XJ600 Cafe Racer project

He has an XJ 600, not an XS. Neither tank will fit the XJ frame without extensive modification to the tank. The XJ600 has a very different frame design.

 

Hey there,
Sadly no tank will fit without any modifications. Some will need only slight change while others will require serious welding skills. With XJ 550 tank you will need to weld new mount points (Simple welding job - 15minutes of work). A friend od mine Has finished his xj750 recently and he used KZ650 tank. I have GS550 tank and it also fits. You can google Xj650 projects and see what tanks are used. Post pictures if you are not sure of donor bike models, i am sure most people here will be able toidentify the bike for you.


By the way, one od my pistons has some pitting marks. Can i safely use it?

 

That's how it looks:

 

On his 650 Maxim?
Fuel tank interchange information

If you're talking about on your bike, then yes.

 

You can use it, but it will fail. How long from now is a matter of guessing. That's from detonation, and once the piston starts to erode it will want to keep eroding, even after fixing the underlying cause.

 

In that case, I'll have to find a replacement piston.

 

Really? Blimey. I'd have probably used it after smoothing down the pits. But then I'm only ever going to do a few 100 miles a year on any of my bikes..

BTW detonation like from hot carbon deposits ?

 

If he wants to smooth it and run it he can. I would, but I'd also expect it to fail at that point later on...someday.

Detonation from what I can't say since I never heard the bike run. It's clear that thee bike was not treated well at some point given the state of the bearing that was found earlier.

 

I will be looking for a replacement piston. I would hate to tear the engine down again. At this point where the engine is still apart, I think that's the best option.

 

GoCrazy I have a set of FZ600 pistons going cheap. Not sure what postage from Canada to Poland is, probably more than Im looking for the pistons.
PM me if you are interested.
I have a 2nd set also if anyone is contemplating making their 550 closer to 550.

 

Hey, just a quick update. I finally managed to put the engine back together and fit it into the frame .....and that is the end of good news as the engine won't start, it cranks nicely though. After some sniffing with a multimeter I found a potential culprit - ignition coils. According to the manual they primary and secondary coils resistance should be:

Primary 2,7 Ohm (+/- 10%) --> my reading - 2,3 which is more than 10% difference
Secondary 12k Ohm (+/- 20%) --> ny reading - 22 - 24 k ohm - no comment

My question is -is it normal for out of spec coils to produce spark? I do get a blue spark, but coils readings suggest that they should be replaced.

 

Not sure - are both coils reading the same?

 

The Haynes manual I have spec's the later models primary at 1.8 to 2.2 ohms, are you sure you have the right spec.
As for the secondary, is that with the spark plug caps removed?

 

These specs come from Yamaha Service Manual, I can post a screen shot

I didn't remove spark plug caps ....should I ? The manual doesn't say anything about that.

 

You can do it either way, but if you leave the caps on you need to add the resistance of the spark plug caps to determine if you are in spec.

Check your manual and it should list a specification for the secondary coil and the spark plug caps.

So 12kohm and you read 22-24 kohm with the caps on. So if the caps are 5 kohm X 2 that would be a good reading.

Likely OK if you have a nice blue spark.

And reading back over the thread, did you ever get good compression readings? A low compression engine is going to be difficult to start. You could try the old school method of adding a teaspoon of oil and see if it will fire up.

Also on carb rebuild, are you certain the enrichment circuits were properly cleaned. It is often overlooked and will cause issues starting when cold.

 

Did some research on the ignition and coils specs. A funny thing Yamaha Service Manual for XJ 600 includes ignition specs ONLY for 51J models, while Haynes Service Manual specifies exact parameters both for 51J and 3KM models of XJ600.

Yamaha Service Manual


Haynes Service Manual



So it seems that ignition primary resistance is more or less OK. As for my secondary resistance - looks like it has to be measures without spark caps, so my 24k Ohm minus 10k Ohm form spark caps results in 14k Ohm which is again more or less OK.

Tomorrow, I'll check the pickup coil resistance and perform a compression check. I am pretty sure that compression should be fine as I freshly rebuild the engine with fresh rings, plus I gave the valve head to be machined by a professional. However, I decided not to assume anything but check everything just to be on the safe side.

Is it possible that I have ignition timing issues? Caused maybe by 180 degrees off timing? What if I set the TDC at exhaust stroke not the compression stroke?

 

What kind of forks are you running on that? Im doing my own XJ project and really love the way yours looks!

 

Stock forks, lowered around 5cm and powder coated. I also bought a pair of rubber boots for around 3$ in a local auto parts store ( They are from a moped or something)