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Hydrolocked By Left Rear Cylinder


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The GDC 6G that we built last year has been plagued by an engine that will not start after a rain. We initially thought it electrical but found some water in the oil. We wondered about head gaskets as the engine has over 65k miles on it now. They are also good.

We have been getting heavy rain this year in the south. We have tried to find an area where water/rain could get into the engien and hydro-lock it unsuccessfully. This past week we confirmed that the only cylinder that is getting filled with water is the left rear.

We have fabbed up various brackets and gaskets to seal the COP's to the 5G heads and do not think that rain is getting in past the COP's.

We have had the airbox off more than 2 dozen times to search for issues and have had the throttle bodies off half a dozen times to look for loose hoses.

We placed the bike on a rear stand for the latest round of thunder storms to eliminate the thinking that leaning on the sidestand was somehow contributing to this.

We have found no loose hoses or vacuum lines that could funnel rain into the cylinder. After a heavy rain the engine will either not move at all when the start button is pushed or (if the left rear cylinder is close to the bottom of the bore) the engine will turn for less than a quarter revolution and then lock. That is not enough rotation to pull liquid in through a vacuum line or loose hose even if submerged in a container of water.

Any ideas or recommendations?

Our next step if we cannot solve this issue is to put the 4G back on the road for commuting and remove the engine from the frame to start over.

TIA

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I just looked at an extra set of throttlebodies in the garage and the injector seal seems a little too small to let as much water in as we're finding. But i haven't actually inspected the throttlebodies that are on the bike so i'll check that out when i get a chance just to be sure.

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It would seem that you have covered virtually all possibilities of where this water/ liquid is coming from.

If I were in your shoes, I would siphon some of the liquid out of the cylinder and inspect it. The questions I would need to answer:

1) is the liquid only water? Are you running water in your cooling system or a coolant/ water 50/50 mix? If the drained liquid is (essentially) the same as the coolant, then you know you have a head gasket/ cracked block/ cracked head. Have you completed a pressure test of the cooling system? Have you had to add coolant/ water to that system? You have indicated that this only happens when it rains; does this mean that if it is parked inside, the problem doesn't exist? I would think this would be relatively easy to reproduce with an average garden hose.

2) Is the liquid a mix of oil & water, or only rainwater? Is it possible that water has gotten into the crankcase and then somehow (bad rings, etc) gotten into the cylinder? There is a dye that can be added to oil that shows under a black light. It is used to spot oil leaks in engines (mostly in automobiles I think) but could also have an application here.

3) Have you done a compression test on all 4 cylinders? How did the results compare with specs and each other? Also, when running, I would spray carb cleaner (or something similar) near that area and see if you could spot some time of external leak by vacuum detection.

4) Lastly, how does the bike run when you are not dealing with this issue? is it running on all 4 or does it miss fire at all? Does it idle different when the carb spray is introduced?

CC - I have read numerous posts from you and know without a doubt that you know what you are doing.... I am hoping that my line of questioning points you to the resolution... please keep us informed of what the solution.

-TC

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Potential points of water entry are the breather system, PAIR system, Evap system or a cracked Vacuum Chamber. Probably could pull the coils and seal the plug opening before it rains to rule this point of entry out if all else fails.

KEB

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Very strange... I can't imagine how any liquid could get past a spark plug (or COP) and into the cylinder. (Provided the plug isn't defective.)

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No water missing from the radiator ? I have heard of crack cylinder walls sealing up when heated and opening up when cool. Working the notion you did find some water in the oil.

Roll On ..

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To try and answer some of the suggestions thus far:

It does only occur when it rains and we have not been entirely successful in replicating it with a garden hose but now that the heat of summer is upon we may be more diligent in our attempt at this.

The liquid is only water, no gas, no coolant and no oil come spitting out when we remove the coil and plug and push the starter button to remove the liquid. We have captured it many times on various clean rags and paper towels.

It runs really well when it starts.

It does not happen when the bike is parked inside even for a long period of time or when my son takes the cover for the bike to work and covers it there before the rain.

We don't think the rain is getting past the spark plug but perhaps filling the plug cavity and getting through some internal passageway in the cam cover but that seems more unlikely as well. Getting past the 6G COP's inserted into the 5G cam covers is more easily accomplished.

At this point we are going back to the pair block off plates and will order some new plates and reinstall them with the original pair covers this time.

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The PAIR plate sounds like a very good place to go looking for the leak; I re-used the original rubber seal when I installed blanking plates. If there's a leak that lets water in, I would think you would also hear an exhaust leak. When I installed mine, I left the PAIR reed valves in place but on one the retaining screw fouled the blanking cap and that cap would not seal, and it was very obvious when started the bike. I removed the reed valves and just left the rubber seal in place, and have had no leaks in 20,000km or riding.

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Unless your gas cap overflow is unhooked, I don't see how that much water gets past the tank and onto the top of the engine much less into the engine. Tell Mini to stop riding on rain days. Problem solved. You can buy me a beer later.

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Had a big thunder storm blow through this afternoon so I put a handful of tools in the truck with the dog and rode over the Best Buy when Mini was scheduled to be leaving...he walks out and asks "Should we try it?"

I shake my head no and hand him the tools. Within 3 minutes he has the tank propped up and the COP and plug removed from the left rear cylinder. "Crank it over." I suggest. He does and we get about 3 ounces of rainwater from the cylinder as the bike roars to life...running on 3 and pumping air where the plug should be.

I wish I had recorded it.

Pop the plug back in and COP on, reconnect the tank and he almost beat me home.

