Suzuki Mystery

[1irishprince]

I have twin 2000 DT140's with EFI. I cant get one of my engines to WOT. I have changed the water seperators, fuel filters, spark plugs, ran sea foam and injector cleaner in a seperate 5 gallon gas can to eliminate any fuel tank issues, checked compression( gave very similar readings to the good running engine), tested TVS, changed gear count coils on both engines. I am pretty good with engines, but these are the first 2 strokes I have ever worked on, so I am still trying to understand the theory of 2 strokes. Throttle is not as responsive either. I can be cruising at 4000 rpms and I can quickly bury the throttle on each engine one at a time and the good engine will immediately go 5000+ but the other engine has a hard time just getting above 4500. I get a similar response while I am in the driveway reving the engines. The good (port) has a good throttle response, but the (stbd) engineis slower to respond. I am at my wits end to the point I am almost ready to take it into the shop, but I have tried everything the shop has told me to check. When I am coming in after a day of trolling and coming through the pass with the rest of the pack, I sometimes like to beat everyone back to the launch so I am not waiting in a long line. So I go to WOT and the stbd engine wants to start stumbling to the point I have to use two hands to adjust the throttle levers because they are so far apart and looses enough power that I am going slower than I was before I throttled up. How embarrassing!
I do notice a strange knocking feeling when I rev the engine at home. I can feel it when I use my hand to push the throttle on the Throttle body. I can only "feel" this "knock" at the point where the + rpms turn into -rpms when I am reving the engine. This is not an audible sound or at least I cant hear it. I dont know if this is a sign of a bad reed valve or what, but the other engine does not do that.

 

[99yam40]

Re: Suzuki Mystery

Monitor fuel pressures and timing at problem RPM on both motors.
That should show you if they are a problem.
If all that is good then I would send off injectors to have them tested and cleaned

 

[1irishprince]

Re: Suzuki Mystery

Fuel pressure is within 1# of what the books says it should be. 38 psi through the whole rpm range and 28-29 psi static after engine is turned off. The engine idles really well and the injectors sound like they are operating correctly, but thats just what I can hear. BTW, it also consumes a little more oil than the other engine. There is always a dark black oil that I see running down the skeg the day following an outing. Dont know if that would have anything to do with it either. That "CLUNK" I feel when my hand is on the engine revving it though has me concerned....but yes, the fuel injectores are the next in line as far as ruling them out....

 

[1irishprince]

Re: Suzuki Mystery

as far as timing goes, I dont know yet how to adjust or tell if the base timing is correct. Its a 2000 model so the ECU is supposed to control the timing.

 

[99yam40]

Re: Suzuki Mystery

hook up a timing light to see what it is doing, just to rule it out if it is in spec.

Sounds like you are dumping too much fuel maybe and causing one or more cylinders not to fire properly or you are loosing spark to some.

That would cause the unburned fuel/oil black stuff down the leg

 

[robert graham]

Re: Suzuki Mystery

Have your fuel injectors ever been removed and cleaned previously?

 

[1irishprince]

Re: Suzuki Mystery

The injectores was next on my list. Just wondering if I am looking at one problem or two. I dont think that clunk is supposed to be there and the injectors wouldnt cause that but I will go through the injectors anyways just to rule them out. Would a malfunctioning reed be a cause if not the injectors? Do all malfunctioning reeds act the same? It is good to have 2 engines so I have something to compare to, but for everything I replace on one, I usually do to the other as a rule of thumb....What sets the base timing on this engine? I know how to rotate a distributor on a car(older) to change timing, but how would you know if your timing is advancing correctly if you didnt have another identical engine to compare it to?

 

[99yam40]

Re: Suzuki Mystery

On the timing you would look in the manual and see what the specs are and then check the timing with a light like I said before to see if they are in spec.

Maybe your clunk it a miss fire or lean sneeze, I do not think reeds will make a clunk

 

[1irishprince]

Re: Suzuki Mystery

On the timing you would look in the manual and see what the specs are and then check the timing with a light like I said before to see if they are in spec.

Maybe your clunk it a miss fire or lean sneeze, I do not think reeds will make a clunk

I will check timing tomorrow. Says for 2000 model is 0degrees @ 850 rpm idle +/-50 rpm to 26 degrees BTDC. If base timing is off, how would I adjust it. There is nothing that I see for mechanical adjustment. Also, I dont think this engine has a seperate ignition circuit for high rpm and low rpm as i heard they used to...

 

[stylesabu]

Re: Suzuki Mystery

since you have 2 of the same motors,switch parts one at a time,i would start with injectors. this should help isolate or eliminate parts. good luck. it does sound like you are running rich on the port side, the black streak

 

[1irishprince]

Re: Suzuki Mystery

Have your fuel injectors ever been removed and cleaned previously?

Took them out, they look brand new to be 11 years old

 

[1Crazymechanic]

Re: Suzuki Mystery

The injectors could still be clogged. There is a company called Correctinject, they can clean them like new and give you a report on how they tested!. Try spraying a small amt of fuel into throttle bodies one at a time when stumbling is happening,if you pick up rpm, its probably dirty injector for that
cyl. Ignition timing and fuel injection duration on this engine are controlled by ecu. There is nothing really to adjust, it uses sensors to adjust
timing/fuel. Potentially intermittent throttle position sensor(just throwing that out there).

 

[1irishprince]

Re: Suzuki Mystery

I dont know that it would be very safe for the engine as the stumble doesnt start to occur until rpms reach 4700-4800. I guess the very least I would need is a remote tach, not to mention that is without a load. I only have one throttle body, so I dont understand what you mean by 'one at a time'. I didnt think there was...nothing in the service manual says anything about how to set base timing so I believe its a fixed point to where the magneto asm is installed. I guess I will have to eliminate both one at a time. I already have the four out on the stbd engine...I guess I can either switch the TPS sensors out then the injectors to see. Then if either of those ideas dont work I'll be back to square one.
That clunk still has me wondering. Hell, that black oil sludge draining down the skeg the day after running all day has always had me wondering. Just on a side note, would too much oil injection cause this problem as well? Spark plugs leave no evidence of this, but I dont run at WOT very often...only for a short time to blow the cob webs out. This engine is just riddled with all these oil lines and they all have their own inline check valves. The picture below is just for one cylinder...hoses 7, 8, 9 each have their own tees and check valves...
View attachment 120926

After really looking through this service manual, I see 90% of the engine is the crap on the outside of it. Very few moving parts on the inside. I guess thats a plus for 2 strokes...

 

[1irishprince]

Re: Suzuki Mystery

just replaced throttle sensor last night...going to see if that was the issue. When I took it off and ohm tested it, it had an open in it @ WOT. Going to take it out today to see if that fixed it