as it last, if it cracks more i can try TIG.

Unless other things are flexing, like the frame, there shouldn't be any hard stresses, but I'm sure these frames flex especially under a load. Tig welding is ideal and it will most certainly warp some, but how much ??? If it is bolted down to a heat sink when it is welded it would minimize warpage , but it really should get remachined after . I'd try some of alustick or JB and maybe leave that bolt a bit loose, I don't know just how much it is critical to have it.Maybe look at making a bracket to mount else ware so that one can be let off. Otherwise your looking at a big fix. This way you "may" get by without , worse case is it doesn't work and you have to weld it.

EDIT : I went out to see how thick that cover is around that mount and have the one off my 3TB sitting there. Well looky here,
http://imagizer.imageshack.us/v2/640.../822/robxy.jpg

Cracked just like yours all the way around to the inside by the sparkplug. I got 2 covers off the older '80's motors and noticed the newer cover is thinner on all the areas for bracing and strength. The dip for bolt/socket clearance right below the hole is deeper and runs all the way out where the older ones just have a shallow droop just below the hole itself . I think we just uncovered a design flaw. I guess I'll be machining this one if I use it on a motor otherwise it's getting gutted of rockers and tossed.

http://imagizer.imageshack.us/v2/640...0/840/6k2c.jpg 3TB
http://imagizer.imageshack.us/v2/640...0/849/qz36.jpg '85ish
http://imagizer.imageshack.us/v2/640.../842/aaxkl.jpg

Then there IS stress there and a weaker designed mount shows this up..... How much plainer can it be. Yes, it will be a problem fixing it. Like Jim said, if you can bolt it down tight before welding, it might not warp, preheating the part evenly should help prevent it if it cools down slowly all over....

No kidding there is stresses , that's why I said if the frame flexes, which they do, but are these mounts truely needed or are they trying to fight movement that doesn't need to be stopped? Sometimes more mounts fight each other and cause more problems than they solve. maybe the newer frames are thinner and move more also and those aluminum covers are the weakest point , add in hot/cold cycles with vibration. Rubber mounted would probably stop the cracking because solid mount do cause cracking ,just because there can be no movement, maybe that's whats happening.
Two of my bikes didn't have those top mounts hooked up, didn't look like they ever where or were taken off early in life with no apparent ill effects. When looking at the frame geometry it is trianglated without the top mount, they may be causing a pinch point .

We've welded enough aluminum to know there will be warping, even bolted down, the weld shrinks that area and will pull up no matter what. Letting it cool bolted down minimizes things but won't stop it. Stainless is 10 times worse.

Thanks for all the info, this is not anything i have experience with. I was thinking of getting a thin rubber spacer beetween engine and the frame monting to unload some of the vibration. If you put like these on both side of all the screws. I dont know why they didnt make it more flexible from factory. Actually the bolt that hold engine should have been thinner with rubber bushing around, the side that cracks has only support backwards and thats a big mistake from the engineer if you ask me. I can buy brand new cylinderhead + cover and after a short time of riding i will experience a new crack at the same spot after spending 800dollars + all worktime.

http://s21.postimg.org/50xiyutcz/rubber.jpg

Iam not shure its possible to get a good weld inside the cover,is it possible to see cracks inside your cover JJrider?

http://s1.postimg.org/o56eeoc5b/topp.jpg
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Are you 100% sure those are cracks and not casting marks??

Mine looked the same before i grinded, it was never in my mind this was crack and possible for oil to come up. After grinding more oil comes up, so what you think is just marks today is maybe a leak tomorrow.

