Ongoing Carb Blowback problem

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Ongoing Carb Blowback problem#14999

By TimG - Mon Jul 23, 2012 11:50 am

- Mon Jul 23, 2012 11:50 am #14999

Guys - thanks for all your most helpful replies. I am going to try and be logical when looking at this. Firstly, I will re-check the new points (still think I may have the gap wrong), check the advance springs, fit a new plug and then retest. If all this fails and I have the ignition system as near perfect as I can, then I will replace the rubber carb adaptor and retest (again). If all this fails I will then be back to tap the assembled wisdom of this site...many cheers
TimG

Ongoing Carb Blowback problem#15008

By PeteF - Mon Jul 23, 2012 3:52 pm

- Mon Jul 23, 2012 3:52 pm #15008

I think this is the most telling part of your post "The inlet stub is a bit aged and seems not to hold the carb very well, even with the clamps done up as tight as I can do them." I'd get that seen to. As to setting the points gap, just turn the engine so the heel of the points is on the high part of the cam then adjust the gap THEN RECHECK the gap after you tighten up the screw. Tightening the screw often changes the gap again. I'd change the condenser as well, they can cause all sorts of ignition problems and are tricky to check. If you replaced the points because they were pitted it could well be the condenser at fault.

Classic C5 Euro 4 at the moment.
Also CBf250.

Ongoing Carb Blowback problem#15009

By Peter 53 - Mon Jul 23, 2012 4:19 pm

- Mon Jul 23, 2012 4:19 pm #15009

Tim - if I remember correctly you are in North London?
I'm just over the water if you need to test the bike with a carb that is ok.
I'm still have electrical issues with mine, going to try getting a new battery to see if that improves things.

Ongoing Carb Blowback problem#15048

By TimG - Tue Jul 24, 2012 12:23 pm

- Tue Jul 24, 2012 12:23 pm #15048

Hi Peter 53 - I am in Barnet (right the other end of the Norvern Line from you...). Thanks for the offer of a carb swap, will have a look at all the quick options first, but might take you up on it...

Cheers

TimG

Ongoing Carb Blowback problem#15049

By Midge - Tue Jul 24, 2012 12:59 pm

- Tue Jul 24, 2012 12:59 pm #15049

On the 500 the rubber connector that attaches the carb to the head is best replaced with part number AM/2622/123 (in page 16 of the catalogue). Don't be put off by the description of being an Amal part, it fits the Mickarb perfectly. It is of a stronger rubber and with correct hose clips I promise you will not be able to pull it off. Maybe yours is letting in air causing a weak mixture or maybe the timing is off, either way, the carb shouldn't come off!