The rehabilitation of Sir Gustave Sabastian (‘Gus’)

[msmckeon]

Originally Posted by Box'a'bits

May also do the camchain, which was reputed to have been done before I bought the bike (but if that's the case, then why am I getting that timing shimmy between jugs?).

They are pretty noisy when worn so if it is quiet not that much to worry about...........?

Michael

[Mark_S]

Originally Posted by Padmei

Working on bikes is the biggest motivation for riding them I reckon.

errr
isnt that arse about face?

[Box'a'bits]

Originally Posted by msmckeon

They are pretty noisy when worn so if it is quiet not that much to worry about...........? Michael

Airhead Cam Chains have a short run, so by the time that they are rattling they are well flogged out. The earlier cam chain tensioners aren't up to much (don't have the ratchet lie on some Jap bikes, so can flog themselves to death). I haven't experience with the new ones.

One issue with replacement is that the sprockets wear, like with drive chains, but aren't always replaced. The bottom cam sprocket is usually good (bigger) but the (smaller) crank sprocket does wear. Likewise the outrigger (nose bearing) in the timing chest. Both add to potential for slop. And this can lead to premature wear.

Slop can affect both ignition timing & value timing.

There are a few symptoms of cam chain wear:
1. Rattles
2. Shimmy when timing.
3. Difficulty getting a smooth idle.

Bikes can run adequately with rattly or worn cam chains. I'm just trying to get one more running variable crossed off. I noted enough of a difference in the way that my R100RS performed after replacing the cam chain, that I am prepared to do the work to check Gus's.

At some stage I am aiming to go to a crank mounted (dual plug Enduralast) ignition - dependent on Igormortis's experience with it. But not now.

Here's Snowbum's take on it (if you have the patience to wade thru it). The photo is the single row (simplex) cam chain - which differs from the duplex that my RS had.



Paul Rooney Cycles:
Here's a link for a site that Tanami has set up re Paul Rooney's work, that is interesting to check out if you haven't already seen it.

Originally Posted by Mark_S

Errr - isnt that arse about face?

I prefer to ride them. But garage time can be relaxing

[msmckeon]

Originally Posted by Box'a'bits

Airhead Cam Chains have a short run, so by the time that they are rattling they are well flogged out. The earlier cam chain tensioners aren't up to much (don't have the ratchet lie on some Jap bikes, so can flog themselves to death). I haven't experience with the new ones.

One issue with replacement is that the sprockets wear, like with drive chains, but aren't always replaced. The bottom cam sprocket is usually good (bigger) but the (smaller) crank sprocket does wear. Likewise the outrigger (nose bearing) in the timing chest. Both add to potential for slop. And this can lead to premature wear.

Slop can affect both ignition timing & value timing.

There are a few symptoms of cam chain wear:
1. Rattles
2. Shimmy when timing.
3. Difficulty getting a smooth idle.

I replaced the single row timing chain on my second R80G/S, at around 120,000 km. Clearly increasing noise was the only symptom I noticed and the sprockets were like new. Job was however very easy, so long as you use the old master link to join the chain while it is over the spocket and then push the new one in from behind (with the joint positioned between spockets). Just like you would to make replacing a drive chain easy.

Easy job as I recall.

Regards,
Michael

[Padmei]

Apart from the noise there is no other way of seeing if the timing chain is good or not? I will pull it apart & have a looksie but not sure what I should be looking at apart from the shape of the teeth.
Had a brief looksie at snpwbums but started to nod off. He needs to use brighter colours to keep us awake.

[Box'a'bits]

Originally Posted by Padmei

Apart from the noise there is no other way of seeing if the timing chain is good or not? I will pull it apart & have a looksie but not sure what I should be looking at apart from the shape of the teeth.
Had a brief looksie at snpwbums but started to nod off. He needs to use brighter colours to keep us awake.

When you get it timed, asked the person if there was some doubling of image.

[Padmei]

Originally Posted by Box'a'bits

When you get it timed, asked the person if there was some doubling of image.

I should have read the post further up the page before I asked.


As usual

[Box'a'bits]

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.

CAMCHAIN:

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)..


TUES 8TH MAY:

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.

[igormortis]

Originally Posted by Box'a'bits

Mandy had a roast on, so I popped the new crank sprocket in the oven to preheat that.

I love it.

[innathyzit]

Originally Posted by igormortis

I love it.

back in the olden days me and dad were rebuilding the benelli engine and needed to get the bearings out of the cases. dad put them in the oven and roasted them while we went back to the shed and done other stuff. when we remembered that the casings were still roasting we went back into the now smoke filled putrid smelling kitchen, opened the oven and the bearings had dropped out onto the tray. Job done we thought and I had learned something.

Then Mum came home.

[Padmei]

Fantastic write up Nutso. I'm surprised you didn't do the other side. I couldn't rest easy if I didn't make sure both sides were the same.

[Box'a'bits]

Originally Posted by Padmei

Fantastic write up Nutso. I'm surprised you didn't do the other side. I couldn't rest easy if I didn't make sure both sides were the same.

Let sleeping dogs lie. That one wasn't leaking. I'll do a compression test soonish, & that will tell me if there is an issue. It was running a little richer & retarded compared to the left side.

[Voltaire]

Good piccies, I did the cam chain as part of the r90 rebuild and the crank sprocket was a hell of a thing to get off. Maybe this younger single timing ones are better.
off topic but it was mentioned in the thread....

I'm putting in a crank fired programmable ignition this week, once its up and running I'll let you guys know. Its fully programmable, has a rev limiter, and can run dual plugs if you want.

[Rosie!]

Originally Posted by Box'a'bits

...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...

What could possibly go wrong? I sometimes leave the welding rods in Clint's oven when I'm cooking, and it hasn't done us any harm

...unless of course you put the sprockets above the food. That's just gross.

[advNZer?]