First Major Problem... Tons of Smoke!!!!

[Vroom4]

So it’s been a while since my last post in the Vroom build thread, but I’ve run into the first major problem with the little xs…

The main problem is a ridiculous amount of smoke blowing out of both the right exhaust and the breather!!? No more than normal out of the left pipe, but tons out of the breather and right pipe! The smoke is pretty thick white and not black. Also when I checked the oil there was almost none in her!(I just changed the oil to Rotella Diesel 15w-40 as some of you may recall from the build thread). I knew there was a little oil sweating from the head here and there, but not enough to even drip, so it must be burning oil too.

It was running fine (maybe a bit rich from the bigger jetting) and then just went poof, up in smoke! My initial thought was that the right piston rings took a crap… but would that mean smoke out of the breather too??? And let me say again this is a lot of smoke coming out of that breather tube!(I will try to maybe take a video or some photos, though I don’t really want to turn her on).

Could it be the valve seals? I know the rings can be tough to get, so it would be great to be able to eliminate other potential causes first. Any ideas?

 

[16VGTIDave]

I'm going to guess the smoke is more blue than white from the exhaust, and white from the breather. Do a compression test and then try not to cry... Sounds like you lost the rings on the right cylinder.

 

[Vroom4]

Yes, that was my first guess as well... wondering if it could be anything else? Valves, seals, etc.

I found a place to get the piston rings in standard sizing that seems to be a good price. I'm trying to wrap my head around pulling the motor and what I'll need. Open to suggestions there... How likely is it I'll need to machine the cylinders? Should just be able to pop on new rings and be okay right?

Also need more on reassembly with timing and valves etc... I think that scares me more than the actual rings? lol

 

[Vroom4]

Okay, so after a bit more research, it seems the piston rings are almost def the culprit

Some important questions:
- Can I just replace the rings with new ones on both pistons and bolt it back up with new seals?
- Is machining the cylinders required?
- If so, does that mean I need new pistons? Or just thicker rings?

Just trying to wrap my head around what is needed... wasnt expecting this to happen so soon :/

 

[Scorpio1963]

I would get yourself a good bead hone and do the cylinder/s if your going to take the top end apart.I would also measure your pistance bore to make sure its not out of tolerances.Not sure what the numbers would be but you can probaly find those numbers in the manual.

 

[Vroom4]

I'm also trying to determine what would have caused so much oil loss so fast... I'm not really sure if the oil burned up quickly b/c the rings went, or if the rings went b/c the oil was low... and if the latter, how did the oil level get so low? No major leaks to speak of other than a lil from the head but it's very minimal.

Also, I've been running the pods straight to the carbs with no h-pipe. I've recently heard the theory that(it was about a honda, but im wondering is this applies to the xs too) the breather tube which connects to the carbs via the h-pipe is actually needed to send a lil oil and fumes into the carbs. The idea is that this lubes the slides while it runs.

 

[MechNewb]

The tube is there to send oil fumes into the engine to be combusted for emission purposes. I think people like to make up theories sometimes and thats why you hear things like the oil is for lubrication.

 

[Scorpio1963]

Thats what I have also read is its hook that way for emissions.Lot guys run the pods hooked up to the carbs direct with just a breather filter over ccvt.Crank case ventalation tube.I have been told by some of our most knowlegeable members that the pods should be hooked up to the hpipe not direct.Im not sure it actualy makes a difference as long as your not using cheap pod filters.
As for the other issues your oil rings on the piston probaly have failed!Your bikes engine will burn alot of oil in a short amount of time.So the bad news is your probaly in for another top end rebuild.

 

[MechNewb]

The h pipe helps straighten out the airflow which is useful for CV carbs. Some bikes like the Honda CB750 can barely run with pods because of the needed vacuum that gets lost with pods. Our bikes aren't that finicky and can be tuned to work with pods. Most people (myself included) go to pods for the added simplicity and looks. I'm not looking to increase horsepower in any significant amount with pods.

Vroom- have you done a compression check? This will tell you for certain that it is the rings. It's most likely that the rings burnt up the oil. How many KMs on your bike? It all depends on how the previous owners treated her.

 

[Vroom4]

Thanks guys. I do know that certain bikes do use the vent system to lubricate the slides, this is def true, but I just wasn't sure about the xs400. I'm considering putting the h-pipe back on, but to be honest not having it was a huge help since it allowed me to see the white smoke coming out of the vent right away.

I have not done a compression check yet. I think this is def the next step I need to be taking, but I am not too sure on how the best way to do it would be.