4-stroke Ignition-

[Unclediezel]

After 20 + years of working on automobiles----I have been stumped with a question about Ignitions on an ATV---Help???

Honda uses a Pulse generator on the camshaft, to determine TDC on Compression stroke, and times the spark accordingly---
Yamaha has only the rotor and stator---with nothing for a Camshaft reference,

Crankshaft revolutions are 2x the camshaft revs --so how does it determine which stroke to fire on????

[danteross77]

The timing advance rotor. (Rotor attached to cam) It has 2 sides, the one with the mark tells the spark plug to ignite, if you have it 180 out, no spark. I was stumped by this on my first rebuild, I double checked everything and no spark, finally in frustation I turned the rotor 180 and presto. I guess when I removed the rotor from the timing advance assembly to clean it and check the springs I put it back together backwards, not knowing there was a particular way it went. I thought it was a no brainer being the cam has a pin that can only attach to the timing advance assembly one way. Forgat that the rotor has 2 sides.

[Unclediezel]

Exactly---Thats a honda---

Yamaha has NOTHING cam related----its all done at the crankshaft---I know it works -cuz our trikes run- But Im stumped---

[danteross77]

I sorry I thought you meant in general, I had a Yamaha once, honestly could never get it running right so I gave up and parted it out to raise money to fix my Honda. Not that I am saying one is better than the other, I just have no experience or luck with the Yamaha's.

[Unclediezel]

I was helping someone "Time -UP" a 185s pulse rotor--when I realized that 4 stroke yammys dont have anything that looks like this-----------My trike is a 2 stroke--so no luck checking there--Im just at a loss here---LOL

[danteross77]

I think the pulse generator is aligned next to the flywheel like in my 250sx or my sons trx 70 not really sure how it tells the difference in the strokes though maybe the exciter coil or cdi ?

[thefox]

Who says it has to only spark on the compression cycle? Why not have it have it spark on compression and exhaust strokes?

[Unclediezel]

--Touchdown---FOX

Waste spark------Like a Distributorless Ignition system-???

[TeamGeek6]

It may have a pulse generator winding on the stator, Ive seen some small motorcycle engines that way. Look for two hot wires to the ignition plus a lights feed if it has lights. I doubt its wasted spark because CDi's need all the charge time they can get at higher revs.