Home for lunch. The #1 spark plug smells like fuel and has an extremely light coat of oily substance on it. I didn't even really see it until I rubbed the end of it with my finger and looked at my finger. It smells more like clean, unburned fuel, rather than with a burned smell like the other plugs. Still, I would think that if the proper amount of fuel was entering that cylinder, it'd be covered in fuel and oil. As it is, the white insulator part of the spark plug is still bright white.
Still planning on spark and compression tests as a first order of business. Looking ahead some, questions out of ignorance:
- If I end up targetting the carb as the issue, does "rebuilding the carb" with a kit like this automatically mean I have to re-tune the carb afterward? My understanding is that the re-tuning is the most difficult part of the carbs.
- It looks like there's a diaphragm and a fuel screen in the Keihin carbs. If those are gummed up or destroyed, I'm sure that can affect fuel flow. Can those be replaced without messing with a rebuild and re-tuning?
Ultimately you have to tune the following things if you completely rebuild them:
1.) Each carb's needle needs to pop at the exact same pressure. This is determined by applying air pressure precisely and observing when it pops then adjusting the spring so it matches the others. This is done on all three carbs.
2.) Each carb has low and high speed mixture screws that need to be set. Each carb will be set a bit differently since each cylinder is a bit different. This is the time consuming part as there is no way to properly set it without being on the lake and the carbs are nearly impossible to adjust without removing them.
3.) When you advance the throttle on the ski there is the little butterfly valve in each carb that opens to allow more air in. It's critical that each carb lets the same amount of air in so each cylinder gets the same amount of power. There are lots of ways to do this...I did it with a piece of cardstock paper. Simply stuck the paper in one carb, adjusted it to where the valve put slight friction on the cardstock, then adjusted each other carb to match that friction.
The only special tool needed is one of these:
http://www.amazon.com/Mikuni-Pop-Of...qid=1414691556&sr=8-1&keywords=Mikuni+Pop+Off I can loan you mine.
IF you tear down JUST that one carb and IF you are DAMN careful to observe the precise setting of the low and high speed screws and you get them back to the precise same spot you might be close enough. But it takes a very small amount of adjusting with them to make a massive change so I would be rather surprised if you were able to get it perfect again on the first attempt. The main point of tuning is to make sure the cylinder doesn't get so lean that it burns itself up.
The process to set the low and high speed screws is something like this:
Low Speed:
1.) Go on the lake, run about 30% throttle for 5 minutes then yank the lanyard off the ski so the engine dies instantly. Don't go to idle before you kill it. Kill it at that power setting.
2.) Now you're floating on the lake, remove the seat, try not to fall into the water or tip over and remove each spark plug. Observe the color. Adjust each carb's low speed as appropriate to get the right color.
High Speed:
Same process as low speed except you run at 100% throttle then cut it.
The results of the spark plug test won't tell you what to adjust if you don't do it precisely as described above. You have to look at the plugs immediately..can't idle around, etc.
Problem is like I said you damn near have to pull the carbs completely off to tweak each screw each test. I probably messed around on the lake with mine for a few hours for a couple days in a row before I had it like I wanted.
