After chats with several encouraging folks here, I finally had the guts and time to start looking into the exploded chain guide issue. Got the oil pan off, shifter side cover off and the engine flipped over. The bottom of the pan was littered with a couple of dozen pieces of guide. The encouraging news is that after 27 years, the engine looks good - no metal in the pan, no sludge anywhere. While the Ones Who Know are encouraging me to replace the cam chain and get a valve job, I am short on $, patience and ability so where I want to go with this is to fix the issues that are known - the starter guide and associated parts, and to make sure the guide pieces are cleaned out of the transmission. There are enough other non-mechanical issues like grounded wires, old cracked insulation, corroded connections, etc, to keep me busy through the winter, so a near-complete tear down holds little interest.

Sounds like the cases need to be split regardless, but the manual's photos are pretty sketchy at best and the descriptions vague. Can I do this job without removing the head and cylinders? Any other suggestions from the voices of experience would be appreciated.

Too bad you can't buy that rebuilt 650 for $50 in "SELL, TRADE". . .

But good luck to you.

Keep an eye on kijiji for a parts bike, it is that time of year...
Seen a few interesting things up your way.... maybe a 650 will pop up as well

PSteele, YES! You can split the case without pulling the head and cylinders (I did anyway). This will save you $$$ on a gasket kit as you only need a few o-rings, seals, and a tube of Yamabond or equivalent (Permatex Grey). Spring the $60 for everything (including the new guide) and do it right.
Best of luck to you, it isn't that hard.

OK Fellas, diving into the engine today I think that the process for splitting the cases is fairly understood. Seems to me that an engine that is pieced-together as a block as precisely as this one and then last for decades is quite an engineering achievement.

Took me a while but I now understand the middle gear Torx bolt problem. The manual says simply "remove the bolts" but as they are spiked - seeing them lead to immediate understanding of the term - I do not know how to remove them, so I searched the forums and found 2 solutions. One is to drill out the spiked portion, but I'm just not that good. The other is an impact driver, which Wally World should have.

Questions:
-Are we talking an electric impact gun, because I do not have a compressor or room for one (or $ for one).
-Can these bolts be reused, or should I use a Home Depot replacement mentioned in one of the forums?
-What is the size of the Torx bit needed? I only have a 50 and that is a monster by comparison.
-By flipping the engine around, are the bits of chain guide getting into parts of the engine that will cause more damage?

From the top:
#1>The Haynes outlines the drilling method nicely. I used their advise successfully and would recommend it as it isn't that hard (really).
I would NOT try to do the impact gun, you will break parts and screw something up going that route.
#2>Yes you can reuse them but I would spring for new from a good hardware supply. A LOT cheaper than buying new from Yamaha.
#3>T-40
#4>Possibly, you will need to do a through looking-over of the engine. I pieced all the pieces I found in my engine to determine I got everything (fortunately, the guide was in large chunks)
Good luck to you amigo, shoot me a PM if you would like to play phone tag on this.

Thanks Robert - may have to spring for a Haynes. I was going to piece my guide back together but after pulling three large hunks from the little side hole and then at least 2 dozen from the pan, that would be an exercise that would waste more time than a through inspection.

After the Torx bolts come out and a look around the innards, you may get that PM.

So, I got a Haynes and the detailed description says that it "is advisable to drill out the staked areas to avoid any risk of destroying the internal profile of the screw heads. Take care during this operation to avoid drilling into or through the retainers."

Well this is an obvious statement! There is no further detail on how to accomplish this task. What I am afraid of is damaging the retainers or the block. Just how hard is the bolt material? Is there another way or do I need a good bit, a steady hand and just do it?

I am in the process of doing the same thing. I removed one bolt with out drilling the second I striped the head (ended up drilling and extracting) then drilled the other two spikes. the last two came out much easier.

The retaining clip is much harder than the bolts

Had a few minutes today so I took my time and had a real good look at the staked Torx bolts. Looked like two were not particularly well-staked and they did undo relatively easily. The other two required drilling and the fear of drilling through something important made this a cautious procedure. For any of you attempting to do this, caution is a Good Thing as the bolts are flat head countersunk style, so there is not a lot of material to remove. After drilling, they came out easily. My only concern is making sure I have all the bits of steel completely removed before moving on.

Next came the clutch side cover and looking at the inside, it seems to me that removal of the clutch is not necessary to split the top and bottom cases. Anyone want to chime in on this?

One reason I do not want to do this is because I will need to buy (yet another) wrench to remove the retaining nut, which looks to be 30mm. One more question about reassembly. Should the Torx bolts be put back in with locking compound, staking or both?

I didn't remove mine, but it would have been easier to put back to gether if it was remove.

Well on this dull grey Sunday afternoon, I decided it was time to finish splitting the cases. However, without a 30mm socket for the clutch center nut, clutch removal has come to a stop. Do the clutch and primary gear HAVE to come out? Does the generator HAVE to come out also?

When it comes time to split the cases, the manual describes the use of an impact driver to remove three countersunk screws that hold the bearing housing. Is this really required?

The cost of required tools is getting out of hand and I may be better off to part the bike out and walk away.

An impact driver isn't an impact wrench. It is a hand held device like a fat punch but when adjusted to either direction, a hammer striking the end is turned into rotational torque to tighten or loosen fasteners. That and the jarring of the threads of the fastener loosens them and keeps the tool firmly into the fasteners drive (phillip, slotted etc) reducing slippage and damage. It isn't an expensive item. I've seen them for less than $20.00


Just checked Princess auto has them for 9.99 for a 1/4 drive and 19.99 for a 1/2. Their SKU number for the 1/2 inch is 8263261. Web site is pricessauto.com

Thanks JF, checked out Princess Auto - what a great place - should have one in a few days. Canuck Tire had one for $40...passed.

Anyway, I struggled for a while trying to find a cheater method to remove the 30mm nut on the clutch pack. Tried everything I knew and finally broke down and bought a socket as the neighbours didn't have the size either. Cleaned some gunk off the nut with a rag before I put the wrench on and the nut came right off...with my fingers.

Stopped, as it's way past sleepy time and I will try to finish the case split tomorrow.