Suzuki DT 85

keelhauled · 03 August 2007, 15:49

Hi all
I'm in trouble again. I have a Suzuki DT 85 with low hours. About once in every 10 trips this motor lets me down. I installed a new fuel filter and thought that solved the situation. It always starts easy enough but about a mile out loses power and will limp home at about 5 knots with throttle wide open. Dont tell me its a fuel line or bulb or get it serviced as the local outboard shop says its a little too old (15 yrs) and dont want to know. Problems its not 1. Prop seizing 2. Fuel line/ bulb 3.Spark plugs 4. Controls or cables. what can it be??? Advice gratefully accepted.

ribfan · 03 August 2007, 17:17

Just a shot in the dark, but years ago I had a similar problem with a 90 hp Mariner. It turned out to be that the fuel pump needed a rebuild. The blended fuel over time damaged the rubber parts of the pump. I bought a rebuild kit, did the work myself, and all was fine. Hope this helps.

Bill

www.eclecticwonders.com uncommon art

keelhauled · 03 August 2007, 18:39

Thanks ribfan I had the fuel pump off and the diaphram and the rest seem Ok but I will get it looked at by a mechanic as it seems that it will be something like that. I have to start the motor with half revs on the throttle and then have to get it into gear without it conking out.

Nos4r2 · 03 August 2007, 22:28

That sounds like the idle jets might be blocked or you've got water in the carbs.

keelhauled · 04 August 2007, 06:55

Thanks nos4rtu that was my number one suspicion it this a DIY fix or a trip to the mechanics???

David G · 05 August 2007, 19:09

Hi,
I have a 1990 Suzuki DT85 and may have experienced the same problem that you describe.

There are still, perhaps, many things that it could be but one fault I had which produced a similar(ish) issue as you describe was a problem with the throttle position sensor attached to Carb2.

For some reason Suzuki made this out of plastic and it got roughened up and would stick.

This sensor tells the CDI about changes to required engine timing advance with physical throttle position.

If you strip it all down and clean it up then it may help you out.

Could of course be something completely different....do you get any alarms when you experience the slow-running? Can you check for dropped cylinder when it starts to run bad? The venting on the fuel tank isnt blocked is it, restricting air replacing burnt fuel in the tank?

Regards,

Orve

David G · 05 August 2007, 19:47

Oh, and another thing; I've had quite a lot of success using data gleaned from here:

www.themarinedoctor.com

if not directly related to the DT85 from other engine forums.

Regards,

Orve.

keelhauled · 05 August 2007, 20:38

Orville
Thanks for your input. Where is this plastic thingy?? I had the RIB out today and no sign of engine trouble. Still as a diver you will realise that the last thing you want to worry about after a deep dive is the fact that your motor might not start.

ps. the only alarm i've ever got is when the engine ticks over for a while and sems to backfire and a whistle seems to come from the engine

David G · 05 August 2007, 20:58

Well, mine is a 1990 and on this diagram it is item 19 attached to the back of Carb 2.

You can strip it down.

http://store.brownspoint.com/DT85/fig005-858800.asp

If your engine is a little younger and you have the serial number to hand then you can get the right parts diagram here:

http://store.brownspoint.com/dt85.asp

Regards,

Orve.

Nasher · 05 August 2007, 21:03

Could the engine be going into Limp Home mode?

The Sender for the 2-stroke oil level on these engines is prone to failure fooling the system into thinking there is only a limited amout of oil in the tank.
The ECU then drops the max revs down to 2500.

In the past I've hard wired the plug for two of these sensors into 'Full' mode when they gave up the ghost. They are a brass tube with simple array of reed switches activated by a magnet on a float in the tank. Cutting the plug off the sensor and looping the wires together is easy to figure out if you open up the sensor to see which wire goes to the top reed switch.
Both I opened up were a mess inside after moisture had got in.

