2011 DT30 overheat when on the plane

[Smiley]

Hi folks

I would be grateful for some help and guidance problem solving a 2011 Suzuki dt30 that appears to be overheating when at high speed only.

I noticed it last week when suddenly I slowed off the plane to a stop and a lot of steam was coming out of the exhaust relief port. I have never noticed before. I also noticed the water flow out of the relief port seemed to be lower than usual and the tell tale flow was flickering. When I come off the the plane the water that comes out of the exhaust relief valve is extremely hot, not quite scolding but close to it. This water quickly cools to be just warm, obviously as the head is cooling.

Upon subsequent tests at high speed the temperature of the head and exhaust plate got too hot to keep my hand on. Is this usual for the head and exhaust plate to get this hot? When I slowed down and the water started flowing out the exhaust port again, the head and exhaust plate quickly cooled down to luke warm.

When idling the water flow out of the tell tale is good and there is plenty of water flow out of the exhaust relief port.

I checked the thermostat to surprisingly find it missing. The previous owner must have discarded it. Local Suzuki dealer says it is common to remove it on the dt25/30 and not surprising.

I replaced the impeller with a full rebuild kit (wearplate, housing trim, gasket, impeller, etc) hoping this would fix it, but my gut feeling was correct, the problem remains. However the water flow at idle and low revs appeared to be a bit stronger.

When I rev the engine to full revs in neutral, the water flow appears to be good out of both the telltale and the exhaust relief port. The problem only occurs when at high speed.

I am worried I am overheating the engine and will cause damage.

I have ordered a compression tester to be delivered in the next few days to test the head compression.

Has anyone else experienced this problem or similar before and can point me in the right direction to resolve this?

I suspect I am going to have to pull the head and exhaust plate off to inspect for salt build up and gasket failures.

Thankyou

[Solarman]

You are probably experiencing a problem of exhaust/ or compression pressures at higher rpms interfering with water flow, either before the water pump, or before the cylinders. Check the spark plugs to see if any moisture is getting into any cylinders? Check compression to see if any cylinders are lower than the others (maybe compression is blowing back into water pas-sages?).
Look for damaged/ loose fitting grommets, damaged aluminum webbing (separating exhaust chamber from water pump chamber), leaking exhaust plate (allowing exhaust into water pas-sage), and leaking head gasket, as mentioned above.

Post back when able to let us know what you find out. The sooner you can find the problem the less damage you will have. If water is getting to plugs, it can cause rust to form quickly.

[Smiley]

Hi solarman, thankyou for the prompt reply, what great support from this suzuki community. I hope i can contribute a return of value to others in need of help on the forum in the future.

I did a compression test which indicated each cylinder is 110 & 113 psi.

Would this rule out the head gasket?

In respect to the spark plugs, i am a bit inexperienced to know what to look for in respect to water ingress due to most 2stroke experience on aircooled engines.

The spark plugs look ok and as if the engine is running slightly rich which i suspect is due to me purposely mixing more oil in the fuel at 75:1 ratio rather than 100:1. The porcelin is amber to dark, with slight traces oil.
If water was getting in to the spark plugs, would they be clean or oiley wet?

I will pull the lower leg off today to inspect the other items you suggested and will post back what i find.

Thanks again

[Smiley]

Hi solarman

Thankyou for your quick reply. I did post a reply the day following your post but it hasn't displayed, so I have retyped another one.

I did a compression check and both cylinders came up at 115 psi. Would I be right in assuming this cancels out the head gasket being a cause to the problem?

The spark plugs don't appear to have any water signs.

I have what may appear to be a silly question regarding the 3 holes on the front of the mid section of the leg, is a lot of water meant to flow out of the 2 lower holes when idling and high revs? The holes are in the section of leg where the shaft extends up to the engine. I don't recall ever seeing a steady water flow out of these holes before. If water is not meant to pump out of these holes, could this indicate a contributor to the problem for further investigation?

I also noticed some of the exhaust plate bolts seemed a bit loose, could this contribute to exhaust back pressure at high speed reducing water flow?

Unfortunately, when loosening and testing each bolt, one broke which now leaks water when the engine runs, so I have to remove the exhaust plate afterall. Will do a thorough clean and replace all gaskets.

Thankyou