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Help needed on re-engineering project on B&S Sprint 375

Posted by CY078 none (My Page) on
Mon, Jul 22, 13 at 8:51

Hi All

long story short .... upon cleaning the carby .. i took apart the throttle plate that connects the throttle cable / butterfly opening on carby / kill wire. (yes I know now this can be done by simply by removing the piece that was on the butterfly opening)

1) I cannot remember how it goes back together, 2) I broke the smaller of the spring that was holding it

Upon observation the system looked over complicated. All the throttle cable was doing was opening and closing the butterfly on the carby.

So I re-engineered the system and it open / closes easily. However I obviously have put the end of the 'kill wire' in the wrong place because I can't turn the engine off.

1) Can I use this setup and put the 'kill wire' in the correct place? If so where is it meant to go. 2) Do I have to go back to the original setup? If so does anyone have a diagram that can guide me (I tried looking on the B&S website to no avail) ?

Many thanks in advance


Follow-Up Postings:

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RE: Help needed on re-engineering project on B&S Sprint 375

  • Posted by baymee LehighValleyPA (My Page) on
    Mon, Jul 22, 13 at 13:26

At the least, you need the longer spring in the foreground. If you have a handle that kills the engine at the handlebar, you can get rid of the throttle cable. If not, kill switch wires are usually self-explanatory.


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RE: Help needed on re-engineering project on B&S Sprint 375

it's been a while since I've had one apart but isn't the larger spring the throttle cable and the smaller one for the choke?. As for the kill wire/cable, mine is broken so i just slide the kill switch mechanism by hand to kill the engine.


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RE: Help needed on re-engineering project on B&S Sprint 375

  • Posted by baymee LehighValleyPA (My Page) on
    Wed, Jul 24, 13 at 13:41

The throttle cable, steel wire, controls the throttle plate and choke. The farther the cable is moved toward "fast", the more the larger spring is stretched, and the higher the rpm. The smaller spring helps to better control the governed speed, as far as I can make out.

Modern carbs went to a primer bulb and no throttle cable. They only run at one speed.


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RE: Help needed on re-engineering project on B&S Sprint 375

I havent had time to touch this since my original post ...... However im still stuck as to where the kill wire should be.

I understand what it does but i cant replicate it.

Before mods .... The engine would die out when i push the chock back to slow. However with the mods the engine wont die out at all. Im thinking ive just grounded the wire in the wrong place but not matter where i put it i get the same results.

Any theories ???


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RE: Help needed on re-engineering project on B&S Sprint 375

The wire itself runs from the ignition coil to the kill switch that the control lever of either the brake arm or the throttle control hits in off position thus grounding the coil.


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RE: Help needed on re-engineering project on B&S Sprint 375

I found the kill switch ... Which was under the throttle plate. Upon testing it worked perfectly 3 times.

However when in action (the first time after emptying the catcher it worked fine) each time after that it didnt work. I had to pull the plug lead off the plug to stop it.

I had some bolts that became loose but the kill switch wire was still attached to the kill switch.

The only thing i can think of is the wire that i used to replace the spring is not returning to the end because the viabrations has moved thus not cutting out.

Any ideas anyone ?????


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RE: Help needed on re-engineering project on B&S Sprint 375

  • Posted by baymee LehighValleyPA (My Page) on
    Sat, Aug 24, 13 at 6:39

Have an assistant move the cable and physically see where the tab moves to. Also, it's unlikely, but the throttle plate is loose to the point of not being grounded.


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