Author Topic: CB750 - No spark - no start. Had to abandon the bike! - FIXED!! (Read 10532 times)

nancy · « **on:** October 24, 2010, 09:24:26 PM »

Rats.
Took a run in the sun - 150km and it ran really well. Stopped in a cafe 40km from home for coffees. Time to leave - but the bike wouldn't start. No spark on plugs. Traced wiring from coils as best I could in the carpark without removing the fuel tank and all seemed OK. Single 15amp fuse OK. Starter motor fires strongly,..but battery (2 months old) showed bad corrosion buildup on POS terminal. So bad - the retaining nut seemed welded to the terminal and I could not unscrew it. My only hope was that the corrosion was causing leakage and the coils were unhappy. I couldn't free up the terminal to clean it. The terminal post started to buckle and come loose! Had to phone for number 2 son to drive out and pick me up and stashed the 750 in the cafe's outside room. Hope it's still there tomorrow.
I'm guessing here - if bike was running sweetly, turn it off. Turn it on = no spark,...the battery could be the guilty party = given the corrosion? I have another battery on charge overnight but I'll take out a trailer to bring the bike home anyway.
Anyone have cooment on the likelyhood of an otherwise strong battery depriving me of spark? Should I look elsewhere 1st?
Regards
Mark

Spanner 1 · « **Reply #1 on:** October 24, 2010, 09:30:01 PM »

Maritime location accelerates battery terminal corrosion due to salt content in air.... IMO... Yep??

Gordon · « **Reply #2 on:** October 24, 2010, 09:32:20 PM »

Did you check the kill switch?

Spanner 1 · « **Reply #3 on:** October 24, 2010, 09:41:57 PM »

Even tho' you enjoyed your run today, your battery was not charging the whole time you were riding. Been there, done that, didn't know ( Can someone make that T-Shirt for me

).... Corrosion on batt. terms. is the prob . IMO. Good luck.

HondaMan · « **Reply #4 on:** October 24, 2010, 09:46:36 PM »

I've also seen keyswitches fail like that, especially the ones offered since 2004 (from EMGO and other Chinese labels). They don't carry the full 750 current load (12 amps peak) as they are 8 amp contacts, slowly burn inside. I've even seen the Red wire melt right off the back of these switches, because it is only 20 AWG size (should be 16 for the Red one).

nancy · « **Reply #5 on:** October 24, 2010, 09:52:51 PM »

Spanner - nowhere near the ocean,well...80km or so.
Hondaman - original keyswitch - and I looked at wiring there, all seemed well. Plus, I get all good electrics to idiot board. Turn and horn OK. Yep,..could be kill switch. I pulled the control off to check that - but there's nothing to see without a lot of delicate surgery - so I put it back together.
Any comments on why a near new battery develops such bad corrosion - seemingly fairly promptly too. Should I blame the battery or the mechanic? Bad earth?

scottly · « **Reply #6 on:** October 24, 2010, 10:06:14 PM »

Quote from: nancy on October 24, 2010, 09:24:26 PM

Starter motor fires strongly,..

Not a battery problem as it can supply enough juice to spin the starter. Sounds like you aren't getting power to your coils. To get the bike home, you could "hot-wire" it, by running a jumper from the battery + to the black wires on both coils.

scottly · « **Reply #7 on:** October 24, 2010, 10:13:46 PM »

Also, if key switch, was bad, the starter wouldn't work. Sounds like a bad kill switch, or wiring To it from the key switch, or wiring From it, to the coils.

Spanner 1 · « **Reply #8 on:** October 24, 2010, 10:15:17 PM »

As soon you get it home, clean the points.. or do it at the location where you left it... my 2cents

nancy · « **Reply #9 on:** October 24, 2010, 10:19:48 PM »

Thanks Guys,
Looks like a trailer job. It could be a fault in the killswitch. I did get into the habit of powering off using the switch. One off too many perhaps. I'll look into the birdsnest in the headlamp too - often find drifting connectors in that hell-hole.
Points - won't rule that out Spanner but I checked the points condition - a bit of suface build-up but looked no worse than last time I checked and cleaned them and that was only 2-3 months ago.

scottly · « **Reply #10 on:** October 24, 2010, 10:31:33 PM »

I wouldn't expect that both sets of points would fail at the same time, especially since the bike was running well before shutting it off. It might be fairly easy to jump the kill-switch, maybe inside the headlight bucket? Sorry, I can't be specific, as my harness hasn't been stock for many years. Spanner, do you know how the kill switch wires are routed?

Spanner 1 · « **Reply #11 on:** October 24, 2010, 10:33:16 PM »

Do us a huge favor and tell us what you found was wrong... it really helps this Forum to know and not everyone that posts a problem bothers to come back to report the solution IMO, so thanks in advance !!

nancy · « **Reply #12 on:** October 24, 2010, 10:40:08 PM »

Right toe Spanner.

