mishmosh Posted October 28, 2015 Report Share Posted October 28, 2015 so my wonderfully reliable, mkIV engined herald, has an little quirk. If I work on it on tickover ( eg, when its Moted ) The no 3 plug (counting from front) fouls up. I then have to remove it and clean all the thick black crud ,off. All others are spot on. Its running an standard head ( and has been for twenty two yrs, no additives used ) so guess that may be the problem. I do around 1500 miles a yr. Thoughts ? Not lifted the head so havent checked rings. Link to comment Share on other sites More sharing options...
Darren Groves Posted October 29, 2015 Report Share Posted October 29, 2015 What sort of crud, Black & Sooty or Black & Wet? Link to comment Share on other sites More sharing options...
Clive Posted October 29, 2015 Report Share Posted October 29, 2015 Do a compression test. head won't be down to valve recession, but could be a worn valve guide. But if wet/oily probably rings. Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 29, 2015 Report Share Posted October 29, 2015 can even be down to plug not firing well at idle , check Clives request and let us know we can all have a guess !! check the dizzy spindle has no side play so cam doesnt open all the points when idling but it evens out at speed Pete Link to comment Share on other sites More sharing options...
mishmosh Posted October 29, 2015 Author Report Share Posted October 29, 2015 not oily. Quite dry carbon.It was tuned at triumfest and wasnt noticed then....Odd. Dizzy is a fairly new simonbbc. Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 30, 2015 Report Share Posted October 30, 2015 If its electronic not on points ,Some of the cheaper electronic units were shown by a magazine to have the magnetic triggers unequally spaced around the trigger hub so timing on each cylinder was different just an idea pete Link to comment Share on other sites More sharing options...
68vitesse Posted October 30, 2015 Report Share Posted October 30, 2015 You could try rotating the distributor 90 or 180 degree's out and see if the fault moves to a different plug. Regards Paul Link to comment Share on other sites More sharing options...
Guest Posted October 30, 2015 Report Share Posted October 30, 2015 mishmosh. That sounds like a rogue plug not operating within its correct heat range (i.e. burning off correctly) OR the HT lead to that plug is starting to break down by not delivering sufficient spark. I would swap that plug with another known good one or better still swap it (after cleaning it up and checking the gap) with one of the others already in the head; do the swap between plug 1 and the dodgy plug 3 - that provides a bit of space between the plugs & cylinders. If the "new" plug goes dirty and the "dodgy plug" stays clean then you can safely say there is a problem with cylinder 3 - be it top or end problem. If the "dodgy" plug goes dirty at cylinder 1 then the plug must be at fault. Once you have established which of the above applies, then you can take it from there. As Clive states, it will be worth doing a compression test at any rate but I would do that after the plug swap; when you may have gleaned more information accordingly. Best wishes. Richard. Link to comment Share on other sites More sharing options...
Guest Posted November 4, 2015 Report Share Posted November 4, 2015 Hello mishmosh. How did the fouled plug investigation go ?? Regards. Richard. Link to comment Share on other sites More sharing options...
mishmosh Posted November 5, 2015 Author Report Share Posted November 5, 2015 Went on a weekend away to lake vyrnwy. Clocked up 250 miles of quite varied motoring up some big hills. Performed well. This weekend I intend to check the plugs. I have noted an increased need to use full choke this year. The choke sticks if it's pulled on full. Link to comment Share on other sites More sharing options...
Pete Lewis Posted November 5, 2015 Report Share Posted November 5, 2015 wonky and sticking choke levers holding the jet down from fully returning I reckon its a built in feature of many an SU Pete Link to comment Share on other sites More sharing options...
mishmosh Posted November 6, 2015 Author Report Share Posted November 6, 2015 And new jets that won't slide easily Link to comment Share on other sites More sharing options...
Pete Lewis Posted November 6, 2015 Report Share Posted November 6, 2015 On the old forum there were ideas that the fuel tube can be too long and this pitches the jet solution was to cut 3mm off the tube pete Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now