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Some how in your build you have created this channel for water to dump right on top of that plug. You know the 6th gen does have a rubber cover over the rear cylinder banks, you mite steal one off the other bikes your not riding and place it over the problem bike and see if it helps.

Roll On ..

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This is just an idea - I don't recall anyone mentioning placing some small bits of absorbent material such as Kleenex in suspected locations to see what gets wet and what stays dry. I have used that method to find small coolant leaks by twisting a Kleenex to a sharp point and probing around hoses, weep holes, etc. Any liquid is immediately apparent.

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Carvers - Plug your exhaust before it rains and see if that helps... it might be coming in through your exhaust valve or your rear cylinder bank PAIR valve. Engines tend to stop in one or two positions when they are shut off, kind of a balancing the pressures. My track bike 5th gen engine is stopped with #3 intake and exhaust in overlap so I have a passage straight through the throttlebody and out the exhaust. Your engine may stop with your #1 in the same config just finishing the exhaust stroke and when you crank it goes down pulling in water then trying to compress it and stopping... it's a thought.

A couple of butt plugs may solve your problem! :goofy:

If you redo your PAIR block off plates I believe the correct procedure is to remove the reed valves and screw... I thought I saw someone mention leaving them in.

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I shake my head no and hand him the tools. Within 3 minutes he has the tank propped up and the COP and plug removed from the left rear cylinder. "Crank it over." I suggest. He does and we get about 3 ounces of rainwater from the cylinder as the bike roars to life...running on 3 and pumping air where the plug should be.

Did you look down in the spark plug cavity before removing the plug? Just curious if the water was in the cavity and when you removed the plug, the water got into the cylinder.

I'm struggling with how the water is getting in the cylinder past the spark plug seal and threads. I guess over a long period of time it would weep past threads, but I would think it would be days for enough to get in there to hydro an engine.

Is there a rubber flapper over that stuff when stock? I know there is one back there somewhere. I think it hooks to the tank hinge bolt. Maybe that is to help divert water away from the spark plug area?

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I'm struggling with how the water is getting in the cylinder past the spark plug seal and threads. I guess over a long period of time it would weep past threads, but I would think it would be days for enough to get in there to hydro an engine.

Me too. If that much water easily leaks past a spark plug that normally seals the chamber when running at a pressure of 11.8:1, you would have blown the plug out clean out of the head by now.

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Some how in your build you have created this channel for water to dump right on top of that plug. You know the 6th gen does have a rubber cover over the rear cylinder banks, you mite steal one off the other bikes your not riding and place it over the problem bike and see if it helps.

Roll On ..

The rubber flaps are all installed just as any factory 6G bike.

This is just an idea - I don't recall anyone mentioning placing some small bits of absorbent material such as Kleenex in suspected locations to see what gets wet and what stays dry. I have used that method to find small coolant leaks by twisting a Kleenex to a sharp point and probing around hoses, weep holes, etc. Any liquid is immediately apparent.

Have thought about placing a "tattletale" material but as the water is ingressing the combustion chamber I have not thought of a material that would not be either ignited or exhausted at those temps and pressures...any ideas?

Carvers - Plug your exhaust before it rains and see if that helps... it make be coming in through your exhaust valve or your rear cylinder bank PAIR valve. Engines tend to stop in one or two positions when they are shut off, kind of a balancing the pressures. My track bike 5th gen engine is stopped with #3 intake and exhaust in overlap so I have a passage straight through the throttlebody and out the exhaust. Your engine may stop with your #1 in the same config just finishing the exhaust stroke and when you crank it goes down pulling in water then trying to compress it and stopping... it's a thought.

A couple of butt plugs may solve your problem! :goofy:

If you redo your PAIR block off plates I believe the correct procedure is to remove the reed valves and screw... I thought I saw someone mention leaving them in.

Not coming in the exhaust via the tailpipe (Staintune 6G exhaust on a catless 5G header) and the engine rotation is never more than 1/16th revolution at most...often you only get an audible *click* from the starter solenoid and ZERO rotation.

I shake my head no and hand him the tools. Within 3 minutes he has the tank propped up and the COP and plug removed from the left rear cylinder. "Crank it over." I suggest. He does and we get about 3 ounces of rainwater from the cylinder as the bike roars to life...running on 3 and pumping air where the plug should be.

Did you look down in the spark plug cavity before removing the plug? Just curious if the water was in the cavity and when you removed the plug, the water got into the cylinder.

I'm struggling with how the water is getting in the cylinder past the spark plug seal and threads. I guess over a long period of time it would weep past threads, but I would think it would be days for enough to get in there to hydro an engine.

Is there a rubber flapper over that stuff when stock? I know there is one back there somewhere. I think it hooks to the tank hinge bolt. Maybe that is to help divert water away from the spark plug area?

The water is not getting around or through the spark plug threads and into the engine.

No water in the plug/COP cavity prior to removal, in fact this time, the COP was dry as it was removed from the cavity.

Rubber flaps on the tank mount ass'y (both) are installed and flapping over the factory areas.

I'm struggling with how the water is getting in the cylinder past the spark plug seal and threads. I guess over a long period of time it would weep past threads, but I would think it would be days for enough to get in there to hydro an engine.

Me too. If that much water easily leaks past a spark plug that normally seals the chamber when running at a pressure of 11.8:1, you would have blown the plug out clean out of the head by now.

Yes. As mentioned in TImmy's post water doesn't compress. :happy: But perhaps I under-estimated the sneakiness of the water.

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