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1983 Honda cb650 hot start problems

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mrr1
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PostPosted: 23:01 - 06 Jan 2019    Post subject: 1983 Honda cb650 hot start problems Reply with quote

righto gents.....

for some bizarre reason I decided to pick up an old 1983 honda 650 Nighthawk. Decent enough nick, rides like a pig- shite in corners, frightening brakes (rear drum almost better than twin discs up front) but howls like a banshee when on full chat and (just about) able to keep up with a mate on his 350 YPVS.

however.....from cold she starts straight on the button but shes a b@$T@&d when hot. Engine turns over happily but just will not catch. Leave it to go cold and all is fine. At the mo' I'm carrying a pocket power pack - a slight glimpse of extra battery oomph and shes away.

Im assuming that either the 36 year old coils may be packing up when hot or shes flooding when hit and standing or something else.....

any ideas?

anyone know anything about the hot start systems on these old bikes?
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jaffa90
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PostPosted: 00:44 - 07 Jan 2019    Post subject: Reply with quote

Does this bike have the correct air filter fitted?

What are you doing with the choke lever & throttle when cold starting AND hot starting??

Does the engine tick over/ idle evenly?

When were the valve clearances checked?
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mrr1
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PostPosted: 09:27 - 07 Jan 2019    Post subject: Reply with quote

Don't know

Full choke on start if cold, don't go near it when warm

Ticks over nicely and evenly

Just after dinosaurs left
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jaffa90
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PostPosted: 11:26 - 07 Jan 2019    Post subject: Reply with quote

You only mention the choke and not the throttle.
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Meatybeaty
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PostPosted: 11:27 - 07 Jan 2019    Post subject: Reply with quote

mrr1 wrote:
Don't know

Full choke on start if cold, don't go near it when warm

Ticks over nicely and evenly

Just after dinosaurs left

Got a couple of 83 Nighthawk Manuals I can PM you if needed Wink
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yen_powell
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PostPosted: 13:13 - 07 Jan 2019    Post subject: Reply with quote

Throttle closed when cold starting?
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mrr1
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PostPosted: 16:43 - 07 Jan 2019    Post subject: Reply with quote

Meatybeaty wrote:
mrr1 wrote:
Don't know

Full choke on start if cold, don't go near it when warm

Ticks over nicely and evenly

Just after dinosaurs left

Got a couple of 83 Nighthawk Manuals I can PM you if needed Wink


You, sir, are a GOD!!
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TRX850, TDM900, ST1300, CB650SC Nighthawk, ragtop Saab, gym membership, messy divorce, large chested blonde fiance
Damn, I'm loving my midlife crisis.
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mrr1
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PostPosted: 16:45 - 07 Jan 2019    Post subject: Reply with quote

yen_powell wrote:
Throttle closed when cold starting?


Yep.

Bike feels like it's flooded. I'm wondering if the hot start circuit is not leaning the mix properly.

Having said that I haven't actually got a clue what a hot start circuit looks like or where it is or how to find it....
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TRX850, TDM900, ST1300, CB650SC Nighthawk, ragtop Saab, gym membership, messy divorce, large chested blonde fiance
Damn, I'm loving my midlife crisis.
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yen_powell
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PostPosted: 17:27 - 07 Jan 2019    Post subject: Reply with quote

mrr1 wrote:
yen_powell wrote:
Throttle closed when cold starting?


Yep.

Bike feels like it's flooded. I'm wondering if the hot start circuit is not leaning the mix properly.

Having said that I haven't actually got a clue what a hot start circuit looks like or where it is or how to find it....
Is it a cable choke with a handlebar lever (they can stick) or a direct lever on the carb itself?
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Blackmail is a nasty word........but not as nasty as phlegm!
KLZ1000 Versys, XRV750 Africa Twin & DR350 (leccy start thank god, had a kickstart DR before, nearly had a weekly coronary)
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mrr1
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PostPosted: 21:49 - 07 Jan 2019    Post subject: Reply with quote

Handlebar choke. All moves freely and throttle body bits move as they should.

From cold bike starts on the button.
Just hot starts are the problem
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mrr1
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PostPosted: 20:24 - 08 Jan 2019    Post subject: Reply with quote

Meatybeaty, got the manuals

Cheers
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Meatybeaty
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PostPosted: 06:11 - 09 Jan 2019    Post subject: Reply with quote

mrr1 wrote:
Meatybeaty, got the manuals

Cheers

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yen_powell
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PostPosted: 15:07 - 09 Jan 2019    Post subject: Reply with quote

mrr1 wrote:
Handlebar choke. All moves freely and throttle body bits move as they should.

