Forum - Briggs & Stratton Racing
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helix

Registered: 08/21/12
Posts: 22
Reply with quote  #1 
I just converted my sons junior to the lo this year. I replaced the coil and slide. First it was hard to get it to idle but thats been fixed. It will idle and hold a temp at about 200 degrees. When on the stand if you rev the engine it responds great but when you let off it will back fire and untimatly die unless you rev it again. After reving it wont hold idle. After it dies its really hard to start again. I tried changing the mix both ways with no success. All it does is change the head temp at idle. Any ideas? It ran perfect before the mods.
CarlsonMotorsports

Registered: 03/04
Posts: 4
Reply with quote  #2 
How much air gap do you have between the coil and the flywheel magnet?  If this airgap is too large, it can cause some issues.  Also, check to make sure that the plug wire is pushed firmly into the PVL coil.

Aside from those items, you may want to drop the bowl on the carburetor and clean everything thoroughly with brake clean, check the float level set correctly for your application, re-assemble, and try it again.

For what it's worth, I don't recommend that anyone runs an engine without load.  You cannot tune a carb this way.  The engine needs to be under load (richer condition) to properly tune it.  It will also build more temperature under load than running without.

Hopefully that helps you out.

Blessings,
Brian Carlson
FasterMotorsFasterMotors

Registered: 06/15/11
Posts: 47
Reply with quote  #3 
Coil air gap that is too small can also cause problems.
It tells you right on the coil what the air gap should be but i set them at .020" and it works just fine.
Sometimes you can have one leg of the coil set properly and not the other. Make sure they are both correct after you tighten the bolts.
If the engine has been in storage for a while it is very possible that if fuel was left in the float bowl it evaporated and plugged up the idle jet.
Using a good screw driver that fits the idle jet properly, i would remove the idle jet (the long skinny one) and blow it out with compressed air.  Push the screw driver into the slot so it doesn't slip and damage the jet.
You should be able to hold it up to the light and see through it. It's about a .013" hole so it is very easy for it to get plugged.
I would not recommend trying to force a drill bit or anything else through the jet for fear of damaging it. If you can't see through it get a can of spray carb cleaner and spray enough into a small container (the cap for the can) and soak the idle jet in it for an hour or so. Then blow it out with compressed air again.
Once you can see through it it's probably ok.
Clean everything else in the carb while you're at it.

http://www.fastermotors.net/Jetdriver.html

http://www.fastermotors.net/Floatgauge.html

Good Luck 




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