went for cruise today and motor started missfiring,checked fuel for blockages not that,front plug burning tan colour,back one burning black like to rich or not firing all the time,leads seem ok,could it be the coil or something else,help needed,

First quick check, pull the plugs out and check for spark, if the rear one is not sparking then swap it over with the front one and try again. That will tell you if its just a plug. If the result of the test is the same you could have a faulty coil or plug cap or ignition lead you can also swap leads over from the coil to do further testing

 

checked plugs,both firing but spark seems weak,will check leads and try again.

what year is the shovel? running points? how is the battery? is the headlight dull with the engine off? always a good test.
Process of elimination.....

It hasnt recently had a top end rebuild by any chance?

hehehehe, looks like kiwidave has had many an "encounter" with the good ol reliable shovel electrical system as well, what a joy.....

Reason I ask re: top end, have seen cheap and nasty bronze valve guides fitted that show a very similar issues on a hot day as the valve starts nipping up. One of my shovels did the same with a nice set of s&s guides, but that was me pushing the envelope with tolerances.

had it out 2 days ago no prob,go out today and prob starts,

going to check all those sugestions tomorrow

thanks

 

83 shovel,running points,battery brand new,headlight ok and bright with engine off,no recent top end rebuild,was ok 2 days ago will look further tommorow.

if its missing when your pulling away or underload its probably your condensor. 

Hi Clarkie,
Kiwidave's got you covered as far as to where to look, and I like DaveP's realistic summation of the joy of Shovel ownership.
Last time you took it out, long ride? Any rough roads? Reason being it does sound like loose electrical trouble, as Kiwidave pointed out. Battery earth is a good start and work from there. Usually it's something simple, sometimes it's not. The good thing about this Forum is that someone somewhere has been there and done that. Just an afterthought, add circuit braker (Ignition) to the list.
Start simple, we'll talk complete rebuild later on. ONLY JOKING!!!!!!! or maybe not.
Regards,
Cris

Sounds like the coil to me. My ACCEL coil I had on my 81 WG did exactly the same thing once.

how did you go clarkie?

hi guys checked over every thing today,battery terminals all ok,replaced advance weights with new ones i had,points,backing plate,condensor are all nearly new,points gap ok,rechecked timing ok,nice blue spark at points,replaced plug leads and plugs,checked compression 85psi in i&2 cyl,pulled carby cleaned out but it was a new one 2 months ago mikuni,good fuel flow from tank,and guess what its stil bloody missing,only thing  i  cant check is coil,how do you check these without replacing it,thats my next step,got me,

hi, when you say bright blue spark at points  ? check in a dark garage with engine running  & cup your hands around the points housing ,  points should be running at orange colour if it bright blue or white the condensor is not doing its job atherwise your points will burn up & pit badly give them a good clean  (elect clean spray ) , also check inlet manifold rubber seals to cly head  ? ,  new spark plugs ?

Good suggestions there by Daddyracer, the rubber bands on the intake manifold tend to perish if overtightened. Most people think that if tight is good , a bit tighter is better. Wrong!!!!. You mention you replaced the plugs, which ones are you using? I bought a bulk box of Champions that were 50% bad. Drove me crazy for a week. Changed over to NGK BPR5S-11, same plug the Evo's use. Have not had any problems with NGK's ever. Only way to check coil is to swap with a known good one. Checked timing?
Regards, Cris

 it lives again,turned out to be condensor,bloody thing was new with backing plate and points 2 months ago,but at least its going,big thanks to all for their imput and help,thanks guys,going out for run,beer,run,and more beer,thanks guys

Glad its sorted for you mate, well done.

That's a good trick Dave, are the readings similar for single fire? I always did the swap coil test.
Cheers,
Cris

thanks dave,i will keep that info for future checks,took the bike out today for a run and had no problems ran well,will be looking into motor work shortly but got a few other things on first just glad to have it going,out of curiousity what should compression be,thanks again for your help.

Spot on about the pushrods adjustments, should always check them before a comp test. I have always (personal) considered that 120  is about the time where you start  grabbing everything you need to rebuild the top (85 is a bit too low). Then wait for a rainy weekend. 140 - 160 is good.

Your low compression could be 1 or more things, when the compression is low in one or more cylinders, you can isolate the problem to the valves or rings by squirting a little 30 weight motor oil into the cylinder through the spark plug hole and repeating the compression test. The oil temporarily seals the rings. If the readings are higher the second time around, it means the rings and/or cylinder is worn. No change in the compression readings tells you the cylinder has a bad valve.

hi, when doing comp test allways  do pushrod adj 1st , before adj  allways tighten & check barrel nuts  , heads & rocker bolts  , set  pushrod tappet adj 1/4"  A.T.D.C.  on the compression stroke  , adj both inlet & exh ,   because when the cly fires the valves must be closed no matter what, (  if you adj  like some people do & have 1 @ full  lift & adj the opposite tappet it won't come  out as good as ) because harley motors are not 180 deg opposite , they have & off-beat firing order ,    if you adj 1 cly @ a time you can do any type of 4 stroke motor tappet adj  even  a radial 18 cly aero engine ,       do barrel & head bolt tighten check with cold motor  & also  pushrod adj cold  ,  when checking comp test  check  with motor hot with the throttle full open ,    i hope this helps