Starting to wonder about this bike.....

[Scottish Badger]

After resolving my previous cold start issues, today I finally rode my 400/4 for the first time seeing as it was a glorious sunny day on the Moray coast. 
Now, I'm not a small chap (around 18st 6) so I never expected any spectacular performance, but it actually surprised me. Not with the speed or acceleration (never went over 60 and I was using a lot of throttle to maintain that speed into a light breeze), but how solid and planted it feels. It corners very nicely indeed, it's surefooted, stable and not upset by road surface changes etc. The highest praise I can give it, it's like a smaller, lighter version of my triumph Thunderbird Sport 900.
There's a minor adjustment required to the clutch, I think I may have taken just a little too much free play out at the adjustment under the engine cover as it wants to slip slightly when changing gear quickly and winding the power on.  BUT........

Slowed to 20mph in a village, started running rough. Into 30 limit, open the throttle a touch and it clears itself. F8&%£"g carb flooding!!  It's had new float needles and seats, float heights set (making sure the floats themselves are level), a filter in the line from the tank, clean fuel, and it's sat running on the bike lift for over two hours with no issues whatsoever. First time out, it floods one of the carbs! Stay over 30mph, it's fine. Slow down below 30 and it does it every time! Maybe it's trying to tell me something.......

[McCabe-Thiele (Ted)]

That is very frustrating - is it always the same carb that is flooding?
I'm guessing at over 30 mph a combination of vibration & fuel use is keeping the flooding at bay.
If it was fine for two hours could it just be some dirt has worked it's way down into the needle valve seat?
Does it still have the narrow plastic pipe between the carbs or has it been replaced with more normal fuel pipe?

[Scottish Badger]

Hi Ted.  Yeah, fuel usage at 30mph and above is enough to prevent the flooding. 
Frustration prevented me from actually checking which carb it was, but I can assure you there was no dirt in there anywhere and the filter is still clean as well.
I'm thinking I'll find what carb it was, drain it down and blow it back with the airline after taking the filter off and see what (if anything) comes out the fuel pipe.
The interconnecting pipes were all like new, more of a plastic than a rubber but still quite maleable - and clean.

[K2-K6]

Certainly a real pain to chase yourself round and round it trying to get it reliable.

Experimental, but you could try adding two stroke oil to fuel, 100:1 so 10ml per litre to see if that'll help things to move effectively in the brass components.

[Oddjob]

That's one of the reasons I asked Piki on the forum to make me some stickers for the overflow pipes, like the ones used on the HT leads, that's so if any start to leak I can look at the label and tell at a glance what carb is leaking fuel. Don't know why no one else seems to have done this before, seems a logical thing to do.

You may have a bent float pivot rod, the small brass ones the float hangs off. You can buy replacement rod off Amazon and make your own. https://www.amazon.co.uk/gp/product/B00JR5CG88/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 I polish them as well before fitting, every little helps.

[Sesman]

From a logical point of view, if identifying leaking carbs by ID becomes a convenience, then there is something dreadfully wrong with the carbs…just saying?

[Sesman]

Did piki make any per chance. I’d be interested by the way.

[Oddjob]

Your right Phil, it shouldn't be a problem, however, it appears that since the introduction of Ethanol in petrol the amount of leaking carbs seems to have shot up, never used to have this problem back in the days of leaded petrol.

Yer, Piki made me a few sets, I'm sure he'd make you some if you asked him. I bought some for my spare carbs as well, thought they'd make a nice extra selling point if I ever sold them. Obviously you need to fit them near the main stand ends of the pipes not up next to the carbs. They are like the HT label ones he makes except I asked him to fit the number horizontally instead of vertically, no idea why Piki thought making the HT ones so you needed to fit them along the lead rather than around the lead was a good idea. 

[K2-K6]

Your right Phil, it shouldn't be a problem, however, it appears that since the introduction of Ethanol in petrol the amount of leaking carbs seems to have shot up, never used to have this problem back in the days of leaded petrol.

I agree with this, just seems more prevalent with these type of fuel.

Anecdotal observation. A long way back we used Trichloroethylene as degreasant in engineering workshops, this used on brass components makes the brass much harder to move in a bearing type situation.  Specifically it's use was to remove all lubricant on the part, which feels similar to how these current fuel we use reacts on these components.  A friend running a garden machinery maintenance and repair company indicates similar, drives them all nuts with problems.

Suggested use of a little oil to help the valves shift and seal is my view of compensation and attempt to overcome this characteristic. 

I have been using castor oil in addition to fuel for this  reason, seems successful, but you'd need to evaluate for yourself and make independent decision to verify if that's for you. Smells like R when burning 

[Sesman]

Thanks, Ken. I’d overlooked the ‘modern’ fuel issue as you so rightly point out. Has anybody on the site worked out a way to refresh the brass on brass float valves? There must be away of grinding them in the same way as valves..maybe? I seem to recall a small ball bearing dodge I read many years ago, but failing memory can’t recall the method.

[Oddjob]

How much castor oil to a tank Nigel? Does it make the bike regular?

[K2-K6]

How much castor oil to a tank Nigel? Does it make the bike regular?

10ml per litre for dosing with oil.

As for regular, extremely effective, as the actress said to the doctor 

[Scottish Badger]

An update.
Leaking float needle seats confirmed on carbs 1 & 2.  I drained both carbs, removed the fuel pipe from the tank (leaving the other two carbs full) and used airline to blow through carbs 1 & 2 in both directions! Reconnected fuel line, fuel tap on, no flooding. Great, I thought!  Rode the bike, within 2 miles it was flooding again, this time on carb 2 only! Took it back home and virtually threw it into the workshop and went for a beer!
A few days later, I removed the carbs completely yet again.... I swear, these carbs should be able to remove themselves by now! After checking for any dirt in the in-line filter and carb float chambers (none), I set up a heath-robinson test rig with an air supply metered at 2psi and used leak detection fluid on the float valves to check for leaks, deliberately opening and closing them to try and provoke something.
I wasn't completely happy with any of them, so I trawled through all the carb kits I've bought (a cheap set from ebay, then another set from an allegedly reputable source after deciding the cheap ebay ones were crap quality!) and sat with some metal polish and a very small piece of tubing that just fitted onto the end of the needles and polished the needles to the seats. I've ended up using the UK-sourced brass with a set of original needles, I've also dropped the float heights by 1mm as well. Whilst it was up on the bike lift, I replaced the standard exhaust with a nice Delkevic system.
Yesterday, I took the bike out for a run and I'm relieved to say the carbs behaved perfectly, with no issues. However.... it seems I now need to replace the clutch, as despite adjustment being correct, it still slips slightly on hard acceleration going up through the gears. I also have a squeaking front brake, I suspect the caliper is binding very slightly, so that's another thing to add to the list......
On a positive note, I feel like I'm finally getting somewhere with it now, and the new Delkevic exhaust sounds just lovely under full throttle.

[Johnny4428]

Sounds familiar on these bikes you get one thing sorted and another issue appears! The squeaky brake issue can sometimes be sorted just by a slight chamfer on the sharp edges of the pads. Good luck with it!