who knows motorcycle engines?
 

been facing a pretty strange problem as of late...

but first, what lead me to this problem...

I bought a used bike about a month ago. It needed some minor work done, namely just oil change, tune-up and the like.

I also had to have one of the spark plug holes on the top block reborred because some idiot previously stripped the threads. So while removing the rocker arms, my idiot mechanic dropped one of the washers down inside the block, which fell all the way down in to the crank case and got wedged in between 2 gears.

I must note that the engine has NOT been turned on until the the washer was removed, so there's no damage from that.

But, now that I had to basically overhaul the engine - which was running perfectly fine before this - the main (head?) gasket - the metal one between that seals the compression chamber - starts leaking oil after about 10 minutes of high idle testing. I've tried 3 brand new gaskets, and all have the same end result. Also, the surfaces on both blocks are flat and smooth and have no damage on them at all.

So I'm pretty much stumped... but if I had to guess I'd say that perhaps the oil isn't circulating properly and is getting built up around that area. I can't see how it would though considering all passageways for the oil are completely clean and oil drains down them properly when I pour oil down from the top block.

Anyone out there who knows more about engines than I do have any ideas?

So is it leaking oil visibly between the head and the block externally, or is it leaking oil inside the combustion chamber causing smoke?

stupid question but you sure you got enough bolt torque for that model? I know they can vary. Too much can do just as much damage as not enough.

both.. it's leaking externally very slowly.. like if after about 10 minutes of the engine running I can see small traces of oil on a screwdriver after scraping along the outer part... and it's leaking into one of the combustion chambers causing smoke from one muffler as well..

Its a bit of a shot in the dark but two things come to mind first before you apply a new gasket polish both gasket surfaces and use a gasket sealer, second, as was mentioned be sure you are torquing the bolts to specs and EVENLY.

That's the first thing that came to mind, along with the gasket shifting and possibly blocking one of the oil ports.

I honestly have no clue... I'm not a mechanic.. and I can't seem to find one worth his weight in beer.. I do know that I refuse to tighten them bolts myself because I've snapped a few of those long shafts/bolts/whatever you call them

by surfaces i mean the surface on the engine not the gasket

Make sure the head is torqued correctly

Also try a steel ruler, on its edge on the head and look for distortion.

Do the gaskets leak in the same place? Got a picture of the head, cylinder, gaskets after its blown?

I'll try that.. haven't used anything but the gaskets thuse far... and I was concerned about them not being tightened evenly as - in my mind anyway - all of those bolt shaft things are the same length, each washer and nut are the same size.. so each of them should be visibly even when tightened... but they're not.

Maybe I need to up and get a torque wrench I suppose

I'll do that tomorrow when I start working on it again, and will take pics if I can't solve the issue...

I thought about that also but there are dowels that prevent that from happening, and oil flows down easily enough when poured in from the top..

Even though they may appear to be even, they stretch when torqued. Make sure if there is a specific pattern that they tell you to follow.. you do so. And if the head was over torqued, it may have flattened the head gasket to the point that it cant be re-used.

Also if I'm not mistaken, some head bolts are designed not to be re-used. Maybe this is the case with yours

Are you certain the heads didn't get swapped? Happens more often than you'd think and will cause leaks. Second, get a torque wrench and look up not just the torque specs but also the bolt order. There is a pattern that must be followed to tighten the bolts, not following it can warp the heads.

Use compressed air to blow out the oil galleys in the heads, these can get blocked and cause leaks as well as the ones in the block.

It probably has to do with them being tightened unevenly.. I'll probably just get a torque wrench tomorrow and do it that way.... if I can find the specs that is.. the bike is an 2003 American Eagle 250cc (it's really a throwaway bike at the end of the day since I mainly bought it to learn about bikes before spending real money on one... but I want to figure hit out if possible considering the leak wasn't there until today so I doubt - hope - no real damage has been done to the head considering I haven't even test driven it yet).. I believe it's made in taiwan and haven't been able to find any info thus far online... As far as the head bolts are concerned... the block has been removed a few times and put back together with no issues until now, so I think they're ok and it's more an issue of mechanic error than anything else.

I'm certain the heads didn't get swapped.. as far as the specs go, I doubt I'll be able to find that info so I'll probably just try different torque settings and stick with the usual cross tighten that I generally do for things like this.

the fact a new gasket is leaking when the oil gets up to temp and thinner should mean the torque on the bolts are not even, you'll need a decent torque wrench, tighten bolt to bolt diagonally until all lock out at the correct setting, just tightening the bolts by hand will cause unevenness even if you cant see it by eye and oil when hot gets alot thinner.

I'd replace the gasket again.

thanks for all the info guys.. I'll likely just pick up a torque wrench tomorrow and start with the honda cr250 spec of 20 ft-lbs since I can't find any info about this specific bike online...

Your head is warped.

You can check it on a perfectly flat surface such as a glass table and looking at it from underneath.

You can also easily fix it with a sheet of fine wet/dry sandpaper (using it wet of course) laying on a flat surface, and moving the head in small circular motions across it. You'll know when it's flat because the sanding marks will be even across the surface.

I grew up racing motocross and really abused my engines in the heat, and rebuilt them often. This is pretty common because the heads are aluminum and warp easily.

^^^ this is Mr Pheer posting from Seth's iPad btw

The coherent post had me puzzled, thanks for clearing that up.

.

may be worth checking out if its the torque first though before you start grinding into the block like that. wouldn't it?

Yes always use a torque wrench on engines. Although once you do it enough times you can put heads on by "feel" and be really damn close without using using a torque wrench. But my method works and it really isnt removing much material at all, if using the proper torque doesnt fix the problem.

thats why i ride an 11 r1 :D

Are you sure it worked properly when you bought it ??
"It needed some minor work done, namely just oil change, tune-up and the like."
It could of been someone trying to dump their problems on you. Soon as you get it running like it should, the problems appear:2 cents:

for oil leaking change your Gasket and Oil ring

https://www.sscycle.com/product/secu...ucts/26012.jpg

ask your motorcycle tech...



HTH :)

Well, I assume it worked right. The only reason the head was removed to begin with was due to one of the spark plug holes being stripped out. If the washer never would have been dropped down inside and didn't get wedged in the gears, nothing else would have been done.

I think it's more along the lines of the faux mechanic I let work on the bike didn't know wtf he was doing.

I'll hopefully resolve my issues later. Thanks again for the tips/advice/suggestions everyone.

check the compression. It could be too high, along with a gasket that cannot handle it. If the compression is low, it could be a bad oil ring, or a cracked piston that gets worse with the obvious rise in temp. The gasket is most likley not seated properly. Also could be after market heads that expand at a different rate than the block. (all supposition . Sorry if I am way off & not any help)

ds

Torquing the bolts in the wrong pattern can warp the head. If it WAS flat, and then you tightened up the first bolt all the way instead of going around tightening them in steps, it'll no longer be flat.

Overtorquing the bolts can stretch them and the set will have to be replaced. You know you've over torqued a bolt and have to throw it away when it suddenly becomes EASIER to turn while tightening. The torque difference been proper temporary stretch and permanent stretch isn't that much. (Think of a balloon that has been over inflated - it will never again shrink back to it's original size.

The flatness tolerance is tiny because a head that is flat sitting cold on the bench can not be flat when torqued and hot. Since any torque will distort the head in done way, it's critical to minimize that situation - torque in three steps, in the right pattern, to the right stretch, with bolts that haven't been over stretched.

Okay, it could be a few things, but let's not jump to the extreme that your heads are warped, especially if it was not an issue before.

When you put the heads on there is an order of tightening the bolts and they have to be done a couple turns at a time. Get some new head gaskets, learn the tightening order, get a torque wrench, some head gasket sealer (ask in the AM and I will go to the garage, don't recall name of what I use).

Pull the head and do it over again. Might as well put heads on a sheet of glass to see if warped, but would not think so.

. . . sorry, just scrolled to bottom . . . . what raymor said.