Bore sizes

All, just dismantled my 1981 xj550 uk spec engine 4v8 ?? Standard
I had hoped it would be standard bore of 57mm and i would hone/ deglaze the bores fit new rings do a valve refurb and rebuild.
I measure the bore and Piston diameter and find it to be 59 mm.

Is this possible as all imfo i read over here is max bore is 1 mm oversize . I.e 4 times 0.25 mm

I wonder if anyone can help or do i look for second hand cylinder block .

As you are aware this model was not a big seller in uk compared to US/ Canada so parts rare second hand and carraige costs on large parts from N America are prohibitive.

Look forward to any reply that may help.

 

It sounds like a different engine has been installed..............what is the engine code on the block and the cc size on cylinder jugs....see Page 4 and up:

http://www.xj4ever.com/catalog/frame-engine-id.pdf

 

XJ600s and Radians have 58.5mm bores. Could be one of those with a +0.5 or standard bore and inaccurate measurement. 598 on the block is the tell-tale sign of a 600 a 550 is in fact 528. Is your compression down? Before messing too much bear in mind a set of rings x4 will be over 200 quid.

BTW 550s sold well in the UK, 2nd hand parts parts are plentiful on UK ebay and German ebay..

 

Engine number *4V8. 000501*
Number on block 528

Hold fire , i might get different measuring tools as i was using a new digital vernier and an internal bore micrometer( old and no calibration date)
You wouldnt think they would both be wrong but thats where i suppose could get thrown off track.
So will get back when ive done above.
Dont suppose a 528 block could be bored out to accommodate larger pistons etc?.

 

Could be, but if so, someone went to a LOT of effort to do so, since Yamaha only makes pistons in 4 oversizes, the largest being +1.00mm (thus 59.00mm on a 528cc engine). BTW, O/S pistons are normally stamped on the crown with the o/s dimension, i.e. +.25, +.50, +1.00, etc. Cutting a 58.00 bore engine (the 528 engine) to that large of a diameter would mean running really thin cylinder liners......although 598 engines use the same physical size jugs, their liner bores are cast slightly bigger, so that the larger cast-iron liners can maintain their specified thickness (3mm, I think, but don't quote me on that............).

 

Will check piston crowns tomorrow to see if any numbers stamped on them, in mean time thanks for your help both

 

there is an old thread about doing over sized bore for larger pistons to a 550

 

The piston crowns have between the valve recesses the letter C and an arrow facing front of the engine. On the piston at the ignition pick up side there is a very faint line which might be seen as a number 1 but not definite.On next piston a 2 then next a 3. On the piston at the clutch side there is only the arrow and the C . I suppose if these are numbers for the pistons then number 4 is obvious by default.

Any ideas? New to forum is it difficult to upload pictures?

 

you can use a photo host site and post the link, or click upload file or more options for photos

 

I thought the 528 motor used 57mm pistons..

Kickaha (the 550 modification expert on here) I think suggests 2mm as minimum bore liner 'meat' is acceptable.

BTW does your motor have a rev-counter drive coming from the head?

 

Yes rev counter from exhaust side of head.

 

You are correct, my error.

The arrow is correct, as it indicated proper orientation of an installed piston (the arrows should point towards the front of the engine). But pistons are not labeled/cast with a piston location mark (1, 2, 3, or 4) from the factory, it may be that someone was inside that engine previously and marked them for "correct" re-assembly purposes.

 

That was a figure given by my engine builder, I had it bored to use standard 58.5mm XJ600 pistons using the XJ550 cylinder barrel

 

OK so Rev counter means its a 528 head - If they are 59mm pistons you're looking at a 566 cc motor - which I dont think I've heard of. A set of original size 528 barrels should be easy enough to pick up and if they are under 50k miles a new set of rings
will see you good I think. BUT if the 59mm bore is real has the head been machined to match?

 

All, thanks for your help, i have been in France for work purposes so unable to confirm accurately the piston/bore sizes. Will do so shortly when i aquire measuring gear and expertise and also as is best second person to confirm my measurements. Back soon

 

We'll be waiting ;-)

 

Sorry for delay in coming back. To update, I took a100man advice and managed to source a cylinder block complete with pistons which are standard bore (57mm) from internet.

Hopefully this weekend I will hone bores to deglaze\freshen up and source new set of rings and start rebuild. .

Thanks all.

 

Hi Hamish

I would measure your ring end clearance before consigning them to the bin - new ones are expensive and somehow unlike Honda SOHC stuff quite rare - lthough Len stocks them at I think the best price. BTW what about the head? Was it altered to match your unusually large bore? How about any history of the machine. It is intriguing.

 

My motor builder from back in the day, re- sleeved my cylinders and bored the cases to fit for oversize Honda pistons.

 

Dont think head was altered but i suspect head gasket was blowing between cylinders 3 and 4. Cant help much with the history im afraid. I bought as non runner. Got it running but looks rich. Dont have colortune yet. Mota (neta) exhaust fitted. What jets should be in or does it matter with that exhaust?

 

Standard main is 112.5, pilot 35. Neta exhaust won't affect things I reckon. Pod or K&N filters will make lean. Suggest you check float heights.