IMHO it's not the vibration making the crack....

not hard to imagine that if that top bolt is over tightened, the two soft alluminum ribs will compress a little bit an cause a bending stress on the ear (that does indeed break). first gen gsxrs had same problem in the their bottom rear engine mount.... dont ask me how i know...

now then, when building my XTZ supermono i had to design a new top motor mount and indeed, passing a through bolt didnt make any engineering sense to me.

i therefore ground a bit TWO separate M10 allen bolts to fit from the INSIDE so no compression stress is put on those ribs / ears. might be wise for others to do in the future to avoid such problems.

now that i see this, I will do the same in my XT supermoto engine!

another solution could be to fit a very tight fitting steel sleeve between the ears to take the compression load.

yep, even perfectionist japanese engineers can get it wrong sometimes,

in your specific case i'd surely go for DEEP welding, also from the inside. if you weld only outside the crack will propagate again.

Well i dont really know what causes this, but its good suggestion to insert a steel sleeve inside. I know i never been overtighten this bolt, if dont remember wrong its 65nm on those bolts and thats pretty damn hard..I think its a more complex problem with movements and heat, bad support on that ear+++. If this thread can lead to others not having this problem its fine, i will first talk to someone that do welding all day long before i decide anything. If its a gamble of the head cover beeing damage i will seal up the oil leak and reduce stress to the ear and ride for as long as it last and buy new. I recon the price for welding is so high that i prefeer buying brand new! Honestly, the last thing i wanna do is going back to the seal problem again with cover not align to head...

I can just add that my cover never had been taken off before, it was the original seal on. I had the bike for 6years before the crack came and i never tighten the bolt before, everything seem normal at release.

G600 , it is most positively a crack and not casting lines, in person you can see it better.

Now that it has been mentioned I remember seeing steel sleeves in my 660 motors mounts.

if you decide to just reseal, would actually do it from the inside.

rough up well and clean with solvents all the area to be sealed and use some high quality Araldite, brushed over in a not too thick layer. big blobs will break off...

that said, i've welded heavily long cyl heads in in-line 4 motors i tune for racing and never had warping problems. see very little risk of bad distortion with the valve cover if you weld.

Ok thanks for info, for now i just use some sealent on top, made a sleeve and see if it stop leaking. Hoping it last this summer and get it welded when its cold and rain again...

I may play with mine to see if it stays, worse case is I throw it away or remachine it anyways. The worst thing is the bores for the rockers, they have tight tolerances and need to be inline, one is right below the bad spot and any movement will make them not fit. It would be more work than it's worth to have to bore out any of those to put a bushing in and then re-line bore it.

I can see the crack on the inside, it goes right betweem the 2 bosses for the rocker shaft, a small TIG torch will fit but there won't be any room for the side to side sweep, MIG would work but not as nice, also welding inside would cause the cover to cup inward, how much again ,can't say, but any little bit will be a problem . If I do mine I'll just drill a small hole at each end of the crack and weld the outside.

I have the same issue on my 1990 but the crack is worse. I got the bike at 24,000 miles and it must have been an issue already because it was caked with congealed oil already and when I re-installed the engine it got worse. I put some oem grey gasket maker on there for now and left the mount loose. I haven't noticed any bad side effects as of yet. Why they would thin the mount out and still have 46ft/lbs on such a fragile part makes no sense...

It kills me to have such a ghetto fix especially since the rest of the bike is totally freshened up with OEM parts and well sorted :thumbdown: but I am not taking it apart again unless I have to.

I have about 42,000 miles on it now so those of you with e-start bikes with less miles just throw some rubber donuts on there to maybe keep if from cracking in the future.

Yes i agree with you, it can be done welding but how much fun is it paying for welding and when you come home you cant get the rockershaft in... Tommorow iam taking the bike out for fun again, i also hate to have things like that hanging around with everything else in perfect condition. Looking forward to hear what happens JJ.:thumbup1:

Jens you have over 100k on your bike and no crack?

I've got no oilleak's, havent looked for cracks, but didnt notice any when I rebuild the topend at around 125.000km. Im around 148.000 now.

I will look next time im messing with the bike.

As someone suggested, mount some bolts from inside, and mount nuts on the outside, so you dont overload/stress the top cover.

But I must say, this is the first I've ever heard about this. Theese bikes has been around for ages, even the newer ones are over er 10 years old.

