Pulse generator problems or something else

[rij1]

I'm having a problem with this motorcycle shop. They have had my bike for 3 weeks now and tested everything and lately they had said there is a problem with my pulse generator. They tried 2 different used ones and I got them another used one that I had tested before I gave it to them. They said my bike isn't ready cause they tried all the pulse generators and they said they were bad. Whats the chances of all three plus mine being bad. The guy that I got the pulse generators from said they don't really go bad and the shop said they do all the time. Whos right. So the shop wants to get a new one not a used one.

[Lucky 1]

Only the Honda VF 1000R and Honda Magnas have pulse generators (Magneto's).


What bike do you have?

You probably have an alternator (stator and rotor).

[rij1]

I have a 1982 cb750f

Its this part.

[Lucky 1]

Yes, that is a pulse generator. Now just get the manual and test it like they say.


The motorcycle shop could not seem to do it.

BTW.... Those pulse generators have to have the gap set correctly to work.

            READ THE BOOK.


Those are no longer available, but they almost never fail.
They must be adjusted properly. IT is part of the Spark advancer

Those bikes also used a stator and rotor.


Here you go.

"Ignition System :
I set the gaps on the pulse generator at .012". One was already there, the other had a screw that had worked loose and was rattling around near the big gear (took the screw out and replaced it).


  Source....DOHC website.

[shinyribs]

Thats a magnetically controlled pulser,right?

If it is it should be easy to test. It might take some head scratching to figure out which wire is which,though. The part of that system that mounts to the crank should had a piece of magnet embedded in it. When it spins past one of those modules it will cause a set of contacts to close and fire the coil- hence the name.

You should be able to install it on the bike and rotate the crank.When the magnet passes by the module it will cause it to close/ fire the coil.

I don't know if this will work but it's what I would do:

-Install it all on the bike like it should be
-Remove a spark plug from the engine and put it back in the plug wire
-Ground the plug to the head
-Crank the bike and see if you have spark

[shinyribs]

Wait,you were having charging issues with your bike,right? Is this a separate issue,or are they trying to blame your charging issues on this? Because this is strictly your ignition system-totally unrelated to your charging system.

[rij1]

Unfortunately The bike is still in the shop. And I cant test it. I don't really want to take it cause I don't want something to go wrong with it and them say they should have ran it to make sure it was running good. I'll Be doing all the work my self again when I get the bike back. That's for sure.

They did say that when they get hot they start missing.
 
I will run your advice by them also..

You are the 2nd that told me that these parts almost never fail.

 
I would think they would know something is wrong with how they are working on my bike when they try 4 different parts and it still doesn't run right.

Thank for the info..

 

[rij1]

I was having a charging issue also. It was the r/r. It has been replaced. As far as I know the charging issue is ok now. They also removed engine and rebuilt it and now have this problem.

[shinyribs]

OK,so you just have no spark at this point? I'm with you thinking its not very likely you have that many bad pulse generators. Maybe they accidentally have the wires crossed so it's firing the opposite coil rather then the one needed. Maybe ask them to reverse that and see what happens. If they do reverse those wires it won't hurt anything.

If you do in fact have spark,but the bike just won't start,I'd check that first.

[rij1]

From what they told me with the original p/g that was in it when I took it there. They said it runs good at idle and good till it gets hot. Then it starts back firing upon acceleration. Now I don't know about the other 3 p/g's.

I don't think they made adjustments and just installed the part. I'll keep the switching the fires in mind.

[Lucky 1]

Why not just use a timing light ?

Grounding a spark plug to see a spark is what kids do.

Why not just use a timing light and look at a pulse of light instead.
Save time not having to remove the spark plug, or get shocked.

[shinyribs]

Two reasons Lucky.

1: Some peope reading these posts are working with limited tools.

2: Simple, dependable and easy. Timing lights can fail,their inductive pickups can fail,etc. Pulling a plug is simple, fast and fool proof.

[Lucky 1]

OK...OK I went a little overboard. LOl..lol..lol

[rij1]

I have a question just to rule a possibility out. If after riding till this P/R gets hot, can or do they start to mis fire or have a problem Because of heat?

[Lucky 1]

Do you mean the rectifier?
The fins will get hot from giving off excess current.


P/R ????????? What is that?

Misfiring can result from many issues.

Low battery voltage.
Carbs not set up properly.
Intake or exhaust manifold leaks.
Worn out points or misadjusted points and worn out condensers.
Dirty fuel.
Spark plugs not gapped right.
Bent valves.

[rij1]

No, the pulse generator.

Sorry, Not P/R I meant P/G Pulse generator

[Lucky 1]

The pulse generator just helps get the bike started.
All of those parts are bolted to the hot engine so they will get hot too.

I think you are looking in the wrong place.
You need to be more logical.

If every part of the motorcycle was perfect and it mis fired
I would not think it is the pulse generator.

Get a pulse generator from a bike that runs good and put it in your bike.
I think you would get the same result.

Why don't you tell us more about this bike? Show us a photo.
What kind of exhaust,what kind of intake?

Get a workshop manual so you can test these components.
Do you have a multimeter?
Also check with the DOHC websites for known issues.

If you check Ebay and there are pulse generators for
sale at low prices, it is a clue that they do not fail often.
If they are expensive it means they are needed.


Go get your bike back from the motorcycle shop.

[shinyribs]

We are a DOHC site. We are a CB750 site which entails both SOHC & DOHC models.

As it stands right now...I think we have more guys rockin' twin cams rather than singles.


Anyhoo....IF a p/g is the electromagnetic device that I think it is ,then yes, it could be affected by heat. Since the heat could expand the wire coils inside and possibly cause them to either short circuit or lose continuity all together,depending on what has ''failed'' inside,it could be possible. IF I am correct in my thinking of what they are. I admit I haven't had a chance to fully research these yet.

Have you had the same misfire issue with all of the p/r's you've bought? If so I'd tend to look elsewhere for your issue. It's entirely possible,but highly unlikely, that you've received 4 different p/r's all suffering from the same issue.

Misfires can also be caused by:
-deteriorated plug wires that are leaking
-deteriorated,loose fitting spark plug caps
-poorly grounded engine
-maybe a stuck spark advancer ???

[Lucky 1]

Shinyribs, that "pulse generator" is the same as a magneto basically.

Just a fancy name for an old idea.

[shinyribs]

Magnetos still have points to pulse the coil. All the one's I've seen at least. The magnet part of the magneto is just where the current is created that the coils operate off of. These bikes have coils drawing current from a battery. And the coils are pulsed by the p/r.

How exactly the p/r operates I do not know.