I have a Gravley with a Briggs 16HP Vanguard V-Twin OHV Model 303447, Type 1143-A1 3082, Code 95001611 engine. Carb is a Nikki 6100 22-131 808070 47M.

Upon starting, the engine runs for about 10 -20 seconds before gas starts spewing out of the carb and muffler. I checked the float and needle and they seem OK. The gas almost seems under pressure.

I am thinking the problem may be the Mikuni fuel pump but have no way to check it! Any thoughts on solving this problem would be appreciated. Thank you.
Bob

I think you probablem is with the carb needle valve and seat rather than the pump. Open the bowl and clean both the seat and valve , then reinstall. Let me know if this helps or not.

I think you probablem is with the carb needle valve and seat rather than the pump. Open the bowl and clean both the seat and valve , then reinstall. Let me know if this helps or not.


I'll try that again in the morning but I had the needle out already. Any thoughts on dims for checking the float level?
Thanks.
Bob

With the bowl still off reinstall the needle and the float. If you can rig a gravity fed tank to this you will get raw gas quickly dribbling out of the open carb, now raise the float, it should stop 100% immediately. If it conitnues to dribble even a little I'd replace both needle and seat.

With the bowl still off reinstall the needle and the float. If you can rig a gravity fed tank to this you will get raw gas quickly dribbling out of the open carb, now raise the float, it should stop 100% immediately. If it conitnues to dribble even a little I'd replace both needle and seat.


Were going out for parts. First I'm going to drop the new needle in and hope that it does the trick. Do you know where I can see an exploded view of this engine? If I need to take the carb off to replace the seat, the intake will have to come off as well. I'm assuming that the attaching bolts are under the dust cover but really am not sure. I'd hate to take off anything I don't have to. Thanks.
Bob

Start your search here. Search Results - Briggs & Stratton (http://www.briggsandstratton.com/search/index.aspx?q=Vanguard+V-Twin+OHV+Model+303447&x=4&y=3) Do not bother with any Gravley sites, they don't tell you about the B&S much at all.

I just took the top off the carb again and it is really clean in there. I cleaned out all the gas and blew out what I could with a air hose. I redirected the gas line to the carb (by-passed the pump) and the bowl seemed to fill up a reasonable amount before the flow of the gas was stopped by the needle. Tried starting it again and the gusher was still there. What I did not notice before is that the gas is coming from the large tube that in in front of the carb. Its large diameter and hooks up to the underside of the air filter housing. Any thoughts? Thanks again.
Bob

Did you figure it out? Is that the vent hose from the crank case? Any back fire r cough when it runs? Sounds like a leaking or sticking valve?

did you figure it out?? is that the vent hose from the crank case? any back fire r cough when it runs? sounds like a leaking or sticking valve??

The machine is running now. It must have been something stuck under the needle and keeping it from stopping the flow of gas into the carb! I did try the gravity feed and raising the float did stop the flow. The gas spewing out of the breather tube was due to the crankcase being full of gas. Changing the oil (at least 2x the amount there should have been) did the trick, no more geyser. Good thing it didn't blow up and I'm glad it didn't run long or the cylinder wall probably would have been trashed! Thanks for your help.
Bob

I've decided to rebuild the carb and am having a problem finding listings on the net for rebuild kits. The carb is a Mikuni 6100 22-131 808070 47m . The only kits I seem to be able to find are for bikes and jet ski's. Any have a source for Mikuni small engine parts? Thanks.
Bob

I just ran into this myself. The mikuni carb is a nice piece. It has a rubber point on the needle valve off the float and actually a brass seat which is not replacble. I found the kit right at my local place but its 25 bucks. I just cleaned mine all up and checked the electric shut off valve too. Runs like a dream after before it was dumping raw gas out the exhaust. Unless the rubber tip is destroyed you don't need a new one. Hope this helps. Now I just need a new ujoint for my driveshaft and shell be perfect