3k Carby Trouble

[3KE70]

Evening guys.

I have just stuck a 3K-C into a KE70; for about a day she went just fine, a good 3 hours total.

Prior to insertion, the engine had been out of action for at least a year, but fired up strong and clean; it had been rebuilt prior to being laid up.

Fired first go, didn't blow smoke, pulled well up until ~5000rpm, after which it would still rev, but not make power.

And now drama has struck.

 

It seems like it keeps running out of fuel; It will start, run for a few seconds, and then die. If you touch the accelerator, it dies.

After a few seconds of cranking, it will do this over and over.

If I leave it say, half and hour, it might run for 30 seconds?

 

I then realised that if I start it with foot flat to the floor, or the choke fully on, it will rev, and then die until it *almost* stalls and then rev again. Over and over.

 

The first thing I checked was the filter (by bypassing it), no probs.

Then the fuel lines to the tank, which I had cleared prior to starting it up; no worries there either.

Then the pump; pulled the fuel line off the carb and cranked it, solid jets of fuel came forth.

 

So from that, I'm pretty sure the carb is getting plenty of fuel.

 

Next, I pulled apart as much of the carb as I dared; pulled the top off and drained it, and using a piece of spaghetti hose, blew through every orifice I could see.

Took out the ?venturis? (circles with nozzles inside suspended in the airflow) and blew through them.

Unscrewed the little brass pinhole things inside the fuel reservoir and blew through them.

Wiped all the gunge out of the bottom of the reservoir (?float bowl?).

 

Found nothing that was an obvious obstruction, but as you can tell, I know bugger all about carbs.

 

Reassembled it, exactly the same. Hit it with a good whack of Clean-R-Carb; nothing. Also tried trick I've heard of; getting a big rev up and then sealing mouth of carb with a gloved hand, to create vacuum to suck shit out of the pipes. Also nothing.

 

So at this point, the narrowest diagnosis I can come up with is "carby's f@$ked".

Short of just attempting to put a 4k carb on it which I have spare, and playing the guessing game with umpteen spaghetti pipes I have even less of a clue about, I'm out of ideas.

 

Help!

 

Thanks for reading this epic post, any help would be greatly appreciated.

 

Cheers, Nathan

[Bamboo]

random guess....needle and seat are R/S

[Raven]

Vacuum leak.

 

Check that your carby is bolted down tight, check that all your vacuum ports on the carby are hooked up, and check the hose from the brake booster to the manifold.

[3KE70]

random guess....needle and seat are R/S

 

 

Needle? Seat? As you might have gathered from my tentative use of the words float bowl and venturi, I know these things exist and are carb parts, but I have no idea where they are, what they do, what they look like, or how to tell if they're shagged...

 

Thanks for the reply though.

[3KE70]

Vacuum leak.

 

Check that your carby is bolted down tight, check that all your vacuum ports on the carby are hooked up, and check the hose from the brake booster to the manifold.

 

Check, check and check. Tight as a drum. Plenty of brake boost, and plenty of vacuum when I did the hand over intake trick. No hissing or sucking noises when it's running.

[Evan G]

carby mixtures? ignition timing?

[rockinrolla]

when you get it to rev place your hand over the top of the carbie and block it off this will create a vacuum inside the carbie and remove any small blockages but, if this doesnt work go on to ebay and buy a carbie gasket kit ($45) pull it apart and follow the instructions inside the packet and clean the carbie and replace all gaskets, needle and seat, o rings and washers as applicable. (learning process) :dance: :) :D

[rockinrolla]

it sounds like you have grit of some sort in the fuel bowl, the easiest way to find out is to take the top off of the carbie and clean it out.

[3KE70]

it sounds like you have grit of some sort in the fuel bowl, the easiest way to find out is to take the top off of the carbie and clean it out.

 

Hey,

Thanks for all your replies.

Problem solved!!(Onto the next problem...)

I took the carby top off, and after much dicking around (related to not having a wide enough screwdriver) managed to get the seat unscrewed.

It's only a little mangled :dance:

The fine mesh filter that sits on top of it was packed with fine grit.

Assembly was the reverse of removal, voila, running 3K.

 

I promptly took it out for a thrash in todays fine Corolla weather, but alas, the slidiness was curtailed by the mongrel refusing to make power over about 3500rpm.

I checked the carb again, but no, plenty of fuel coming from both jets now.

It's quite strong down low and doesn't misfire, so I'm guessing that it's not an issue with spark, but with timing...

[rockinrolla]

your float level maybe set to low, when setting the level you only have to move the tab the smallest amount.