Suzuki reccomend they are changed as a service part every other year, only they are a couple of hundred quid each.

On the other hand its probably something completly different.

Nasher

David G · 05 August 2007, 22:02

Quote:

Originally Posted by Nasher

Could the engine be going into Limp Home mode?

The Sender for the 2-stroke oil level on these engines is prone to failure fooling the system into thinking there is only a limited amout of oil in the tank.
The ECU then drops the max revs down to 2500.

In the past I've hard wired the plug for two of these sensors into 'Full' mode when they gave up the ghost. They are a brass tube with simple array of reed switches activated by a magnet on a float in the tank. Cutting the plug off the sensor and looping the wires together is easy to figure out if you open up the sensor to see which wire goes to the top reed switch.
Both I opened up were a mess inside after moisture had got in.

Suzuki reccomend they are changed as a service part every other year, only they are a couple of hundred quid each.

On the other hand its probably something completly different.

Nasher

This would be accompanied by an oil alarm would it not? (just for future reference as this part has never been changed on my Suzi !!!)

and no oil level lights up the middle of the multi-function guage?

Orve.

Nasher · 05 August 2007, 22:50

It would, but not everyone has the multipurpose gauge fitted.

Was just trying to give another possibility.

Nasher.

Bulligmore · 05 August 2007, 23:29

I would say it is dirt in your fuel tank or dirt in you carb. I had this problem before and changed the filter but did not clean the tank, it was not till I cleaned tank changed filter and cleaned carbs that all was well.

The alarm should sound if it was an oil problem and if it does not I think the engine will stop. A compression test also would be worth while.

Needing to use the throtle and quickly shift it to gear would mean a fuel or timing problem not oil.

I would say your carb has dirt in it and you have dirt in your tank which is re-infecting the system. If you can see anything in your tank it is to much.

Downhilldai · 06 August 2007, 00:13

DT85 also has a gauze filter in the oil line. If this gets gummed up and impedes the oil flow, it will put the motor into 'safe' mode, limiting the rpm to 2500/3000. Should also get a warning buzzer with this fault though.
Another common(ish) problem is the float switch which senses that water has reached the cylinder block, but this again should also sound the warning buzzer.

keelhauled · 06 August 2007, 06:38

Thanks Nasher, Downhilldai, Bulligmore and the rest of you guys I'll follow up all this advice and keep you posted. If this dont work someone will be getting a mooring block.

keelhauled · 09 August 2007, 20:16

The cowl on the motor does not fit 100% due to falls etc. I noticed a small amount of water might have been able to get in under the cover in a following sea or when I pulled up suddenly. Could an ill fitting cover allow the engine to suck up water? I've used an old diving trick of using a three inch strip of inner tube across the joint till I get a better fitting cover. Last three trips went without incident but my confidence in the motor is not good. I keep the aux in prime condition knowing I'll surely need it soon. Thanks again to everyone who contributed a comment.

David G · 10 August 2007, 08:23

Quote:

Originally Posted by keelhauled

If this dont work someone will be getting a mooring block.

I hope you manage to sort the problem and gain some confidence in the unit.

Don't turn it into a mooring block though, I'd posssibly like to take it off your hands instead if you decide to get rid of it

Cheers,

Orve

keelhauled · 02 September 2007, 06:27

Finally sorted. It went to shop for a service and the mechanic said that a service would sort out prob 99% of time. Picked up on a Friday and with great anticipation launched on Saturday morning. I had rounded the harbour wall when it started to splutter again. SH$T. Limp home AGAIN. Look under the hood everything seems in order. I notice that the bottom plug cap is slightly loose on the threaded plug. A close look shows that cap is completely corroded inside. Up to the chandlers and 3 new plug caps. She starts up smoother than ever and is now running sweet as a nut. So thanks again to you all and sometimes its the simple things that get you back on the water. Also after paying €150 for a service I would have thought a mechanic would have spotted faulty plug cap.