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Discussion Starter · #1 · (Edited)
Hey Kawasaki Community,

I bought a project bike, 2008 Vulcan 1600 Nomad, that had an unknown problem in the front cylinder. I removed the engine and found two blown exhaust valves in the front cylinder. The top of the pistons looked great. Couldn't really see the piston rings cuz the clearance is so small but I've since done a compression test and the compression is good. I had a reputable machine shop replace the bad valves, inspect/machine seats, and replace all stem seals. I, myself, replaced the timing chains and put everything back together with new gaskets and everything. Torqued everything to spec per the appropriate Kawasaki service manual.

So now that it's back together it does actually run pretty well except the front cylinder still blows lots of smoke. It seems like "blue" smoke (oil right?) but maybe it's just white smoke (possibly running rich?). The coolant level does not go down after a 15 minute ride. The smoke is almost indiscernible at idle but as soon as I load the engine it pumps out a huge gust of smoke. I compression tested and it actually got up to about 90psi, which is 5 over the spec in the service manual. It also held the compression well. After getting to this point I replaced the air intake assembly and nothing changed. While idling I did the little test where you pop off the spark plug leads to make sure the cylinder is firing, and sure enough the idle got really rough when I did that.

So now I'm stuck. What is the last piece of the puzzle? Where is this smoke coming from? Is there a possible sensor or something that is leading to a rich mixture or high oil pressure in the front cylinder or something? Could the piston rings still be the problem somehow even though I have good compression? I'm hoping I'm missing something easy. Please ask if you need more info or clarification. Thanks in advance!
 

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Hi Kaxorpie,
  • Your spark plugs will tell you a lot.
  • A sooty black plug is a rich condition
  • A wet looking plug is either oil (by feeling the fluid) or failed ignition (by smell of fuel).
  • IF the 'smoke' condition is indeed coming from one cylinder only then You could almost rule out a fueling issue. A failing/malfunction injector would be the only cause.
  • White 'smoke' is actually water vapor and occurs regularly during warm up in bikes where humidity is common in the environment.
  • Coolant has a distinct odor even after going through the cylinder and into the exhaust. Another indicator to help isolate the 'smoke' cause.
  • Brownish black emissions are most definitely unburned or partially burned fuel.
  • Bluish white smoke that fills the air is oil burning off. Water vapor rises and/or dissipates into the air quickly.
  • You need to perform a LEAK DOWN TEST. This will tell you of any potential ring, valve or gasket sealing issues.
  • Again check the plugs and see what they are telling you.
 

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Discussion Starter · #4 ·
Hi Kaxorpie,
  • Your spark plugs will tell you a lot.
  • A sooty black plug is a rich condition
  • A wet looking plug is either oil (by feeling the fluid) or failed ignition (by smell of fuel).
  • IF the 'smoke' condition is indeed coming from one cylinder only then You could almost rule out a fueling issue. A failing/malfunction injector would be the only cause.
  • White 'smoke' is actually water vapor and occurs regularly during warm up in bikes where humidity is common in the environment.
  • Coolant has a distinct odor even after going through the cylinder and into the exhaust. Another indicator to help isolate the 'smoke' cause.
  • Brownish black emissions are most definitely unburned or partially burned fuel.
  • Bluish white smoke that fills the air is oil burning off. Water vapor rises and/or dissipates into the air quickly.
  • You need to perform a LEAK DOWN TEST. This will tell you of any potential ring, valve or gasket sealing issues.
  • Again check the plugs and see what they are telling you.
Ok, so I did determine it is definitely oil in the cylinder. The spark plugs on the bad cylinder had a bit of oil in the threads when I removed them. Also, the fouling on them seems consistent with your description and what my limited experience is for oil in the cylinder. I didn't do a proper leak down test with a pump but I did plug in my compression tester and turned over the engine several times. And actually compression tops out around 150psi in the bad cylinder. The good cylinder gets to about 120psi. The service manual says something like 50-85psi is the spec. So is that a weird thing/problem? I left he pressure in the cylinder for about 5 minutes with zero drop in the pressure. Is that diagnostic enough or do I need to use a proper leak down gauge? Air was not bubbling out of the coolant.

It might be very important to not that this bike has been modified by the previous owner to remove the ICV valves and plug the vent hose from the crankcase. This may be pertinent because after I turned over the engine about 5 times for the compression test I opened the oil filler cap and the crankcase definitely had positive pressure that escaped.

As another side note the right pipe which exhausts the bad cylinder has no muffler packing in it. So it's basically just a straight, unmuffled pipe. The good cylinder exhaust pipe DOES have the muffler packing still. Maybe this causes an imbalance on back pressure? I suppose I could remove the muffler part of the one for better comparison but don't know if that's really going to make much difference.

Thoughts on all that? It seems pretty cut and dry here for bad/seized piston rings right? But maybe if I vented the crankcase somehow or use a Lucas oil additive or something it could improve without another complete tear down?
 

