Ignition Control Modules for 85 VF500F

Does anyone know if these two modules are interchangeable? I know I have a bad front coil, but also want to be able to check the control module that feeds the front cylinders. The rear works, so right now my VF500F is a twin bike. I have a used set of coils coming, but wanted to be able to check other areas of the ignition circuits.

 

If their quality is anything like what we're see in the after market car industry, they are most likely junk. I know a few true ignition guys and they swear at them not by them. One those guys has done a lot with factory super bikes and pro racing. So I can really only go what he tells me.

 

Hey tinkerinWstuff, thank you very much for the link. The info that I found in there I think has me on the right path now to getting my bike running.

 

So I'm down to my problem either being one of the coils or one of the control modules. Coils will be here late this week and I have some control on hold from one of the members of this forum.

 

Let us know what you find out. The rule of thumb that I have always heard is "If you think it's the coil, it's probably not the coil." My experiences are similar, whenever I've thought the coil could be a possibility it's always been something else. The spark boxes are a known failure and also the pulse generators. Those two parts would be where I would start (especially the pulse generator).

 

Pulse generator is good. Did the test that the manual suggests (resistance check). I also swapped around the control modules and one worked, the other didn't. The known good control module didn't get the suspected bad coil to fire, so I'm thinking I have a bad coil and control module for cylinders 2&4. I have found used coils and control modules for a really good prices and went ahead and ordered them for a fraction of the price of new ones. They should all be here withing a week. At that time I should know if everything works or not, which I hope it does. I can't wait to here my bike run on all 4 cylinders

 

Did you check it when hot? Often times a bad pulse generator will check ok when cold.

 

cold check only. I can get the bike running and check it again.

 

Looks like you found out...yes...the ignition units are interchangable on all the early 4 cylinders that use two boxes. An integral part of troubleshooting ignitions is 'the swap'.

Pulse generators can be intermittent, mainly failing when hot. But in my experience, you always have to drive around and get the PG failed in order to test it bad. Since yours is failed 'period'...it's unlikely the PG would test good and cause your problem.

The sure way to find out would be to find the PG connector, pull the two terminals in question out of the connector, plug 'em into the good circuit and check for spark. Same logical concept as the 'swap' of the ignition units.

Don't overlook simple checks for battery voltage. With the key turned on and kill switch in run...make sure you have battery voltage at all black/white terminals...to the coils and ignition units. Use the solid green terminal in the ignition unit of the non-spark as a ground for your test. You'll be verifying THAT particular ground as well.

 

My pulse generator tested good without running the motor, but I have found another one that works just in case.

 

Great intel, thank you for the post. To verify, you have found that all 1st Gen Honda's (500,750 and 1000cc bikes) use the same ignition units and that the individual units can also be interchanged? Thx!

 

No...that's not exactly what I meant. Not all those ignition units are interchangable, though some may be. And I don't know exactly which ones are. What I meant was you can use ignition parts (on 1st gen Hondas with separate front and rear bank ignitions) as 'known good' to troubleshoot on the same bike. It's unlikely both coils, ignition units, pulse generators would fail at the same time. So switching leads to separate components and observing spark moving from front to back banks allows for 'logical' troubleshooting before buying parts.

I can see my previous post could be read the way you did. Sorry I wasn't totally clear. Thanks for pointing it out.

 

Okay, thanks for clarifying.

Do I have it right then that the front and rear ignition modules on an individual bike (a specific model and year) can be interchanged?

Thx!

 

Yes that's what I meant. Matter of fact you can also switch leads on coils and pulse generators (of which there are two each) and see where the spark comes and goes...using logic to verify or eliminate the problem component. Of course if you switch leads on the pulse generators the ignition timing will be 'turned around' and the bike won't run but you can do visual spark inspection. This is the fastest and best way I know to troubleshoot cases where spark is lost on either the front or rear cylinder bank.

In cases where spark is lost on all four plugs, the best place to start is checking for battery voltage (always black/white to my knowledge) to ignition units and coils, with the key on and kill switch in 'run'...to eliminate or verify the 'run' and ignition switches.

 

Thank you for the tech tip!

 

Ok, finally got my coils and spark units. I installed the coil for#'s 2&4 and the spark unit that corresponds (both weren't working before). Bike wouldn't start at all. Prior to this, the bike would only run on the back two cylinders. I've tried swapping the spark unit and nothing changed (bike wouldn't run at all). I took out the old coil and did a resistance on it with the following results: primary = 2.8 ohms, secondary = 14.4k ohms (had to measure between both leads, couldn't get any reading between secondary and mounting bolt like the manual said - got the same results on another coil as well), plug leads were about 5.8k ohms (according to the manual, higher is better).

I was hoping that these would have fixed my problem, but it looks like the source is elsewhere (good thing I didn't pay much for the coils and spark units). My next step would be the pulse generator. I've tested it cold per the manual and both side read good. I thought I had a used pulse generator lined up, but the deal on that seems to have fallen through. A few websites show that I might be able to buy a new one (not 100% sure). What would be best, try to get a new one if available or keep looking for a used one (if anyone has one they want to sell, please PM me!)?

Any help would be greatly appreciated (I'm getting really frustrated!)

 

So...do you have power to your components with key on, kill switch on? Have you checked for a good ground to your ignition boxes? Have you verified continuity on your harness between Coils/pulse generators and ignition unit? Have you checked for a pushed out or loose fitting terminal connector?

Sounds to me like you have a poor connection somewhere, rather than a component failure.

 

Haven't verified anything electrical yet. That's what I'll be working on this weekend. Checking that I do have power, that the connectors are clean and making full contact, ground is good, etc.