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 Post subject: 750 Sport run issue
PostPosted: Mon Apr 23, 2018 12:03 pm 
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Joined: Mon Apr 16, 2018 8:37 pm
Posts: 5
Location: Finland
model: 750 Sport
year: 1989
Hello everybody,

I got my bike started for the first time after it's been sitting for 4 years. To my surprise it started right away with not much effort...WIN! :) However I noticed that when it being on no choke, idle revs are less than 1000rpm and battery light is on. When slowly touching the throttle to rev up I hear spitting from right side muffler and then suddenly engine revs up and then settles down again. What could this be about?

Here I have a video clip from the situation: https://youtu.be/1hBfxPTRn8E

My ideas: Either one of the carbs is stuck and not giving enough gas to the engine or spark plug is in the end of its life?
Next I'm going to try to add some gas system cleaner. If this is not helping then change for a new spark plug.

What could be the reason for low idle revs?


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 Post subject: Re: 750 Sport run issue
PostPosted: Mon Apr 23, 2018 1:49 pm 
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paso grand pooh-bah

Joined: Thu Jun 21, 2007 12:00 am
Posts: 1432
Location: Gothenburg, SWEDEN
model: 907 I.E.
year: 1991
Sounds abit strange, you sure it is running on both cylinders?
Check that both get spark and fuel.

Battery status?
When you raise RPM, do voltage over battery terminals rise to around 14V?

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Gert

907 I.E. -91
M900 -97


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 Post subject: Re: 750 Sport run issue
PostPosted: Mon Apr 23, 2018 10:12 pm 
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paso grand pooh-bah
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Joined: Sun Jul 18, 2004 12:00 am
Posts: 5182
Location: southern Germany
model: 750 Paso
year: 1987
Running on one cylinder is typical. The usual reason is low voltage at the coils. When throttle is opened voltage increases and the other cylinder will kick in. Since there's unburnt gas in the exhaust it will spit or backfire.

First of all: good that you got the oil screen filter out. ;)

Do measure the voltage at the coils when the ignition is on and at idle. If it's lower than battery voltage check the FAQs for the wiring modification. That should fix it.
Make sure the spark plugs are clean or better install new Champions. Did you drain the tank and use fresh fuel?

Quite sure it's ignition not carb related.


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 Post subject: Re: 750 Sport run issue
PostPosted: Tue Apr 24, 2018 9:33 am 
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Joined: Mon Apr 16, 2018 8:37 pm
Posts: 5
Location: Finland
model: 750 Sport
year: 1989
I see, that's a good point. I'll check does first. I was going to do the wire modification anyway, so hopefully it will help too :)

In the video battery light goes on when on low rpm. Is this normal or is it because of bad coil?


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 Post subject: Re: 750 Sport run issue
PostPosted: Tue Apr 24, 2018 6:25 pm 
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paso grand pooh-bah

Joined: Thu Jun 21, 2007 12:00 am
Posts: 1432
Location: Gothenburg, SWEDEN
model: 907 I.E.
year: 1991
Not normal, indicates low charging of battery.
But, after a first ride of 40-50 km`s, battery should be fully charged and no light.
Do check voltage over battery as mentioned.

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Gert

907 I.E. -91
M900 -97


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