From cold bike starts on the button.
Just hot starts are the problem
Does the cable split anywhere. I have seen the join of split cables open (on one of my old Hondas) and the sheathing dislodged against each other so the choke was permanently partially on even when the lever was in the off position.
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Blackmail is a nasty word........but not as nasty as phlegm!
KLZ1000 Versys, XRV750 Africa Twin & DR350 (leccy start thank god, had a kickstart DR before, nearly had a weekly coronary)
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mrr1
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PostPosted: 14:28 - 11 Jan 2019    Post subject: Reply with quote

Hmmmmm, I'll take a look.

Think I'm going to strip the main starter, coil and plug leads and clean up / replace. I carry a pocket jump starter and the hint of extra current brings the old girl straight back to life whenever this hot start shite happens....

I'm trying to figure out which bits can go shitty when warm........coils? Leads? ECU?
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Dr. DaveJPS
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PostPosted: 14:51 - 11 Jan 2019    Post subject: Reply with quote

Are the spark plugs are the right temperature?
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mrr1
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PostPosted: 15:40 - 12 Jan 2019    Post subject: Reply with quote

Checked out choke system, all seem to be good.
Stripped back main battery feeds to solenoid and starter. Fitted new feed to solenoid, cleaned all contacts especially the furry ones on the starter. Seems to be happier starting when hot.... I think.

Am currently having a sausage cob in Stalkers cafe, about to give it a real world test. Wish me luck........
Dunno if Chris walker really want a fat old fuckwit trying to bumpstart a shitty old honda in front of his Kwakker dealership...
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Damn, I'm loving my midlife crisis.
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jaffa90
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PostPosted: 16:30 - 12 Jan 2019    Post subject: Reply with quote

Why check the choke system and battery feed to the starter when you say,
"" from cold she starts straight on the button""
""Engine turns over happily but just will not catch ""
""Ticks over nicely and evenly ""
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WD Forte
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PostPosted: 17:06 - 12 Jan 2019    Post subject: Reply with quote

AFAIK soem CB650s use similar pulsers to the CX Eurosport 500 and 650s of that era.
I have them on my Euro 500 engined bike
They're pretty rugged and reliable but can break down so
if symptoms oersist, it may be worth checking them.

On a CX the initial test is to check the resistance on any pair of same coloured wires
Mine are 550 ohms +/- 50 ohms, (this goes up to 600 ish when hot)
Your manual will give you the specs for the CB650
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mrr1
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PostPosted: 18:31 - 12 Jan 2019    Post subject: Reply with quote

Thanks WD. By "pulsers" do you mean coils or the cdi igniter box under the seat that feeds the coils?

I actually had a really interesting run. Started out dodgy. Ran for half a mile and started missing on one, then two then totally died. Then remembered the frigging fuel tap (doh!!).

Gave her a bit of a caning for ten minutes then sat and enjoyed my tea and butty.

After fifteen minutes I tried the starter. This was when I was seeing the issue before.


Absolutely bang on the button!!!!!!! I think with old age maybe a few bits and bobs are getting fusty when hot and killing some of the spark. As I said before the engine would turn over and over on the starter but simply not catch. I think / hope / reckon by sorting the solenoid and starter contacts I've allowed the starter to do it's job without taking too much of the battery's lovely electric goodness and actually leaving some for the ignition circuit.

I'm about to use the seven most deadly words known to man.


Fuck me, I think I've fixed it.
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TRX850, TDM900, ST1300, CB650SC Nighthawk, ragtop Saab, gym membership, messy divorce, large chested blonde fiance
Damn, I'm loving my midlife crisis.


Last edited by mrr1 on 18:51 - 12 Jan 2019; edited 1 time in total
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mrr1
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PostPosted: 18:48 - 12 Jan 2019    Post subject: Reply with quote

Dr. DaveJPS wrote:
Are the spark plugs are the right temperature?


Good question....don't honestly know. Should pull one and check spec. Plugs all look nice colour and gapped ok so.......

I've made this mistake before; bought old watches and cameras for "nostalgia" reasons and then remembered how much bloody work they take to keep running properly. That's the thing that us old gits keep forgetting about "the good old days": everything used to break down all the time.
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Damn, I'm loving my midlife crisis.
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