86 Mercury 25XD Wont Run.

[Colton1012]

Have a 86 25XD that will fire up but instantly die out, primer bulb is hard, I see fuel going to filter, and carb has been cleaned and rebuilt. Plugs are also wet so I know its getting through… any ideas?

 

[brodmann]

If the plugs are wet, It's probably running too rich. When you say you've cleaned the carbs, did that include complete disassembly, soaking overnight in carb cleaner and after that blowing out all passages with compressed air? Some of those older carbs had brass floats that would develop small holes in them and would fill with fuel and sink causing flooding of the motor. How is your idle mixture screw adjusted? I believe it's right in front on top. I'd screw that in until it just bottoms out and then start by screwing it out 1-1/2 turns. That's a good point for getting the motor to start and they you can adjust a little at a time to get it running erfectly. Are you getting good spark to the plugs? You can pick up a spark gap tester at an auto parts store for under $10. Set the gap at about 3/8" and make sure you're getting a strong enough spark to jump that gap. If it's a pull start, you'll need a helper. Basically, you have to have good compression on all cylinders, a good fuel supply and a good spark to make these thing go.

 

[Colton1012]

If the plugs are wet, It's probably running too rich. When you say you've cleaned the carbs, did that include complete disassembly, soaking overnight in carb cleaner and after that blowing out all passages with compressed air? Some of those older carbs had brass floats that would develop small holes in them and would fill with fuel and sink causing flooding of the motor. How is your idle mixture screw adjusted? I believe it's right in front on top. I'd screw that in until it just bottoms out and then start by screwing it out 1-1/2 turns. That's a good point for getting the motor to start and they you can adjust a little at a time to get it running erfectly. Are you getting good spark to the plugs? You can pick up a spark gap tester at an auto parts store for under $10. Set the gap at about 3/8" and make sure you're getting a strong enough spark to jump that gap. If it's a pull start, you'll need a helper. Basically, you have to have good compression on all cylinders, a good fuel supply and a good spark to make these thing go.

 

[Colton1012]

Took carb apart, and it was very clean inside to begin with but yes completely took it apart, blew all the holes out with carb cleaner and compressed air, new gaskets, etc. Bottomed out idle screw and came 2 full turns out, have good spark which was tested with a spark tester. Compression is 110 across both cylinders.

 

[QBhoy]

I’d take the carb off again.
But before that, can I be cheeky enough to ask if you’re familiar with this engine in a normal and running properly state ? Or is it new to you and just trying to get it running ? If the latter, can I ask if you are maybe leaving the choke on too long ? Or if you’re fairly well versed on the wee tricks and techniques these 2 strokes usually take to start easily ? Usually a bit of choke and throttle first cold start…she will kick or cough or even start up…then die. Then it’s a case of choke off usually and open the throttle to see her right. Or if she does start with the choke on…bring the revs up and turn the choke off pretty quickly…or she’s die and flood.
Alternatively, can I ask if she’s maybe a key start set up and started from a remote control box ? That being the case (and forgive me if you’re not new to this and know fine well already)…are you using the choke function at all ? You might have a push key in to choke type function there.

 

[QBhoy]

Have a 86 25XD that will fire up but instantly die out, primer bulb is hard, I see fuel going to filter, and carb has been cleaned and rebuilt. Plugs are also wet so I know its getting through… any ideas?

Just saw your previous post regarding this engine. In your picture there, that remote control you have fitted. Has a push key choke. Are you using this to help her fire up and run ? Apologies if you are and well aware of such things.

 

[Colton1012]

Just saw your previous post regarding this engine. In your picture there, that remote control you have fitted. Has a push key choke. Are you using this to help her fire up and run ? Apologies if you are and well aware of such things.

The electronic choke is not connected, but yes first 2 stroke.

 

[QBhoy]

The electronic choke is not connected, but yes first 2 stroke.

Ok. Excellent. So are you using the choke manually then ? With some throttle opened up to her ?
Vent on the tank opened too obviously

 

[Colton1012]

Ok. Excellent. So are you using the choke manually then ? With some throttle opened up to her ?
Vent on the tank opened too obviously

That is correct sir! Im unsure if my linkage is messed up when I put it in throttle only carb valve barely opens. Im sure you cant see it in the video, but it will open all the way up when in gear.

 

[QBhoy]

That is correct sir! Im unsure if my linkage is messed up when I put it in throttle only carb valve barely opens. Im sure you cant see it in the video, but it will open all the way up when in gear.

Ok. So that particular remote box you have there. Most of a certain age I know the same..are very very stiff to open beyond a certain point. If you pull it up with a little more force…it will free off I’m sure. Very common

 

[Colton1012]

Ok. So that particular remote box you have there. Most of a certain age I know the same..are very very stiff to open beyond a certain point. If you pull it up with a little more force…it will free off I’m sure. Very common

I have a video to post but it is too large.

 

[Colton1012]

Did get it to run for a few minutes until it died out, now back to a crank no start lol.

 

[QBhoy]

Hi. I’d do a compression test on that. If you haven’t already. Sounds like it’s possibly not firing on both cylinders or only partly at best. Have you cleaned or replaced that fuel filter ?