 

color tune and sync before thinking about changing jets. it will give you a baseline

 

All, sorry for long absence. About to fit used cylinder barrel after sourcing. Can anyone advise of dimensions of the piston base tools used on assembly so I can make some.

 

I just use my hands.
Set the inner pistons so they are a bit taller than the outers so you can get the rings started easily.

 

Oh, and don't do what I did and get the cam chain guide stuck on the outside and then wonder why the cylinders wont go all the way on.

 

Thanks Guys, will take info on board. Will update when I re assemble

 

All, after nearly a year away now stuck in lockdown back at bike engine. Have second hand barrels rehonedvwith new rigs fitted , valves lapped and block ,head and rocker cover painted . Hope to reassemble soon before blasting frame and cycle parts .
Question is this. All parts list show rubber blocks that go between the cooling fins at numerous places. What are their function. I assume they are necessary or Yamaha would not fit them.
Any advice would be grateful as

 

they keep the fins from singing the rubber kills the vibration

 

They prevent the cylinder fins from vibrating and "ringing" at certain rpm ranges; the stiff rubber "supposrts' the fins and tense's them, preventing the almost-microscopic level of movement that creates an unpleasant "buzzing' from those areas.

P.S. XJ550H was quicker on the draw than me...........so, exactly what he said!

 

but you explained it much better

 

Thanks both.

 

Sorry folks just playing at uploading pictures.

 

that head gasket is kind of rough

 

not sure but I think something is missing
nice job

 

But, it's not trimmed to size yet.

 

Sorry guys replying on my old profile for some reason . Yes no cyl head gasket or rocker cover gasket and some have noticed no block or crank cases . Away to refit valves etc and mate to the block. Now I can upload pics will bore you with all the steps. Unless of course it doesn’t run. It could be a while as I am going to overhaul and repaint all parts including fuel tank to as high a standard as I can do myself. Don’t want to put components out to specialists(at this point) as I want the satisfaction of knowing I did it myself. I have managed to source original uk tank and side plate stickers.

 

Can anyone advise of the black paint ral code for uk spec 1981 xj 550 standard bike with mars bar colours to go with stickers attached.Seems to have a brown tinge opposed to just jet black.Thanks in advance

 

Hi all, back again after fitting head I am about to torque cyl head nuts. The manual I have shows a sequence working from the outside - in to middle of engine with the exception of the 4 small nuts around the cam chain track.
Looks like official Yamaha manual ( copied on to dvd) , but all my agricultural engineering training always advised to start sequence in middle of engine working to the outside To flatten the head gasket in that direction.
Can someone assure me the Yamaha Manual is correct .

thanks in advance.

 

in the time I have been on this site there has never been mention of that sequence being an error. There have been many head gasket replacments here following that sequence.
our supporting vendor would have spoken up by now if it were incorrect because thats the kind of service he gives.

so I am comfortable following the manual for head gasket replacment.

 

Well, that makes sense, but actually Yamaha specifies it being done in the same manner (inside , working your way outwards), so I'm wondering where you are getting this info from? I would follow the Yamaha proscribed sequence, as they are quick to point out that you MUST follow the factory procedure, values, and tightening sequence when installing your cylinder head, as: THE #1 CAUSE OF CYLINDER HEAD GASKET FAILURE AND HEAD WARPAGE IS DUE TO IMPROPER HEAD INSTALLATION PROCEDURES!

 

Thanks as ever, here is the manual I am using and the picture of the sequence in it. I will go on the premise that Yamaha and you guys know more about Yamaha engines than me and proceed with the advice and follow sequence below

 

Wow, you are correct daphnebroon, and I think that diagram is NOT correct, it is completely opposite from ALL of the other XJ/XS engines, which do indeed follow the "inside-out" sequence. Even the FJ600 manuals (which is basically a 550cc engine with larger jugs) show the inside-out sequence...........

Hmm......I'll change my opinion and say to use the inside-out sequence rather than what the Yamaha service manual shows!

ALSO:

Note that the 12 cylinder head-to-crankcase stud nuts are torqued before the head-to-jugs nuts are torqued. The typical sequence (all except the XJ700-X water-cooled engines) is:

1) the CYLINDER HEAD NUTS, center outwards in criss-cross pattern
2) the REAR STUD NUT(S) on the cam chain tunnel.
3) the two M8-SIZED REAR STUD NUTS (these are the fasteners just inside of the #1 and #4 intake ports on engines that use them…these are typically only used on “YICS” engines)
4) the FRONT STUD NUT(S) on the cam chain tunnel.

 

Another mislabled photo appears to have been found.
How many errors are we up to now in the various service manuals? 20?

 

You're missing a zero............

 

Hmmm, that would be for removal?? Ie removal and refitting are reversed sequence - are you sure you're not misreading it?

 

Minimutly is absolutely correct...........the image shown above is the REMOVAL sequence, and the install sequence is the inside-out sequence.

 

Yes, I dismantled in this sequence but I can assure you the diagram is in the re assemble section of the manual.
Luckily I asked you guys to confirm my instinct. I guess the manual writers just copied the dismantle procedure picture into the reassemble part.
Anyhow I have torqued head down inside to out as everyone agrees this is the correct procedure.
Thanks all once again.