Fuelling issue

[CharlieK]

Guys after your great advice with my last brain fart can I run this one past you?
The choke although physically operating as it should has no effect on idle speed, so the only way I can get the bike to run is to start it and hold the throttle open till its warmed up. Even then its not running right, pulling the choke on then also has no effect and its very slow to rev up throught the range, bogging down quite badly in the midrange.
I have followed the carb jetting guide, so its currently got, raised needles by 0.5mm( two washers), 2.5mm holes drilled, the diapragms are in good nick and seated correctly, 120 jets all round, emulsion tubes in the right way round and no holes blocked. I have set the float heights to recommended 6.5mm and set the idle screws to 2.25 turns out. The valve clearances have been done and its running a standard exhaust system and Viper end can.
Tonight I had the carbs off, replaced the carb rubbers with new ones and new clips, changed the front jets for 118s and rechecked the float heights. Yet to run it, its 1 am, didn't think id bother the neighbours! Anyone got any suggestions before I fire it up again?

[MexicanGringo]

How did it run before adding the washers? What are the state of the plugs? If they'r very black id recommend taking at least one washer out as its probably running way too rich

[Cammo]

so the only way I can get the bike to run is to start it and hold the throttle open till its warmed up. Even then its not running right, pulling the choke on then also has no effect and its very slow to rev up throught the range, bogging down quite badly in the midrange.
I have followed the carb jetting guide....

None of your mods you've done should give those symptoms.

Are you sure the choke rods on front and rear carbs are moving when you work the choke lever? I still think it might have been an air leak originally (to do with the carb rubbers).

Take it out and give it a good fang. If problems persist - check the electrical system.

[CharlieK]

Yer plugs are a bit black, Ill take it back to one washer, new carb rubbers are on now, just going to reset the idle screws to factory settings and I'll let you know the result.

[NGneer]

The choke although physically operating as it should has no effect on idle speed

Silly question but got to ask.....did you make sure that you reconnected the other end of the choke cable to the arm on the front of the carb block when you refitted the carbs? Is the movement of the choke lever actually moving the associated rods on the carb assembly?

[Deviant400]

The choke although physically operating as it should has no effect on idle speed




Silly question but got to ask.....did you make sure that you reconnected the other end of the choke cable to the arm on the front of the carb block when you refitted the carbs? Is the movement of the choke lever actually moving the associated rods on the carb assembly?

or check the little clamp that holds the end of the choke cable is tight too

[CharlieK]

Ah ha, one of the carb plungers was welded full on, I have stripped it, lubed it and stuck it back in all works as it should now. Tried to start it and fouled my plugs badly, probably flooded it, which hopefully explains the oily black looking plugs (Please don't be shagged piston rings )
My next problem is the rear plugs aren't sparking, off for dinner, more later.

[MexicanGringo]

The plugs foul very easily, clean the plug contacts and around the ceramic part thoroughly, run some fine sandpaper between the electrode to get any carbon off, they should spark then.. the front plugs are more of a bitch cos uv got to drain the radiators and move the top one forward.. 'Wet' looking black could be oil or just flooded plug

[CharlieK]

Top advice mexicangringo, luckily it was just fouled plugs because I had been turning the engine over for a long time, it was trying to fire but only on one or two pots. The oily black sludge on the plugs was from flooding the cylinders when she didn't fire. I followed your advice cleaned them up and using fine wet n dry cleaned off the contacts and stuck them back in. A continuity test from the ignition module to the HT leads proved I had some dodgy wiring going on, (this bike was a f***ing dog when i bought it) so I stripped and put new connectors on all the wires going from the loom to the HT leads, tank back on, and Raaaaa off she went straight away. All cylinders firing nicely and fuelling issue sorted (due to one carb choke sticking on).
Very satisfying. I wouldn't be getting this far without your help so I better become a site supporter!

[CMSMJ1]

That is all