Got a RC24 again......

[keny]

So I made a offer on a 1986 VFR750F RC24 on Friday as I was bored, and I got the offer accepted! So Friday evening I did pick it up! 

A bit rough bike but runs. 

Nice things are, aside it's red 😜, it has a Devil 4-1 exhaust, fairly fresh front brake discs as pads front and half worn tires. Battery as R/R are one year old and fork has stiffer springs.

Plastic has cracks, seat cover needs to be changed and fairing inner panels are missing.

Biggest issue is, even it runs good, the engine dies after 10-15 minutes of riding. This was mentioned in the add, but sounded like a fuel cut relay issue, BUT after a ride today I don't think it's the issue. Engine dies like ignition switched off, and after a 15-20 minutes wait it starts again but dies again after 5-10 minutes, same thing starts after a wait again.

Anyone has had this issue? What to look into? 

[Captain 80s]

Cool.  

 

Heat related maybe?

 

[tsmitty]

Nice bike Keny! It looks good in red.

[keny]

8 hours ago, Captain 80s said:

Cool.  

 

Heat related maybe?

 

Yes, the bike dies as it fully warm, then as cools down runs but dies again after you ride a bit can be just minutes of riding.

[Grum]

Nice bike Keny.

Do some good ohm measurements on both the Pulse Generator coils and the Cam Pulsar (if it has the Cam Pulsar) especially if you can get the engine hot. These coils can become flaky/intermittent with heat, make sure they have good continuity in wiring back to the Spark Unit.

Also make sure 12v Power (Black/White wire) to the Spark Unit and the Ignition Coils, and the Ground (Green wire) to the Spark Unit is good.

And.......It goes without saying! Make sure battery terminals are clean and tight.!

Good luck with the bike.

[Dutchy]

Keny changes bikes more often than I my underpants... 

[keny]

6 hours ago, Dutchy said:

Keny changes bikes more often than I my underpants... 

I just added one 😂

 

And you onec did say I will be back after I sold my last VFR some years back 😁

 

We only live once 

[airwalk]

Exact same issue on my ‘86, after exhausting trouble shooting & replacing parts that are/were fine(ecm,etc) found 1 of the 2 pulser coils near starter clutch would cut out totally when heated. Oddly enough the other 1 is fine but faulty coil acted just like the ign kill switch, somehow stopping any ignition. Took me weeks to find it so hopefully it’ll help your problem!

[keny]

Well it's now confirmd it's the pulse generators that is reason bike stops. Sadly a one year only part and new is not in stock anywhere 😞

Even a working used would be great to find!

Anyone has something in the drawer?

OEM par number is 30300-ML7-003 

Hope to find one or I have to score hole ignition system from a 87-89 one completely whit trigger wheel.

[Fastdruid]

Are they totally failing when hot or are shorting to earth? My 86 manual says they should be 450-550 Ohm. 

 

I guess there is little risk in taking it off and investigating the wiring itself or even investigating aftermarket replacements of just the coils themselves. 

Might be worth asking Electrex for example if any they make would work.  https://www.electrexworld.co.uk/acatalog/Online_Catalogue_Pick_up_Coils_403-p1.html

 

Between the pickups failing and the trigger wheel/sprag clutch housings breaking there are a few common failing but unobtainium parts for the 86 bikes now in part because they updated them for the later bikes and then kept them the same for many years.  

 

It's not particularly helpful to you right now but I really should get my arse into gear and swap out the pickups and trigger wheel from my 86 engine for the ones out of a RC35 engine I have, if only because then I can sell them on to someone else who needs them to keep an 86 bike going! 

 

Personally in your shoes I'd go for the upgrade, pickups from a 88-89, trigger wheel from a 87-97 (unfortunately they *ALL* have a reputation of breaking the sprag so they're a bit in demand), a 88-89 ECU, fuel cut relay and tacho. Rewiring is pretty trivial as you can pickup the connector shells easily pop out the pins and swap them over to match. 

 

You could probably even go for RC36 pickups and ECU as well, despite what the HBoL says, timing is the same on all of them (according to the Honda manuals) although the wiring would be harder as it's a totally different connector. 

 

Not entirely sure what the difference between 88-89 and 90-97 pickups are, different part numbers but might just be in the connectors/wiring and even work with an 88-89 ECU as well.

 

[airwalk]

Keny..found used on e-bay from the US, so far they’ve worked fine. If you’re desperate I could send along the good 1 that I saved, wiring could be wrong color but that won’t stop the electrons flowing!

[keny]

On 9/12/2023 at 5:09 PM, Fastdruid said:

Are they totally failing when hot or are shorting to earth? My 86 manual says they should be 450-550 Ohm. 

