1994 GTX 657 – Sudden Heavy Smoke, Oily Plugs

[micro222]

Hey everyone,

I’m troubleshooting my 1994 Sea-Doo GTX (Rotax 657) and ran into a weird issue:

• Suddenly started producing thick white/grey smoke
• Both plugs are oily
• Compression is 110 psi on both cylinders (was 140)
• Engine runs fine, no power loss
• No premix, stock oil injection system
• Blocking the oil feed doesn’t change the smoke
• No oil visible outside, and no oil sprays out the plug holes when cranking
  

Has anyone seen this happen on a 657?

Thanks!

 

[mikidymac]

At 110 compression I am surprised it even runs on the water. If it was 140 and you lost 30 psi compression that engine is done, time for a rebuild.

 

[MAL]

Hey everyone,

I’m troubleshooting my 1994 Sea-Doo GTX (Rotax 657) and ran into a weird issue:

• Suddenly started producing thick white/grey smoke
• Both plugs are oily
• Compression is 110 psi on both cylinders (was 140)
• Engine runs fine, no power loss
• No premix, stock oil injection system
• Blocking the oil feed doesn’t change the smoke
• No oil visible outside, and no oil sprays out the plug holes when cranking

Has anyone seen this happen on a 657?

Thanks!

If both cylinders dropped to 110 at the same time from 140, you should check your compression gauge

 

[AquaEye]

If both cylinders dropped to 110 at the same time from 140, you should check your compression gauge

I had 150ish on both cylinders accompanied with one debilitating/loud knock & this is what I found..

Either way, surgery.

 

[MAL]

I had 150ish on both cylinders accompanied with one debilitating/loud knock & this is what I found..
View attachment 68818
Either way, surgery.

Not sure what you are getting at here. The original poster sounds like he had a sudden drop on both cylinders from 140 to 110. Might be a blown engine, but he says it "runs Fine with no power loss." Checking the tester is the next logical step to me...then pull the head.

Your piston doesn't look like it had 150ish compression.

 

[MAL]

Hey everyone,

I’m troubleshooting my 1994 Sea-Doo GTX (Rotax 657) and ran into a weird issue:

• Suddenly started producing thick white/grey smoke
• Both plugs are oily
• Compression is 110 psi on both cylinders (was 140)
• Engine runs fine, no power loss
• No premix, stock oil injection system
• Blocking the oil feed doesn’t change the smoke
• No oil visible outside, and no oil sprays out the plug holes when cranking

Has anyone seen this happen on a 657?

Thanks!

Water in the combustion chamber will cause white smoke.

 

[micro222]

According to chatgpt, a seal on the crankshaft could allow oil into the combustion chamber and a drop in pressure would go along with that.

 

[Grim]

I would check your oil pump, it may have broke/wire snapped which will set the oil to max output! Also I would remove spark plugs, crank it over and get any extra oil out of the cylinder and then recheck compression. Maybe get a different guage, if you can!

 

[AquaEye]

Not sure what you are getting at here. The original poster sounds like he had a sudden drop on both cylinders from 140 to 110. Might be a blown engine, but he says it "runs Fine with no power loss." Checking the tester is the next logical step to me...then pull the head.

Your piston doesn't look like it had 150ish compression.

Not sure what you are getting at here. The original poster sounds like he had a sudden drop on both cylinders from 140 to 110. Might be a blown engine, but he says it "runs Fine with no power loss." Checking the tester is the next logical step to me...then pull the head.

Your piston doesn't look like it had 150ish compression.

Fact stranger than fiction

 

[MAL]

View attachment 68821View attachment 68822View attachment 68823

Fact stranger than fiction

I think you need a new compression gauge too. Did you add oil before testing?

 

[AquaEye]

I think you need a new compression gauge too. Did you add oil before testing?

Compression gauge is spot on & working just fine.
Add oil? just a very small squirt in both cylinders so as to start & make YT video. Comp test was performed after cool down.
Over 4 decades of wrenching on two smokes (kawi's & yami's), seen this before, nothing new. (This is my1st SD 2 stroke).
It happens few & far between though.
Now back to our regular scheduled thread...

 

[mikidymac]

According to chatgpt, a seal on the crankshaft could allow oil into the combustion chamber and a drop in pressure would go along with that.

As usual AI is wrong. An oil sea could be bad and allow the engine to flood with oil but it will not cause low compression.

 

[mikidymac]

I think you need a new compression gauge too. Did you add oil before testing?

You don't add oil to a 2-stroke when checking compression, as you will get false readings. The only thing that controls compression on a 2-stroke is te rings so if it is low it is the rings and/or piston and only step next is to pull the head and cylinder.

