spark timing

[mikefitz1000]

Hi all. im new here, i hope you can help me. i have a 1981 gs450l. it runs on one cylinder, it has spark to both and fuel to both. Good compression on both. so in theory, it has everything to fire on both cylinders but it will only fire on the right cyl. im presuming that it is a problem with spark timing, what is the cause, cdi or pickup? or something else. if it is either of those, where can i get a replacement unit, everything online is used, anything new seems to be a crazy price. with carbs off, spraying easy start into each cylinder, it fires on the right, nothing on the left despite having a strong spark and good compression, so that eliminates a fuel problem.
thanks in advance.

[Brendan W]

How are you sure you have spark to both?
Have you swapped plugs and HT lead end caps and checked the core of the HT lead at the end for corrosion?

[mikefitz1000]

Yeah thats all done. strong blue spark to both plugs. it looks like the left one must not be timed right. so thats the answer im looking for.

[Brendan W]

Have a look at this thread.

https://www.thegsresources.com/_forum/forum/technical-forums/electrical-ignition/73547-gs450-timing-issue

[mikefitz1000]

yeah that goes on about valves and carbs. all that is done valves reseated, clearance perfect, perfect compression, valve timing perfect, definitely not a fuel issue as i said, carbs off squirt easy start in to right, it fires, into left, nothing. spark on both is perfect, it must be spark timing, but i dont know anything about how to fix that

[mikefitz1000]

im thinking cdi unit or pickup or both. Does anyone know where i can get them?

[Nessism]

Your bike doesn't have a CDI.

You might want to try a shot of starting fluid in the airbox to see if the 2nd cylinder fires. If it does, you have carb problems.

[Gorminrider]

You'll find more help in the https://www.thegsresources.com/_foru...rical-ignition section. THIS section is for 'General Information about the forum, not motorcycles.

[mikefitz1000]

Hi folks. update on the problem. as I thought it was the cdi unit. a new bespoke unit from ignitech.cz solved the problem. well done to them, they are professional and helpful. they can be contacted at
ignitech@ignitech.cz

[attovus]

Hello Mike. I have the same bike and lost power on a ride the other day - not getting any spark now and I am wondering if the unit you bought was listed in the Ignitech website ( i was unable to find it ) or did you have to order it specifically?

[unfocused]

If you have a timing issue on one cylinder in a multi-cylinder engine you're going to know this...Spark is going to still ignite the fuel so it's going to be popping somewhere.

Also, your timing isn't set/controlled through the CDI if you have one. It's set and forget with the pick-up or it's adjustable (points plate)...

The CDI ONLY controls the timing advance per throttle input (tps style sensor on side of carbs) or rpm...

Could the CDI advance the timing to the point of not firing a cylinder... ?

My experience with CDI's - they work or they don't - your not going to have spark and a dead cylinder because of it...

[rphillips]

"81" won't have points nor points plate. I've not seen an adjustable ign. plate on a GS with electronic ign, Only way to change timing is slot the holes in the plate so it can be moved... I think.