Checklist

[The Prophet of Doom]

@QBS
You wouldn't have liked it.  I certainly didn't.  I wear safety glasses in my shop at ALL times and have a fire extinguisher in each corner as well.  Which seems overkill till you have a 1m fireball coming off your bike and sharp shards of plastic flying 5 metres.

@ Rikugun
It's the rear carb overflowing, same as the backfiring one. 
Today I'll pull the carbs and swap in a new float valve.  They both have brand new o-rings but unless I can get the bowl level right, I'll never get the bike running right.  It will make it super rich/wet and hard to burn - definitely signs of liquid fuel in the exploded YICS.
I was going to have a handmade YICS on the other bike.  I'll have to make two now.

I never did do a compression test, but finally broke down and bought a gauge yesterday.  Should arrive tomorrow.

@ Dinglebeery
Not done one at a time, but sure rear is the major problem.  Inlet valve for sure, though not sure how - it passes the blow test while manually pushing the floats up AND it works on the bench, just overflows on the bike.  Very curious.

Yes, I also suspect issues with the valve timing with that much backfiring.  I'll pop the top off and check that too.  It's not too hard on the rear. 

I had a thought last night that perhaps I switched the trigger sensors round the wrong way.  Firing the spark 70 degrees out would cause all sorts of issues

[dingleberry]

you can have my yics if I haven't binned it already.

[The Prophet of Doom]

Thanks Dinglbeery.  I think the Fab time for a new one would be about the same as sealing up an old one so I'll stick with that plan first, and give you a yell if it comes unstuck as my plans often seem to.

[Rikugun]

Back on the 31st when you first reported it running you didn't mention it backfiring then. Was it? Was it overflowing fuel then too? Doesn't seem like valve timing or ignition would suddenly change. Have these symptoms developed or mostly there from the beginning?

I agree the fuel level has to be right and that is strange how it test ok yet leaks. Try new floats and rely on a fuel height measurement rather than float height.

How do you think you may have switched the pulse coils?

[The Prophet of Doom]

Back on the 31st when you first reported it running you didn't mention it backfiring then. Was it? Was it overflowing fuel then too? Doesn't seem like valve timing or ignition would suddenly change. Have these symptoms developed or mostly there from the beginning?

I agree the fuel level has to be right and that is strange how it test ok yet leaks. Try new floats and rely on a fuel height measurement rather than float height.

How do you think you may have switched the pulse coils?

No it was running sweet.
I don't really think it's timing, but it's easy enough to check, and I might just do a twingle while I'm in there - I don't think I can wait till the other bike is done

Fuel hight was good on the bench.  I'm thinking the float might be hanging up somewhere I've already replaced the float.

Switching the triggers is easy to explain.  When I pushed the connector into the TCI they all fell out the back.

[Rikugun]

Switching the triggers is easy to explain.  When I pushed the connector into the TCI they all fell out the back.

That could do it and is worth checking.

Did you initially run it on a pony tank but now on the bikes fuel tank? If so, is the tank spotlessly clean?

[The Prophet of Doom]

Spotless... Ha.

I don't think I've ever seen a spotless vision tank.  I do have gold filter though. 

[pullshocks]

Your issue with the carb needle and floats ---

Worrisome to me because I was having something similar before cold weather hit and I stopped working on it.

Bought some slightly oversize o-rings for the needle valve body, very snug fit so that is not it.
With the carb top off the carb body I connected plastic tubin to the fuel inlet and tried to blow through it.  Very gentle pressure on the needle produced  a very good seal

But with the carb reassembled and tested with fuel, I was not getting consistent behavior.  I will mess around with it some more as soon as the weather starts to warm back up.  Single Carb  Vision was kind enough to send me a couple '83 floats so I can see if those make any difference.



some time ago there was a thread with similar behavior that turned out to be some kind of porosity in the casting.

[The Prophet of Doom]

Glad to know I'm not the only one.  Did I say that I had nice new viton o-rings myself.  They benchtest fine and cut-off well when I do  blow test on the fuel inlet.  Floats seem good.  It has to be binding somewhere but I can't see where.  Grrr

Can't believe porosity in this case it's too fast

This bike is haunted

[The Prophet of Doom]

The front cyl seems to be going fine - I took the valve cover off the rear to check the clearances.  That's a LOT easier with the coolant hose removed but I didn't want to do the whole drain thing again.

The clearances have drifted a little since I bolted it up, so I'll switch a couple of them out with one bigger size.  I'd be a lot happier doing this job with a decent metric feeler gauge (in nice small metric steps).  The one I have is in imperial (standard) steps & metric equivalents which equates to only 3 steps per 0.1mm and they are all over the place.  Totally arse for doing the shims.   If anyone knows where to get one of these (who will ship to NZ at reasonable prices) please let me know.

