Leakless XS Assembly

[grizld1]

OK, Six-Five-O, I'll kick off your request for a thread on this topic 'cause I probably have the least to say, being the least experienced of the three guys you called on.

For starters, the single most important thing for the novice is getting the surfaces clean. If they aren't clean, they won't seal. Be gentle and take time.

Take a look at the construction of the engine. Unlike the Brit. vertical twins, the XS650 top end is put together on 8 long studs that extend from the cases through the head cover. They make sticktion and stretch serious issues in assembly. When I put one together I let it sit overnight and retorque, let it sit and retorque again, until I get steady readings; the engine doesn't go into the frame till then. Then it gets put in minus the head stay, warmed, cooled, and torqued again. Then it gets ridden, still without the head stay, for 50 miles or so, and torqued again. Mamayama says to take down your ignition to access the small head bolts by the spark plugs. A better option is to grind a 12 mm 1/4" drive socket down to a low profile, bend a right angle in a piece of 1/4" square stock, cut a groove 12" from the socket center in the square stock, and hook a good-quality spring scale in the groove. Pull at a right angle
and you have a torque reading.

I don't ride competition and build fairly mild compared to Dwayne and Jack, so my mills aren't subject to really extreme stress; I use Vesrah gaskets and generic aftermarket seals without a problem. On the head cover, however, I use copper washers in place of Mamayama's rubber seals. I've used KopperKote on the base gasket and never had one seep. This time around (got one ready for assembly) I'll probably pucky the base with Three Bond 1104. It's the same stuff as grey Yamabond except that you don't pay extra for Mama's autograph, and it's what to use on the head cover.

[crazypj22]

Good start. I'd say you need to be careful taking it apart as well (just like grizld1 did) loosen the tappet adjusters off before you get the engine in bits, its easier to hold them and if they are all the way loose you have 2 advantages. less pressure from valve springs on reassembly and there is no chance of adjuster catching on valve tip and bending it.
Except for the cylinder head use the recommended torque as well, too tight distorts covers and causes them to leak ( maybe not when cold, but give them a few heat/cool cycles.
If I get the chance I'll pull the head back off and take some pics (copper gasket so it wont get damaged) may try and persuade wife to take pics of me reassembling top end (not this weekend though ;D)
PJ

[crazypj22]

First few pics, dissassembly, without splitting cam chain
img327.imageshack.us/my.php?image=bearingremoval11co.jpg
img327.imageshack.us/my.php?image=bearingremoval27ah.jpg
img327.imageshack.us/my.php?image=camchainremoval4tz.jpg
Remove bearings both sides. Spanner (wrench is just to hold cam up while i take pics, If bearings dont slide off relatively easy they are not 'square' to cam, find out which way they are tilted and tap back on slightly while pulling on the 'low' spot
The cam chain has to come off to the right (looking from rear of engine, normal seating position) unless your splitting chain and re-riveting it.
Mark on cam is just reflection and I know theres a hair on the exhaustt valve spring ( well, not anymore ;D)
I'll show the set up for finding TDC next and maybe how to check cam timing. (head as been milled so I know its off, just not sure how far yet.
PJ

[mercurymorse]

I like Gaskacinch for base gaskets, with center punch in the two surfaces, as with high RPM motors, pushing it out can be a problem due to crankcase pumping; 3 bond 1104 is really for metal-to-metal surfaces--fine if you're not running a base gasket. I do use the copper wahers under the studs, as the stock sealers are a little gooshy. For the head gasket, it is important to put some sealer like Permatex Ultra Gray or1104, around the camchain tunnel and the studs with dowels, which are drain backs.

[jerry57g]

What do you mean center punch in the two surfaces? I 've been having trouble getting my 750 to seal right keep blowing out bases gaskets. Possible reason is the cyl is not a mate to the cases. The cyl I had on it was a mate to the cases from day one at Yamaha. I know even though things are exchangable things might not work together. I also have checked the cyl for square and its ok. I've ordered a copper base gasket and head gasket from Cometic. hope this cures the problem.

[jerry57g]

Oh also going to do the cold, hot, cold, hot, torque method also.

