Bike does not start... troubleshooting - one step at a time

[fret not]

Emulsion tube is about mid way between the accelerator nozzle and the "cap" you just referenced.  It is under the round impression in the gasket just adjacent to the "key hole" shaped impression near the accelerator nozzle.

[Rikugun]

Regarding the missing cap - there is not supposed to be a cap on the front carb. It has something to do with getting fuel to the accell pump. You'll also notice on the lower side of the capped one there is a drilled hole at an angle. On the uncapped front carb, the hole is not drilled.  The castings are the same but when machined and capped it becomes the rear carb body.

Also, this has nothing to do with the carb overflowing. I'd check the fit of the o-ring on the brass seat and it's fit in the carb body as well as the float height.

[Enzo]

Thanks for the directions to the emulsion tube.  The exploded view diagram in my Haynes manual is a little confusing with respect to the location of the tube. 

Now to find a set of carb gaskets...  I think it is more likely that I will need to cut my own from gasket material.

I also discovered the likely cause of the weak spark at my rear plug.  The secondary winding o f the ignition coil showed an infinite resistance, so there must be a break there.  I am amazed there was any spark at all.  I will be ordering two Dyna Coil (model DC3-1)  coils to replace the stock units.

[Rick G]

I sell float bowl gaskets for $15.00 a pair at you door. I have the punches and patterns to make them.

[Enzo]

Rick G

Thank-you.  I will take you up on your offer.

Just send an e-mail directly to me at
busto@shaw.ca
to exchange information.

[Enzo]

I looked more closely at the front and rear carbs.  I think that the "cap"-"no cap" difference is related to the functioning of the accelerator pump. Can anyone confirm?

[Rikugun]

Gaze upwards several posts and ye shall find your answer.  :) :D

[Enzo]

Thanks Rikugun.  I suffer from tunnel vision sometimes.  ;D

[Rikugun]

No problem. It seems you figured it out yourself so good work.  :)

[pinholenz]

Hi, can I jump in on this thread? Having a frustrating conundrum at present.
Had a hole in my tank which I de-rusted and repaired. Dropped the carbs out and gave them a clean but since the bike had been running pretty well, didn't fix what I knew wasn't broken. Re-assembled, dropped a bit of gas down the throats and she fired up OK. Some adjusting and oiling the accelerator cable and the choke cable, all seemed good, fired up, idled sweetly, revved comfortably.
THEN didn't start her for a couple of weeks during some nasty weather and haven't been able to start her since.
Spark seems OK when cranking, battery fully charged etc. Dropping some gas in the carbs doesn't help. I got Some nasty backfires and if I hadn't known that the timing was factory, set I would have thought the timing has slipped.

I do notice that  when I twist the accelerator, I don't get a spray of gas down the carbs? Is that normal? If I cover the throats with my hand while she is cranking there is plenty of gas sucked in to the carbies. Also the spark was orange rather than the blue-ish spark I would expect from a car. If the spark is weak from a starter overload, I guess a tow start might be worth a try.

Any other suggestions. ? Thanks

[QBS]

Assuming that your starter is not oil affected and you're cranking with a strong battery, try starting by putting a shot of ether/starting fluid down the intakes.  If your problem is fuel delivery related the bike will fire and run until the ether is burned up.  This indicates that the problem is probably not ignition related.  If the bike does not fire the problem is probably related to ignition.  The key in both tests is that the battery and starter motor must be in excellent condition.

[fret not]

Make sure the "engine kill switch" is in the ON position. :-[ ;)

I have found that both the HIGH/LOW BEAM and ENGINE KILL switches can be bumped without knowing, and there you are.  This would be too obvious so I almost didn't mention it, but one never knows.

[QBS]

Excellent note Fret.

[Rick G]

You have experienced the Vision "12 gauge" backfire, welcome to the club! The orange tint to the spark is normal. bikes do not produce the old
"blue lightning "spark. Pull the plugs and see if there wet fouled.  Also, If you take a spark plug  and cut the ground electrode off , it makes a great spark tester. If it will jump that gap, the ignition is fine.

[Enzo]

I received the cab gaskets from Rick G a few weeks ago, so I scraped the old ones off and pulled the emulsion tubes to have a look.
The rear one came out easily, I just gripped the top with my fingernails and pulled gently; however, I played with the front emulsion tube for quite a while before deciding to follow Lucky's tip of drilling the top, inserting a screw, and prying as gently as I could. 

YUCK!  What a difference in condition!


Emulsion Tubes by VLB_river, on Flickr

I was unable to remove the pilot jet from the front carb - the screw slot on the jet may be stripped.  (I had no problem removing the pilot jet from the rear carb.)

Just dipped the lower half of the from carb in Kleen-Flo carb cleaner.  Now I have time to tackle a little rewiring ...

Good thing this is a holiday weekend  :)

[Rikugun]

That looks yucky!  :(    :D If the front pilot looks anything like that emulsion tube, dipping may net be enough. Maybe pass the same size wire that goes through the rear jet through the (still installed) front jet just to make sure the opening is clear? It's better than nothing and could make all the difference.

[Rick G]

You can salvage your emulsion tube . After you dip it and clean it up , just solder the hole the screw is in  and re use it. The non-removable pilot jet may be more of a problem, there can be a lot of gunk trapped behind the jet . You really need to get the jet out or replace the body.
You can try to drive a small instrument screw driver in to the  jet  and turn it with vise grips , But first soak in it in PBlaster  for a couple of days. I've only had one,I could not remove.

[Enzo]

Rick G, I had plugged the screw hole in the emulsion tube prior to getting your soldering suggestion.  The options I considered were soldering or epoxy putty, and I ended up going with the epoxy.  Once the front emulsion tube was cleaned up I could see pitting of the surface.

I will have another go at the front pilot jet.  There is a a front carb body listed on eBay I will consider getting if I cannot sort mine out.

An annoying thing is that the previous owner paid a local Yamaha dealer for an ultrasonic cleaning of these carbs only last year.  Good money for work not well done.  If the dealer was in the Olympics for carb servicing they would win a corroded brass medal.   I think I will deal with them as little as possible.

[Enzo]

I installed the carbs, and managed to get the bike started.
So I also started a new thread.

Thanks for your help guys!

[fiatracer]

i had to go to an AGM battery on both my XZs. They both start flawlessly now! The carb lean is pivotal. I had both my sets ultrasonically cleaned and completely rebuild. Now they start in 3 revs! Watch your choke setting too. My 83 starts best full choke while my wifes like half! to own one your gotta love them! lol Gunna try the new lithium ion battery where in a few months see if the results are better than AGM! Jon