Bike has many many miles and this chain made half of them, still in ok shape.
The issue is that when the chain stretches some, it starts to rattle at idle.
With the tensioner in place it can idle at 500 rpm and it’s totally silent.
Oil pump well in specs.
I’ve rebuilt the gearbox a couple of years ago, shimmed all gears and did the 2nd gear fix.
Have a low miles spare engine, so all the best parts were used.
It’s a very robust and over-engineered engine.
I guess you are you talking about the shock absorber inside the clutch assembly? It’s indeed the week point of this engine.
It really gave me a hard time, but managed to flip over the worn, to death, cylinders and gave it a new lease of life.
Very interested about the rubber ring shock absorber ring mod in your tool box… any pictures available? Please PM if you are considering selling it.
Very interesting!
My first bike was a 50’s BMW R26… no synchromech…
Re-bored cylinders, new 0.25 oversize pistons and rings, replaced bent valve, lapped all valves, new stem seals and gaskets.
Stainless screws all around.
Engine back together, started right away!
No clickity clangs, so I must have done something right.
Still have to sync the carbs.
One thing:
Havent take it out for a ride yet, but when I blip the throttle, in neutral, there is a puff of gray/black smoke, running rich not burning oil.
Think the needles need lowering.
Any suggestions?
I was thinking it was a cushion for the middle drive. But no. It was a long time ago but I think the 1977 model had the issue. The “compensator” ramp would cam over and pop the cover off. So the field fix was to put a rubber ring under the cover. It limited the travel of the cushion ramp, The factory probably changed the ramp angle and increased the spring tension. All these parts are unavailable from Yamaha. So if yours is working… I’d leave it alone. Do you remember any sign of this shock load cam rotating too far?
Never had a problem with this, cam fits tight with lobe and never jumped.
My XS is the second generation, so they must have addressed the problem.
What I was referring to is the assembly #1 in the diagram.
For those unfamiliar, it’s an arrangement comprising of four very hard washer springs (item #5), two needle roller bearings and four pins sliding in banana shape slots thus compressing the springs when a rotational force is applied creating a damping effect.
Rotating the pins 180° gives it some new life but there is no way to compensate for the wear in the slot.
And this is what happens to the contact pins after a wile…
They should have used bearings instead, or just plain old springs.
Ah, I remember that device now. So long ago…I think there were stronger belleville washers as a field fix. Again likely a running production change. I could be missing remembering, however. The design engineers were coming off the disastrous TX750. The XS series led by the triple had some teething issues, but grew to be a good bike. Heavy, a LOT of gear lash, but ultimately a reliable piece. But if you thrashed it hard…some problem areas. A 3 into 1 exhaust made a beautiful…Jaguar like sound. Two pipes muted the melody a bit.
Yes, don’t laugh, computer fans, and it works.
22w and 200cfm combined, feels like a 30km/h wind, will provide some air flow when the bike is not moving.
The Temp sensor puts them at full blast at 120°C.
And it looks cool !!
Aristides
1 Like
Timeisrelative
(Jason Miller 1993 XJS 4.0 convertible, 1997 XK8 coupe )
53
Nice idea! I ofthen thought it wouldn’t hurt to have extra cooling!
The biggest outlet is indeed at one end but there are also two openings under the cams, in the rear. There are some massive cooling fins in the valley.
At full blast there is a lot of air coming out.
After some testing, the 120°C thermostat is way to high and never kicks in…
As the sensor does not touch the head the temps it sees are much lower. I ordered a 50°, 60° and 70°C to see what works best.
Engine warm, stationary in neutral.
Lowered the needles one notch, and it’s somewhat better.
Haven’t taken it for a ride yet.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
59
And would presumably immediately get cooled off when the fans come on, so likely to cycle quickly. Maybe it’d be better to have a sensor in contact with the head.
Yes indeed, so I modified the arrangement.
This time I used a bi-metallic thermostat mounted in an aluminium bracket that when in place it touches the head.
Tomorrow I will test and see which thermostat is best.
I believe that this will work.
Up and running great !
Happy to report that the prime chain tensioner works fine, no noise even at 500rpm and just a gentle whizz at high rpm.
Replaced the thermostat for the cooling fans with a 65°C and it now kicks in when the head reaches 100° - 110°C.
Adjusted the carburettors, nice and smooth.
And the bling bling polished engine looks great…!
