Flywheel Out Of Balance And Noisy

[codszilla]

Hey all,

Just yestrday i was doing around 3000 rpm (suzuki dt85 95 model) when the outboard suddenly made a strange noise . I pulled the cowling off and noticed the flywheel moving unevenly and also noticed large amounts of air bubbles which were coming out of the water intake holes on the leg! I hope someone is aware what these symptoms mean , the motor has been so good otherwise i really hope its not as serious and expensive fix...

[Shark Bait]

Hey all,

Just yestrday i was doing around 3000 rpm (suzuki dt85 95 model) when the outboard suddenly made a strange noise . I pulled the cowling off and noticed the flywheel moving unevenly and also noticed large amounts of air bubbles which were coming out of the water intake holes on the leg! I hope someone is aware what these symptoms mean , the motor has been so good otherwise i really hope its not as serious and expensive fix...

If your flywheel is still turning straight (not wobling) you could have a blown head gasket. This would cause a leak between your combustion chamber & water jacket which would cause a strange noise, 1 cylinder to stop running (making the flywheel turn unevenly & cause the motor to shake) & your compression from that cylender will go into your water jacket through the blown head gasket & out through your water intake & tell tail. You could do a compression test to confirm this. If your head gasket is OK, all 3 cylinders should have roughly the same compression (about 155 PSI).

If you have a blown head gasket, you have water in your combustion chambers & you need to get it out before it destroys your motor. To stop the water damaging your engine, take out your spark plugs, put a teaspoon of oil in each combustion chamber through the spark plug holes & crank the motor over with the starter. Leave the spark plugs out while you crank the motor because with the spark plugs in, the extra oil in the combustion chamber won't compress & could bend your crank shaft & conrods cause it has no where to go (so leave the spark plugs out). Crank it over every couple of days for 5 or 10 seconds to prevent the water from rusting & pitting your cylinder walls, crank bearings & conrod berarings. If you're unable to do this yourself, get it to a mechanic quick cause the water will destroy your engine very quickly. The longer you leave it, the more it will cost.

If your flywheel actually wobbles while it turns (looks bent) you probably have a bent crankshaft & the bubbles coming out your water intake are caused by a broken water jacket caused by part of your motor internals hitting a hole throughyour water jacket. This is terminal. Get a second opinion from a mechanic.

Hope it's simple,

Rick.

[codszilla]

You are the man!... thanks ample shark!

If your flywheel is still turning straight (not wobling) you could have a blown head gasket. This would cause a leak between your combustion chamber & water jacket which would cause a strange noise, 1 cylinder to stop running (making the flywheel turn unevenly & cause the motor to shake) & your compression from that cylender will go into your water jacket through the blown head gasket & out through your water intake & tell tail. You could do a compression test to confirm this. If your head gasket is OK, all 3 cylinders should have roughly the same compression (about 155 PSI).

If you have a blown head gasket, you have water in your combustion chambers & you need to get it out before it destroys your motor. To stop the water damaging your engine, take out your spark plugs, put a teaspoon of oil in each combustion chamber through the spark plug holes & crank the motor over with the starter. Leave the spark plugs out while you crank the motor because with the spark plugs in, the extra oil in the combustion chamber won't compress & could bend your crank shaft & conrods cause it has no where to go (so leave the spark plugs out). Crank it over every couple of days for 5 or 10 seconds to prevent the water from rusting & pitting your cylinder walls, crank bearings & conrod berarings. If you're unable to do this yourself, get it to a mechanic quick cause the water will destroy your engine very quickly. The longer you leave it, the more it will cost.

If your flywheel actually wobbles while it turns (looks bent) you probably have a bent crankshaft & the bubbles coming out your water intake are caused by a broken water jacket caused by part of your motor internals hitting a hole throughyour water jacket. This is terminal. Get a second opinion from a mechanic.

Hope it's simple,

Rick.

[kingpig]

I would think it is more likley that the woodruff key holding the flywheel in position on the crankshaft has sheared and the motor timming is out.

Put a spanner on the flywheel nut and see how tight it is if you can move it then it is definately not tight enough and more that likley the flyweel has turned out of position.

