95 suzuki dt225 dropping a cylinder at lower rpm??

[stratos20]

Its an EFI outboard and I noticed the other day while leaving the ramp that it was running rough and shaking a bit at idle speed all the way up to 2000rpms after that it was pretty smooth and running perfectly fine. It feels like its dropping a cylinder or 2 at lower rpms. Is this normal on this motor? I've heard about the Yamahas doing it to save fuel at low rpms. Any help will be greatly appreciated thanks.

[Solarman]

In 95 these features weren't done on outboards. Heck, they were just a few years into EFI systems.

So, it appears you might have a plug or two failing at lower rpms. When did this begin, and how long since new plugs were installed? Or possibly an injector or two is acting up at those rpms?

Gear counting coil, TVS/TPS, pulse sensors, spark Plug coils, ECM, and magneto are some other things that can act up if going out, but like injectors, all can be very pricy.

Some of these items will cause your monitor Guage light to flash. If Getting a code, look up in your manual what the two sets of flashes indicate. This could help.

Post back when able. Good luck.

[stratos20]

In 95 these features weren't done on outboards. Heck, they were just a few years into EFI systems.

So, it appears you might have a plug or two failing at lower rpms. When did this begin, and how long since new plugs were installed? Or possibly an injector or two is acting up at those rpms?

Gear counting coil, TVS/TPS, pulse sensors, spark Plug coils, ECM, and magneto are some other things that can act up if going out, but like injectors, all can be very pricy.

Some of these items will cause your monitor Guage light to flash. If Getting a code, look up in your manual what the two sets of flashes indicate. This could help.

Post back when able. Good luck.

Installed new plugs about 4-5 months ago and injectors were cleaned and flow tested by a pro around the same time. I haven't seen any lights flashing or any codes thrown. The motor starts and runs fine, idles ok I think but it does shake a bit at idle and it feels like a cylinder is not firing. I will pull plugs check them out and report back. Another thing is I have never decarbed the motor and I have no idea if the previous owner ever did, should I go ahead and try the Dunk's decarb method to see if it helps?

[Solarman]

Haven't heard of dunks method? But if you have high compression differences between cylinders, then that might help if rings are sticking?

If you have access to a clip-on timing light, you can compare the flashes between each cylinder, and see if all are flashing equally. If one or more are missing, it might help identify where to look?

Have you purchased fuel from different vendor, that might be less than good? Just a thought.

If the timing light shows any difference, note the cylinder(s), then rotate the plugs around, if no difference, then what coil fires that plug(s)? The manual can be helpful for testing coils and sensors mentioned in previous post.

Good luck, post back if you find anything

[seaox230c]

you need to absolutely verify which plugs are not firing. This can be done with a timing light fairly easily. If your plug wires have the plastic sheath over them...you must peel them back or clip the pick up only on bare rubber or it will give poor readings. Once you verify how many plugs are missing....we can proceed

[stratos20]

How do I check which plugs are not firing with a timing light, I have never done it? I could pick up a cheap one at harbor freight If I need to. I was told to unplug one plug wire at a time while motor is running to see if it makes a difference or is the timing light method a better option?

[seaox230c]

I guess a cheap one will work but a good one from sears might save you time and money in the end...but....you hook up the wires with the battery clips to the battery then the last wire has an end connector with a small square cutout. The spark plug wire fits in that cutout . The wire must be the bare rubber spark plug wire with no plastic sheathing around it where it sits in the cutout...then just start the motor and squeeze the trigger. a good firing plug will consistently and steadily flash the light with no odd misses or blanks. The freq of flashing depends on rpm but it will be obvious which plugs are not firing properly. If they all fire good then its a fuel issue

[stratos20]

Pulled the plugs today and it seems that the bottom port side cylinder is not firing.

[seaox230c]

Remember this is a 2 stroke and the plugs will appear wet even when working...if you want to make sure...get an extra plug and remove 1 plug lead...connect it to your extra plug and then use a good sized alligator clip and connect it from the threads or hex and attach the other side to a good known ground...if the plug sparks then the coil is working...If not then get a replacement coil or swap with another one and do the test over. do the extra plug test on a known good coil to see what it looks like. there is no computer driven fault that will only take out one coil and if the coil is bad then it shouldn't fix itself at higher rpm's

[Solarman]

It's also possible to get a bad plug when you bought the new plugs.

Good luck.

[stratos20]

Well I checked the plug coils with a timing light and they all had spark. I will go ahead and do a decarb and install new plugs to see if it helps and report back thanks.