 

 

They are falling totally, no measurable connection.

 

I gamble a bit, as I orders set of used 88-89 pulse generator to see if it works, it might not, but of then I will order bits I need more to make it a 88-89 ignition specific 

 

 

 

[rc24dk]

Where do you measure?

[Fastdruid]

44 minutes ago, rc24dk said:

Where do you measure?

 Between yellow and yellow/white for one and blue and blue/white for the other. 

 

The 86 & 87 wiring is slightly different to the 88-97 but only in the loom after the connector from the pickups (it joins the blue and yellow).

[Fastdruid]

5 hours ago, keny said:

I gamble a bit, as I orders set of used 88-89 pulse generator to see if it works, it might not, but of then I will order bits I need more to make it a 88-89 ignition specific 

 

Fingers crossed! According to the HBoL[1] the pickups are the same resistance from 86-89 and 91-97 (90 is apparently an oddity). 

 

I think they should work but my worry would be that the physical location of them to the starter clutch might vary *slightly* and hence would affect the timing because the 87+ use a totally different way to do the ignition. 

 

The 86 has a very simple trigger/pulse generator, the 87+ is an actual crank position sensor that uses a missing tooth wheel to work out where the crank is. 

 

[1] Although that says they all have slightly different ignition timings while the Honda manuals all say they're exactly the same! 

[rc24dk]

It could be a bad connection in the loom/connector ...? Suspicious about both dying at the sane time.

[Fastdruid]

2 hours ago, rc24dk said:

It could be a bad connection in the loom/connector ...? Suspicious about both dying at the sane time.

 

On the 86 they are separately wired. So while on the 88/89 a single failed wire (the yellow one) in the loom would see both fail on the 86 you'd have to have two wires fail. Not impossible but less likely. 

 

Still obviously worth double checking you have connectivity from the "ECU" to the pulse generator connector (pretty sure everything after that is sealed so you can't probe it). 

[keny]

Well I got the 88-89 pickups today, might see what a difference tomorrow if nothing to critically come ahead 

[Fastdruid]

Did you get a new gasket too? Chances of it popping off cleanly are slim (certainly mine ripped into many pieces last time) and I've been led to believe the tolerances are critical enough that leaving it off and just using sealant can lock up the starter idler gear (or worse). 

 

....Although that said I guess you could just put it back on and try it if it does rip! It won't leak badly enough to be that big a deal for a test and if it doesn't work you'll need to take it all off again anyway!

[keny]

2 minutes ago, Fastdruid said:

Did you get a new gasket too? Chances of it popping off cleanly are slim (certainly mine ripped into many pieces last time) and I've been led to believe the tolerances are critical enough that leaving it off and just using sealant can lock up the starter idler gear (or worse). 

 

....Although that said I guess you could just put it back on and try it if it does rip! It won't leak badly enough to be that big a deal for a test and if it doesn't work you'll need to take it all off again anyway!

Yes, will just try it if looks the locations are right. If works I just change the gasket simply, if not working the bike will probably stay some time until I have found what I need. 🤞

[keny]

So I did test fit the 88-89 pulse generator and sadly they do not angel up so didn't bother try to stay engine

 

OEM 86

 And 88-89

Marked the OEM location on the starter clutch from where the difference show quit clearly.

So on the hut after 88-89 part's....

[Captain 80s]

Can the pickups/pulser coils be transferred over to the 86 brackets?

[Thumbs]

Just what I was thinking, judicious use of a hacksaw and dremel is worth trying 

 

Alternatively this might be useful https://www.rexs-speedshop.com/product-category/ignition-system/replacement-pick-ups/honda-pick-ups/

[tsmitty]

Don't forget to keep an eye on the pick-up/trigger  .013 - .014 sounds about right.

 

 

[Captain 80s]

23 hours ago, Fastdruid said:

Did you get a new gasket too? Chances of it popping off cleanly are slim (certainly mine ripped into many pieces last time) and I've been led to believe the tolerances are critical enough that leaving it off and just using sealant can lock up the starter idler gear (or worse). 

 

....Although that said I guess you could just put it back on and try it if it does rip! It won't leak badly enough to be that big a deal for a test and if it doesn't work you'll need to take it all off again anyway!

 

I had to take the clutch cover off of my Hawk GT after installing a new gasket the season prior.  It tore in a couple places.  I didn't touch a thing, but gave both sides a gentle wipe with some contact cleaner on a rag, and put a nice, thin even smear of Hondabond 4 around the whole cover side (cuz that was the easiest on the bench), perhaps giving a little extra attention at the breaks.  Let it dry overnight before adding oil (and not tilting it vertical) and not one leak all Summer long.