Cant wait to se the solutions you guys come up with, and if it helps.

Damn 148k thats amazing, in my early days there was this transalp with 200k with no rebuild. I dont know about putting weight on each ear like that, better off with sleeve inside. What did you do in the rebuild?

The XT600 Thread - Page 359 - ADVrider

Look here for solution to your cracked rocker box.

Bored/honed the cylinder, new piston with rings, and a new camchain since I was in there.

Theres an xt600 here in Denmark which got 250.000km on the clock before the first rebuild. A think it was from 1986, its one owner, and used for commuting.

well, couldnt resist the urge to, first check if my xt600 suffered form the same crack (even if there were no leaks) and second, check if the solution of two bolts in order not to compress the ears could work.

Well, it does! about one hour of work, not exactly super easy, but reasonable for anyone with good hands.

So the easy way of fitting from the inside two M10 allen bolts like i did in my XTZ/TZ supermono racer can not work. the distance between the ears in the XT motor is smaller and after you fit one bolt there's no room to fit the other one.
So went the other way around, with nuts on the inside! thing is that the width between the ribs is about 15.8 mm, smaller than the width of an M10 nut which is 17mm. ground two nuts on a sanding belt + some dressing, and it works like a charm. A bit tricky to put back because of lack of space around but it's all back together and i could hear the head releasing a sigh of relief for not being stressed between her ears :)

Took photos too, just bit busy this evening, Brazil vs. Germany in TV, will post in the next few days.

It wont help those with the crack, but could be good prevention for all others. Maybe the admin will want to make out of it a sticky: "Turboguzzi's head fix" :)

Good show, anxious to see it.

ok here we go, first pic shows the xtz top ears and you can see that hey are wider spaced so i could fit two bolts form the inside.

so this is how i modified a normal M10 nut, sanding it down to about 15mm and also rounding the two corners as the cavity has some radius from the inside.

you really have to make sure that the nut will fit freely in there and seat over the flat area. if it's too it will wedge the two ribs appart and crack them... take the time to dress it until it fits well.

used two M10 X 25 bolts to bolt it all back together.

BTW, the original long bolt has fine pitch, so no surprise that it will puts so much compression force on the ears... i used two normal pitch M10 bolts and some loctite.

Nice!!

How about using two buttonhead bolts and grind them down? That way one could have the nuts on the out side... could that work?

http://images.esellerpro.com/2407/I/...Cap_Socket.jpg

The solution you have on the xtz is good, if you only have bolts in each side and use same bracket as original i dont like the idea. You get no support from the other side and the center, if there is a small twist when riding it will brake of the ear fast. Iam not a engineer but just my 2 cents..

I would think a bushing between the mounts to squeeze against would be better as you can use the same bolt and get the same amount of support but not squeeze the sides together, breaking them. The bushing would need to be a tight fit to be effective.

my 2 cents

Either solution is better than stock , my 1/2 cent.:innocent:

I actually have a degree in engineering and did aeronautical structural design for five years, but didnt get around to do any finite element analysis before doing the mod :)

the tube fix is just as valid, but you'd need to find a tube with 15mm OD X 10mm ID (very unlikely) or turn one on a lathe (as well as hand fit it so it's really tight and takes the load). what's nice about the two bolt solution is that it's really DIY, you need only a bench grinder or file the nut till it fits.

but there's another angle to it: with a single bolt & tube solution (but also in the stock situation), when the head expands under heat, the single bolt creates an even bigger bending force on the ears (the steel bolt expands less). who knows, that might be part of the stress that cracks the weaker ear on the right (it has a shorter base with a deep 90 cut at the front that creates stress concentration, really bad design practice).

With the two bolt solutions, the ears can easily expnand (the 3mm steel plates are not that stiff) without any thermal expansion stress.

so there are pros and cons, but surely both are better than the stock solution where the ears are ALWAYS under a bending load from the bolt.

Really good analyses, thank you.