Cam fitment

[Aches n Pains]

All,

Well, I'm learning more and more about the PO of the '79 Special. He replaced 7 of the 8 valves (can't imagine why but I'll replace the last one). The valve cover was just set back on and held in place with two bolts. Figured I'd pull it off to confirm that everything looked good.

Surprise, surprise. The intake journals had not been installed and are missing from the parts box. I hate to use journals off another cam but may be forced to do so. My question is whether or not the cam journals off a 1979 Yamaha XS1100F will fit my '79 Special. Are journals from other years interchangeable?

By the way, I went ahead and pulled the cylinders. Pistons and rods look very nice but while I'm in I think I'll go ahead and replace the rings. Piston sleeves look great. Any suggestion re: where to get good OEM rings and valves?

Thanks,

Aches n Pains (Doug)

[DiverRay]

The cam journals are fitter to each head, and may not work. IF you can get "new" ones, you should have them line bored to make sure everything lines up and is the proper size. If they are bad, the head needs to be replaced! The head and caps ARE the cam bearings
For rings, try to find 1st over and file to fit. I don't think the "stock" size is available, but I could be wrong. Valves can be had from geezer, I think. I know he was going to have some made, I just don't know what happened with that.
If it gets bad, you can always post you need a serviceable head. I'm sure there are a few of us with a spare or two.

[natemoen]

Yeah the cam bearing caps will interchange from any year but it is sort of one of those matched set parts that is machined together. I guess if you dont have them you have no choice but to use caps from a different engine, it sucks but ya gotta do what you gotta do.

I would say to do a gentle break in of the cams and then check them every 100 or 200 miles for the first 1000 just to make sure everything is wearing together well.

[mack]

Po

First thing I'd do is contact the PO and see if he forgot to give you some parts. He may still have them. They are not something you'd intensionally throw away.

[crazy steve]

Yep, if you're missing the caps, you probably will need to get another head. Like Ray said, the caps/head are machined as an 'assembly' and swapping parts is generally a big no-no.

What you could try is this; pull all the valves, then install both cams and torque the caps. I'm assuming you have the original caps for the exhaust cam and can get some caps for the intake. If the intake cam turns as easily as the exhaust cam (and I'd check it with a beam-type inch-pound torque wrench), then you'll probably be ok. If it's looser or harder to turn, then you're talking machine work that will greatly exceed the cost of another head...

[Aches n Pains]

As an alternative, I have a spare 81 head. Would that be interchangeable with a 79?

[crazy steve]

As an alternative, I have a spare 81 head. Would that be interchangeable with a 79?

That will lower your compression slightly, and you'll need to check piston-to-valve clearance as the '80-81 heads have larger valves; your '79 pistons may not have large enough valve reliefs. You may have to swap the '81 pistons to make it all fit. One thing you can do is install the '79 cams in the later head as that will give you a slight power gain as they're a bit hotter than the later cams.

[crazy steve]

Actually, what you should do is pick up some Plastigauge (most auto parts stores should carry it) and check the cam bearing clearance with that. If you come in within spec (as per the manual), you should be good...

[WMarshy]

Actually, what you should do is pick up some Plastigauge (most auto parts stores should carry it) and check the cam bearing clearance with that. If you come in within spec (as per the manual), you should be good...

I second the plastigauge. If you think about it, the clearance is all that matters. Yes its probably likely that during the machining or these motors they were all machines together. Don't let loosing a bearing cap keep you from using that head, you can pobably buy a few and find one that gives the correct clearance. If the bearing caps were machined for a specific cam with a specific clearance then its safe to say that those clearances are going to change with a cam from another motor. In that case, your looking at all the caps having possibly too tight or loose of a clearance, and instead of having one cap out of tolerance now all of them are... to me, the logical decision and cheapest would be to buy a cap or two and plastigauge it.

[DGXSER]

Interesting thread. On one hand it is stated that the cmas and caps and heads are a matched set, and it would be difficult at best to interchange them. Then there is a suggestiont o swap cams between engines. The two would seem to exclude each other.

I would definitely start with the PO and see if they are still laying on his work bench. If that failed, I would think your probably going to have better luck finding a head than just caps. For the exact reason stated here that they are a matched set, I know when my 81 head got trashed in the wreck, I scrapped it cam caps and all. I saved the cams for a while, but no one ever had interest so they went to the scrap yard as well.

[79XS11F]

Your not likely going to find cam caps separately from a head so to get them you would likely end up buying a head with the caps. If you can find caps alone you can use them with care. It's all about the clearances so you would have to check them very closely and break them is with care as is required when you change crank and con rod bearings. If you get a different head salvage the new valves, best springs, keepers etc.
Rob

[skids]

Obviously, if any of you are thinking about buying a used head, make sure you ask questions about whether the cams, and caps, and head are original. I have seen numerous postings on ebay for those items sold separately. The same holds true for middle drives!

[crazy steve]

Y'know, after looking in the parts fiche and at the semi-disassembled head I have, there may be no reason why you can't swap caps between heads. I know, I know, that flies in the face of everything I've been taught about bearing journal machining, but there's several interesting things going on here..

First, there's no locating dowls. In every case I've seen where you have 'matched' parts, either it's machined to only fit one way or there's a locating dowl to index the part. These are conspicuous by their absence. Second, Yamaha shows these as a replaceable part, and what's more, they show them as generic i.e. the same cap fits in all positions except for the center thrust cap (While these do have locating dowels, it's same thing here; one part # for both caps). These are also the same parts for all years/models XS11. Given the rather large allowable clearance spec ('normal' is .0008 to .0021", but you can have up to .006" or almost triple), swapping caps may not be a big deal. I would very definitely check journal clearance though...

To thicken the plot a bit more, this isn't true of the XJ head; here, the caps aren't shown as separate parts but are only available with a complete head. So, did Yamaha screw up, then come to their senses with the XJ head, or is the XJ head somehow different enough that these parts won't swap?

[natemoen]

Each cap Does have its position and orientation labeled on the cap itself though.

[skids]

Each cap Does have its position and orientation labeled on the cap itself though.

That is what I remember also...