Dt85 1985ish

[dt85gaz]

Hi im new and looking for help please

I have a DT85 non oil injection which i doesnt want to run properly.
Its symptoms are

Rough idle wanting to stall i can keep it running by blipping the throttle,it also sounds like it is spitting back although i dont suspect reed valves.

I thought if i lifted the tickover a little on the carbs i could the adjust mixture and timing.
So i lifted the tickover just a bit and the engine started to rev what sounded like it was past the rev limiter.
I turned the key off but it kept running so i pulled the plug leads off and it was still running then i disconected the fuel BUT it still ran then i flicked the choke on and managed to stop it.
May i say that the throttle was set at idle all the time and the carbs were only just open.

I will say that before i lifted the tickover i always thought that it was very slow to settle back to idle speed if it had just been revved.
This is an engine i have just bought and dont know any of its history.

Would i be right in suspecting an air leak?

Any help will be much appreciated

[dt85gaz]

Well i had a look around and found what it might be.
Hot carbon on the pistons behaving like a spark plug "preignition" caused by either poor fuel or running too lean and or incorrect ignition timing.
I google searched "runaway outboard"
Anyway its like siberia in england at the moment so it may be a day or two before i have another look at it.

[dt85gaz]

well ive sorted it out and now it runs perfect.
The fix was simple really,it was running too lean.The mixture screws are back to front as they control air not fuel.
This means to give more fuel screw them in this gives a richer mixture.Mine are about 1 turn from being seated and it runs fine.

Only problem now is i have lost reverse gear so if anyone has a cheap long shaft gearbox lying about give me a call.
Im in the north west of england 07966 143823