Hello everybody,

In my family we run a 1981 Yamaha XJ550 (black with the orange pin striping)which we have owned since 1989 and used since as everyday transport all year round (winter and summer). It has now reached roughly 90,000 miles without an engine rebuild as yet (but read more of later) and still on original clutch/drivetrain.
Naturally during our time of ownership it has had a few replacement exhausts (thanks to all that lovely corrosive salt they put on the roads in the winter in the UK ), we've had to do a partial re-wire (original fuse box etc. carroded to bits), many tyres, many fork seals and many chain and sprocket kits plus many, many regular oil and filter changes. The panels/frame are still the original ones except the front mudguard which we replaced in '98 due to the original rusting (lovely UK Climate again). Only mods/Extras on bike are a JMC back suspension and engine protector bars.
Not a minter but a well used and reliable mode of transport.

However this week we suspect we have a burnt valve .
So a top end strip down may be required, my mechanical apptitude is fine due to years of running old timers/Jalopies/bangers of various sorts but I will be asking little bits of info, so firstly here goes
Does anybody here have the torque settings and tightening sequence for the cylinder head (Yes I know I should get a workshop manual ...and will be ...how I've managed till now I do sometimes wounder ).

Many thanks and happy riding.

I can give the the torque settings for the 650 & 750. If I'm not mistaken, these will also be for the 550, since all these engines are basically the same, the only difference being stroke and bore. The CAP nuts (on top of the head) are tightend to 3.2 kgf m (23.1 foot pounds). The smaller 8MM nuts that thread onto the upside down bolts on the outside of the block are tightened to 2.0 kgfm (14.5 foot pounds). If you have a YCIS model, the 6mm nuts have no tightening spec, they are just snugged.

As for the sequence, you have two rows of nuts. Six on the intake side of the engine and six on the exhaust, with three nuts on either half of the engine. Using "N" for the intake side and "X" for the exhaust side, label the nuts 1 through 6 from left to right as if you were sitting on the bike. The sequence is as follows:

3N, 4X, 4N, 3X, 2N, 5X, 5N, 2X, 1N, 6X, 6N, 1X. In other words, it is a cross pattern across the head. Then tighten the two nuts in the middle of the head, first the intake side nut, then the exhaust side nut. These are the two nuts that go under the part of the head cover that protrudes out in the middle, front and back.

Hope this helps, but please make sure you double check the torque settings when you get your manual, just in case. Cary.

XJ550 Torque Specs and Sequence

It's a bit cryptic, but I think you start with the bolts that go up under the head first.

Many thanks to you both (ckyle29 & MacMcMacmac)that is precisely what was required :) , however …

…(and many apologies for this) I don’t need to take the head off (thankfully).
As stated earlier I thought internal damage had happen such as a burnt/chipped valve etc. because on number 3 cylinder petrol was going in but not igniting yet a sparkplug tester showed a superb spark on all four leads to the plugs, plus new plugs where fitted, the carburettors operated correctly (linkage etc.), so naturally you can understand my thought of some form of engine damage. So the rocker cover was removed and the engine just turned over to check that the cams operated the valves up and down etc. Then I thought even if valve was burnt it would still ‘fire up’ in the cylinder so rocker cover put back on and I decided to take the top off No3 Carburettor …and …believe it or not …but a good piece of fibre/cotton/cardboard was in the carburettor tube, stopping all movement of the carb piston, hence ‘neat petrol’ going into the cylinder and flooding everything. It would appear the air filter element has broken up and a few bits of its fibre went in the carb.

The bike appears to be running fine now (famous last words :rolleyes: ) but for a short while did smoke a bit due to all the unburnt fuel that has gone down the exhaust.
So my question to you all this time is …can anyone scan me an exploded diagram/picture of the carburettors (sorry to pester again :rolleyes: ).
Although every thing is running fine I’m just a little concerned about the carb (rubber diaphragm at the top cause I’ve disturbed it for first time in 24 years etc.) :unsure: .
Plus can anyone think of any damage that might have been cause by this?

Thanks again for help.