Weekend(s) Task?: Splitting the Crankcase

Hey All,

So in fixing my last problem with a valve opening while the piston was on a compression stroke, the camchain tensioner guide slipped into the crankcase.

I didn't think this was possible, but as have not found the guide laying around my garage, and I forgot to reinstall the tensioner assembly, the only place it could be is down in the crankcase.

So obviously, I now need to split the crankcase to retrieve this guide, and inspect for any damage to bearings or other parts. (The bike was not in operation as this occurred, i was turning the crankshaft by hand to diagnose the timing issue)

I don't expect there to be any serious damage, maybe a scuff or two on the tensioner guide, but that isnt important.

What I want to know is, how difficult is it to disassemble/reassemble the crankcase, is it a weekend thing, or two/three weekend project.

I have the time, but the service manual, again, is not super descriptive. It seems like there is quite a bit of removing crucial parts, and the manual doesnt specify what special tools may be required.

On a scale of oil change to top-end rebuild, how difficult is this. any tips?

EDIT: of course I just found a thread that details this task, after posting. I guess I will still ask for any advice though...

In my opinion, it's a fairly involved task that mainly requires patience to do well, especially scraping away the old gasket material. You could do it in a weekend if you have all the parts at hand, and everything cooperates.

IanW said:

In my opinion, it's a fairly involved task that mainly requires patience to do well, especially scraping away the old gasket material. You could do it in a weekend if you have all the parts at hand, and everything cooperates.

Click to expand...

Not having done an XS400 but having done an XS650, in the middle of one of those right now, I would say that the most important thing is to have everything as clean as possible before starting. Also make notes as to where what fasteners come from and where any washers may be located. And if it does not come apart real easy keep checking for that bolt you missed!

I did an engine teardown/rebuild in my build thread.
Actually I did two DOHC engines this past winter...the first one took about a week (working on in th evenings after work), the second one took a week(same working schedule).
Then one of those sprung a leak at the front of the crank case si I had to re-split the whole thing, that was done in one day(an 8 hour Day)...

As I'm in the middle of a rebuild now, I have split two crankcases in the past 3 weeks. Keeping track of everything is the most involved part, as well as removing old gasket material. Get a bunch of cardboard and use the cardboard trick to help keep track. Also, a large amount of ziploc bags to label EVERYTHING.

Tips I would say are:

1. order new gaskets now! Before you build, so they will be ready by the time you need them. I ordered these ones from eBay (partly because they were low price, and partly because the seller is also in Canada like me).
2. Removing the gasket stuff is a pain in the ass. DO NOT be tempted to use any kind of steel scraper, because it can gouge the aluminum crankcase more easily than you think.
   • I found peeling and picking away at the old gasket with hard plastic bits and Scotchbrite pads/kitchen scrubbers (Credit cards, bbq cleaners, etc) worked well.
   • You'll also need some kind of solvent, that's essential. Gasoline works well, as does generic Brake Cleaner spray-on fluid (Gunk brand is solid).

This is just some advice from a first-timer that I wish I knew first!

Theres some bolts on the top of the crankcase, and most are on the bottom. Its not too hard. The case will split freely. It seems like a lot of people on here are so eager to split an engine when they dont need to at all. Its a slippery slope

Honestly, Id probably buy a bore scope because the thought of me having to split my own engine again makes me feel woozy. Dont get me wrong, I loved every second of it and the satisfaction of hearing my engine start up and ride it for the first time was amazing, but finding parts and shelling out a fortune to get them......No thanks. If I do another build, I will do a bike where the parts are easier to come by...