DT140 EFI high rpm

[SeriouR]

I have done a shock treatment of ring free and then seafoam and it has made a difference. My compression on each cylinder is 120-125psi (used a new compression gauge as mine is inconsistent). The seafoam definitely made the most difference with black stuff coming from the exhaust when sitting in between treatments. Pretty sure this engine has never been decarbed its 520 hour life. It is definitely running better and no fouling of #4 spark plug.

I have another issue now which is #1 and #2 spark plugs fouling slightly and has an occasional miss on these two cylinders, mostly noticeable in neutral idle-2000rpm.

I have tested my magneto and was ok but decided to have a look at my flywheel magnets as i hear there can be problems with them. Well my magnets loot like something has gone through that area and damaged the magnets somewhat. I have now installed the flywheel/magneto from my spare motor. Still have the same miss issue. I have tested the pulser coil and gear tooth coil and they are good but will also order new ones as the sensing end on both was quite rusty.

Also what do the lubrication hoses on the EFI Dt115/140 models do as i checked the check valves and hoses which are good but there is no oil in the lines and i cannot see how it would get oil from the oil pump??

Nearly feel like something related to low rpm ignition is failed/failing. thinking of also changing out the ECM from my other motor but would be good to get any other ideas.

[Solarman]

No oil!! Not good! Those oil lines provide the only lubrication to the moving metal parts inside the motor.

You should be pre-mixing all fuel with oil (50:1) until all tubes are full of oil, and the oil pump, check valves, and everything else is working properly.

Any solvent type fluid (starting fluids/carb cleaners) used on a 2 stroke motors (ringfree?) may cause oils to be washed away where needed? Make sure they are safe for 2 stroke motors before using.

It is good that you found the flywheel magnet problem, those magnets coming loose can eat up stators.

It is good to run seafoam in every tank of fuel, especially if running ethanol fuels.

Check plugs, wires, and coils for possible problems on 1,2 plugs first off.

Good luck, post back on what you find out.

[SeriouR]

Just to be clear about the lubrication hoses its the ones in this diagram https://www.brownspoint.com/store/pc...il.asp?ID=6209

Where do they get an oil feed from as all the hoses go from the intake to piston skirts? I can see on my spare block the cylinder #4 hose starts at the intake by the oil pump and one from the bottom of the crank to the top but i cannot see how they get a oil feed. Is there an internal freed from the oil pump to the engine block by the oil pump drive shaft?

I have checked both spare engine I have and there is no oil present in these lubrication hoses (especially after the check valves).

My VST is receiving an oil feed, if i premix than i am just feeding the VST with oiled fuel instead of the system doing it.

For the miss fire i have changed plugs, coils and leads, flywheel, magneto. Checked all connections and resistance checked all of it, all of the old components and new components test fine.

I am not running ethanol fuel but I am running 98 octane fuel. The ring free is a yamalube product and also used yamalube combustion chamber cleaner which has lubrication in it. Sea foam is hard to get in New Zealand but I will get more and will run it and yamalube ring free for a while... that is if i can get this lube system working.

I also have a Clymer manual for this engine but feel it is not very informative on a lot of aspects of DT140EFI. I will try and get the Suzuki manual

Also i have a inlet air temp and manifold pressure sensor on my engine though the MAP sensor if not connected to the intake just sits above the throttle body. So they have them there but they are not used???

[Solarman]

That sensor above the throttle body, I believe is the ambient air sensor. Have never seen a MAP sensor on any 2 stroke Suzuki outboard yet.

The oil flow can be increased or decreased, but no adjustment between cylinders (per Suzuki service manual), but if doing anything with oil system, (premix - yes, it may smoke a bit, but safer than running dry?) the manual mentions marking the oil tank to make sure oil flow rate is good, before straight fuel.

Also, the manual mentions to pre-mix fuel if motor has been not run for a period of time/ a season or more.

Good luck, post back on what you do.

[SeriouR]

Yes the ambient air sensor is for atmospheric pressure, on the DT150-225 EFI it is plumbed into the intake manifold but essentially doing the same thing. The air temp sensor is right next to it and they both trim fuel pulse and timing.

