How I stopped the dreaded flat spot / stalling on Suzuki DF4 outboard.

[fredrussell]

Thought I'd post this info as I'm sure there will be owners of Suzuki DF outboards searching this common problem in future.

These outboards have the infuriating habit of stalling if the throttle is opened even slightly too hastily. Its a pain in the ar5e.

In my DF4 the main jet - found inside float chamber - is a .70mm, the pilot jet (found on top of carb at an angle) is 0.35mm.

Having read various threads online re the stalling issue I purchased a precision drill bit set at Machine Mart for a tenner or so. I ran a 0.75mm bit through the main jet and a .40mm bit through the pilot jet.

Bingo! Massive difference. Outboard starts better, opens up perfectly under load and if there is a difference in mpg it hasn't been noticeable yet after a few tanks of fuel used.

Your cordless drill chuck will probably not hold a 0.4mm drill bit too well - I use a cheapo dremel copy for that on slowest speed.

 

[CLB]

I believe this is all emissions related. I spoke to one of UK supplier of one of the main Japanese outboard manufacturers about this problem on my 2.5 and they admitted they had to run them so weak to meet emission standards that performance was affected.

 

[macd]

I believe this is all emissions related. I spoke to one of UK supplier of one of the main Japanese outboard manufacturers about this problem on my 2.5 and they admitted they had to run them so weak to meet emission standards that performance was affected.

I'm sure that's right.
You'll often read the ill-informed view that two-strokes have been banned from sale in the EU. In fact there's no such regulation, but emissions limits introduced about a decade ago could not be met at realistic cost by small two-strokes. Four strokes generally can meet them, just, but often with the sort of penalty the OP has ingeniously side-stepped.

 

[Billows]

Maybe your Suzuki DF4 is now a Suzuki DF6

 

[fredrussell]

The general consensus of opinion 'over the pond' is that these outboards are jetted lean so as to pass emissions controls. I read several threads where people returned their Suzuki DF outboards to dealers who fixed issue under warranty by installing larger jets supplied by Suzuki. My results would certainly suggest these reports are true. My outboard has gone from being barely useable to like new, or at least, how it should have been as new.

Another bugbear I've had to deal with is the gear shift lever seizing up. The interweb suggested this was a very common fault due to Suzuki not putting a grease nipple on housing of said shaft. Added to that is the example of engineering genius whereby the friction control for limiting/increasing the amount outboard can be rotated off the centre cannot be reached when in operation on the transom of a small trailer sailer. Why not put it near all the other controls within easy reach?

All in all these various issues have given me the firm belief that small Suzuki outboards should be avoided like the plague. These are very basic design considerations that have been overlooked - shocking really.