1987 dt115 firing issue,only half throttle

[igotit]

I am fixing up a 1987 suzuki dt115,motor satup for 10 years.previous owner says it lost power and his boat wouldnt plane out.....so it sat there till i recieved it.
I rebuilt the carbs,changed waterpump and driveshaft bearing housing.
Ignition switch was faulty....new ignition switch.
First fire up she ran great on land,after 30 mins of running max outside cylinder temp reached 128 f.
Put the boat in the water and she wont plane out,ran great below 1/3 throttle.past 1/3 throttle she starts missing and bogging.
Ive ruled out fuel being the issue,if i apply any amount of choke she will lose more rpms and die from flooding.
Electronic parts are pricey for this ol zuki.
So before i start throwing parts at her.....does anyone have any information on testing the sensors?
I tried unplugging temp,tps,and oil sensor.....no change in performance.
Compression is around 140 psi on all 4 cylinders.
All plugs fire.
Thanx for any insight......advise.

Im leaning towards throttle position sensor,ir cdi unit.tps tells cdi how much advance timming to send engine.

 

[robert graham]

Maybe some debris from the fuel delivery system(tank, lines,etc.) has plugged a carb jet again since you cleaned them.....carefully check on motor fuel filter, drain each carb float chamber onto a clean white rag to inspect for debris. Does your motor have a fuel/water seperator type cartridge filter?

 

[igotit]

I run a raccor filter,flushed the fuel system again a few hours ago.also rebuilt the carbs today.
Previously i had cleaned them.
Still the same problem.
Carbs are pretty spotless,jets are clear,i set mixture needles at 1.5 turns on all 4 carbs.
Not sure where needles should be.

 

[ondarvr]

Put a timing light on each plug wire and see if it's firing on all cylinders when it's acting up.

 

[igotit]

Thats my plan soon
Timming light on all 4s
Thanx
Also going to clean tps and try again

 

[igotit]

Ran the timming light,cyl 1&2 arent firing.i swapped 3&4 coils with 1&2 still not firing.
I removed tps and manually operated by hand and rpm/timming advances while running but still no fire on 1&2.
So at this point ive ruled out the coils,and tps operation.
So im assuming the cdi unit is the culprit. Not sending signal to cyl 1&2.cyl 2 gets fire every now and then.
So if anyone has any other diagnoses.....guess im shopping for a cdi unit.

Thanx

 

[99yam40]

need to find out what signals the cdi to fire those cylinders,and check that input to the CDI

 

[igotit]

I may be mistaken,but theres 4 sensors around the fly that signals the cdi to fire the coils,and controls the firing order.
Ill try swapping those around to see if my condition changes.

Edit

Pulser coil

http://www.brownspoint.com/store/pc/BP_AP_AssemblyDetail.asp?ID=6161

 

[igotit]

Swapped around all 4 pulsator coils,still not getting fire to 1&2 cylinders.
My understanding the 4 pulsator coils are the timming and firing order,each pulsator when activated tell the cdi to ignite the coils in firing order.

 

[99yam40]

measuring the voltages is a better way to make sure the proper signal is getting to the CDI

 

[igotit]

Even if i measure the voltage,i swapped 3&4 pulsator coils with 1&2 pulsator coils.
We know that 3&4 is working properly because thats my only 2 firing cylinders keeping my motor running with an occasional 2 firing whenever it feels like it.
Ontop of that.....what is the signal supposed to be in volts.
Its bassicaly a charge coil the as the fly makes its way around and activate each pulsator its on a milisecond spike.
My meter wouldnt register voltage when i turned the cylinder over.it would flicker a number that was gone before i could reconize it.
As i said if pulsator for 1&2 werent up to par then after the swap my issue would have now been 3&4 no fire issue with 1&2 now getting fire.
But that wasnt the case.
Still 1&2 no fire.
Thanx

 

[99yam40]

so is the wiring and connections between the CDI and puler coils OK?
DVA adapter and DMV will usually get the readings needed. but I have never worked on a DT so not much help
Get the service manual and the proper test equipment ,if you want to test properly.

or throw parts at it until you find the problem

 

[igotit]

I agree,i need to get the proper test equipment.
But funds are limited.
Im bankrupt,fixing the motor my 70 year uncle who is also a financialy challenged commercial fisherman.
Dva adapter is $30-40.....ill have to work on that.
All wiring is in good shape,ohmed out great.
I dont wanna throw parts at it.....purpose of this thread.
My local suzuki shop wont touch it,its too old and they cant plug into it.
Thanx

 

[99yam40]

you can make a DVA yourself,
do some searching on line.
the proper capacitor was the hardest thing for me to find

 

[igotit]

Ill look into it,thanx

 

[igotit]

Update
Ive bought a used electronics set from a 88 115 for $400,swapped the power pack and she runs and gets up ontop like she should.
But the idle up know isnt working,ill arrange time to diagnose and swap it out.
Thanx for the help guys.