Good luck

Kingpig

[codszilla]

Thanks guys your suggestions have been pivotal in working out what to do. After reading Shark baits comments i went straight out and had a real good look at the flywheel for physical movement without the engine running and there was none, so i started the sucker and looked at the side of the flywheel (eye level ) and could see it wasnt running true by about 4 mm . Having then turned the motor off i pulled the spark plugs as Shark suggested and before putting teaspoon of oil in the cylinder i turned the crank for about 5 seconds keeping an eye out for any kind of debri including moisture leaving the spark holes but i could see nothing. I seriously believe the head gasket is fine , and after a couple of sleepless nightsi think i understand why this has all happened!..i bought this engine from Sydney your neck of the woods some 6 mnth ago and i reckon the crank was bent when i recieved the engine! i come to this conclusion because i have done nothing that would cause that kind of damage and the feedback through the water inlet at the leg is just a sign of the bent crank creating further damage! The bummer is unlike the clever %%%%% who palmed this engine off i`am not inclined to do the same to some unsuspecting fisho. I may be jumping the gun guys but i reckon this is the case. My next move will be to pull the flywheel or rather check the compression then pull the flywheel as Shark suggested but i think i`am going to be asking around for a second hand crank so i can start rebuilding as i really dont have many other choices. Thanks for your replies fellas i`ll keep you informed as i go..

I would think it is more likley that the woodruff key holding the flywheel in position on the crankshaft has sheared and the motor timming is out.

Put a spanner on the flywheel nut and see how tight it is if you can move it then it is definately not tight enough and more that likley the flyweel has turned out of position.

Good luck

Kingpig

[Shark Bait]

Codzilla,

Right on the end of your crankshaft there will be a centre drill hole. Before you take the flywheel off (which you will need a puller for), have someone turn the motor over with spark plugs out while you watch the centre drill hole. If you see the centre drill hole is running out, you definitely have a bent crank. If the centre drill mark is running concentric, your flywheel may have moved on the crank as kingpig suggested. However if the flywheel moved on the crank, your ignition timing would be out & the motor wouldn't run.

I don't want you to pull your motor apart for nothing, i'm only speculating. If you think the crank is bent, get a professional 2nd opinion. It will put your mind at rest.

If you get a proffessional opinion, PM me before you commit yourself to any repairs.

Edited February 22, 2007 by Shark Bait

[codszilla]

I cant thank you enough for your advice Shark and others. Its not often i get to the pc , the boat is at another location but after reading your last post i``am heading off this minute to check the drill hole and i`am so hoping it is runnung concentric. although there are exeptions i wont trust opportunistic professionals at this moment until i`am certain what the problem is. thanks again mate , I`ll keep you posted and dont worry your advice is not gonna make me do anything hasty its actually saving me a lot of time , money and giving me some very practical insight in determining the problem.

Codzilla,

Right on the end of your crankshaft there will be a centre drill hole. Before you take the flywheel off (which you will need a puller for), have someone turn the motor over with spark plugs out while you watch the centre drill hole. If you see the centre drill hole is running out, you definitely have a bent crank. If the centre drill mark is running concentric, your flywheel may have moved on the crank as kingpig suggested. However if the flywheel moved on the crank, your ignition timing would be out & the motor wouldn't run.

I don't want you to pull your motor apart for nothing, i'm only speculating. If you think the crank is bent, get a professional 2nd opinion. It will put your mind at rest.

If you get a proffessional opinion, PM me before you commit yourself to any repairs.

[codszilla]

Shark.

I checked the hole at the top of the flywheel mate and unfortunately the shaft definately seems bent. Lastly before i put this issue to rest could you please explain how a bent shaft could put a hole through water jacket and if that is the case does it mean that the block is then history. And if anyone could give approx costs of block and crank or any alternate ideas wld be appreciated. Finally thanks again Shark bait

I cant thank you enough for your advice Shark and others. Its not often i get to the pc , the boat is at another location but after reading your last post i``am heading off this minute to check the drill hole and i`am so hoping it is runnung concentric. although there are exeptions i wont trust opportunistic professionals at this moment until i`am certain what the problem is. thanks again mate , I`ll keep you posted and dont worry your advice is not gonna make me do anything hasty its actually saving me a lot of time , money and giving me some very practical insight in determining the problem.

[Shark Bait]

If your motor has an internal heamorrhage, a broken rod or detached piston could crack your block/water jacket & damage your head. In your first post you mention a strange noise, flywheel running unevenly & bubbles coming out of your water jacket. With nothing else to go on, i figured lots of bad noise means terminal damage, bent crank & cracked water jacket. Not much noise means farting head gasket, combustion gasses passing out your water intake, & your flywheel turning unevenly because 1 of your cylenders has a blown head gasket making your motor run rough.

A blown head gasket could bend your crank. While parked, water could seep past your head gasket into your combustion chamber. If your piston is on its way up & has already closed the ports the water will be trapped by your piston. When you try to start your engine, the water in your combustion chamber won't compress. Occasionally, with the right conditions, something gives. In your case, perhaps your crank twisted.

2 stroke cranks are a series of crank pins & discs pressed together. You only have to put a ratchet on the crank nut & hit the handle with a hammer hard enough to twist the discs on the pins (which bends the crank). This happens often on motorbikes when people try to remove the magneto from the end of the crank without special service tools.