Duke McDukiedook · « **Reply #13 on:** October 24, 2010, 10:47:36 PM »

killswitch or ignition switch is my guess, any coil changes lately?

Spanner 1 · « **Reply #14 on:** October 24, 2010, 10:55:14 PM »

Well has his bike got a K1 wiring loom ?...... If ya want to open the h/light bucket and find a black going to the right handlebar along with a black/white... then undo them in their connectors and plug'em together , black to black/white, now the kill switch is bypassed....that is the two wires described from the loom, not the two that go into the handlebar......why do I have such a prob. telling this

O.K.... look in the bucket... see black wires and their connectors.. see black/white wires connected together... unplug bk/wh that comes from loom and connect to any spare black connector in bucket... now kill switch is by-passed.... Good luck.

scottly · « **Reply #15 on:** October 24, 2010, 11:07:50 PM »

Quote from: Spanner 1 on October 24, 2010, 10:55:14 PM

why do I have such a prob. telling this

Because it's damn hard to do!

Thanks for taking the time and effort to help unravel the Honda wiring maze...

andy750 · « **Reply #16 on:** October 25, 2010, 04:24:41 AM »

Good luck Mark in figuring it out. All good advice so far and nothing really to add but change the battery. Corrosion build up for whatever reason is not normal. Go AGM

cheers
Andy

nancy · « **Reply #17 on:** October 25, 2010, 11:42:34 AM »

killswitch or ignition switch is my guess, any coil changes lately?Nope. But it's my main guess that the killswitch is the culprit.

nancy · « **Reply #18 on:** October 25, 2010, 01:20:33 PM »

Andy - just to really rub it in - th epostie just delivered my new Hyperpro front springs this morning! No bike!!!

andy750 · « **Reply #19 on:** October 25, 2010, 02:46:29 PM »

Quote from: nancy on October 25, 2010, 01:20:33 PM

Andy - just to really rub it in - th epostie just delivered my new Hyperpro front springs this morning! No bike!!!

Oh man that is rubbing it in!!!

But to make you feel better Ill give you a few examples of breaking down on my K4:

1. In Mexico in the middle of nowhere (really no where) in very hot conditions and the bike just dies...check everything and nothing wrong! Reassemble after about 30 min of trying and it works!! Never did find the cause $:-\$

2. Stock ignition switch slowly packed it in....this happened on the way to Holland from the UK - the contacts had worn out and it would cut out intermittently on the highway...great fun when passing trucks etc only to have the bike "die" on you and you need to drift over to emergency lane.

3. Bike dies after filling up with gas. Its the cheap-ass EMGO ignition switch this time (as Hondaman mentions above). Lucky i am only 3 miles from home and get the g/f to bring me the spare switch.

4. AGM battery dies in town and I need to kick it to get home....dies at every stop light and need to kick it to get going...fun, fun...

Next time try bypassing the kill switch using Spanners method - it works!

good luck!
Andy

nancy · « **Reply #20 on:** October 25, 2010, 03:08:11 PM »

Yep - I'll try it out when I get it home - assuming it is a killswitch fault. It seems most likely. For now I am stratching my head trying to decide whether to drive back and hope that fixes it. Or,..take a small trailer and hope I can lumber the hulk up a small makeshift ramp - dunno if that will work,..or bite the bullet and splash out $70 to hire a furniture removal float - which as a ramp and is fully covered. I'm thinking of the easy one - the last..but I'm fighting the urge to "go,, you can fix this"!

andy750 · « **Reply #21 on:** October 25, 2010, 05:30:04 PM »

Go... you can fix this!!

Take spare battery in any case and re-wire inside headlight = good to go

And if it dosent work blame Spanner!!

Good luck!
Andy

nancy · « **Reply #22 on:** October 25, 2010, 09:44:22 PM »

TOooooo late Andy..I'm back. Old girl in a furniture transporter. Parked er in the shed and I'm not even going to look at her till tomorrow - make her suffer.
I put the new Hyperpro springs on a bench next to her bed - where she can smell them too! She be BEGGING for me to dealt to her tomorrow!
I'll post an update.
Cheers
mark

nancy · « **Reply #23 on:** October 26, 2010, 01:59:54 PM »

OK Guys - fault confirmed as kill switch wiring. Just to rub it in to me....I went out and checked her for 1st time since garaging her last night after the trailer ride home. Measured output voltage on the battery at 12.7 and igntion on with lights down to low 12 something. Happy with that. Gave the starter button a press and BANG she started up...what the FFFFF!!!! Anyway, shut it off and no repeat - back to no fire again. So off with the headlight bucket and courtesy of the good advice received - rerouted the back/white wire to a black and - yep that did it. SO,..now to find the source.....control or wiring...
Regards
Mark

andy750 · « **Reply #24 on:** October 26, 2010, 03:01:04 PM »

Good news Mark and I think you owe Spanner a beer for that one

cheers
Andy

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Author Topic: CB750 - No spark - no start. Had to abandon the bike! - FIXED!! (Read 10532 times)