| Author | Message | ||
     Reepicheep |
I just finished a fairly major top end rebuild on my KLR-250, and its running great except for an issue with the cooling system (darn unreliable water cooled bikes  ). I fill the radiators, bring the overflow bottle to the full mark, and run the bike. Runs cool and flawless... for about 10 miles. Then it starts to get hot. Then it starts to get hotter faster. Then the temp starts to run away, and it's pull over and shut down *NOW* (learned that lesson the hard way). Pull the radiator cap while still hot (yeah yeah, I know) and the radiators are almost empty. The fluid is pushed out into the external tank. Blow on the vent line to force it back into the radiators (cap off), fire up the bike, and its cool as a cucumber and ready to go again. I was worried about a head gasket leak, so I ran the bike with a balloon over the overflow vent, and if anything it was drawing a vacuum. Seems to me that if I was leaking through a head gasket, the balloon would be inflating. Plus both oil and antifreeze look uncontaminiated. I also pressure tested it, found a couple minor leaks, and fixed those, but its still doing it (after one ride). Maybe I need to be patient and let it burp itself, but it sure seems like something else is wrong. Ideas? Strategies? Thanks! | ||
| Johnnylunchbox |
There may be bleeder valves in the system. It may not be a self-burping system. All pure conjecture on my part since I know nothing about the KLR, but may be food for thought. | ||
| Reepicheep |
The manual says a heat cycle will take care of it, but clearly it hasn't. The more I think about it, it seems like it has to be a head gasket leak. I can't see how else that much fluid (full contents of radiator) could be forced out. I'll check a few more things before I pull the head... again  | ||
| Hughlysses |
Reepicheap- they used to sell a cheap detector kit that you could use. IIRC it was something like litmus paper that would change color in the presence of combustion gases. You held it over the radiator inlet with the engine running. Not sure any such thing exists any more, but it might save you an unnecessary head removal if you could find one to confirm the problem. Maybe it's something simple like the thermostat is in backwards? | ||
| Reepicheep |
The thermostat vanished sometime during the 20 year lifespan of this bike. I pulled it to check when I was rebuilding the head, and it was just an empty shell (you need the frame for the o-ring to seal the bracket). So I go to the parts bike I bought, figuring I would check that thermostat. Yup, you guessed it, another hollow shell. Thats the problem buying a parts bike to fix up your 20 year old dirt bike... your parts bike is a 20 year old dirt bike also My parts bike needs a parts bike  I'll look for something that will detect exhaust in my coolant... thats a good idea. | ||
| Bandm |
Here's what I use to check for head gaskets blowing air into the cooling system. Usually check overflow first, then radiator filler. http://buy1.snapon.com/catalog/item.asp?P65=&tool= all&item_ID=69954&group_ID=1505&store=snapon-store &dir=catalog Mark | ||
| Hughlysses |
Reepicheep- if you've got a shell of a thermostat to work with, you could go to the auto parts store and try to find one that'll fit. Somebody on our Yahoo group came up with one to work on Honda Ascots like mine; ~$5 Stant that works as well as the $35 Honda original. | ||
| Thumper74 |
Your local Napa/CarQuest will have a chemical to put in the coolant that will turn colors in the event of exhaust gas being in the coolant... It saved me the trouble of a headgaskt on my focus. I was losing a tiny amount of coolant and was convinced it was the headgasket. After trying that stuff and not seeing anything. I checked the cylinders with a leak down guage and found nothing out of the normal hot or cold. I pressurized the cooling system and lost a tiny bit of pressure overnight. I put some UV dye in the coolant and found that the thermostat housing was seeping onto the head and mostly drying before it ever hit the ground... | ||
| Kenb |
maybe the impeller on the water pump is bad, not circulating water so it overheats. just a thought | ||
| Reepicheep |
I'll check those. A new head gasket is only $20 or so, and maybe 1 to 3 hours work (depending on how much I hurry), so I may just replace it if the local place has it in stock. Thats a 20 year old part in there anyway... Meanwhile, I'll go take a ride with a balloon, mainly just to entertain myself  | ||
| Miamiuly |
Meanwhile, I'll go take a ride with a balloon, mainly just to entertain myself That'a funny as hell, almost makes me want to try it just to see what kind of looks I get. Mylar or a nice shiny color is the question, and helium filled of course. | ||
| Thumper74 |
If you pull the head, have it pressure checked at a machine shop | ||
| Xl1200r |
Reepicheap- they used to sell a cheap detector kit that you could use. IIRC it was something like litmus paper that would change color in the presence of combustion gases. You held it over the radiator inlet with the engine running. Not sure any such thing exists any more, but it might save you an unnecessary head removal if you could find one to confirm the problem. You can still get these. They also sell kits that do the same thing with a fluid (turns from blue to green to yellow), but they're pricey because you need to fluid plus the tool. | ||
| Reepicheep |
