Top end rebuild "running in problems"

Also the bike has only ever been idled with a few short low rpm revs since the rebuild and it’s first start 2months ago.
As I havnt finished the build yet so I couldn’t ride it. Last weeknd was the first time I have ever moved the bike under its own power and I guess the plugs wore well and truely fouled by that point. Hence the fouled wet plug on 3. So maybe I should get smaller jets with some new plugs and take it for a decent ride to bed in the rings??

 

Before tackling the oily deposit you need to get the jetting right.
Rings take time to bed in and seal properly, so that oil may end up going away altogether. With the jettung right the plugs will get hot enough to burn the oil, and you should get a much better looking plug.
Did you replace the valve stem seals?

 

Okay that sounds like a great plan I will order those and see how I get on.
Yes to new valve stem seals.
Thanks heaps for help guys!

 

Have you done a compression test since it went back together?

 

I did one not long after it’s first start and it was 120 even across all 4
And I was told that will go up once the rings bed in.
Much better than the 75-90 I was originally getting when I first got the bike.

 

Okay guys we have a update!
New jets 42/116. (was 45/120)
New plugs and a colourtune

This all took awhile to get to little old New Zealand.

Fired the bike up no problem rode it around the block to warm it up.
Already a huge difference in acceleration! And bike was also sounding nicer.

Got in the shed plugged the colour tune in
Cylinders 1&2 wore lean so I set them to a nice blue spark.

Plug 3 was very rich so I adjusted that also

Now plug 4 was not igniting at all unless I opened the throttle.. just sparking.
So I obviously have a blocked idle circuit because I can fully unscrew the mixture screw and nothing will change in the way of combustion.

Is it normal for say 1&2 to need such big difference in idle mixture Turns to 3&4?

What a awesome wee tool!!
So I guess I need to find that blockage and then go from there as well re sync the carbs too...

Will try upload a video

 

Until you get cylinder #4 firing the results on the other 3 cylinders will be somewhat meaningless.............

 

Sorry it’s probably not the best video
But do you think it could also be the idle circuit if I can wind the mixture screw right out and nothing happens?
But if I give it a rev/ change over to main jet it’s fine ?

Once firing properly it’s sync then colour tune then repeat is that correct?

Thanks

 

Try going all the way in and back it out 2 turns and start these what happens ...or have you already tried that?

 

I have not tried that no. When I started the bike with the colourtune on #4 I had no combustion like in the video so I just adjusted the mixture screw out. But nothing changed.
I’m pretty sure this idle circuit has been blocked the whole time that’s why the plug has looked so clean.
I will try this though before pulling the carbs for a clean.

 

If you are patient, and have a magnetic tipped screwdriver with a 90º bend, you can remove the float bowl from #4 without pulling the rack.
I do agree that the idle circuit on #4 is probably clogged since you can see that there is no fire on 4 until the main jet is in play, and the colortune plug is working with the other cylinders.
It could also be that the pilot jet backed out and is sitting in the bottom of the float bowl.

 

I will definitely see if I can try do that moe
The less I’m pulling on those old intake boots the better.
And try unblock the circuit on the bike.

 

Ok so I pulled the carbs today to try clean out that pilot circuit.

When eyeing up my butterflies
#4 has light shining through no mater what adjustments I make to the syncing screws.
The other 3 close nice and snug to the carb body ( idle screw backed right off)
I pulled the butterfly and noticed this notch is that ment to be there? I feel like it’s stopping the plate from sitting how it should ?

 

The throttle plate should all be round(ish) with no notches. Set it on the shaft with the screws loose and see if you can file it to make it fit correctly. You'll have to take it easy and make sure that you don't overdo the material removal process. File a little, check for fit, repeat.

 

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Okay so I cleaned the throttle plate up
Cleaned the carb out, double checked everything
Bench synced.
Fitted and ran the bike vacuum synced the carbs
#4 was out so adjusted that which brought the revs right up and now it idles quite high with the idle screw backed right off.
And still no combustion from #4 below 1/4 throttle.
All needles on the guage looked like this and that says vacuum leak.

Took it for a spin around the block
Runs very well quite surprised how well
As I had never ridden a XJ before.
All plugs has white tips. Lean.
So guess I do have a major vacuum leak?

 

don't look at what's printed on the face of the gauge, that's generic stuff written for every engine ever made. all your looking for is they all read the same numbers.
i don't think there is even a spec given in the factory book about vacuum

 

I thought that might be the case...given that it’s a cheap kit.

 

how high is the idle now?
try this, set the mixture screws at 2 3/4 out, hook up your sync gauges, start it and turn the idle knob in until the rpm goes up a little, now check your sync and readjust as necessary, use the idle knob to bring the idle down, check the sync, if at any time the idle knob won't bring the idle down and the sync is still right, then you have a vacuum leak.
if your idle is 3k, that's good enough to start with. if you keep the sync right the idle knob should stop the engine.
i think #4 butterfly is holding the rest of them open

 

When I ran it from bench sync it idled nice around 900
Once I adjusted 4# to suit the vacuum gauge it rose upto 2-2.5k
Given all this it still wasn’t firing on 4

I will try this though.