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Thanks for tbe info. I currently have a left arm like Popeye!

That looks like a solution to a problem that doesnt exist.

Sorry to rain on your parade but mikuni slides are most definitely not all the same size. A 34mm carb is physically smaller than a 36mm so the slide is smaller - trust me. Going back to the original question, can any of you guys tell me what you have INSIDE your miks. Pilot jet, main jet, needle, needle jet and slide

Unfortunately I purchased the bike as a box if bits and there was no carb with it. I would have lut a bing back on it if I could have found one. The price of a new 36 bing would make your teeth bleed, hence the mikuni.

400 main jet? You must be running on methanol! This thing will start from cold with no choke at all. I have gone as small as 22.5 on the pilot and it STILL goofs up.I am rapidly appproaching resolving the issue with a bale of straw and a zippo lighter as it seams impossible to get some ballpark settings to work from.

I have done a search on this site and the only settings I can find are 30 pilot, 290 main, 6dh4 needle, q2 needle jet, 2.5 slide. I have a q2 needle jet but as yet havent had the chance to try it. Maybe I  have a Friday Afternoon Mikuni because this thing is truly awful, especially off the bottom where it will gas up at every opportunity. I was expecting a fairly useable power delivery  
or are they all basically unrideable? Mine is the only 250 HS being "raced" in the south of England and its proving to be a bit of an embarrassment when it should be an unfair advantage in the pre 74 class Looks lovely sat on the box though.

27.5 pilot, 310 main, 6DH4 needle, Q6 needle jet, 3.0 slide. Running a K and N filter with a brand new repro pipe from pollino diron. Cylinder has original porting with a new 72mm wiseco piston abd the correct twinplug head. Ignition timing is spot on, rewound motoplat, non resistor llug cap, new crank seals!

If you cant get it running, I'll have it! [][][]

Have you changed the plug cap? As I recently discovered, Motoplat ignitions will only work with a non-resistor type plug cap.

Thanks for the compliments - these things are super rare in the UK. Sourcing parts was a bit of fun, thank the Lord for the internet.

The air boot is a new reproduction meant for a Bing. The only way I could get it to fit was to stretch it over a beer bottle and leave it there for a couple of weeks as the rubber is incredibly stiff. After much cursing I managed to get it onto the back of the Mikuni. You will need to cut the carb down a bit to get as much room as possible. I then put the carb on the bike by removing the airbox (two bolts) put the airboot onto the carb, then onto the airbox and then put the assembled unit back into the bike (This method is a lot easier than trying to wrestle the carb on with the airbox in situ). If you are toying with the idea of fitting a Mikuni it will provide hours of amusement. On the plus side, she runs real crisp. There are a number of posts on here about fitting Mikunis - this is just the way that I got mine to fit.

Just as a matter of interest, what would you guys value this at? Pretty much everything on it is new.

Bit of a long shot but the piston could be machined wrong where the pin goes through. What piston are you using?

...or an aluminium tank. Looks like a business opportunity for someone.

You will need an epoxy resin sealant - a company called Caswell do a kit that will do the job. I have just restored a 74 Hare Scrambler and sealed the tank with a similar product as modern fuel destroys fibreglass. So far, it seems to have worked.

Hope this helps,