Zenith Carb rebuild

[CaptB]

Ok guys decided to strip down and rebuild my Zenith 1366B carb 1988.
First issue I have is how do I remove idle tube (9)
2nd to remove check valve 8 it says use screw extractor can anyone explain this in more detail.
3rd issue, I bought a large carb kit part no 2910-01-028-4326 5704828, when I looked at the parts I noticed the following
1) the diaphragm spring is a larger diameter
2) the accelerating jet has a larger diameter hole
3) the power valve assembly looks like it might have a smaller hole (not 100% sure with this one )
So do I have the wrong kit or will it work as long as I replace all the new parts
Also I would appreciate any other tips on the rebuild

[Fil Bonica]

Go talk to Rick Faunce , the guru of carb rebuilds.
He knows the insides of all 151 carbs!


Fil Bonica

[W. Winget]

From your other posting you said:

"The nos carb is a reproduction I found on e bay"

If it is not an original, the chances are the repair kit may not fit exactly.
I have never heard of a reproduction Zenith, as they are so plentiful, but they may be out there, especially in Europe.
V/R W. Winget

[Rickf]

Last run of the 151 13660 carbs came from Taiwan on contract to Zenith specs. They are exactly the same as the 13660 but they have a different number on top. If his says 13660 then it is a true Zenith.
To answer the questions
I will answer this tomorrow when I am more awake as it will take some explaining. If turning the bowl over and tapping it on a couple blocks of wood spaced apart so the jet has room to drop does not work you don't have too many options. If you try the tapping method be very careful that the tube has not started to come out and you slam it down again. Instant broken tube!!!
d
Do not replace the one way valve unless you are positive it is bad, I have only ever seen one bad one and that was because someone dug at it with a screwdriver.

1, Use your original diaphragm spring.
2, I have never seen this but if it is actually larger this will give you better acceleration so do not worry about it!
3, the power valve opens fully at wide open throttle when the accelerator pump diaphragm pushes on it, do not worry about the hole.

So basically you just use the kit as it comes without worrying about replacing the one way vale unless spraying carb cleaner at the outlet side blows right through it. If the carb ran fairly good before the valve is fine.

If you cannot get that idle tube out of the bowl by tapping the inverted bowl it is best to just spray carb cleaner through it both ways and call it good. If you try to pry on it or use pliers you WILL destroy it. One thing to make sure you do in a rebuild is to pull out the idle mixture screw and spray carb cleaner down there and also in the holes in the carb throat. and follow up with air pressure but not extreme pressure or you will blow out the welsh plug from the idle passage on the back of the flange.

[CaptB]

Ok, thanks a lot Rick thats cleared things up

[CaptB]

One other thing I have noticed is that the fuel valve assembly in the new kit is different, the old one is a triangular or cam shaped the new one is square and slightly smaller but I assume its ok to fit as long as I use the new valve seat with it

[Rickf]

You have quite the eye for detail! Someday I will look through my can of spares and see what the ratio of tree to four sided is. I probably have close to a hundred sets in there I have no idea why I save all that stuff but like accelerator pumps, if it is not bad I will throw it in there and if someone needs one in a pinch I can send it out to them, no guarantee but from 45 years experience I pretty much know if it is good or bad for at least short term use.

While on the subject of the needle and seat be sure to get that float setting correct at 9/32", These are very touchy about float level. Float drop I am not quite so critical about and I will let it go just a little below the 3/8" sometimes because it is such a pain to set. Just don't let it drop too far or it will splash the fuel in the bowl and you can get flooding issues and/or a jammed needle.

[CaptB]

Ok it's been a while but finally got back to working on the mutt. Fitted the rebuilt original carb, new inline filter and new fuel. She fired right up, adjusted the idle to around 600 rpm and everything seemed great, idled ok and no splutter when revving. Took it for a spin about 5 minutes driving, stopped at my neighbours for 10 minutes and when I tried to start again it took a few goes. Got 500 metres down the road and it cut out and would not start. Took the air intake hose off and could see fuel spraying into the carb when it turned over but it would not fire. After around 20 minutes I tried again and it fired right up, drove home 500 metres, let it idle for 10 minutes, revved it a few times then again it cut out and wouldn't start. An I looking at a carb problem or should I start looking at the coil.

[W. Winget]

Asking the 1st question:
Did it do this before the carb rebuild?

Obviously the carb is functionong well, it starts/idles/drives well.
A small chance that it was possibly vapor locking seems negated by you seeing fuel squirt in when checking it hot.

So coil may be a good place to start, but was it doing this before, and you rebuilt the carb to fix that issue or is this a "new' issue.
V/R W. Winget

[Rickf]

Sounds like a coil to me. Keep a spare spark plug and a wrench to take the plug wire off of one and the next time it does it immediately swap your spare plug onto the removed wire and lay the plug on the valve cover and see if you get spark. Naturally if the vehicle now starts the test will not work but if the vehicle still will not start I will bet you do not have spark so that narrows it down to coil or electronic control module. The coil is the usual culprit since modules usually die and do not come back. It has been know to happen but it is not usual.

[CaptB]

Ok this has been a problem since I got the mutt, tried various things to fix it like changing coils etc nothing worked. So decided to go back to the beginning checked valves, rebuild carb, set timing. So update, this morning she started first kick idle for 15 minutes with me revving it a few times every 5 mins, no problems. After around 15 mins, as soon as I hit the throttle she cut out and would not start. Left it for around 30 mins, again started first kick repeated the test same result. Changed the coil (it a good one) repeated exactly the same. The distributor has a swiss unit NOS with no signs of heat damage. What next, its driving me mad

[W. Winget]

Fuel cap vent in open position?
If you do the same test and she won't start, see if you open the fuel tank cap and an inrush of air occurs. -whoosh-

Short of that if it does it almost the same time each time, it may be something obstructing the fuel pickup which floats around until it clogs the pickup or filter then drifts away after resting without suction for a few minutes.
V/R W Winget

[Rickf]

Have you replaced the ignition module yet? It could very well be the module. They usually go out once and done but I have seen many reports of this happening with these modules just like the coils. The easiest way to diagnose it is to keep a spare spark plug handy and as soon as it dies be quick to change the wire from one of the plugs to the spare plug and lay it on the valve cover and try to start it. No start and no spark then you have a problem with the coil or module. If it starts then try it again the next time. The reason I say use a spare plug is very little time is wasted in changing the wire over so little time is given for it to cool off. If it starts you could even leave the spare plug in and do your test again just running on three cylinders, the ignition does not know the difference since it is still firing four plugs. Watch the spark for it to change from blue to yellow or orange and if it does I will bet it dies shortly afterwards.

[CaptB]

Thanks guys, I have tried the removing the fuel tank cap several times no inrush of air and no difference. Haven't changed the swiss module yet, I will try the test with the spare plug. I also have a spare distributor with a Prestonlite module that I was planning to revert to points and give that a try. I will report back

[muttguru]

Rick, I can't fight it any longer. I HAVE to ask......

CaptB...

do you have a plastic or metal fuel filter installed in the feed pipe from the fuel tank to the carb?

Ken