Unable to fix this DEMONIC MACHINE FROM HELL in a decent time period I went off and bought a car which has held things up a bit.  I couldn't quite bring myself to get a Corolla, but bought another "C" car just to keep Rikugun happy.  Ironically the colour is called "Lucifer Red", and I can't have it for a few days as it's at the menders.  Are these bad signs?

Did you initially run it on a pony tank but now on the bikes fuel tank? If so, is the tank spotlessly clean?

Thinking about this more ...
Yes, No
I was testing it on a virginally clean pony tank with fuel straight out of the ground.
The XZ tank was (nearly) empty when I got it so I just sloshed it out with fresh fuel, then put in 5L of fresh. 
Yesterday I accidentally slopped a bit into a work tray when looking at the carbs.  It was a strangely strong colour so I left the tray out to evaporate and was left with an unusual lot of sludge.  I think my fresh fuel must have loosened sludge from the tank, and then overnight gummed up my float valves.

I'll do a more thorough tank clean and re-do the carbs before I try them again.  This is never ending.  I haven't touched my proper bike since November last year!  and I can't really sell this one till it's actually going.

[Rikugun]

hmmm, Lucifer Red you say...   I wonder if you found the car or the car found you. A match made in Hades!?  :D  Well, maybe the evil forces will even out and all will be right as rain. Congrats on the Citroën and hope it serves you well.

Regarding the possible dirty gas tank - I hope that's it. At least you'll then know what's wrong and can begin resolving it.  :)

[dingleberry]

Yeah two negatives equals a positive. Nice tidy looking car, but a Frenchie? Maybe you should have my signature now.

[The Prophet of Doom]

OK so the French bombed New Zealand in 1985.  That's no reason not to buy their cars. 

[The Prophet of Doom]

My new compression gauge arrived today. 

HAYNES says to measure when hot - but I'm not so keen to pull plugs and thread the gauge on a hot DOHC.  Is it OK to do it cold?
Specs are 142std 128min 156max  What sort of PSI figures should I expect when cold?  Any other compression measurement tips?

[dingleberry]

Wouldn't think it would make a huge difference. Pistons are pretty close to bore shape at the crown/ring lands generally but a bit tapered at the skirt (not sure about visions). I would turn over a bit with plugs out to make sure there plenty oil on bore perhaps before test. Test with wide open throttle.

[The Prophet of Doom]

Today I checked the jets, valves and accelerator nozzles.  All looks fine and I can't see why it was overflowing, and can't repeat it on the bench.  It's a mystery indeed.  Flushed them any ways.  Not really sure what to do next as float level IS important for good running.  I'll pop them back in and see.

I double checked the shims.  No problems there - Initially I thought they had drifted or something, but I was just turned around because the bike was facing the other way.

While I was in there I twingled the bike.  With a little care and the tensioner removed you can do it without removing the cams...

On the rear cylinder I took it to TDC with both lobes pointed up (where you measure clearances), then rotated a bit less than 1/4 turn CCW (all turning done with my finger in the tensioner hole).  Don't go too far or cams will start to depress buckets.
Then slipped 4-5 teeth on intake cam, Then slipped 4-5 teeth on exhaust cam - this can be done by hand as long as the cams haven't engaged. 
Repeat 3 or 4 times trying not to miss the timing mark
Done

Actually I did miss the timing mark so had to repeat another 2 turns then lost count as I had a visitor.  Just kept going round till the timing mark shows on the flywheel and then checked I had both valves opening close together by rotating more and looking at the valves down the intake tract.

Final cam alignment was made with the marks on the cam, not the sprocket.



Buttoned it back up and checked the compression.  Cold as discussed earlier
95 Front / 100 Rear

Tank flush, carbs back in and fire-up Thursday; I'm busy doing car stuff tomorrow.

[Rikugun]

I kind of hoped you'd get the carbs leak free and running well before altering the cams but I'm still very interested in the results. Good to know about not having to R&R the cams. Also good to know valve lash hasn't changed - that would be troubling.

Did you turn the engine to TDC rear cylinder but on exhaust stroke then orient the cams to the conventional compression stroke cam and sprocket markings? Did you need a wrench on the cam  sprocket bolt to turn the cams "off the buckets"?

[The Prophet of Doom]

Yes, change one thing at a time etc.  If I had any sense I would listen to the advice I give others  ;D
I know you are probably concerned about not getting any before and after bum-dyno results.  Don't worry, I haven't forgotten how this bike runs

I've updated my prior post to be clearer - thought it best to keep instructionals together.

[dingleberry]

Don't think I should tell you this, but, a good running XZ400 just sold on TradeMe for $285 in Invercargill. :'(

[Rikugun]

Ouch! that's like twisting the knife...

POV- after reading your tutorial I think I'll stick to my way   :P

I'd hoped someone else would have commented on the compression numbers. How do you feel about them?