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Starting issues (hot)

Started by FFGO, September 06, 2024, 08:10:10 PM

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FFGO

I have a persistent but intermittent starting problem.
1984 FJ1100. The bike usually fires up right away when cold. Sometimes on the second crank after the vacuum has allowed fuel into the carbs. I'll run down the hill and do some errands in town, stop and go traffic. On one of the stops it won't fire up right away and it seems like I only get 2-3 tries and then the battery is too low to get a good crank. If I put some cables and a booster battery on it, the bike will flash up immediately.
I bought the battery last year. Plain Jane lead acid. I went through an issue with the alternator last year but that's sorted. Do I need a battery with better CCA? Should I run relays to the coils?
What do I need to fix this unreliability?

Pat Conlon

Could it be that your starting problem isn't electrical related, but fuel?
 I suspect your fuel petcock is failing.
Take the petcock vacuum line off at the intake manifold, clean the end of the hose, and suck on it...can you draw air? (You shouldn't) while sucking on the hose put your tongue on the opening of the hose, does it hold a vacuum? (It should)
1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3

FFGO

Thanks Pat. I'll check it out tomorrow.
It does seem like the battery gets weak, but the next stop/start it will be fine. I should definitively eliminate the possibility of the problem being a vacuum/fuel issue.

Meltdown480

I also have a similar issue. Starts cold on choke fine, will drive 15 min to gym in 100 degree weather. Then when I get back on an hour later wont start even with full choke until I give it throttle. Have rebuilt carbs and a new rpm petcock
Jackson S
1984 fj1100

Pat Conlon

For ALL FJ's with vacuum petcocks ('84-87)
Double check to make sure your fuel line is routed correctly.
 The oem fuel lines get soft when hot and can pinch off fuel flow if routed incorrectly.
The correct routing looks counter intuitive...still, follow it.

See my signature line.
1) Free Owners Manual download: https://tinyurl.com/fmsz7hk9
2) Don't store your FJ with E10 fuel https://tinyurl.com/3cjrfct5
3) Replace your old stock rubber brake lines.
4) Important items for the '84-87 FJ's:
Safety wire: https://tinyurl.com/99zp8ufh
Fuel line: https://tinyurl.com/bdff9bf3

FFGO

I took the petcock apart, and all seemed good. Fragile little unit, I could see how it could easily get hung up.
Yes, I'm always diligent about the fuel line routing. Yamaha felt a label was necessary so I've always felt it must mean something.
We've had company over the weekend so I haven't tried it out since. See what happens this week. 
Thanks for the help.

FJmonkey

On my 86' I found cracking the throttle open just a little when hot cranking helped. A 4 brush starter has fixed this problem for many as well.
The glass is not half full, it was engineered with a 2X safety factor.

'86 Ambulance - Bent frame, cracked case, due for an overhaul
'89 Stormy Blue - Suits my Dark Side