Stumped

johnwh

johnwh

Full member
About 3 months back the Jota dropped out on a cylinder.
Because I have been away it has stayed that way until I had some time yesterday to look into it.
The problem is on start up and idle and continues through the rev range with some improvement as revs increase.
Just gives an occasional fire on the third cylinder, otherwise dead. Haven't isolated which cylinder yet, they all had equally warm headers
Swapping leads, replacing caps and checking coils to no avail.
Did a test run with some old plugs with missing electrodes. Good healthy spark through the whole range.
Have pulled the Mikunis off and cleaned them up also to no avail.
Not sure what to check next.
John
 
Check your compression, have a look at your valve adjustment. Check the cam lobes for wear. If OK you probably have an intermittent open/short circuit in the wiring for that cyl. You don't say if it is a 120 or 180, the systems are different.
 
Hi Maurice.
Back home for quite some time I hope. The last few trips were to much excitement for an old fellow.
When I get this bloody bike sorted I will be up for a ride.
Cheers John
PS Its a 180
 
pickups, pickups, pickups,

I chased the same sort of problem with the Gelati, sometimes it was good, sometimes it was running on two or 1 or none

what ignition pickups are you running?
 
Hi Cosi and Terry
It has an IIS system which has been great for many years but am wondering if it is starting to play up.
It dosen't have ballast resistors
Thanks guys
Cheers John
 
Marty's 3C probably has the oldest IIS setup fitted,his was the prototype and he was having a few issues lately.He rode it to the club night on Wednesday after fining a bodgey wire so hopefully thats sorted.I think Red has some bits,probably worth looking at having a loner black box to rule in or out  the box.There was some talk about the magnet loosing magnetism over time but I expect that would take out all the spark.
 
Cheers Vince. I was thinking the same myself.
I have checked everything I can think of and still no go.
Just did a compression test.
L 190, C 180,R 180.
I just did the valve clearances about 200 klms ago.
Going back a few years, after Red had rebuilt the motor, we were having all sorts of dramas getting it going.
It ended up being the magnetism dropping off.
The symptom was there was enough to get it started at cold, but when the heat built up, it would simply die. What was even more confusing was we had fitted a poor quality replacement which continued the same symptoms. This one has been in about 4 years now and has been good.
I think it is nearing time to drop Red a line
Cheers John
 
my iis did exactly the same -would misfire when hot,cool down for a bit and away she would go(till it got hot again) -now got a sache
 
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