Air cooled Seca II overheated, wont start

[mpg9999]

Just got back home. Waiting for the tow truck to call me now. Basically I was sitting in Northern VA traffic for a good 45 minutes, barely moving. I could feel the engine getting hot with my knee's. It also started sounding different. Developed a rattle... Possibly detonatio :neutral:. I wanted to pull over and shut it off, but there was no shoulder. I finally get to a side street, cut in front of stoped traffic and take it. As im on the turn the engine shuts off. I let it cool down but it wont start. It cranks over just fine, but wont start at all. The crankcase/oil has a sweet smell now, slightly sulferish. I really hope the engine isnt dead. Any idea guys? When I get it home, im gona pull the plugs, compression test it, and see how the plugs look. If that checks out im gona check for spark. After that I dont know. Ill probably end up changing the oil too. Any help would be appreciated. Wonder how difficult it is to rebuild the motor, or how expensive it would be to replace. Or maybe I can fit a more powerful motor on it :razz:

[KZ-Rob]

I over heated my KZ real bad once, but it was in the summer, I don't think it would do it now. anyhow, it started right up after cooling off. Definatly do what you said, unless you cooked it totally, it should start again. Compression would tell the truth. Spark is a good idea too, you may have overheated an electrical component.

[mpg9999]

http://www.photodump.com/direct/mpg9999/edit.jpg

Best picture I could get of the plugs (to lazy to take the fourth out, figure its no big deal). Gap looks good. The electrode and tips are pretty black. The electrode insulation is a slightly lighter black/brown color. What do you guys think? Just running a little right, but ok? Time for a compression test, if I feel like doing it tonight.

-Mike, pissed off at his broken bike AND broken car, all at the same time

[Derick]

N o
G ood
K rap

[mpg9999]

N o
G ood
K rap

Are you serious? In the nissan world, NGK's are highly regarded.

[Derick]

From a number of mechanics I use, they refer to that happy little acronym. I dont really care one way or the other...thats just what they say.

[mpg9999]

compression test isnt looking good Im going to buy a new compression gauge tommorow though, because the one im using now is probably from the 60's. Wonder how hard the head gasket is to replace?

[MarcS]

Those plugs look pretty bad; I would replace them. If they are plugged into the coils and you hit the starter while looking at the plugs, do they have a strong spark? Idling for that long may have resulted in incomplete combustion and fouled the plugs. Spark check would be my first test.

Also, make sure the engine isn't flooded -- some bikes have a hard time starting when they are hot due to valve clearance issues or overly rich running; did you try cranking the motor with the throttle wide open? Leaving it overnight with the plugs out should get any fuel left in the cylinders out. After that, you might want to make sure the engine is getting fuel, that the carbs didn't get gummed up, and that you're not out of gas. Make sure that you have spark and fuel before testing compression, esp. if you need a new tool.

[mpg9999]

Those plugs look pretty bad; I would replace them. If they are plugged into the coils and you hit the starter while looking at the plugs, do they have a strong spark? Idling for that long may have resulted in incomplete combustion and fouled the plugs. Spark check would be my first test.

Also, make sure the engine isn't flooded -- some bikes have a hard time starting when they are hot due to valve clearance issues or overly rich running; did you try cranking the motor with the throttle wide open? Leaving it overnight with the plugs out should get any fuel left in the cylinders out. After that, you might want to make sure the engine is getting fuel, that the carbs didn't get gummed up, and that you're not out of gas. Make sure that you have spark and fuel before testing compression, esp. if you need a new tool.

I did check to see if they are getting spark. They are, but I dont know what a strong spark looks like. I have no frame of reference. Maybe ill replace them, I just dont want to throw unnecesary parts (and money) at it. All the plugs are out right now. Ill let it sit overnight like you said, and maybe try to start it again. How do I check for fuel? I've never worked on anything carb'd before. Thanks.

-Mike

[MarcS]

If you can stand unabashed christianity and patriotism, this site is useful.

http://www.dansmc.com/

Logical thinking:
http://www.dansmc.com/logicalthinking.htm
Overview of lots of troubleshooting tips:
http://www.dansmc.com/troubleshooting2.htm
Compression testing:
http://www.dansmc.com/compression_test.htm
Spark plugs:
http://www.dansmc.com/sparkplugs1.htm

The above site basically encourages first checking compression (which you already did, but you didn't say what your results were -- just that your gauge was not reliable and that the results didn't look good), then spark, then fuel.

Fuel is a little more tricky; I'd save it for last, but the troubleshooting above page gives you a quick cliff-notes version of what to do. I'll re-post it here since that site has an ad which is quite annoying, and you may not have time to read all the above stuff:

Ok, we now have spark. If the old spark plugs are real clean you can use them, otherwise put in new ones. Put all the plugs back in the engine and connect up all the plug caps to the plugs. Check the air cleaner and air box. Make sure mice or bugs haven't gotten in there and built a nest, plugging up everything. Look at the air cleaner. If it's a paper type, blow it off and use it until we are sure the bike will run and the gears work. Then get a new one. Paper tends to plug up, as it ages. If it's a foam one, clean it in solvent. As you clean it, rub the foam somewhat roughly. Not too roughly, just a little roughly. If the foam starts to come apart in your hands you will need to get a new air cleaner. A lot of bikes must have that air cleaner in the system. If you leave it out, the engine may run too lean. This, of course, makes you think there is something wrong with the carb. I had an old Suzuki GS750 come in once. If you just took the air cleaner cover off, it would refuse to idle. Put it back on and it idled perfect. The owner put over 60,000 miles on that bike. Ran great, but it had to have that air cleaner on. I've seen a number of different makes and models do the same thing. Sometimes, even a crack in the air box can make them run funny. I've also seen a lot of bikes where having the air cleaner on or off made no difference in their running. If your not sure, leave the air cleaner in place while you work on the engine.

