93 No Spark Issue

[lnghrndada]

I've proudly owned my 93 since 2008. Bought it with 60k, and now have 88k on it. Put the first 10k on it in under a year going to school and back. Starter clutch failed me, so I put a new one in a few weeks ago, and now she spins like new when I hit the starter button. Now the problem is I have no spark. I found a couple of posts on here, but didn't get to any real solutions. I assume they found the issue and didn't reply the results. Something I'll try hard not to do. 

I've downloaded the manual, and went through testing several electrical components.

1)Kill Switch, has continuity when in the on position, and none in the off position. 
2)Eliminated the sidestand switch a few years back when it failed on me

3)Tested 2 of 4 coils with resistance, and both came back at 3 ohms, when range declared okay is 2-4.

4)Fuses under upper right fairing are all functional, and in good shape(even removed them all and cleaned the contacts)
5)Diode- This is where I thought I was on to something. Diode testing in manual showed mine to have failed. Ordered a new OEM diode, put it in today, and no joy. Tested it before putting it in, and according to the testing procedure in the manual, it is bad too. 3 prongs. 2 parallel, 1 perpendicular. Put my positive lead to perpendicular, and ground to top if you were to hold the perpendicular to the right, and parallels on the left. Should be reading continuity, but it doesn't. I only get .689 (can't remember if it was ohms or volts) when I switch ground to the perpendicular, and positive to the bottom or top terminals. Did I get a new one that is defective? My old reads the same.

6)Oil sensor switch hasn't been tested-oil is at correct level on dipstick, and it cranks over(not sure if it wouldn't crank if the sensor was bad)

If I remember correctly, there was a method for testing the ECM/ECU, but it was beyond me, or I was so disgusted that I didn't give it much effort. 

Bike hasn't been rode in 2 years, and I'd really like to get her out again. Harley just isn't giving me the thrill of hearing those gears whine and that Two Brothers exhaust roaring as I'm laying into a corner.

 

I'm open to all suggestions. 

 

Tomorrow I'll be taking the starter clutch cover back off to double check that the one I got off fleabay from Russia is the same as the one I had, and that the timing marks are lined up correctly. Seems as if I'd have some kind of spark, even if it was late or early. 

 

Torn in Oklahoma,

Eric

[douglasthecook]

I had the same issue during a track day at Spa a few years ago. I was the ECU. If you have not downloaded a Clymer or Honda manual for your motorcycle, I believe that you can find them in the download section of this forum. An easy way to verify that it is the ECU, is to get a donor ECU from another VFR (same generation) and swap it out. Yes, the manual will take you through all the troubleshooting steps, and it is rather easy, but you need a good multi meter, and the manual. Swapping out the suspected bad ECU for a known good ECU is the easiest and quickest way to verify that it is the ECU. 

 

If it is the ECU, you will not get ANY spark, I know this for a fact, as I tried to compression start my VFR going down the paddock at Spa, and it wouldn't crank at all. Trust me on this! Hopefully this helps.

[lnghrndada]

That's what I was afraid of. Guess I better get one on order. Not sure how it goes out just sitting there, but I've also had the battery in and out swapping it for a new one, and recharging it when trying to crank it during testing. Guess I could have hit the terminals incorrectly sending just enough juice back to it to make it quit on me. I was reading about how to test voltage coming to coils, so that is my next move. If I have no voltage, then I'm for sure dead in the water I suppose.   

[douglasthecook]

see if the 3rd and 4th gen ECU's are interchangeable. Also check eBay, as that is a decent source of inexpensive parts. A new one is rather expensive, so you might also want to check a bike breaker/junk yard.

[lnghrndada]

Just sent an email to a junk yard about 40 miles from me. Good idea about 4th gen.

 

Thanks

[lnghrndada]

Negatory on compatibility according to part number. 1990-1993 is part number  30410-MT4-601. Part number for 1994-1997 is 30410-MZ7-003

[douglasthecook]

Well, at least now you know, and you know what they say about knowing. It's 1/2 the battle. Sorry, couldn't resist. Hopefully you'll find an ECU. They are out there, it just all depends on how much you're willing to pay. Hopefully the junk yard will have what you need.

[lnghrndada]

Yep,  they are all over again eBay,  just not going to easily convince the boss of dropping another bill on this old thing.  Going to have to get creative with finding one.  

 

You think this could also be related to why my low fuel light hasn't come on during the last year of riding? Or that the fuel pump doesn't try to build pressure when the key is turned to the on position? I jumped it and the pump is still functioning, just curious about the initial surge it would normally make during the first couple of seconds. 

