501 carburation

Maestro, SEI-V
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pedro
Posts: 311
Joined: 04 Nov 2010 21:14

501 carburation

Post by pedro »

I bought a 350/501 which came to me with pod filters, I was never really happy with the carburation, and so I thought that I would book a slot on my pals dyno. We got it running really well, mixture smack on, revving out easily, then I took it out on the road, hopelessly weak. The airflow over the pods when your on the move creates very different conditions than on the dyno. To go back to the standard airbox was not an easy option, since this very non standard bike has all its electrics where the box would have been. I had tried small pods tucked under the tank but was not happy with that setup either. I am now running standard carb to airbox rubbers but with nothing on the end of them, no filters at all. I don't really see it as a problem, they are tucked out of the way of debris, and in pretty much the same air conditions. I obviously had to increase the main jet size (from 108 with the pods to 145 now) The bike seems to run really well like this, the only problem is that on a full throttle plug chop the back cylinder plug looks spot on, the front ones a tad rich, fairly black in fact. Has anyone had to jet their cylinders differently or should I leave it as it is?
pedro
Posts: 311
Joined: 04 Nov 2010 21:14

Re: 501 carburation

Post by pedro »

Update on this, I've gone up and down on the jets, and while that obviously affects running and the colour of the back plug, the front plug remains black whatever, which has me thinking that it must be an electrical issue, I can't find anything loose connection wise and the bike runs up to the red line very willingly, but the front plug remains black, should I just forget it? What do you think (Paul).
morini_tom
Posts: 920
Joined: 05 May 2006 13:47
Location: Northampton

Re: 501 carburation

Post by morini_tom »

Check the condition of the float on the front carb- if it's sticking, punctured or at the wrong height, or the needle valve isn't sealing then you'll be running rich on that cylnder.

Remove float bowl and check the needle valve sealing by holding the float up lightly while the fuel is on. If fuel flows then there is your issue. Releasing the float should see fuel flow out (make sure you're doing this in a well ventilated place with something to catch the fuel underneath.

If that checks out ok, next check the float isn't leaking. Remove it from the carb body by withdrawing the pivot pin (good pliers and a firm grip on the pin end). Shake the float, it should be obvious if it's got fuel in it. Place the float underwater in a bowl of water for a while and then recheck to see if it's filled up.

If the float isn't leaking then refit the float and check/set the float height (you need the carb off the bike to do that)

Let us know how you get on.
pedro
Posts: 311
Joined: 04 Nov 2010 21:14

Re: 501 carburation

Post by pedro »

Thanks for that Tom, all is well in the float bowl, the float height was out, should be 23.5 - 24.5mm it was in fact 26mm, put that right, went out for a thrash and whipped the plug out, exactly the same, black and dry, NOT wet, never has been. Maybe I should try swapping the carbs to see if the problem (if it is one) goes with with them.
pedro
Posts: 311
Joined: 04 Nov 2010 21:14

Re: 501 carburation

Post by pedro »

Update, I have now swapped the carbs around and guess what, exactly as before, back plug showing correct mixture, front plug dry but black, so it's not a carburation issue, bike seems to run fine so I'm not sure if I should be worried or not. Help please Paul!
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