ET: Engine (Twin) 229/289 Carb Set Up

[Rob H]

Thanks Greg, did not know that about the nut. I have checked the float levels by removing the float bowl arm and bottom cap and nut from the carb and the level of petrol reaches just below the edge of the bottom cap.

Will buy a pin vice and some drills, so max drill size is 0.5mm?

 

[Rob H]

Have ordered some drills smallest 0.3mm so will check what size the existing holes are and post for info.
The carbs are both original brass bodied.

 

[greg brillus]

Any larger than 0.020" and it will run too rich at idle.........

 

[Rob H]

Hi Greg,
The original drills I ordered were rubbish, sizes bore no relation. Eventually got a 0.4mm and 0.5mm.

Found the 0.4mm to be a loose fit in the pilot hole but the 0.5 a shade to tight..

I am estimating the size of the pilot hole to be about 0.018". Is it worth taking the hole out with the 0.5?

I did have the carbs working ok in the past..

regs

 

[greg brillus]

Rob, I think 0.018" is the original size, but sometimes the hole is burred and not quite true to size. Opening out to 0.020" will not hurt anything and should give you some more useful adjustment of the mixture screws. These should be approximately 1 and a 1/4 turns out from the seated position. If this does not help, then I would be looking at the slide cutaway and the float levels. The stock number 4 slides tend to be a bit lean on modern fuels, although this does not explain why it ran ok before...........Keep trying.

 

[Rob H]

Thanks will give the the drill a try. I did reduce the cutaway a little already by trimming off the bottom of the slide to give approx 3.1/2

 

[Rob H]

Just a quick post to update, took out both carb blocks and tried with a 0.5mm drill. One was a loose fit but the other was a bit tight. Don't think this was an issue of being too small but more gummed up as I was able to open it up by just twisting the drill between two fingers.

The other issue that was spotted was that the air screw on the carb was further out than the other. this was due to the air screw becoming tight when screwed in well before the actual stop point and thus gave a false setting (not wishing to force it). Both screws were closed fully to the stop and opened 1 turn. Needles raised one notch.

The result is - success - the bike now runs and ticks over with no hesitation on pick up. I think it is probably a bit rich so will just lean it off a little at a time and try it.

Thanks all for the help & advice. I am assuming the fuel gummed up the pilot jet a little which in conjunction with the air screw setting which I assume was also gummed up making it tight would explain why it had worked fine in the past.

bloody modern petrol or so they call it!