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Intermittent misfire

Posted: Sun Aug 04, 2019 3:58 pm
by Tyler
Hi all.

Haven't been on for a while.

My question is, I have what seems to be an intermittant misfire. I have changed the spark plugs,leads,condenser,points, changed coil, an engine service, fuel pump, distributor cap, rotor arm looked fine. This was all done serveral miles (about 200 miles) prior to the event of this happening. Would anyone have anything else to suggest I try. Think I'm going too do a compression test. Symtoms seem to happen at low speed also and not all the time. :banghead: Thanks for your comments in advance.

Re: Intermittent misfire

Posted: Sun Aug 04, 2019 4:29 pm
by Tyler
Ps. it's a 1600 with 32/36 dgav

Re: Intermittent misfire

Posted: Thu Aug 08, 2019 9:25 pm
by nigecapri
Crap in the carb?
Whip the top off taking care that the thin gasket doesn't tear. Mop it out with kitchen paper & clean out any sandy deposits in the bottom of the float bowl then take the jets out & inspect for build up of crud. Make a note of which jet goes where because they have different functions. The alloy accelerator jet nozzles will just lift upwards, these should spray fuel when you twist the throttle open (pump jets.) Make sure the flaps are shut if you're dangling little bits of metal over the carb.

Re: Intermittent misfire

Posted: Fri Aug 09, 2019 8:52 am
by 340truck
Check valve clearances..1600s are susceptible to recession which will cause the kind of misfire you are having. If you find the clearances are tight and the problem comes back a few thousand miles after you reset them then it's time for hardened valve seats.

Re: Intermittent misfire

Posted: Fri Aug 09, 2019 9:21 am
by Mc Tool
nigecapri wrote: Thu Aug 08, 2019 9:25 pm Crap in the carb
How often do I have to do that ? :xd:

Re: Intermittent misfire

Posted: Wed Aug 14, 2019 11:15 am
by Major_Tom
Mc Tool wrote: Fri Aug 09, 2019 9:21 am
nigecapri wrote: Thu Aug 08, 2019 9:25 pm Crap in the carb
How often do I have to do that ? :xd:
:lol: :lol: :lol:

Re: Intermittent misfire

Posted: Fri Aug 16, 2019 6:44 pm
by Tyler
Thanks guys for your comments. I took the top of the carb off and cleaned it out, was a bit dirty. Put it back together and still the same. Taken carb of and doing a rebuild. Also going to check valve clearance too. Just bought a new rocker cover gasket today. Let hope this cures it.

Re: Intermittent misfire

Posted: Fri Aug 16, 2019 9:19 pm
by Mc Tool
Doing the valve clearance is a must do as tight clearances will have some effect on running ,but I would think that you would be seeing rough idling and a reluctance to answer the mixture screw ,rather than a misfire.
It's not unknown for new components to fail shortly after fitting. Did you clean the points before fitting ? Some have a preservative coating on the contacts that will burn off and dirty them. Try refitting your old condenser ,and get a good spark plug and fit it to each cylinder in turn just to make sure one of the new ones isn't failing
How's your back :) , leaning over the guards to do a tune up is enough to do my back in bad enough to require the (oral)application of alcohol . Bit like accupressure , alcohol flowing over the back of the tongue seems to be therapeutic for other areas of the body.....but not the liver :tongue:

Re: Intermittent misfire

Posted: Thu Aug 22, 2019 6:10 am
by Tyler
Well I'm very happy. Been for a couple of runs out and fingers crossed all is ok. Tappets adjusted and 2 exhaust valves were tight. Carb stripped and rebuilt and put through the ultrasonic tank, points cleaned and reset, changed condenser. Then had emissions checked. Hopefully a good run to dunton then on to brooklands. Yes I had to spread my legs apart to get low enough to reach. Being 6 foot tall it a long way down. :xd: