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Old 03 August 2007, 11:49   #1
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Suzuki DT 85

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.
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Old 03 August 2007, 13:17   #2
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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.

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Old 03 August 2007, 14:39   #3
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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.
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Old 03 August 2007, 18:28   #4
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That sounds like the idle jets might be blocked or you've got water in the carbs.
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Old 04 August 2007, 02:55   #5
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Thanks nos4rtu that was my number one suspicion it this a DIY fix or a trip to the mechanics???
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Old 05 August 2007, 15:09   #6
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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
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Old 05 August 2007, 15:47   #7
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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.
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Old 05 August 2007, 16:38   #8
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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
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Old 05 August 2007, 16:58   #9
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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.
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Old 05 August 2007, 17:03   #10
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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
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