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Your getting back pressure into the cylinder plus your compression is 3 times what it should be. There is the possibility that with some Lucas or some marvel mystery oil you could free the rings but from my experience it doesn't usually last long if it works at all the only time i have ever seen it last was on a engine where the rings were stuck from sitting. Yours are stuck from being cooked by burned valves. Those rings are jammed against your cylinder walls hard which is not a good thing. They are waring the heck out of the wall every time the bike is running. It sucks but you need to get the jug off and get the rings sorted out. and take a good look at your cylinder wall for wear when you do and the piston head may need to be replaced if the ring seats are to damaged. Cross your fingers and hope that its just burned on oil that has them stuck. You may even be able to reuse them once you get the crud cleaned out of the ring seats and was the oil ring out really good.


Thats just my opinion and what i would do. Some may have other ideas or opinions
 

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Hi Kax (for brevity),
  • So oil in your cylinder basically comes from two sources:
    1. Bad intake valve seals
    2. Weak or stuck oil rings in the piston usually the top ring.
  • High compression readings can also be a result of fluid sealing caused by excessive oil surrounding the piston crown and sealing the gap between the piston and cylinder wall.
  • Excessive crank case pressure comes from piston ring blow by which would be another indication that the rings are stuck IN and not sealing against the cylinder wall.
  • An open exhaust can cause damaging lean conditions without adjusting fuel to compensate for the increased flow into and out of the cylinder.
  • Unfortunately, you will likely be taking the front cylinder off to be at least honed and to re-ring the piston. At a minimum.
  • Worse case scenario, the cylinder has to be cut to go over a size which would mean doing the same to the rear cylinder. This would include new pistons and rings and, gaskets. Not a difficult job with the correct tools, equipment and technical information.
  • You have to decide if the bike is worth the financial investment.
 

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Also,
  • You cannot do a proper leak down test with a compression gauge. The compression gauge HOLDS the highest reading and will not LEAK DOWN with any change in the actual cylinder pressure.
  • Your high compression reading could also be the result of failed decompression mechanisms on the cams. Something you will examine should you choose to do the leg work of the top end tear down on your own.
  • However, it seems that your compression readings are due to hydro sealing of the piston-to-cylinder wall gap.
  • When reassembling the unit, I would suggest returning the ICV system back to it's original condition OR at least ask in the forum how others have SUCCESSFULLY bypassed it.
 

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Another option should you find the front jug damaged is instead of having it cut and then the required mod to the rear is source an replacement front jug that is not damaged. Cost would be lower than having to have both jugs bored out. It also saves on the additional gaskets that would be needed for a rear jug reassembly. Just a thought.
But motmedic is right your only choice now is to pull that cylinder apart and find out what the heck is happening
 

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Discussion Starter · #9 ·
Another option should you find the front jug damaged is instead of having it cut and then the required mod to the rear is source an replacement front jug that is not damaged. Cost would be lower than having to have both jugs bored out. It also saves on the additional gaskets that would be needed for a rear jug reassembly. Just a thought.
But motmedic is right your only choice now is to pull that cylinder apart and find out what the heck is happening
Excellent input guys. Looks like I'm pulling the engine again. Luckily, when I had the head off just a bit ago the cylinder walls and top of the piston looked really good. The walls didn't look scored or anything. So I'm planning on just replacing the piston rings with factory rings. No machining. Is that dumb of me to not bore the cylinder? Are there microscopic scratches I can't see that I'm ignoring possibly? What are your thoughts on that?
 

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  • Microscopic scratches would not matter. When honing a cylinder you actually put visible scratches on the cylinder wall in a pattern called "crosshatch".
  • Re-ringing a cylinder that has reached or exceeded the piston and/or ring limits won't do any good.
  • The cylinder will have to be measured to see if an over bore is needed or not.
  • One wear characteristic is known as out-of-round. This generally determines whether or not the cylinder has to be cut or not.
  • As far as buying a used cylinder: You will have to weigh the costs between the two options. You may buy a used cylinder that will need to be cut or maybe it won't. If the seller is smart enough and properly equipped to measure the cylinder and let you know that would be a plus. Most won't because they figure that if your that far into an engine rebuild you probably had plans to hone at a minimum.
  • And then there is the top wear ring in the cylinder. Assuming your crank, cylinder and base gaskets were perfectly machined and assembled the same as the ones from the used cylinder you won't have any issues. Otherwise you run the risk of having a new piston and rings running into said top wear ring and your tearing the engine apart again.
  • SO....if you plan to keep this machine for a while and/or you just have disposable income and a desire to learn about engines and building them, I would have both cylinders measured. And if one needs cut then both get cut.
 

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Before you remove another bolt, you must have a positive crankcase vent system. If the front crankcase vent has been plugged, you are building lots of crankcase pressure that is going to go somewhere. It can force oil past the valve seals. If the other components have been removed, connect a hose to the port on the back side of the air intake housing, run bike long enough to burn off any oil residue.
Doing a compression test on these engines tells you nothing as the auto compression release slightly opens an exhaust valve in each cylinder for easier starting.
 

