1996 DT140 (2 stroke), top two cylinders not working

capecodmfg

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Compression is good. Spark is good. Plugs are good. Ignition coils are good. But when I spray fuel (carb cleaner) directly into the pistons, the top two don't bog down (choke) like the bottom two. I'm getting fuel in my exhaust, so I'm guessing it's not being consumed by combustion in the top two pistons. All this work has been done on land, mostly at idle rpms. I don't want to put it into the water with fuel coming out the exhaust... I'm at a loss as to what to do next!! Any ideas?

Thanks! Justin
 

99yam40

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Re: 1996 DT140 (2 stroke), top two cylinders not working

Have you checked to see if fuel pumps are leaking fuel into crankcase?

I do not know if they are tied to those 2 cylinders, but something to look at

Not sure how you can spray carb cleaner directly into pistons, but do not do that. Use a fuel/oil mix in spray bottle
 

capecodmfg

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Re: 1996 DT140 (2 stroke), top two cylinders not working

Thanks for the input! I apologize for my lack of correct terminology... I sprayed carb cleaner through the front of the carburetors, which essentially chokes that cylinder, unless it is fuel starved, right?

I haven't checked the fuel pump situation at all. Is there an easy way to this? Will there be obvious fuel coming out somewhere besides the exhaust?

Admittedly, I'm biting off a bit more than I can chew, but I'm hoping to avoid having to wait a month for the mechanic during the peak of the season!

Thanks again!
 

99yam40

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Re: 1996 DT140 (2 stroke), top two cylinders not working

unbolt from motor and hit primer bulb to see if fuel comes out of pulse port
 

capecodmfg

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Re: 1996 DT140 (2 stroke), top two cylinders not working

Just checked this... No fuel is leaking out the pulse port. Will go back and check compression, spark, plugs, carbs again...
 

capecodmfg

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Re: 1996 DT140 (2 stroke), top two cylinders not working

Have really been hitting this hard the last couple days. Compression still good (120psi each), spark looks goods, plugs are good, carburetors are delivering fuel cleanly (have swapped out carbs from the working cylinders to the non-working cylinders, and vice versa, and nothing changes). The reed valves all look great: clean and not bent or broken. Ignition coils work great (switched the bottom two with the top two and nothing changes). I'm at a complete loss now. Any ideas????
 

robert graham

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Re: 1996 DT140 (2 stroke), top two cylinders not working

Compression is good. Spark is good. Plugs are good. Ignition coils are good. But when I spray fuel (carb cleaner) directly into the pistons, the top two don't bog down (choke) like the bottom two. I'm getting fuel in my exhaust, so I'm guessing it's not being consumed by combustion in the top two pistons. All this work has been done on land, mostly at idle rpms. I don't want to put it into the water with fuel coming out the exhaust... I'm at a loss as to what to do next!! Any ideas?

Thanks! Justin
On the boat, in the water, is the motor running poorly? What's it doing wrong?
 

stylesabu

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Re: 1996 DT140 (2 stroke), top two cylinders not working

how are you checking spark?have use swapped spark plugs to other cylinders. just curious, how do you know spark plugs are good?
 

capecodmfg

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Re: 1996 DT140 (2 stroke), top two cylinders not working

Robert, the motor actually runs pretty well, but only on two cylinders... The fuel from the top two cylinders just comes right out the exhaust into the water. I can just barely get on plane on the two firing cylinders. But I'm not going to run it with all that fuel going into the water.

Stylesabu, I have switched plugs, used three kinds of spark checkers (one with compression added), and put brand new plugs in each chamber. Still only get the two bottom cylinders firing.
 

99yam40

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Re: 1996 DT140 (2 stroke), top two cylinders not working

too much fuel is just as bad as not enough fuel to the amount of air in a cylinder, either one will keep cylinder from firing off with spark plug.

I would tear apart carbs and clean them up and adjust like service manual calls for
 

capecodmfg

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Re: 1996 DT140 (2 stroke), top two cylinders not working

99yam40, I have swapped the carbs from the working cylinders to the non-working cylinders as I suspected this problem too. As with everything else I've switched, the problem remained in the top two cylinders and the bottom two worked great!
 

99yam40

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Re: 1996 DT140 (2 stroke), top two cylinders not working

A lot of carbs are not the same on the motor .
check your part numbers to make sure you can even try that.

You give no info , not just all is good.
All that is needed is good compression, spark, proper timing, and the proper fuel/air mix to fire the cylinder.
 

Fragamag

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Re: 1996 DT140 (2 stroke), top two cylinders not working

Sounds interesting. I think 99yam40 is on to something here. Could there be a linkage problem causing these carbs to choke or run rich?
 
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