Purchasing xj650

color tune is for adjusting pilot circuits mixture screw not syncing .
syncing is adjusting the carbs to motor

 

I'll look into it, I'm new to the whole syncing thing.

As above, I'm new to the syncing side of things. I'll look into what k moe suggested and see where I get!

This evening, after remeasuring and ordering my shims I replaced all the 'doughnuts' on the valve cover bolts - it was made easier with the brass cone from Chacal

 

I'm a cone head too. surprising difference between the new and old donuts isn't there?

 

A massive difference. I don't think the valve cover has been removed since it left the factory...

 

I think the valves get ignored on most bikes. Then they get bought by members of this site.

 

That is no kidding, I can't think of one bike that I have worked on that they were in spec. This last XS was close, I think the PO swapped #3 & 4 EX shims, that is how close it was.

 

Half of mine were out by at least one shim size.
Most of the ones I've worked on were at least that far out.
One Virago I worked on was nearly at 0 clearance on all 4 valves. Stupid thing to do since they are so easy to adjust (screw and locknut).

 

Mine were out too made a great difference once l fitted the correct shims. Glad the shims are on top of the buckets on the XJ.

 

I hope it makes a big difference with the tuning. One thing I cant get my head around is how the clearance would affect the carbs i.e. not being able to tune correctly and getting a lean or rich mixture

 

Valve clearances affect engine breathing. If clearances are too large valves open later. Conversely too narrow clearances valves open earlier. You want them opening properly by the clearances being correct. Some of the guys can explain in more detail as l am not an expert on carburetors.

 

Yep these engine are really just air pumps. Sure there is a fire in there, but the air come in and goes out. How well the valves work (open to the right depth, time and then seal tight) makes the air pump work better.

 

Yes air pumps is what they are. Spinning an engine on the starter without fuel would just pump air. Add fuel and with all the other parameters correct they burst into life.

 

Modern cars actually have variable valve timing by having dephasers fitted on the end of the cams. Its all about maxmizing power and efficiency throughout the rev range.

 

Well that makes sense, cheers

 

Thanks to Chacal I was able to source I a new clutch cable here in the UK - the PO had fitted a 4K0 clutch cable that was far too short and didn't pass through the front forks.

This meant when steering left the handle bars were hitting the cable before the steering stops - that would be an MOT fail here in the UK

 

Nice find. Are you on yamahaclub.com? This is definitely the forum to be on for the XJ series. Work out the electrical before you start pulling cam shims. You may find something you don't want in the head, like cap galling or excessive lobe wear. If it will run and build compression I would not take the engine diagnostics much further just yet. Once you try tuning it and you find issues with compression or what-not then you can decide to either swap the engine or tear it down. I have a 650 head in the garage and it looks very similar to the 550, just with larger pistons, head and case.

 

Thanks, the bike is running fine at the moment (if you exclude the fact it's running rich). I've yet to split the carbs, ultrasonic clean and replace fuel o rings and butterfly seals.

New shims will be here tomorrow so will fit them asap and will then move onto splitting the carbs from the racks. Once all done, it's a syncing job.

I looked at the site you linked however xjbikes is dedicated to the xj series, the link you posted isn't.

 

Oh, we're friggin' dedicated! Some of us are so dedicated, we should be committed!

 

New shims are in and all valves are in spec.

Two questions:

1) Can the shims be saved and be reused at a later date?

2) Does anyone recognise these as being the original shims from factory?

 

Yes, just make sure you keep them in oil so they don't oxidize as corrosion will affect the dimensions of the shim.
I'm not aware of anyone that makes shims for these heads. Every shim I've seen is OE.