How to convert Briggs 5hp from gas to alky?

AlexRex · Joined: 13 Nov 2001 Posts: 4

Exactly what needs to be done to a Briggs 5hp to run on methanol? What parts neeed to be replaced, etc.?

Thanks

Roy Randolph

Alex, basically you need to advance the timing on the fly wheel, use a offset timing key, and then change out the jetting in the carb. You will need a larger jet. And after every race night purge the Alky from the system. (alky VERY corrosive) I pumped out all the alky from the tankand put in a little pump gas. Cranked the engine to burn the alky up. It will run rich with the gas but you need to do this. Also you need to change the oil everytime, because your oil will get contaminated with the alky, learned the hard way on that one.

Whooo.. I am tired just thinking about all the work I went through racing a Briggs. Makes me appreciate my Rotax even more

Jack Burroughs · Joined: 18 Jul 2001 Posts: 144

First thing you need is a selection of jets from .050 thousandths upto .060 by drill sizes. Usually run about .052-.055 for normal and .059-.060 for restricted. Just don't leave fuel in tank for long periods. Don't run gasoline if you are running a big or national event, residue can be detected and cause DQ. I use a siphon hose with a hunk of steel tubing that reaches the bottom corner of the tank.

Jack Burroughs · Joined: 18 Jul 2001 Posts: 144

Forgot to mention also need Denso plugs from 22 to 27. (I use the cheap ones) 24 plug usually works good. Also run CHT temp @ 400-410 for best results.

Bob Evans · Joined: 03 Aug 2001 Posts: 65

http://www.4cycle.com/karting/html/carburetor.html

Bill Angel · Joined: 04 Oct 2001 Posts: 839

The metering holes behind the jet need to be opened up. Maximum size per WKA rules is .062 large hole and .028 small. These are no go measurements. You can get by with enlarging just the large hole. As stated in previous posts a larger jet will also be needed, probably something between .048 and .062.

Jack Burroughs · Joined: 18 Jul 2001 Posts: 144

Alex, you don't have to B.P. carb to get it to run, but if you really want to do it right follow Bob Evans' suggestion, 4-cycle.com will help you more than you could ever immagine. There are people there that can and will help you a ton, some of them will even make you think about things you can't even immagine.