I have cleaned the entire oiling system (beside pulling the pump) and found a faulty check valve on the lubrication hose that goes from the bottom to top crankshaft bearings. The other lubrication hoses in the diagram i posted above are scavenging post for fuel/air/oil mix. Would really like to find out if my lubrication hose from bottom to top crank bearings should have oil in it or if it is a scavenging line. The manual says it is a lubrication hose but i cannot understand how it get a feed from the pump. I bled the oil line to the VST tank as per manual and ran premix while running engine on muffs. Also ran premix for the first hour out on the water to ensure it was getting oil and then ran normal fuel for the rest of the day and noted oil usage on the side of the oil tank.

I have also adjusted my VST float as per the Suzuki manual as the Clymer manual i had only had setting for a different part numbered float. I have the VST tank too full by the looks so hopefully this helps my High RPM issue. I also checked the low pressure fuel pump again, clear check valves and diaphragm are all good. I have sent my injectors for cleaning a flow testing an they are due back this week.

Last time i went out (before all the work above) i installed a fuel flow sensor. My fuel flow at WOT 5800 RPM was 64 litres per hour (17 Gallons per hour) which seems a little on the high side. The boat is a 16ft fibreglass cabin boat with 80-100 litres of fuel on board and two people no extra gear. This is also with a 13 1/4 x 17 SS prop.

I have just also installed a new TVS sensor and set to Suzuki spec. The original sensor tested ok as per manual but i got a new one for a good price. My coil counter sensor tested fine too but was not able to get it to the 0.5mm away from ring gear on the flywheel so i have drilled the mounting holes (on the sensor) slightly to get it spec until i can replace it.

I will take the boat out next week and report on how it is going now.

[SeriouR]

Solarman have you ever had faulty/damaged reeds? I say this because the misfire i have been describing is actually more a backfire... pulled my spare power heads intake off and some of the flaps don't seem to seal as well as others. Seems like a bit of a mission to take intake off on the complete motor an really have to get gaskets before i check them. Seems like this would explain the lower RPM rough running/fuel consumption. A crank case leak down test would prove whether a reed is bad?

[Solarman]

Seriour, personally I have never had any reeds go bad. I have heard stories of reeds breaking and not sealing.

I also know that if you're using too much oil, between premix and oil injection, your going to experience some loss of rpms, and it may foul plugs quicker, and smoke more when running.

If reed valves aren't seating properly, it can affect both vacuum and pressure for that cylinder.

Good luck, post back on what you find.

[SeriouR]

So out of 8 injectors i got the best matched set of four with new filters/orings So far on muffs it is starting, idling great and holds the revs much much better below 2k rpm. It still has a small occasional backfire if you rev it up and then close the throttle. Do most two stroke do this when on muffs due to there being no back pressure in the exhaust as it is not submerged in water?

I have also done another seafoam shock treatment over a few days (running seafoam gas until warm then cutting air supply to fog it, leave it for the day and repeat). After leaving it i come back to a carbon oily sooty patch on the floor under prop each time. Have now run normal gas through to clear the seafoam gas out and changed plugs ready for a test run on the lake.

I am going to order reed gaskets and Boyesen reed kit and change them just to ensure reeds are 100%.

I think the main part of my issue was incorrectly set float level in the VST tank and dirty injectors but also lubrication hose check valve and TVS sensor was set to .9VDC instead of .73VDC on closed throttle. With the TVS set to .9VDC did make it run better (it did try set it to .73VDC as per manual but ran terrible) with these other issues but I feel with these resolved the original TVS was still not 100%. The resistance scale of the original TVS was 500 ohm - 4900ohm where as the new one is 300 ohm to 5000 even though the TVS does not use the lower and higher end of its scale when installed.

I think my cutting out issue at High RPM was due to the float being set too high which would mean a higher fuel level in the VST tank and was possibly not letting the pressure regulator work correctly (pressure regulator return to VST was submerged in fuel rather than being above the fuel level in the VST).

I will report back after this coming weekend with how it ran and fuel consumption.

Does anybody have/know where to get or how to replace the flywheel magnets? I have another motor which is virtually complete besides flywheel and cowling. These motors seem to be common in UK and US with examples still in good condition whereas in New Zealand they seen to all be badly maintained and corroded.

[SeriouR]

Done a 3 hour test run on Lake Rotorua today. Motor ran great. No cutting out at high RPM, smokes less on initial start and restart after stopping for a short while. More power down low, smoother idle and low rpm.

Need to adjust idle to be at 650 RPM when in gear at idle as it is set too low currently.

Need to raise motor up as at 5000+ rpm the motor is trimmed to full height. Hopefully this will bring down the fuel consumption.