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[Wheaters]

My Indian home market 350 Electra has suffered ongoing problems with fuel starvation. If I hold the throttle wide open for longer than about 30 seconds the bike misfires then stops. If I close the throttle for a few seconds it picks up and runs normally again. If I close the fuel tap when it begins to misfire the engine immediately dies and will not restart (insufficient fuel in the float bowl). If I turn on the fuel tap again and wait five seconds it starts first kick. I've tuned the bike a bit after the exhaust valve seat was replaced at just over 3,500 miles from new because the original one was soft; I've gas flowed head and retarded the inlet cam by the usual one tooth. It also has a cone air filter and a Gold Star silencer. I've adjusted the mixture using a 105 main jet and the richer slide produced by our hosts. The plug colour doesn't show excessive richness - I fitted a 100 as a first guess but had to go one size bigger still because the plug centre showed mixture weakness after carrying out some "plug chop" runs.

The bike will still do about 70 mpg so it's not losing fuel for any reason and there are certainly no fuel leaks.

I've tried a different design of tap (packaged as OE Royal Enfield in the Indian plastic packaging) and since gone through a process of removing its internal bowl filter and drilling out the fuel passages to remove any possible casting flash, so I doubt that's the root cause of the problem.

I tested for a blocked fuel cap breather very early on. The tank drains through either fuel tap at the same rate with the filler cap on or off so that's not a factor. I've also removed the OE inline fuel filter from the supply pipe - it's a plain pipe now. The tank is pristine inside, no debris or signs of rust at all.

I'm now suspecting the carburettor needle valve assembly - the bike has the OE Mikcarb 24mm carb.

Has anyone else found a similar issue? I don't think the bike would benefit from a bigger carb, it just needs better fuel flow to the existing one.

[Bullet Whisperer]

If your fuel tap is the type with the alloy lever, they are just about useless on machines tuned to any degree. There is a rubber disc inside with 5 holes and three of them are too small and restrict fuel flow to little more than a dribble. I 'fixed' a lethargic 535 GT with carb conversion recently by making three of these holes slightly larger, but it is fiddly to do. The other two holes just locate the disc on some dowels and can be left alone. Ideally, one of those chrome, lever type taps would be a good upgrade.

[Wheaters]

Pal, Thanks for your prompt reply. The fuel tap is same as this one: https://www.ebay.co.uk/itm/ROYAL-ENFIEL ... SwT5tWPuai and that's the one I dismantled, drilled out and removed the nylon gauze from the bowl filter. The bike originally had one of these: https://www.ebay.co.uk/itm/Royal-Enfiel ... SwuAVcifTY The problem is still there.

[Wheaters]

Sorry, I meant to correctly address you as PAUL! But thanks, Pal, lol!

[Adrian]

Check the petrol cap on the fuel tank, sometimes they don't vent properly. If the fumes cant get out, it also means the air can't get in as the fuel level starts to drop when you ride the bike, causing a partial vacuum in the tank which will stop the fuel flow. Have had this happen more than once.



For fuel taps, just get a standard 1/4" BSP type e.g. as fitted to Triumph T120s and T140s pt no. 60-4511.



A.

[Wheaters]

Adrian, Thanks, that was the first thing I checked - please read the fourth line up of my first post.

[Adrian]

Sorry, missed that. It does help the likes of me if you can split larger chunks of text up into smaller paragraphs. Try typing < b r > < b r > (without the spaces). Hopefully our hosts' new forum won't need this.



With an unblocked cap vent and free-flowing taps that leaves only the fuel lines and the carb itself, unless it's one of those carb problems that turns out to be electrical!



I'll get me coat...



A.

[papasmurf]

It could be a dying coil.

[Aethelric]

You have checked how fast the petrol comes out of the tank. It may be an idea to take off the float chamber and see how fast the petrol comes out of the carb. You'd need at least 150cc per min.

[Wheaters]

I'm certain it's not electrical due to the ability to replicate and cure the problem as described. I've had various coil failures on various cars and bikes over the years and it's not the same sort of thing. I can ride the bike all day in any temperature as long as I don't use full throttle for more than a few seconds.


I'll get around to stripping the carb again soon. I've done a thorough carb check and clean up a number of times, firstly when I first got the bike then later during the valve seat replacement episode and a couple of times since for re-jetting. I'm now thinking of fitting an alternative if I can't cure this fault.