carb trouble

[DavidZ1R]

Just put my cleaned up carbs back on my little z250 project, put petrol in the tank, crossed fingers and hey, it started first time, amazed myself, however the bugger is only going on one cylinder took out the plug and it was dry, with no petrol fumes at all from it, ran it for a bit, checked again, still no juice, good spark, any help please?


Before


After

[CAT3]

Is there fuel in both float bowls ?

[DavidZ1R]

not checked yet will do tomorrow, what could be prob if the bowl is dry? also likely for bowl full?

[z1bman]

hi have you removed both emulsifying tubes from the carbs most likely cause of your problem make sure items 10-11-12-13-14 are removed + cleaned

[CAT3]

Definately check z1bman's suggestion.

If there's no fuel in one bowl then it's possible the float valve, item 18, is stuck in the closed position. Failing that it would be a process of illimination, tracing the fuel route from the fuel line T-piece to the float bowl. Somewhere between the two would have to be blocked, possibly when you cleaned them, (depending upon how you cleaned the carbs).

Another option could be a hole/rip/crack in the rubber diaphram, item 5, which would stop the slider & needle valve lifting up & allowing fuel to pass.

Before you refitted the carbs I assume you checked the choke butterflys & main butterflys moved freely. Also, if you push the two sliders up into the top of the carb, they should move freely back to the closed position.

[DavidZ1R]

Thanks guys, there is fuel in the bowl, I take it that the main jet must be blocked, the carbs were done by FJ Motorcycles in Skelmersdale, stripped, ultra sonic cleaning then vapour cleaned, thanks for the pointer Adrian (kas750), I was advised that a simple jet swap might be needed on testing, since the carbs have not been used for 25 years, not bad going. Will remove them and open up!

[steve.w]

probably be the pilot jet .. take it out .. u should be able to see through it ..

[DavidZ1R]

Well I have stripped them out and checked the jets are clear seem ok, put back on, now seems to be running but the exhaust pipe is getting very warm but not as red hot as the other side, can hold the pipe but not touch the other? at a loss could it be something worn?

[z1bman]

in your first photo above the choke flap there is a oval slot cut into the carb body. if you blow through this the slide in the carb should move up +down. if it doesn't you have a problem with the carb diaphragm. can you see light through no 13-14 in the exploded view of the carb

[CAT3]

Swop the diaphram assemblies, items 2,3,4,5,6,7 & 8, in the two carbs & see if the hot/cooler exhaust scenario swops sides.
Make sure the tab on the diaphram aligns with the cut-out in the top of the carb.

If it does, the problem will almost certainly be with the diaphram.

[Garn 1]

DavidZ1R, don't laugh... Unlikely but.... Could the twin carbs be swapped over such that the petrol doesn't flow into both carbs?
RegardZ

[DavidZ1R]

Diaphrams ok, going to change the pilot jet, if not that then down to more drastic measures, will let you know many thanks guys.

[DavidZ1R]

Well, finally, swapped both pilot jets on both carbs, from #38 to #35, unscrewed the adjuster on both to reset, big lump of jelly on the troublesome side, washed it out with high flash cleaner, put back and wroooom of it went , a carb guy from manchester told me to rev over 5 thou rpm, if it was the pilot the main jet would kick in and run right, I revved it and it did, just as he said, sorted, many thanks again guys.