Engine Overhaul - Assistance Needed

Hello all:

I bought this bike a while back. I was experiencing some rattling noises and cylinder 4 not firing despite spark and compression. I feared that the rattling was a loose primary chain and the cylinder 4 not firing, I figured a whole engine teardown was in order.

Getting the engine apart was an ORDEAL to say the least. It took some extraordinary persuasion to remove the cylinders and in the process, one of the studs fell(broke?) out. See picture attached. Are these press fit or is there any way for me to re-install the broken stud, or is it game over?

Another piece is that one of the side covers (non-pickup assembly side) had considerable rust on the screws holding the cover on. Trying to remove the screws proved impossible and the screws ended up breaking off after giving them some considerable force. There is a screw still lodged in the upper half of the crankcase, and 2 screws lodged in the lower crankcase. Pictures are attached. Is it possible/advisable to drill and tap new screws, or how should I go about removing these screws and securing the cover?

One other piece: Maybe I'm overlooking it in the manual but I have no idea how to remove the valve stem seals - the piece that is somehow secured inside the valve ports that guides the valve. Once again, if someone can point me to the correct section/page of the Haynes manual or a video/thread describing the process that should be sufficient.

Thanks all for the input. This is my first real bike project and it is proving just as tedious and frustrating as I expected lol, looking forward to the payoff though. I'm really fortunate for the amount of online resources and the active community.

Cheers
-SS

 

Long engine studs: they screw into the top of the lower crankcase section (which is threaded to accept the threaded bottom end of the stud). Replacements are available, we have them listed in our catalog at:

https://www.xjbikes.com/forums/threads/xj-parts-catalog-section-e-engine.44640

It appears that you're missing the rear stud between cylinders #1 and #2:

HCP5757 OEM cylinder head-to-crankcase LONG STUD, for all XJ650, all XJ700 air-cooled, all XJ750 air-cooled, and XJ900RK, RL, N, F, and FN engines, use 4 per engine, one each in the following positions: in-between cylinders #1 and 2, rear; #2 cylinder inner rear, #3 cylinder inner rear, and in-between cylinders #3 and 4, rear. NOTE: the original stud used (only) in the #2 rear inner position had a shouldered bottom that limited the depth of entry of the stud into the upper crankcase threaded bore hole. These studs no longer have this feature. Each:


Side cover screws: if you're really good and steady with a drill, then using a proper sized EZ-OUT tool may be successful, and that is after soaking the holes with penetrating oil for a few days. If you're not really steady with a drill, or if the ez-out process fails, take the cases to a machine ship which can precisely line up the drilling process so that the threads in the case don't get damaged......there's not a lot of extra "meat" around those holes, and a replacement threaded insert ("helicoil") may not even be able to be placed for repair.


Valve stem / guide seals: the seals don't really "guide" the valve.....that's the job of the valve guide, which is a 2" or so long hollow tube that is pressed into the cylinder head (and normally do not need replacing.....or even if they do, no one ever replaces them anyway.....). The seals sit at the top of the guide and provide for a controlled flow of oil to lubricate the valve stem and the valve guide. To get at / replace these seals, the valve keeper/spring/collets (and finally the valve) must be dis-assembled and removed from the head. A valve spring compressor tool allows the tension to be removed from the springs (there's actually 2 springs per valve) and the collets and retainer can then be removed, the springs removed, the valve dropped thru the seal and the guide, and now you can remove and re-install a new seal.

Typically, stem seals are removed / replaced as part of the "head job" a/k/a "valve job" and involves other tasks, such as checking / surfacing the head for absolute flatness, grinding the valve faces and valve seats, checking valve springs and valve stems for straightness and meeting specifications, and checking / replacing the valve guides as needed. Although all of these tasks can be done "at home", I'd recommend finding an automotive or powersports machine shop to do the complete job for you.