Common internal failure? My friend is killing his second one!

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TTaylor

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Now with video! Common internal failure? My friend is killing his second one!

I've got a good friend, who probably shouldn't own a motorcycle. I'll leave that at that, and of course we all know lack of attention will eventually cause anything to fail. Getting that said and out of the way, he has killed one XS400 engine, and now the XS360 that I swapped in for him seems to be on the way out. I generally think it's a lack of paying attention to the oil, but I'm wondering what specifically it might be the first parts to fail.. the 'weak links' so to speak. An engine is an engine, of course, but they all have their particular chinks in the armor.

The original engine locked up on him at highway speed, but acted like it was loosing power first. I don't know what locked up, I never torn it down, but we found that it would start again later on. It had a terrible piercing clacking to it, though. There was plenty of ferrous metal in the oil, too.

Well, he's ridden this one until the mufflers had broken to bits, and I finally got the moron to stop and let me look at it. The oil has metal in it again (what was left in there!) and it's making a terrible clacking, but not ALL the time. I can rev it, and then arbitrarily it will start, and then sort of taper off. This is after changing the oil, of course.


Just wondering if their is any insider knowledge particular to this engine. Thanks!
 
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If the engine has a bad bearing in it, that will cause it to go through oil like crazy. Could also be bad piston rings scraping away the bores, then burning up the oil. Either one you could teach your friend some oil maintenance before he buys his next bike as well. Grinding metal sounds when you start the engine means to stop before you go any further, otherwise you will guaranteed rip it apart beyond fixing. Although I'm not sure even with fresh parts those engines can be salvaged.
 
I don't believe he's going to be getting another bike, if I have anything to say about it. I've tried to teach him.. he's just not the type to own a bike (or anything, for that matter). I've been a mechanic myself for seven years, he relies on me too much but has no sense when he's off on his own. He hasn't learned a damn thing.

I'd imagine it's burning the oil because it doesn't have any leaks, and who knows how long the piston rings sat. It ran great after I swapped it in and got everything tuned up, I rode it quite a bit making sure it was ok. The oil in it was old but looked fine when we got it. I changed it, of course.

Anyway like I say, I'm just curious if these have a tendency to spin bearings, etc, or what.
 
TTaylor said:
I don't believe he's going to be getting another bike, if I have anything to say about it. I've tried to teach him.. he's just not the type to own a bike (or anything, for that matter). I've been a mechanic myself for seven years, he relies on me too much but has no sense when he's off on his own. He hasn't learned a damn thing.

I'd imagine it's burning the oil because it doesn't have any leaks, and who knows how long the piston rings sat. It ran great after I swapped it in and got everything tuned up, I rode it quite a bit making sure it was ok. The oil in it was old but looked fine when we got it. I changed it, of course.

Anyway like I say, I'm just curious if these have a tendency to spin bearings, etc, or what.
Click to expand...

Honestly I just bought an XS400 a few weeks ago. I have no clue what is the easy part to go wrong on these bikes. But from the sound of it, it does sound like bad piston rings. The engine might spin over when one gets compression luckily, but at running speed fails to make compression and dies. Thats why you said itll spin over then die. You wouldnt get enough seal and the oil would just burn up, thus overheating and the rings would scrape the steel cylinder barrels, thus making compression even harder to attain with the wider clearances. Also the lack of oil will also cause oil starved bearing at the crank and camshaft, which would chew those up quite easily and make metal in the oil reservoir.

This is the first motorcycle I've owned myself, but I make my living as an aircraft mechanic while going to college, and there aren't too many parts involved to affect your compression, as well as the amount of parts that will easily create metal in this engine, along with any other engine, bearings are the first to go usually, then that begins to damage the other parts of the engine in severe ways. But the root cause is probably in your case, and most often, oil starvation.
 
I do know that one thing that is detrimental to these engines, is if they sit for a long time, the steel cylinder barrel can rust if exposed to moisture and left long enough. Best to run them often to keep them cleared. Your piston rings may have ate their way through the rust causing this problem as well.

But two engines coincidentally? Likely, yet equally unlikely.
 
the 400 with its plain crank bearings is a lot more susceptible to crank failure than a roller bearing lower end in a low/dirty oil situation, the next on the list of failure items would be seizing pistons, galled bores, stuck rings.... a roller bearing lower will usually seize the piston(s) first
 
No, the engine doesn't cut out; I was just referring to the jarring noise it makes. I almost wonder if it's detonation but that doesn't make much sense. I've been an aircraft mechanic myself for seven years! I started out with a non-running $200 KZ550 (which I still have). These XS400's are nice little bikes.. although my friend seems damned to prove otherwise!


Yea, I'm pretty positive it's oil starvation.. I just wondered if there's like "yea, this ALWAYS gets trashed immediately if the oil gets low" etc. Say and SR500, they have an oil like that goes right to the head because top end oiling has always been an issue.

At least with the other engine, the top end looked fine, I did pull that. I'm thinking it's maybe rod bearings and rod knock/ piston slap.

I think it'd pretty well done. I should shoot a quick clip of it for science.
 
I've been on the forums here for a little while now and I cannot say I see very many posts about internal engine problems. The thing is, I rarely see higher mileage bikes. Other than my observations in regard to what people are asking I cannot be of more help.
 
oil is the key componant in these bikes.

The cam runs in the head with no bearings, if they wear then the bigger gap will lower oil pressure and affect the mains.

to do any damage you need to run the oil low, never change it and red line it from cold
 
Now with video, for science, of course. The sound picks up, and can really be heard when the camera comes in close. It sounds much more resounding and metallic and generally more alarming in person.. so much so that I thought it was from a loose exhaust pipe itself or something like that. Maybe the hollow metal of the pipe helps to transmit this specific sound it to the human ear in a way the camera can't replicate. At any rate..

Can't figure the embed function out..

 
TTaylor said:
Now with video, for science, of course. The sound picks up, and can really be heard when the camera comes in close. It sounds much more resounding and metallic and generally more alarming in person.. so much so that I thought it was from a loose exhaust pipe itself or something like that. Maybe the hollow metal of the pipe helps to transmit this specific sound it to the human ear in a way the camera can't replicate. At any rate..

I'm not sure how to embed it here..

Click to expand...

sorry yo, came up with the embed code so i trimmed it, but you already took care of it.

 
All the adjuster nuts are tight and in place. :shrug: I haven't check the clearance, but it looks like there is alot of adjustment yet, even if they are on the tight side.

I wonder if it could be the cam chain
 
TTaylor said:
All the adjuster nuts are tight and in place. :shrug: I haven't check the clearance, but it looks like there is alot of adjustment yet, even if they are on the tight side.

I wonder if it could be the cam chain
Click to expand...

possibly, could be thrashing with worn guides.

only was to tell is to take the cam cover off
 
I saw puffs off blue smoke come out the front of the muffler where it joins the end of the header when you revved it up. About 0:06 of the video, blowing the opposite direction I mean towards the front of the bike?
 

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