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Old 05-06-2012, 02:27 AM   #818
Box'a'bits OP
In need of repair
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Joined: Sep 2008
Location: Wellington, New Zealand
Oddometer: 2,391
Fixing the head oil leak & replacing the camchain:

I’d already part disassembled the bike last weekend, to replace the left head gasket, which was leaking. In doing so I disturbed the barrel base seals, so needed to pull the barrel to remedy this. I chose to part pull the barrel, then take out the circlips & gudgeon pin to release the piston, to avoid needing to use a ring compressor for reassembly. The base & stud o’rings were a little hard & were coated in silicon gasket material, so weren’t really reusable.

That shiney thing inside the engine & under the crank is the camshaft.

Once I realized I’d need additional parts, I stopped for the day. I put in a parts order including base & stud o’rings, pushrod seals, & also a new camchain kit, crank camchain sprocket, & crank bearing. I’d wanted to look at the camchain given issues getting the carbs to sync, & some double imaging when I re-timed Gus.

This Saturday I managed to clean the old gasket material off the head & barrel, & some of the carbon (not much on this head). The valves look good. Not much recent movement (albeit but the right inlet was a little tight this time when I checked that side after I finished the left).

The bore still have cross hatching.

Pulled the cam followers using a bit of wire down the hole in the follower pushrod seats. They both looked good

I would have liked to pull the valves to check the guides, but don’t own a value compressor. Maybe next time.

The barrels & heads went together okay. Included a light smear of Locktite 518 on the base (left over from KTM repairs), for extra sealing.

BTW the head gaskets are sided. The printing goes on the outside, otherwise the pushrod holes don't line up. So is the timing chain gasket. The piston has an arrow on it pointing forward (useful if it spins in the barrel while you are cleaning the carbon off). Rob Farmer recommended copper pennies are a good carbon scraper, given they are a softer marterial than the piston.

I chose not to pull the right side.


Pulled the starter cover & disconnected the beancan & alternator wiring. I don’t have a diode board, so no issues there.

Pulled the front cover & removed the alternator (using the special tool), & bean can.

Pulled the timing chain cover.

The old paper gasket was a shit to remove. Ended up soaking it, then carefully using a Stanley Knife to lift it in sections. Knocked out the crank seal using a 36 mm socket, which I also subsequently used to introduce the new seal.

Ensured the bike was at TDC, indicated at the flywheel cover, & also that the two marks on the camchain sprocket (12 o’clock) & the crank sprocket (6 o’clock) were aligned. You need these two aligned for reassembly to prevent expensive damage.

Removed the camchain rail (bolt & nut at the left looking at the camchain. Also removed the circlip for the tensioner on the right, & removed the tensioner

Pulled the bearing using a medium sized three jaw bearing puller, & a penny across the crank nose (to prevent damage). Needed a little heat to get it to move.

The single row camchain has a masterlink on the engine side of the chain, usually on the cam shaft sprocket at circa 3 o’clock.

Used the puller to remove the Crank sprocket. More heat.

Mandy had a roast on, so I popped the new crank sprocket in the oven to preheat that. Made reassembly real easy with a bit of freeze spray on the crank. Didn't impress my wife though, even though I explained they were new & unused parts...

Not too much wear on either the camchain or crank sprocket, but enough to give some play.

And that’s where I’ve stopped for the day. I looked at the camshaft sprocket wondering if I needed to replace that. I *think* its okay, so won't (GBP34 - ouch)..


Back at this tonight for an hour or so.

I boiled the billy with a little engine oil to heat the bearing in front of the crank sprocket. Then freeze sprayed the crank again, & the bearing just slipped on. In hindsight I would have put on the camchain prior to doing this. I just got excited I guess.

Before you fit the camchain make sure that the tensioner spring & piston are fitted. You can't fit them once the camchain is fitted. DAMHIK.

I fitted the camchain with the masterlink at the bottom of the cam sprocket. It's tighter, but its harder to lose the masterlink into the guts of the motor if it goes flying off, and you can use the crankcase for a little leverage. The masterlink goes in towards the crankcase according to everything that I'e read. But looking at the Snowbum photo, the link is on the outside of the chain? The camchain travels clockwise, therefore the masterlink open end goes to the right, away from the direction of travel. I held the master link back plate & then the masterlink in place with a little grease & a magnetic screwdriver. I used a flat bladed screw driver to clip the link back into engagement, pressing to the right. Note the masterlink on the new chain has a darker link than the balance of the chain. In the picture below I have already spun the motor to check for smooth rotation, & to visually check the masterlink clip is properly seated.

Check that the sprockets indicators still align, & that the flywheel still shows as TDC. If you stuff it up then expensive things may happen the first time you fire it up.

The camchain guide then bolts back in place, parallel with the camchain, & the tensioner goes on the right side, tensioned by the piston & spring, & held in place with a small circlip on the pivot.

Of course by the time you get here you will have thoroughly cleaned off the old timing chain gasket. The new one appears to have the same rubberised feel as the sump gasket - I suspect that it seals with heat. I didn't use gasket goo on that. But there are two small round paper gaskets to go at the top of the timing chest, to space that out properly, so the timing chest cover sits straight when you torque it down. You could use a bit of gasket goo to hold these in the right place, because they are a right bugger if you are juggling a hot timing cover & trying to fit these at a later point.

I heated the timing chest with a paint stripper heat gun (but if you are feeling brave, or live by yourself, then you could put it in the oven). Got it up to sizzle spit temp. You need to open the clearance to allow the bearing to sit squarely & fully in the timing cover.

Freeze spray the bearing to get that to contract. Welders gloves help pushing the timing chest on without burning your hands.

From there on its straightforward, replace the alternator stator, rotor, diode board (if you have one), bean can (you did note where that sat didn't you?), plug everything back together, adjust the ignition timing, & then you are pretty much done.
My '91 R100GS thread is here
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It's just better when there's twins involved....

Box'a'bits screwed with this post 05-13-2012 at 10:57 PM
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