winter project No: 581

[Christian Raith]

Fuel through a vac......luck you are still with us mate.
The air goes over the motor which has a commutator which means sparks
Suck fuel from the carb into vac possible
KABBOOMM.

some useful stuff here

[Jonesy]

Hey Christian
tried a variation on your suggestion....put palm over air box snorkel and felt suction. Tick
off with the carbys, dunno about you blokes but for me theres no finnesse getting them off, just straight out brute force and ignorance.
cranked the motor again with palm blocking each manifold one at a time and  got suction at each cylinder. Tick.
With the carbs on the bench, and just for the hell of it I hooked a vaccuum cleaner up to the motor side of the carbys.....geez these things can deliver some fuel with that sort of suction
Main fuel circuit clear. Tick
Next, with the bowls still full of fuel I got the compressor going and blew air through each of the 3 holes on the airbox side of the carby and discovered the choke circuit on No:4 blocked, happy happy  noth'n better finding a problem when you fault finding. got that cleared and then pulled the bowls off and found 3 of the 4 starter jets that pgnz suggested  checking were blocked, how F'n happy do you think I felt to find that. Mr pgnz this is for you  ...in a blokey sort of way 

back on with the carbs tomorrow and a quietly confident 2nd attempt at firing up. and winter aint over yet

[Christian Raith]

Block a carb with your palm open the throttle a little and turn her over a few times and while turning over take your hand away. See if it fires and also if you have fuel on your hand.

[Eveready1100]

Can you hear the carbs sucking air in while you're cranking it over? Maybe a compression test to confirm all is in order machanically-wise?
If it's got low compression, it'll have very low vacuum so the carbs wont suck the fuel up.
Just to be sure, to be sure.(from Mr Overkill)
Other than that, it's got to be an internal carb blockage.

[Jonesy]

Hey Errol
Yeah I pulled the plugs out of the bowls and turned the taps to prime and got fuel flow. At this stage I'm ok with the fuel level just going off how much drained when the plugs came out. If I even got just a pop or a hint of combustion I'd get into more fine tuning with levels etc.....but theres not a sign of any thing near as positive as that.
no new bowl gaskets were used.
I think I'll be pulling the carbs off tomorrow,
might even suss out a way of making one of those level guages for the solid hex plugs mines got in the bowls just to have for later on.

It was all going so well too, with 4 days of winter left when i first hit the starter 

[Eveready1100]

Mate, there's nothing more disheartening than start-up blues with your pet project.
Couple of Q's.
Fuel taps - set to prime?
Fuel lines. Are they flowing fuel right into the carb tees? Are you running fuel filters? Not kinked at all? When you had the carbs apart, did you put new float bowl gaskets on? (maybe floats are caught under intruding edges of new gaskets)

Actually, just undo the bungs in the bottom of the bowls to see if fuel runs out.. That'll eliminate most of my prior questions.
If all the above check out, maybe try setting up something like this to check fuel levels in the bowls



as per this thread - CLICK

[Jonesy]

thanks pgnz
I'll definitely suss that out

I'm really loath to pull my other XS apart (if it aint broke dont touch it) but if your suggestion doesnt help I might have to do a carby transplant to really prove its the carby, but thats a real last resort. I'm already pretty confident the problem is carby related

[pgnz]

 starter jets.  tip gas or water down the tube.  should flow back thru the inlet hole if clear
 

[Jonesy]

Ok to answer some Q's, in no particular order
Pete,
no popping or backfiring etc, just winding over
I think the pick up coils are ok, not 180 deg out, because it did fire briefly, I didnt remove them and the length of wires to each pretty much makes it difficult to get back to front.
Jeff
all I did to repair was unsolder the speaker wire that PO used to repair and just rejoined/soldered the original wires then wrapped in some of that stretchy black 3M splicing tape.
I tested continuity to the plug behind the fuse box, no other tests. I realise the solder is a stiff joint and will break again, but it should last long enough for the purpose of test running and ironing out any bugs.
Another test I did before sitting down to write this was to remove the vacuum caps off 1 & 4 rubber inlet manifolds to squirt a quick shot of aerostart then replaced caps......it did run for a couple of seconds till the aerostart burned up, then nothing again, so its looking very much like the carbys are at fault.
The carby settings are 1 & 1/2 turns out on the mixture screw
float heights are right in the middle of the 24.7 -26.7mm range
main jet needle circlip is in the middle groove.

Next I'll wind it over again to see if the plugs come out wet or dry.
Any more ideas are most welcome
edit...some time later, the plugs came out dry

[excess.11]

A quick way to ascertain if its more likely to be fuel or electrical..............after cranking with some throttle applied.........remove the plugs to see if they are ....wet or dry.

As a matter of interest.......did you do a resistance test on the pick up coils at the TCI connector.......how did you repair them........and what was the reading ?

[pgnz]

the holes in the carb,

 lower left screw-in pilot air jet.  flows air to pilot jet.
 
 lower right  fixed main air jet.   flows air to main circuit/emulsion tube

top slot just vents the diaphragm bowl

top left hole is a fuel bowl breather.   goes to fuel bowl gasket, under the gasket the choke/starter jet pokes thru and the bowl breathes from a thin channel right there if that gasket hasn't got the appropriate hole to match the breather,  then she's gonna be a bit stubborn to run.  that's 78-79 carbs

main breather tubes run in from the top as well

[petejw1966]

jonesy, is it backfiring or anything,
or just turning over?

could u have the pick ups out by 180 degrees?

[Jonesy]

Dear brains trust
You know how you get that  "she's all humming along nicely and everythings falling into place feeling"? ......well forget it .....the bastard wont start.

Heres a few fast facts
Initiallly the motor fired straight away.....for about a second, and hasnt given a hint of firing since.
A few checks I did
1) All 4 plugs have spark
2) all 4 carbies have fresh fuel
3) Fuel taps are flowing correctly
4) timing light check while cranking shows spark within a degree or so of the "F" mark
5) fuses are all good, dont know why I checked 'em? I know, getting desperate
6) good strong fast cranking battery.


you blokes got any ideas?.......all the basic things to make it go are there. I'm stumped

[Jonesy]

Funny you should mention that Geoff coz I had the first stab of the button today. With plug leads off and spark plugs removed = no compression and an easuy time for the starter , and yes it is a have i got everything right type moment.
I wasnt quite ready to start it yet it, no exhaust fitted etc etc
but I added oil to the final drive middle gear and motor and wanted to circulate the oil to fill up the completely drained cooler........yes theres one on it, for the moment
hooked up the battery pack and hit ither button while I watched the oil drop in the sight glass
This proved a few thing too
starter motor work tick
oil pump works tick
oil pressure s/w works tick....the red light actually stayed off for about 30 -40 seconds after I'd stopped winding. not quite sure what that means but i'd like to think its a good tight motor with no exessive clearances where it matters so the pressure stays up for a while after
Lights battery action


Next step on with the pipes]

Then its the PLEASE start phase

[steptoe]

nearly ready for a stab of the start button,
here is the next hottly debated step, how to do an initial start up of a brand new motor,

some "experts" say to start on full throttle to have instant oil pressure,,

personally I wind mine over with a ratchet and socket, or a good strong drill to get the oil up, then hit the button,and let it idle,, , each to their own I guess

it,s certainly a butterflies in the stomach moment though,, you done well mate