john_p_b
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| posted on 5/5/07 at 07:24 AM |
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pinto on twin 40's running a bit rough.
i'm having some problems with spitting back through the carbs and a missfire on my 2.1 pinto running on webber 40's.
had the carbs set up a few weeks back so shouldn't be a problem with them.
once i get above roughly 3000rpm it seems to clear the missfire but then when cruising even at 70-80mph it still spits back through the carbs!
could this be a timing issue?
anyone know what i should set my ignition timing at? spec if it helps is 2.1 pitno, stage 1 head, kent fr31 cam, twin 40's with 130 mains,
bestek non vac ignition system.
any clues would be very much appreciated because other than a bit of a cough and splutter from time to time it drives great and summer is getting
close (honest!)
built a car, built a home, had a family. lost the family, lost the home, still got the car.
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flak monkey
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| posted on 5/5/07 at 08:28 AM |
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Set the timing to about 12deg for a starter.
Usually when you get spitting back its a timing issue, rather than anything to do with the carbs.
If its doing it at low revs it can also be that one cylinder is running a touch lean. Take the filters off and try and spot which choke is spitting
back. If its consistently one choke then richen it up half a turn on the idle screw, and see if that solves the problem. Sometimes it does.
David
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britishtrident
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| posted on 5/5/07 at 09:59 AM |
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Sounds like excessive weak mixture on one or more cylinders
First thing to do is check the carb jets aren't blocked.
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john_p_b
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| posted on 5/5/07 at 10:35 AM |
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carbs shouldn't be running weak etc as they were only set up couple of weeks back using all new mount washers and rubbers etc.
been doing some research this morning and everything is pointing to ignition timing being too advanced. when starting the engine it kinda kicks back
as if the battery is flat, does this a few times then off it goes. surely if i've got the timing way too advanced then could simply be a case
that i've got a inlet valve still open slightly while it's on ignition?
built a car, built a home, had a family. lost the family, lost the home, still got the car.
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flak monkey
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| posted on 5/5/07 at 10:37 AM |
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If its kicking back on the normal starter you have probably got about 16deg advance. Agreed, back it off slightly. If you have strobe its easy
enough.
If its randomly doing it across all cylinders, it will be timing issue. If it is consistently one cylinder, then that cylinder is slightly too weak,
so richen up as mentioned previously 
Sera
http://www.motosera.com
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britishtrident
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| posted on 5/5/07 at 09:59 PM |
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Spitting back when running is not a ignition timing issue.
But you do have too much static advance which is causing your starting problem.
Try setting the ignition at 10deg BTDC at idle.
Check the carb jets are clear and the jet holders screwed home.
Check the carb rubber mountings and "O" rings.
Check the float chambers for signs of water in the fuel.
Check the valve clearances are not too tight.
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