 

[MAL]

You don't add oil to a 2-stroke when checking compression, as you will get false readings. The only thing that controls compression on a 2-stroke is te rings so if it is low it is the rings and/or piston and only step next is to pull the head and cylinder.

I know that. I was questioning how in the heck Aquaeye got 150ish psi out of that cylinder. I accused him of adding oil to boost the numbers.

 

[micro222]

As usual AI is wrong. An oil sea could be bad and allow the engine to flood with oil but it will not cause low compression.

I'll see if I can borrow another gauge in May. The machine is sitting under a pile of snow at the moment. I may have a boroscope by then so I'll take a peek in the cylinders.

 

[MAL]

I'll see if I can borrow another gauge in May. The machine is sitting under a pile of snow at the moment. I may have a boroscope by then so I'll take a peek in the cylinders.

I had oil getting into my crank case. I pressure tested Rotary valve cavity. It held absolutely zero pressure. That means the crank seals are bad on my ski. But that was not where he oil was getting into the crankcase and combustion chamber. My oil pump was leaking as it sat in storage. I converted to premix and that solved the oil problem. My Rotary Valve chamber uses very little oil even though the crank seals are bad. You need to determine if it is the pump or the crank seals. The crank seals require a pressure test. I think it is 5 to 8psi, but don't trust me on that. and the oil pump can be removed and watch it for dripping as it sets for a few days or so. I was ready to tear my engine down and put a crank shaft in it when I saw a puddle of oil coming from the disconnected oil pump.

 

[burtshaver2021]

I had oil getting into my crank case. I pressure tested Rotary valve cavity. It held absolutely zero pressure. That means the crank seals are bad on my ski. But that was not where he oil was getting into the crankcase and combustion chamber. My oil pump was leaking as it sat in storage. I converted to premix and that solved the oil problem. My Rotary Valve chamber uses very little oil even though the crank seals are bad. You need to determine if it is the pump or the crank seals. The crank seals require a pressure test. I think it is 5 to 8psi, but don't trust me on that. and the oil pump can be removed and watch it for dripping as it sets for a few days or so. I was ready to tear my engine down and put a crank shaft in it when I saw a puddle of oil coming from the disconnected oil pump.

Hi @MAL do you know where/what valve on the oil pump leaks? Picture if you have one. I believe my 95XP did this from sitting, I had the carb off it to rebuild and the bore in the intake was full of oil but not the crankcase, the rotary valve was closed on that cylinder. It seemed to fix itself lol as I have had no issues since in the past 3 years. You can private message me if you like so I’m not hijacking this thread.

 

[MAL]

Hi @MAL do you know where/what valve on the oil pump leaks? Picture if you have one. I believe my 95XP did this from sitting, I had the carb off it to rebuild and the bore in the intake was full of oil but not the crankcase, the rotary valve was closed on that cylinder. It seemed to fix itself lol as I have had no issues since in the past 3 years. You can private message me if you like so I’m not hijacking this thread.

I don't think you are high jacking the thread, the original poster complained about oil on the plugs. Maybe its not his issue if there is no oil in his crank case in the spring.

The oil was leaking right through the pump itself past what ever impeller is in it...my pump is bad. You can remove it, connect it to an oil source and watch for drips, unless there is a different test that I don't know about...pressure? but I don't think the system is under much pressure. Mine leaked while sitting a weak or two and it had trouble starting due to oil in the crankcase. Yours must have just backed up into the intake. Based on my experience and yours, I think crank seals often get blamed when the pump is at fault. There is no way that the crank seals filled your intake with out filling the crank case first. With the carb off it may have been vented better to allow flow.

 

[burtshaver2021]

I don't think you are high jacking the thread, the original poster complained about oil on the plugs. Maybe its not his issue if there is no oil in his crank case in the spring.

The oil was leaking right through the pump itself past what ever impeller is in it...my pump is bad. You can remove it, connect it to an oil source and watch for drips, unless there is a different test that I don't know about...pressure? but I don't think the system is under much pressure. Mine leaked while sitting a weak or two and it had trouble starting due to oil in the crankcase. Yours must have just backed up into the intake. Based on my experience and yours, I think crank seals often get blamed when the pump is at fault. There is no way that the crank seals filled your intake with out filling the crank case first. With the carb off it may have been vented better to allow flow.

Makes sense about the extra venting with carbs off. Something for me to look into, in the future if time permits. Thanks Mal

 

[mikidymac]

The oil pumps don't hold oil the check valves do. On a 580/650/720 they are on the pump outlet banjo fitting and on the 787/951 they are on the intake manifold fittings.

 

[MAL]

The oil pumps don't hold oil the check valves do. On a 580/650/720 they are on the pump outlet banjo fitting and on the 787/951 they are on the intake manifold fittings.

That is awesome news. Does anybody sell new banjo fittings?