Guys
I've got a 1992 RR-N in my workshop for a starting problem. The bike is bog stock 100%.

I have ultrasonically cleaned the carbs, set the pilot screws at 1 3/4 turns out, carbs balanced, choke plungers checked, valve clearences checked, new fuel pump & filter, new Iridium plugs fitted.
When the engine is cold, and the choke all the way out (all plungers checked for full functionality), it won't start without throttle. When it does "fire" it feels and sounds a little fluffy (rich) but once you have given the throttle a blip it clears and will run on choke absolutely fine (though the revs don't rise to what you would normally expect on choke).
Leaving the engine to idle off choke and to get up to temperature, the engine runs as sweet as a nut and ticks over perfectly.
I have allowed the engine to run right up to the temperature where the fan kicks in, all still running perfectly.
However, as soon as the engine is turned off, and you attempt to start it again, you HAVE to give it throttle to start it, again it sounds very fluffy until you rev it to clear its throat.... it will again then settle down to a steady tickover and all seems perfect. The longer you leave the engine to cool down though, the harder it becomes to start, to the stage where it just wets the plugs.

Any ideas really appreciated and thanks in advance for any help.

Regards, Will

 

Sorry the thread meant to say SC28 ☺

Obviously the float heights are non adjustable, and all floats are fuel tight.
With the carbs hooked up to a slave fuel supply, the fuel shut off valves all seem fine too.
Don't know what to try next....

 

Hey, Will, saw your post. Im no mechanic, but i do bounce around the internet quite a bit. Searched " bike only starts while giving gas " . Brought me back to this very forum. You can search under " related topics " section...lots of input to check out . One i found interresting was from " Bored and Stroked" 9-4-15. ' post. Said this can happen if battery spins it seemingly fine, but is not quite up to snuff. Hook up charger or jumpers to rule this out. ......just sayin' . Thats all i got...

 

I might have missed it, but is there an idle screw/screws? I mean basic mechanical ones? Ones that would actually have the throttle plates open further if adjusted?

I had a dual carb twin dellorto setup on my Dads Lotus a few years back that did this. I had to set those basic throttle closed stops to be a bit more open, then re synch each carb and re adjust everything else after that, so it ran good again, but once I did it would start like a hot damn every time