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  • So try this: Do a compression test with the oil filler cap removed
  • With properly operating ACR's (Automatic Compression Release) you will get the factory spec compression readings.
  • IF you still are getting the high readings then either or both of the following are happening:
    • ACR's are not working
    • Oil in the cylinder is sealing the piston-to-wall clearance
  • Maybe you have potatoes stuck in the exhaust pipes. That can cause high compression readings also.
 

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Discussion Starter · #13 ·
Before you remove another bolt, you must have a positive crankcase vent system. If the front crankcase vent has been plugged, you are building lots of crankcase pressure that is going to go somewhere. It can force oil past the valve seals. If the other components have been removed, connect a hose to the port on the back side of the air intake housing, run bike long enough to burn off any oil residue. Doing a compression test on these engines tells you nothing as the auto compression release slightly opens an exhaust valve in each cylinder for easier starting.
Awesome. Ima do that tonight! Thanks!
 

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Discussion Starter · #14 ·
  • So try this: Do a compression test with the oil filler cap removed
  • With properly operating ACR's (Automatic Compression Release) you will get the factory spec compression readings.
  • IF you still are getting the high readings then either or both of the following are happening:
    • ACR's are not working
    • Oil in the cylinder is sealing the piston-to-wall clearance
  • Maybe you have potatoes stuck in the exhaust pipes. That can cause high compression readings also.
Awesome. You all are so helpful. I'll do this. Thanks!
 

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IF the pipes are OPEN at the ends and is sat for a long period it is possible that critters made a home in the pipes. Checking to make sure they are clear would be a good idea.
As far a a cylinder jug goes yes you would need to check yours and see if its in spec. If not then yes having it cut would be required. If sourcing a jug then any reputable place should be able to give you a jug inner diameter measurement any place that was not willing to send you pics of the tool actually giving the measurements at different places inside the jug should be bypassed.
This was just a possible solution to a full rebuild and cut of both jugs. I avoid cutting the jugs when ever possible since it reduces the number of times you can rebuilt that jug. Not saying its a bad thing it some times is your only option. Just tossing the idea out there.
 

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Discussion Starter · #16 ·
IF the pipes are OPEN at the ends and is sat for a long period it is possible that critters made a home in the pipes. Checking to make sure they are clear would be a good idea.
As far a a cylinder jug goes yes you would need to check yours and see if its in spec. If not then yes having it cut would be required. If sourcing a jug then any reputable place should be able to give you a jug inner diameter measurement any place that was not willing to send you pics of the tool actually giving the measurements at different places inside the jug should be bypassed.
This was just a possible solution to a full rebuild and cut of both jugs. I avoid cutting the jugs when ever possible since it reduces the number of times you can rebuilt that jug. Not saying its a bad thing it some times is your only option. Just tossing the idea out there.
Cool, that makes sense. I've already verified for critters. :)

As far as the jug goes, I've worked on cars much more than motorcycles, so this option is kind of new to me. From my brief research after your comment it looks like the cylinder/jug just comes off as the next step once the head comes off. Dang, can't believe I didn't just pull it during the first time I had the engine off. So are you saying that instead of re-machining the cylinder I could literally just swap it out for a replacement jug and piston? Otherwise, it sounds like I have to re-machine and buy oversized piston rings right?
 

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Yes if your jug is out of spec you may be able to find one thats in spec. If your piston head isnt damaged you just put new rings in and back together you go. If your jug is good then just hone it out and same thing. The big question right now is total wear on your cylinder and if there is any damage to your piston ring seats. If the piton head is damaged you may even be able to press the pin out with our cracking the case open to disconnect the rod. I have even see some that the min is held in with a C ring. Not sure if that's the case on yours but its possible. I have done top end rebuilds on a few bikes this way.
 

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Discussion Starter · #18 · (Edited)
Hey guys. Just wanted to report back. I pulled the engine and took the front cylinder apart. Surprisingly the rings were not completely stuck and grinding the cylinder, but instead a piece of the piston in between two of the rings was completely broken off and trapped in place. That was obviously my second problem I missed the first time (first problem was the burnt exhaust valves I mentioned in my first post). My hypothesis is the piston broke first, thereby causing the burnt exhaust valves. But I have no way of verifying.

Anyway, I ordered a used cylinder/piston combo online from a lower mile bike and replaced it. Put it all back together and now it runs great! Actually, it started right up after only a few seconds on the starter. It burned off a bunch of the caked on oil left over in the exhaust as it warmed up and now it runs clean and smooth. Thank you guys for encouraging me in the right direction. It went from being a piece of garbage to a nice bike again.

Lastly, I have one last thing I'm scratching my head over. It runs super good when it's warm, but it struggles to idle when it is started cold. Once it warms up I can turn the idle waaaaay down and it doesn't die. I know it's fuel injected, but the previous owner removed the ISC valves and the left side air filter (uses only the right one now). I presume this gives it more power somehow but probably at a cost of wear and tear on the bike. I did reconnect the crankcase ventilation to the intake so hopefully that's helping. However, I'm wondering how I can get it to idle better cold. The choke seems to do nothing. Any ideas?
 
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