suzuki DT9.9 backfire

[iceman52]

my Suzuki outboard backfires through the exhaust, it starts ok, runs, but if you try to idle down it will slow the engine every time it backfires till it dies. I checked the compression and have 95# on both cyl. has had carb cleaned, and new plugs. the backfire is a constant thing at low rpm every 2 or 3 seconds......any ideas,....sorry if this is a double post but can't find my first one..........JIM

[Solarman]

It sounds like carb(s) mixture screw(s) is/are set too lean.

Check the service manual on what your idle mixture screws should be set at. For multiple carbs each mixture screw should be set the same.

Yes, an air leak at base gasket can cause a lean running condition, similar to yours.

If still not running right, carb(s) should be cleaned again.

Good luck, post back when able to let us know how it's going.

[iceman52]

update on dt 9.9

yep, good advise, was adjustment screw, had to run it almost to the limit of adjustment before it quit backfiring......thanks JIM

[Solarman]

What do you mean the "limit"?

Post back when able.

[iceman52]

i'm almost to the end of the spring tension, book calls for 2 1/2 turns, i'm over 3 1/2 turns, will have to keep an eye on it to see that it doesn't back on out,..been thinking about a little loc-tite for insurance

[Hoosmatroos]

In your other topic I posted this:

Could be an air leak somewhere. Gaskets from carb to inlet oke? Adjustment from the carb to lean?

I thought I posted here the mixture screw setting to back out to get it richer but that one is gone?

[Solarman]

Iceman, if you have mixture screw that far out, then your air pas-sages in the carb are partially blocked, and carb needs to be cleaned. Air pas-sages need to be blown out, with compressed air. The mixture setting in Suzuki manual for your motor would be fine if carb air pas-sages weren't dirty.

Good luck, post back when able.