Now drain the old gas out, put some new gas in the tank and turn the fuel petcock to "PRI" or "ON", and check that there is a flow of clean gas to the carbs. Tanks that are badly rusted will require a filter in the gas line to the carbs. If not see the Gas Tank Page. If the gas starts to come out the carb over flow tube(s) tap the carbs gently, but sharply with a plastic hammer or the plastic end of a screwdriver. Do this to each carb several times or until the gas over flow stops. If it does not stop you will have to take the carbs apart and find out why the fuel valve (needle and seat) is not working. See the Carb page. If it will not start, try to drain the fuel out of the carb with the float bowel drain screw. If nothing comes out, nothing is going in ! In other words the needle and seat are stuck closed. Again, if tapping the carb doesn't start the gas flow, take the carb apart to find out why.

Check for water in the gas too. Water is heavier than gas, so the gas floats on top of the water. Drain some fuel into a glass container and look for water at the bottom. You can also take a cotton rag and catch some gas in it. Usually, the gas will soak into the rag, and the water will ball up on the surface of the rag.

If it just will not start, try putting an eyedropper's worth of fresh, good, (as in "Buy It New !") gas down each carb. If the problem is only with the carbs, the engine should start, rev up, and die. Put in another eyedropper of gas, and it should do it again. You can do this even if the carbs are off the engine. Just put the gas down the intake port. Keep your finger on the kill button, in case it revs too high. If it doesn't start, DO NOT keep putting gas down the intake. If the raw gas works it's way into the exhaust pipe, it can vaporize there, EXPLODE, and blow your exhaust (and other things !) pipe clean off ! You can use starting fluid or spray carb cleaner for this too. Just remember to use a LITTLE ! Too much and it can blow things up, just like gas. If it still will not start, it means something else is (mechanical or electrical) wrong too. This will work for both two and four stroke engines.

If it starts with the choke, but will not idle with the choke off, check to see if the idle jet is plugged. If it will not idle, but seems to rev up, down, and then dies when you try to adjust the idle. You got an air leak in the carb manifold or gasket. If your ignition timing is way off or if the automatic spark advance is stuck. These things can cause erratic idling and strange running. If it starts and idles good, but loses that good idle as it warms up. Check the valve clearance. If a valve is just a bit tight, it can leak a bit after things warm up and expand. Once you know the engine will start and run, I would turn it off and change the oil and filter. You don't necessarily have to do this. If the original oil looked and felt good, you could run it for a while. However, oil is cheap. Why not replace it ?

[mpg9999]

Got my new compression gauge. It was something like 100, 70, 35, 65. So needless to say, thats a problem. Head gasket maybe?

[mpg9999]

I just put oil in the 65 cylinder. It jumped to 230 psi!!! I need to mess with it more tommorow.

[asp125]

Tighten down the cylinder heads and rerun the compression test. It may have overheated the heads enough to warp, causing the leak.

[Derick]

what's the spec compression?

[mpg9999]

Spec is 150ish. asp125, as far as I know, tightening down the cylinder head wont help if the gasket is blown or the head is warped. Only solution is to remove the head, resurface it if its warped, and replace the gasket.

Apparently if your pressure goes up alot with oil, it means its the rings. It may just be fuel wash out, crossing my fingers on that one.

-Mike

[Derick]

I wish i had your know-how, i envy you in this situation. I'm fretting about getting these stupid throttle cables replaced... :0

[mpg9999]

Its a beautiful day, in the 60's. I had less then an hour before I had to leave for class, but I just got this strange feeling that I need to try to start my bike. I go out back, pull the choke, and crank her over. It actually started to "catch", and almost start. Hmm, wasnt able to do that before. Crank it over again and work the throttle some, and BAM, it started!!!! It was a little rough at first, but it ran!!! Smoke was kind of heavy especially from the right exhaust pipe (which connected to the cylinders with the worst compression). I thought ok, it at least runs, but I still need to replace these rings. After about 20 seconds or so, the smoke let up. I was so freaking excited. I guess the smoke was just the oil I stuck in the cylinder burning off. I ran inside to grabbed my helmet, and took the bike out on the road to see how it felt. I got onto a main road and got on it a little, and it felt great!!! So my bike is back to normal, and I couldnt be happier I was so excited that my bike was running now I let out a nice yell riding down the road (I KNOW you other motorcyclist do similar stuff, sing, talk, whatever. You can hear yourself really clearly in your helmet).

So, right now I am going off the theory that the rings where just washed out from fuel and the oil helped them regain there seal. I am going to do another comopression test soon. I also sent out my oil to blackstone, which should be interesting since it smelled like sulfur. I still dunno why it didnt start until today, and not after I put the oil in it, maybe the oil needed to drain out of the cylinders before it would start. I also still don't think it should have overheated in the first place. I think I should take a close look at my carbs and see how those are. Anyways, Im back on 2 wheels

[LoDownSinner]

Glad to hear it's running, but I'd still be concerned abut the cylinder that showed 35. A wet compression check basically 'forces' the rings to seal.

On checkig the spark, blue=weak, white/yellow=good.

[mpg9999]

Road again today, and the compression is perfect at about 150 all the way across :).