86 suzuki dt40 acceleration problem

[iblly]

I have an 86 suzuki dt 40 with a jet drive. If I crack the throttle to wide open it accelerates fine from the start then stops accelerating at what seems to be about half throttle, if I leave the throttle wide open it will hit full throttle about a minute later. It does the same thing if I try accelerating slowly, just seems to stop reving up half way even with throttle wide open. Then Bam, it's wide open !
Starts first pull and idles like a dream, when it decides to hit full throttle it also runs like a dream. Just seems to be that dead zone between idle and wide open.
The problem is worse with carb cover and engine cover on ? Takes less time to rev up with covers off ! Air issue ?
Carb is rebuilt, fuel pump rebuilt, all fuel lines are clear. While looking into carb during the dead zone there appears to be lots of fuel going into carb and lots of fuel moving through the filter. Also new fuel filter.
Also, oil injection has been removed. Any ideas ?
Pilot air screw, how many turns out from seated ? Pilot jet, doesn't seem to be adjustable. Is it ?

 

[waffles1]

Re: 86 suzuki dt40 acceleration problem

I can look up the settings for your air screws in my manual but I believe it's around 11/2 turns out from lightly seated. The other jets are fixed and not adjustable. Have you checked the throttle cable to make sure that when you open the throttle up that the carb lever is opening wot too? Just wondering if maybe soemthing is getting stuck and just takes a bit to free up. You could check that in the driveway. It doesn't really sound like a vent issue on your tank but you may look at it, too. Check your plugs and see if you are getting strong spark and make sure they all look about the same. Do you have any misses during all this? Does the engine have any odd noises like a "sneezing" or backfire?

 

[iblly]

Re: 86 suzuki dt40 acceleration problem

No throttle cable or carb lever problems, every thing opening fine. Plugs look good. No odd noises, as I said it idles like a dream and when it's running wide open it's smooth as silk as well.

 

[iblly]

Re: 86 suzuki dt40 acceleration problem

I have an 86 suzuki dt 40 with a jet drive. If I crack the throttle to wide open it accelerates fine from the start then stops accelerating at what seems to be about half throttle, if I leave the throttle wide open it will hit full throttle about a minute later. It does the same thing if I try accelerating slowly, just seems to stop reving up half way even with throttle wide open. Then Bam, it's wide open !
Starts first pull and idles like a dream, when it decides to hit full throttle it also runs like a dream. Just seems to be that dead zone between idle and wide open.
The problem is worse with carb cover and engine cover on ? Takes less time to rev up with covers off ! Air issue ?
Carb is rebuilt, fuel pump rebuilt, all fuel lines are clear. While looking into carb during the dead zone there appears to be lots of fuel going into carb and lots of fuel moving through the filter. Also new fuel filter.
Also, oil injection has been removed. Any ideas ?
Pilot air screw, how many turns out from seated ? Pilot jet, doesn't seem to be adjustable. Is it ?

Anyone with ideas ?

 

[bullelkklr]

Re: 86 suzuki dt40 acceleration problem

Is your oil reservoir full? The dt40 has a safety check that will cut the rpm to about 3k if you get low on 2 cycle oil....not sure about it going to WOT after a lag time though.....

 

[99yam40]

Re: 86 suzuki dt40 acceleration problem

"The problem is worse with carb cover and engine cover on ? Takes less time to rev up with covers off ! Air issue ?"

almost sounds like it is running too rich if more air helps( less air restriction)

Has someone played with the jets trying to get more HP out of it by drilling out for more fuel?

 

[Yepblaze]

Re: 86 suzuki dt40 acceleration problem

I've seen more than one 80's Suzuki losing their foam hood liner in little bits that enter float bowl vents, and lodge/dislodge in main jets at will.