Difficulty starting ST90

Suzuki van tech question and answers.
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Gniknotle
Posts: 4
Joined: Thu Oct 22, 2015 10:10 pm
Location: Melbourne

Righto guys, I've got an '82 ST90 running the standard F8a and 4sp, the thing has always started first turn since adjusting the valve clearances, timing, new plugs etc and runs like a dream
Recently the starter was playing up and as it turns out it was just the connection to the solenoid - easily rectified and now it's cranking just as it has been this whole time. Since then however it really struggles to start, push starts fine and also after some persuasion will start off the starter but it's really killing me. I've checked spark and regapped the points, then proceeded to get the timing gun onto it and reset the timing... The engine runs perfectly (when it's running) but just won't start. Also it has taken to occasionally running on... From what I've read this could be a build up of carbon deposits in the combustion chamber? It does seem to be running quite rich (mixture screw on the carb is all the way in)
My current train of thought is to do a compression test, as if any valves are too tight this would lead to inadequate sealing of the combustion chamber and without compression there is no bang, and hence it won't start (although it's running the best it ever has and comfortably sits on 100, as it did this morning)
If there are any gurus out there who know some gypsy magic to get this thing back on track that'd be great!

Cheers, Elton
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Brayden
Posts: 9101
Joined: Sun Apr 11, 2004 3:09 am
Location: Canberra ACT
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You shouldn't be able to adjust the idle mixture screw all the way in without the engine stalling. Sounds like the problem is the carby. My guess is a dirty needle and seat is flooding the engine making it hard to start, run rich, and overrun when you kill the ignition. Could also be caused by a damaged float or some other carby-related issue.
F8B EFI turbo - Three pots and a snail.
Gniknotle
Posts: 4
Joined: Thu Oct 22, 2015 10:10 pm
Location: Melbourne

Ok so we're thinking its losing spark as the starter cranks, because it only starts once the key for the ignition is no longer in the 'start' position... Looking at the coil and also the starter there's a couple of loose wires... Can anyone chime in with what's meant to be running off the coil in particular?
Cheers, Elton
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Brayden
Posts: 9101
Joined: Sun Apr 11, 2004 3:09 am
Location: Canberra ACT
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Is it a two or three post coil?
F8B EFI turbo - Three pots and a snail.
Gniknotle
Posts: 4
Joined: Thu Oct 22, 2015 10:10 pm
Location: Melbourne

It's a two post coil with a resistor - turns out it was missing the wire from the starter solenoid (opposite side of the solenoid than the switch to engage the starter) to the positive on the coil (I think it feeds the coil 9v when cranking then 12v once started) or something along those lines
All sorted now :)
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