[crazypj22]

The main problem isnt the gaskets blowing out, its the crappy engine breather which allows cases to be pressurised in the first place.
Think how a two stroke works, pressurises case then transfers that pressure through quite large ports relative to cylinder capacity. 650 (or 750conversion) has a single 7mm hole to breath through. Even though the case volume is much larger in comparison to two stroke motor, it is still going to pressurise cases. If you dont believe it , try getting engine up to temp then clamp off breather, see how many other leaks develop. If you have standard air box fitted the intake vacuum will help a bit, when its removed you only have atmospheric pressure to help things along. I'm pretty certain ( although I havnt done any tests or math) that at some rpm there will be a reasonance set up which will suck air into cases ( I saw a 750 Triumph triple suck a quart of oil into crankcase through engine breather when I was a kid, may have been the oil pump scavenge but owner said it was the air moving about)
Just my 22cents ( more than 2 ;D)
PJ

[crazypj22]

One thing I remembered, (well today, when I started putting cam cover on for real) Gasket goo wont stick if there is any oily residue on mating surface, wiping it down isnt enough. I did it automatically only thought about it later, clean off/degrease with brake cleaner first. Used Three Bond 1104. Couldnt find cam end covers and as I'm going to use 79 generator/ignition (no points ;D) I decided to make a leakproof cam end cover ( will make one for 'points' side later). It isnt finished yet, going to tidy up the cutaways for rocker shafts and polish.
PJ

[shifty]

crazypj22 said:

The main problem isnt the gaskets blowing out, its the crappy engine breather which allows cases to be pressurised in the first place.
...........
PJ

The pic below explains ... I was wondering about the rubber orfices in my breather box. I don't see them listed in parts lookup. Why are these orfices there? Are they needed? The one on the right seems to be 'sucked' deeper inside.

[jeepurze]

jarmore Ive got another question using your pic on the breather plate, looking at the inside, a metal mesh , should this part be soaked to clean inside. if so in what , what is inside more wire mesh

[crank172]

The only place I get leakage is around the cam housing, I replaced the cam seal, new gaskets, and even popped for new srews/star washers.....still dripping...on both sides!!! What's the secret??

[crazypj22]

You need to find out if its the gaskets or the seal leaking as the fix is different.
If its the seal you have oil inside the cover and can see where its leaking, or at least where its running from. Usually means you have a blocked or restricted engine breather or breather hose
If its leaking from the screws or externally its a gasket problem.
If its the gasket it means the seal holder isnt fully seated and the bearings probably need 'adjusting' remove one cover completely, check there are no burrs on seating surface. Find a piece of tube 47mmOD, (roughly one and 3/4") Put it up against the bearing outer race and give it a tap with hammer to make sure bearings are located central on cam and tight together ( I have a 3/4" Whitworth socket which is the perfect size for this ;D)
Re-fit cover with gasket, etc. remove other cover and do the same.
You may need to buy a number 3 Phillips 3/8" drive socket screwdriver to get torque right, overtightening just distorts the cover/seal holder and makes leaks more likely ( better check the back is flat when you take them off as its pretty thin around the mounting screws
PJ
Almost forgot, check the depth of screw holes and check the screws dont bottom out before the cover is tight. happens when silicon or similar gasket sealer gets into holes as a 'cure' for oil leak (use a small electrical screw driver to prod/clean holes)

[crank172]

crazypj22,

Thanks for info, as always its spot on around here, I thought the seal was suppose to make contact with the bearing, it looks like there's channel, just one more rookie mistake. But anyway, a little tap with my craftsman socket, a little torque and the leak is fixed. ;D

Thanks a lot.

[crazypj22]

Couple of new bits.
Make sure you de-burr all threaded holes, I use a 90degree countersink bit (Do all the bolt holes really). The edges tend to pull up slightly and can prevent gasket sitting flat.
I fitted half of a two stroke reed valve to engine breather, not sure if I'm going to make a PCV type valve to let oil back into engine or make a 'hollow' dipstick and run oil through that to below normal oil level?
PJ
img60.imageshack.us/my.php?image=reedvalvebreather8zq.jpg

[billp]

I am also in the process of tear down and complete rebuild. The leaking around the cam bearings and the cover could be fixed if you have the ability to make a new cover in a shop. My bike is a newer engine with no points inside the cover. I could make a thicker cover out of aluminum and us socket head cap screws instead of the flat head screws with lock washers.

Am I right?