Fuel mix issues?

[mudcatwilly]

I have a 1990 Suzuki DT85 and it runs fine at WOT, but tends to stall at idle, especially when shifting into gear. I pulled the spark plugs (which are a couple of years old at least) and noticed that they are wet with a bit of black oil on them. There wasn't any unusual wear or discoloration on any of them. The fuel lines/fuel filter are new. I am using a premixed 50:1 gas/oil ratio. Should I try mixing the fuel at 40:1 or adjusting the idle, or should I just change the spark plugs and see how it does?

 

[JB]

Re: Fuel mix issues?

Your fuel mix is fine, Willy, and so are your spark plugs, though they might do well with cleaning and regapping.

When was the last time the engine had a thorough link 'n' synch, by the book? Your idle might be a bit low or it might have been set without back pressure (on the muffs).

 

[mudcatwilly]

Re: Fuel mix issues?

It does seem to idle a bit rough. I have no idea when the motor was really gone over because I've only had it for a little over a year. This is my first boat and I'm learning as I go. So far, I've changed out the lower unit (bent prop shaft), but I haven't done anything to the motor itself. I don't even know how to adjust the idle/fuel/air mixture.

 

[JB]

Re: Fuel mix issues?

Get a good Service Manual and start learning, Willy.

The "link 'n' synch" I referred to is the step by step procedure for setting the idle and synchronizing the advance of the linkage to the carb throttles and the ignition timing when you advance the throttle. Even if the idle is correct, unless the ignition timing is set correctly and begins advance at the correct (angle) of the linkage stalling is one probable result.

As for the spark plugs, as long as they are clean and properly gapped there is no benefit in changing them except that with a lighter wallet it may go a bit faster.