Suzuki DT25 1984 oily spark plugs running problems

[Jimnorman]

Hi I hope someone can help I have a DT25 1984 model which is not throttling properly in or out of gear makes the plugs oily and dribbles oil from the exhaust port.

I have tried cleaning carb, replacing plugs (resistive type), checking fuel pump and fuel filter, have the mixture valve 1 1/2 turns out from fully in (soft position), all of which have had no effect.
There is combustion pressure when pull start is pulled which feels pretty even but I have not measured this.

The engine will tick over and will run but feels bogged down like it is misfiring.

Any help would be appreciated

 

[waffles1]

Re: Suzuki DT25 1984 oily spark plugs running problems

Do a compression check and give the results.

 

[Jimnorman]

Re: Suzuki DT25 1984 oily spark plugs running problems

Hi thanks for your interest and sorry for the delayed reply but I had to source a pressure gauge.

Both plug ports give a reading of 100psi

The measurement was made pulling the recoil starter as quick as possible I hope this is correct.

Jim

 

[waffles1]

Re: Suzuki DT25 1984 oily spark plugs running problems

Are you using oil injector or premix?

 

[Jimnorman]

Re: Suzuki DT25 1984 oily spark plugs running problems

I am using premixed

 

[Jimnorman]

Re: Suzuki DT25 1984 oily spark plugs running problems

I have mixed at a 50-1 ratio 340ml to 17 litres.

 

[James R]

Re: Suzuki DT25 1984 oily spark plugs running problems

When was the carb last removed and cleaned. Sounds like the needle valve is sticking or the float is incorrectly set.

 

[Jimnorman]

Re: Suzuki DT25 1984 oily spark plugs running problems

Hello thanks for your post.
The carb has been removed last week and looked very clean float hangs horizontal when carb is upside down and needle valve appeared to be operating ok.
I have adjusted the air/fuel mixture screw and it does seem a little better but still not right and still quite a run of oil from exhaust?

Jim

 

[James R]

Re: Suzuki DT25 1984 oily spark plugs running problems

Not good enough old chap. The carb must be dismantled and cleaned thoroughly. Spray cleaners are a no no. They can do damage. Strip the carb and soak the parts in Gunk Parts and Carb cleaner, available at Advance Auto. Follow the instructions on the can. all the carbs I do are done this way. This cleaner will not damage plastic parts.
Replace the needle valve and gaskets.Good regulated fuel flow and lubrication is the life blood of the internal combustion engine.

 

[Jimnorman]

Re: Suzuki DT25 1984 oily spark plugs running problems

Hi
Thanks for your response.
The carb has now been dismantled and cleaned as suggested and is spotless.
I am still having the same problems oil running from exhaust port, more than I would expect (like a paint run) and lumpy running (struggling to throttle) I hope you may have some other ideas I could try.
Cheers

Jim

 

[James R]

Re: Suzuki DT25 1984 oily spark plugs running problems

Sounds like one cylinder is not running. That would account for the oil and for the lumpy running. Clean the plugs and try running it. With it running pull each plug wire off in turn and see what it does. If one wire pulled makes no difference then that cylinder is in question.
Could be a plug but you can check that by switching the plugs around. Then we could get into coils, switch box, stator and trigger.
First confirm that the spark is good or bad. Pull both plugs and ground them to the motor case. I use a piece of household copper ground wire fastened under a bolt on the engine block. Wrap the copper wire around the plugs threaded portion to make a good connection. Turn the motor over and look for the spark at each plug.

 

[Jimnorman]

Re: Suzuki DT25 1984 oily spark plugs running problems

Hi thanks very much for your post I think having tried everything else it probably is an electrical problem.
Both spark plugs are fine the both spark and are brand new as were the previous pair can you advise how to check the other points you suggest please.
Thanks again
Jim

 

[James R]

Re: Suzuki DT25 1984 oily spark plugs running problems

Sorry for the delayed response.
Did you try running the motor and pulling each plug wire in turn from each cylinder to see if there is a change in rpm.
It is rare that the Suzuki ignition systems have a problem but using a spark tester will provide a better evaluation of the spark than the plug test. The spark should be able to jump a 1/2 inch gap.