Got it started but not sure why

discussion about the 750 Sport and '89/'90 900SS, which share many mechanicals with the Paso series
1989750Sport
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Joined: Thu Nov 02, 2017 12:16 am
model: 750 Sport
year: 1989
Location: UK

Got it started but not sure why

Post by 1989750Sport »

So I got the bike out today and it refused to start
1. Checked fuel
2. Checked spark

So I was wondering if I flooded it, but it didn't seem as I did. I decided to do a little cleaning and see if anything looked amiss. I ended up loosening the return hose under the tank to see if there might be an issue with the pump. There was gas as evidenced by a few drops coming out. I plugged that back and it fired up immediately.

Is this a voodoo ritual which must be done after Weber carbs sit for the winter?
Desmo Tutu
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Joined: Mon Oct 24, 2016 8:21 am
model: 750 Sport
year: 1990
Location: Norway

Re: Got it started but not sure why

Post by Desmo Tutu »

Yes

Don't know if it had something to do with the Weber, you will never know. You have to do some Voodoo rituals every spring to wake them up.
Bikes who don't need some sort of Voodoo are usually from Japan. They have no soul.
1989750Sport
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Joined: Thu Nov 02, 2017 12:16 am
model: 750 Sport
year: 1989
Location: UK

Re: Got it started but not sure why

Post by 1989750Sport »

Thanks ... my voodoo must be weak as I added gas yesterday for a long rid. It backfired twice and then never fired up
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paso750
paso grand pooh-bah
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model: 750 Paso
year: 1987
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Re: Got it started but not sure why

Post by paso750 »

Do measure if you get the full battery voltage at the coils. It might be the ignition switch that's causing the problems.
1989750Sport
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Joined: Thu Nov 02, 2017 12:16 am
model: 750 Sport
year: 1989
Location: UK

Re: Got it started but not sure why

Post by 1989750Sport »

Thanks! I put 2 new plugs in and it fired right up but I needed to use cables to do so ... evena fully charged battery doesn't get everything spinning for a cold start
1989750Sport
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Joined: Thu Nov 02, 2017 12:16 am
model: 750 Sport
year: 1989
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Re: Got it started but not sure why

Post by 1989750Sport »

Btw ... how do u make a photo small enough to post?
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paso750
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Re: Got it started but not sure why

Post by paso750 »

What's the exact problem? File size is limited to 5MB. Pictures up to 1024x768 pixels will be shown directly in a post, larger pictures will appear as a link. If you don't have a software to resize your photos just google 'image resize online' and you will find some websites where you can upload pictures and resize them.

If the engine needs to turn over several times to fire up check the voltage at the coils as suggested. There's a wiring mod you'll find in the FAQs. If the starter turns over slow it could be an old battery, bad electrical connections or worn starter brushes.
One way to improve the starter wiring is to replace the old cables with better & stronger ones w/ good quality connectors. If there's a local car stereo shop they can probably make some if you bring them the original ones. Then get some heat shrinking tube and install that over the new cables. Done.
1989750Sport
Posts: 50
Joined: Thu Nov 02, 2017 12:16 am
model: 750 Sport
year: 1989
Location: UK

Re: Got it started but not sure why

Post by 1989750Sport »

Ok .... I know how to test coils .... sort of. 3-5 oms at the pigtail and 10-15 k at the secondary coils ... what readings would I expect when the bike will spark and run, but will not turn the starter?
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paso750
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year: 1987
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Re: Got it started but not sure why

Post by paso750 »

Let's get back to the beginning please. What's the exact issue? You said it refused to start, but then it did. After the backfiring it didn't fire up again but with jumper cables it did and now the starter does not turn. Does the starter not turn or does it but the engine won't start?! How old is the battery?

It's not about testing the resistance of the coils but about the voltage they get. However the resistance you measured is ok.
Now try to connect your voltmeter to the yellow wire at the coils (if possible w/o disconnecting it). Turn the ignition on and read the voltage. Then read again while turning the engine over. At last see what voltage the coils get when the engine is running. Ideally the voltage would be the same as when measured directly at the battery (under those three conditions). If you find a voltage drop that's a possible cause for misfiring, bad starting etc.
Of course that has nothing to do with the starter. If that doesn't turn the issue is in the battery, wiring or the starter itself.
1989750Sport
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Joined: Thu Nov 02, 2017 12:16 am
model: 750 Sport
year: 1989
Location: UK

Re: Got it started but not sure why

Post by 1989750Sport »

So ... I think my first issue was a pinched fuel line, then old plugs ... the problem left is that a fully charged, newish battery ... barely get the engine to move ... sounds like one full cycle before it gives up. Think this was what causes the flooding and the demise of the plugs. The voltage regulator has been recently changed. So where to start?
1989750Sport
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model: 750 Sport
year: 1989
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Re: Got it started but not sure why

Post by 1989750Sport »

Battery is a few months old
1989750Sport
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year: 1989
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Re: Got it started but not sure why

Post by 1989750Sport »

Also read the ignition switch thread ... are later switches better ... supposed it is not plug and play to go to a 96 key switch?
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paso750
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Re: Got it started but not sure why

Post by paso750 »

While the ignition switch can cause numerous electrical problems it has nothing to do with the starter motor. The starter is connected to the starter relay which is directly connected to the battery. Replacing the key switch will not solve a starter problem. Newer ones may fit but I'm sure the electrical connectors are different.

Some more questions:
Is the engine original (no aftermarket high compression pistons)?
Have you tried to connect the battery directly to the starter to see if it then turns normally?
Does the starter turn over the engine effortlessly once the spark plugs are removed?
Is the oil level correct?
Was the regulator/rectifier installed correctly? (battery voltage should increase by at least 1,5-2V when the engine is running compared to when it's off)
1989750Sport
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Joined: Thu Nov 02, 2017 12:16 am
model: 750 Sport
year: 1989
Location: UK

Re: Got it started but not sure why

Post by 1989750Sport »

No hi comp pistons that I am aware
Will look at the oil level and battery voltage when running whe I go riding again next Tuesday
1989750Sport
Posts: 50
Joined: Thu Nov 02, 2017 12:16 am
model: 750 Sport
year: 1989
Location: UK

Re: Got it started but not sure why

Post by 1989750Sport »

So my starter motor is toast ... is the starter the same as the newer ss 750 and 900ss 91-98? It's all I can seem to find on the net
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