Yamaha Bravo in warm weather

[Dand]

Rex, I'm enjoying all the good info you are posting but I thought I'd start fresh.  I've had my boy out 2x trying to hunt on nice sunny days and we began having troubles with the Bravo - 250.  First time out we discovered we had never taken out the powder snow baffle on the front scoop and boy was the enging and clutches hot.  Engine would bog and get slow. Finally figured that out but still had trouble. Finally took out spark plug and it was fouled. I had put some oil in the gas tank back when it was a lot colder.  Traveling light the thing ran fine the rest of the day.

Next time out hunting and getting firewood we start having the boggy performance. It wasn't near as warm and we were quartering into the breeze but towing a small empty sled.  Had more fresh gas too.  Things seemed hot so we stopped and cooled off, took belt guard off for more air on the belt and cluthes.

Plug was gunky again too.  Guess I better put a filter on the fuel line if I can find a place.

I'm beginning to think about cutting some louvers in the cowl for more air but hate to hack up a brand new cowl. 

I'm open to any suggestions on what I should be doing. I wonder if I should check the jetting?  We have an ancient short track Bravo that seems to run on anything at any temps with no complaints.

HOpe to try one more time for bunnies and ptarmigan before we lose our base.  Nice nippy mornings have kept the snow for now.  I wish for COLD for 2 more weeks.

[Rex in OTZ]

In spring I remember the guys removing the belt guards and the cowl so engine could bleed off excess heat in spring when hunting waterfoul, it looks like hell
 I suggest checking the oil injecter rigging, mabe crank in the mixture valve a tad (lean), lean too much will over heat the cylinder and cook your engine, too rich and you will be fouling plugs and bogging, also suggest seeing if the choke is all the way open as a slightly hanging choke can be rich and foul plugs too, as I remember them yamaha carbs were butterfly and the choke was a plunger, also mabe your primer may be feeding while engine is running take a look at the primer line and you could see if fuel is moving through it (if primer is mounted).

make shure that rubber grommet boot plugs off air loss around the sparkplug (loss of cooling air)
I had modified the hot engine outlet port to duct directly up (1984 Yamaha 340ET)

[Dand]

Thanks Rex.  I'll check those ideas.  The fouling we're getting is hard brownish ash. When I used to get sloppy mixing outboard gas I'd get black goo on the spark plugs with too much oil. 

Looking at that bravo, venting straight up might be easiest - maybe work like a wind shield defroster if I do it right. I've seen some photos where trappers have ducted air to behind the windshield to blow on a GPS to keep it thawed and running in real cold.

Shucks, might rain Saturday - was hoping to take the boys camping - I'll just have to see.

thanks again.

[Rex in OTZ]

Sounds like your oil fowling, another sight you can garner info off of is www.snowmobileworld.com