I am going insane! I just took apart my carb for the 5000 th time, because I am having real problems starting the bike after a rebuild. Would you believe it, noticed on the side it is Dellorto PHBL 26 and not 25 as stated in the manual. Took the digital calipers to it, in case it was my eyesight and it is 26mm intake. My question is, will this make a massive amount of difference and is this the source of all my woes. Please help, someone please. The men in the white coats are coming.

No, it should work. Did the bike run before the rebuild?

No it was a basket case. Has a very strong spark though.

Compression, spark and fuel is all you really need. Does the slide close all the way? (I have seen them in backwards)

Is the plug wet with fuel, or you could put a little premix in the plug hole to bypass the carb.

Had a problem similar w/Dellorto PHBL, was not fully applying choke lever. (rich mixture device)

Luck; Larry

Check flywheel key, they snap if you haven't tourqued the flywheel past what you would think was tight, it will still spark some times

Yes the slide has full movement, but the plug has been wet when inspected.

So if the plug is too wet it will not spark. In that case it is flooded on the lower end and needs cleared out.

Thanks for that, but why do you think it is flooding?

I had a very similar problem with a 200 which i restored last year , just could not get it to run right, messed about with the carb for what seemed an eternity. If the carb is original it is likely that the slide is worn along with carb barrel, so impossible to set up. In the end i ordered a new carb off Bill Pye at Frankfield Fantic which came correctly jetted and setup . Fitted it to bike and fired up 2nd kick never missed abeat since. Give Bill a phone he is a very helpfull.

Thanks for all replies. Took the carb apart again after having the petrol tap on and the float bowl was dry this time. Fiddled about with it again and put it back together. Kicked it over and thought there is something not right about this kick start. Drained the oil took clutch cover off. Noticed that the return mechanism stop was wrong side of the holding pin that screws in from the underside. Corrected this (very fiddly) and refilled oil. Kicked it over and sprang into life first kick. Running very nice indeed. ( for the time being)

sorting out that kick start spring is definately a three handed job