[lnghrndada]

Read through your "Ecu's Fried Again,  Why??? " thread. 

 

What was your final culprit? You last said you had the bike running again,  but was missing on a cylinder and that you were digging into suspect components.  

 

[JZH]

18 hours ago, lnghrndada said:

Negatory on compatibility according to part number. 1990-1993 is part number  30410-MT4-601. Part number for 1994-1997 is 30410-MZ7-003

 

It might still work.  Not much changed with the engine between '93 and '94, though the latter had smaller carbs for sure.  The point being that a good 4th gen ECU would probably still fire a 3rd gen, so it would be useful as a test if you could get one cheap.

 

Ciao,

[V4 Rosso]

39 minutes ago, JZH said:

 

It might still work.  Not much changed with the engine between '93 and '94, though the latter had smaller carbs for sure. 

Cam timing is also different. It will run but I do not expect it to run very well.

[lnghrndada]

Gotcha. Thanks to both of you. 

 

Working on getting one.  Seems scrap yards are drying up in my area.  Hate to drop so much on one on eBay not knowing if it's the true culprit,  and/or how long it will last.  

 

Headed to only old school bike dealer in my area now.  Hoping he'll have some leads.  

[lnghrndada]

Interesting find.  Not sure if it's the same in the motorcycle world as it is in the lawn and garden small engine world,  but the numbers on my ECU don't match the newest part numbers I previously listed for the 3rd and 4th gen. In lawn and garden there is often a part number on the part,  but it's actually different in the look-up.  The number on the part is simply for Joe at the factory so that he knows what item to use. 

 

Numbers on mine are M14A-MNE-701A.

[JZH]

I think it's probably MT4A MNE-701A.  Mine then has "3109" below that, but it's a UK-spec '93.  Yes, in my experience in the Honda motorcycle world, the part number stamped on the part is usually not the same as the part number in the Parts Catalog, but it often uses the part number's PCN in some fashion.  In this case, MT4 is the PCN for the early RC36.  More info here.

 

Ciao,

 

 

[lnghrndada]

So I did some more work today.

 

1)Got to remove the side cover to inspect to see if the starter clutch with the T1 T2 etc marks was put  on correctly, and found that it is splined, but one spline is wider than the others, so no wrong way to install it. That's out of the way.

 

2)Ran resistance test on pulse generator, checked out good.
3)Ran input test on ECU, checked out good. 

4)Ran continuity test at ECU plug for coils, checked out good.

5)Checked voltage on coil number 4, and it showed to have just a couple volts lower than the battery in the on position, and while cranking. Has me confused why it's not sparking. Pulled the boot and plug, put plug on frame while cranking, still dead.

 

Had a buddy over and he just put out there as food for thought, "have you tried looking into your ECU, like taking it out of the casing?" I had already thought of it, but at this point, didn't have anything to lose. I got out my Rockwell Sonicutter, and went to town. I cut right down both sides where the factory seamed them together, and straight across the bottom, meeting on both sides where my cuts were. Heat gun, long skinny screwdrivers, and long blade pocket knife were the tools of choice. Didn't get the casing off in nice and pretty pieces, but did get it off. So much glue/resin in there. After a good hour of peeling the resin/glue off, I found several small resistor looking objects, the main chipset, and a few other soldered parts. Not sure what I was hoping to find, well, I lie. I was hoping to see a burnt spot, or a resistor that had blown. Something obvious. Unfortunately, that didn't happen. Looked perfect to my eyes. 

 

So, I guess I'm back to square one with believing the ECU is the only repair. 

 

In between careers at the moment, and my third child is due any day now. Dropping a benjy on another one isn't really the ideal scenario. 

 

Appreciate all the help you guys have given. I'll be sure to let everyone know when I get one, and the outcome. 

 

[COS_VFR]

Looking at the wiring diagram, one side of the coil is always connected to +12V and when the ECU grounds the coil, it fires.  I have tested coils by applying +12V to one side and then using a jumper to quickly ground and then not ground the other side while watching  the plug to see if it fires. If the coil fires the plug then it is good and your ECU not grounding the coil the next question would be why. The ECU could be bad, the power or the ground to the ECU could be bad. It looks like the starter clutch cover needs to have something like magnets in to to trigger the pulse generator, since you replaced the starter clutch, maybe the replacement is not triggering the pulse generator.