Logo
FULL SITE MENU

No Spark New Everything

bill_w

bill_w

Advanced Contributor
Hi again. Back to this 35 hp 1958 Bigtwin. When I got it, I checked the coils, they were original 1958, cracked, obviously no good. I swapped in a pair I had that were maybe good. Okay, one intermittent spark (top), nothing on the bottom. So, bought and replaced coils, points (set to 20 thou), condensers, plug wires, and plugs (CJ6, at 30 thou). Still an intermittent spark on the top, nothing on the bottom. Tried disconnecting the cut out switch, stop button, checked the mercury switch on the tiller control (good), checked all wires for breaks/broken insulation, etc. I can't find the problem. The flywheel is still magnetized, and I'm at a loss for where to go next. Any suggestions?
 
You have set the " airgap " on the coil with intermittent spark ??-----------------You have verified that wire is fully inserted into the coil ??----------------Plug boots replaced ??--------------Head gasket leaking ??--------------Will spark jump a gap of 1/4" or better with a snap you can hear ???--------------------Have you set points with an ohmeter / or know how to use the timing marks on the flywheel and magplate ????
 
In order. Both coils are set flush to the machined marks on the mag plate. New wires fully screwed/turned into new coils. New plug wires, boots, inserts. Head gasket not relevant, plugs aren't screwed into head, grounded out to block to good ground with jumper wires. No, spark will barely jump 30 thou on the one that does fire. Points set with the arrow mark on the mag cam.
 
Learn how to set the points using the timing marks on the flywheel and the magplate.----------------Points could be opening " out of time " with the magnetic fields / current in the coil.--Spark should easily jump a gap of 1/4" on a proper tester.------------Laying plugs on the block is not a good test method at all !!
 
Last edited:
I found the problem with no. 2 cyl. I pulled everything apart again, and found the ground/shorting wire to the cutout switch was pinched and grounding to the mag plate. Made a new wire, and reinstalled everything, now a good spark on both. It shouldn't have affected no. 1 cyl, so I don't know what the problem was there, but it's working now. As far as I know, on an engine this old (1958), the spark timing is strictly controled by the point gap. There are no timing marks on the flywheel or magplate. And I don't lay the plugs on the block, I ground them using a good wire with alligator clips on both ends.
 
Sorry mate -----THERE ARE TIMING MARKS--------------just start the motor and look at / shine the timing light at the 2 vertical lines on the magplate.-------------You will see the marks on the flywheel as well if in time.-----------Just from 40 years of working on these simple motors.
 
My mistake, and I'll blame a bit of it on the Cymer manual too. I found the 2 vertical marks on the magplate, and on the flywheel there are 2 raised vertical lines, 180 degrees apart, that I take to be the timing lines for each cyl. When I get this thing running, I'm guessing that the timing is checked at full advance, but where should the flywheel mark be in relation to the magplate lines?
 
It will fire with the mark on the flywheel in the middle of the two lines on the plate.---------That is how a magneto works.----------Does not matter , full throttle or idle.------Elegantly simple way to set the points so that it fires exactly 180 degrees apart.
 
Learn something everyday. Makes sense, that they will fire at the same spot, regardless of the throttle position. We are not talking a distributer here, with advance weights and vaccuum advance. I was taught (many years ago) that if the points are set to the right gap, the timing will be OK. Too big a gap, too far advanced, and vice versa.
 
There are timing fixtures available ( AOMCI ) to set these points at the exact time for peak spark performance.I have used these for many years.------------Visit----------aomci-----------Frank makes good ones.
 
Back
Top