The balloon (nice little water balloon sized, in blue to match the KLR) stayed empty until the bike came up to temp, and stayed empty for a while there... then "foop", it filled up almost all at once. To about a fist sized ball (which would be enough to pop out my coolant). This repeated a few times, 4 or 5 fist sized "foops", which is way more air then ever could have been trapped in there in the first place, even really heated. Nowhere else it can be coming from other then the exhaust. I reused the original head gasket, so I am not surprised. You roll the dice and you take your chances. Hopefully its not something with the head itself... that was the whole reason I bought the parts bike... Guess what! My local Kawasaki dealer does not stock a head gasket for a bike that was made from 1985 to 2002. Go figure, its those Harley... err.... Import dealers again | ||
| Bob_thompson |
Reep, I have seen head gaskets fail and let coolant into the combustion chamber so slowly that it could not be detected easily from the various methods expressed here. One thing that sometimes will tell is; if you pull a sparkplug it "can sometimes" show coolant getting into the combustion chamber. Usually small brown spots and sometimes, with water only as a coolant it will just look really "clean or appear as lean" By now you might know what they used to look like normally so maybe you will see a difference, but try and not be mislead, a new rebuilt engine may show a great looking plug due to increased compression. Coolant leaks usually start slowly and as the engine heats up and everything expands it gets worse. On the head gasket; you might consider buying a piece of copper sheet close to the same thickness as the stock gasket and make your own. Soft (not tempered) aluminum will also work in a pinch. I have done this several times when old parts were not available. Just use the old gasket for a template and cut very carefully so no edges are overlapping into the combustion chamber. If the sheet copper is too thin, use two and stack them with a copper based high heat gasket sealer. You should always use a sealer anyways with any gasket on both sides. Lets hear back how it turns out. I really like older run-a-round bikes for the countryside. Bob | ||
| Road_thing |
Reep: Is the head gasket copper? If so, you might try annealing it with a torch. Did you end up changing out the head or were you able to salvage the cam bearing surfaces? rt | ||
| Reepicheep |
The original gasket looks like bare or parkerized steel. The parts bike gasket looks like steel, with some kind of silicone coating (in very bad shape). I tried re-using the bare one, and left it bare. I could not find anyone who would touch the head for less then the value of a good used head. So I was looking at $200 easy. Because of the blind hole at the other end, I could not use an adjustable reamer, and fixed blind reamers were pushing $50 and up. That's an expensive "long shot" for a head that is clearly already in bad shape. But hmmm... there is a whole running bike with no title about 3 hours from me selling ebay... I'll make an insulting offer on it ($565 top bid) just in case. You *know* where this is going, don't you? So I find myself with Jack in the car again (my road trip to pick up a motorcycle buddy) with a KLR-250 behind me. Of course, upon pulling that bike apart, that head had "issues" as well, but was more usable. The combustion chamber ate something at some point, and was a bit chewed up, but the important surfaces were all fine. One valve was just about worn through on the edges, so I swapped that from my head with the trashed journals, polished what I could, and swapped it over. After I got it together and fired it up, it did well, but suddenly got pretty "tappy". Figuring I didn't trust my instincts last time and killed the motor, I did trust my instincts this time and pulled the cam cover. One of the jam nuts on the valve adjusters was gone. So the top end came completely apart again, as did a lot of the bottom end (did not have to split the cases). After a tense couple of hours, the nut was found and no other damage appears to have been done (lucky!). Ran OK, but was overheating, and vibrated a lot more then I remembered. Then I remembered that chain that drove the water pump and transmission input shaft. And remembered the statement that the KLR-250 had 4 counterbalancers. Dang. I bet that chain had to be lined up with the crank and two other shafts, so the bottom comes apart *again*, and I fix that. Smooth as silk now, and in fact *so* smooth that I suspect it was wrong even before I took it apart. But now, because I re-used the head gasket, the top comes apart *again*. And did I mention that last time I put it together, in spite of using the *exact* torque Kawasaki wants, two cam cap bolts pulled out of the head and had to be heli-coiled? Ah the realities of a 23 year old dirt bike (or two 23 year old dirt bikes, as the case may be). I need a better mechanic! I found a whole cometic top end gasket kit (including head and base gaskets) for the bike for $30, so that is already ordered. Hopefully that will clean things up. | ||
| Bob_thompson |
Just remembered another thing I have encountered and what I did. On single cylinder aluminum heads they occasionally warp slightly and will not seal a thin gasket very well. My fix was and is to coat the gasket surface with bluing (a magic marker will work also), and draw file carefully until all the bluing disappears and you have a "perfectly flat" surface. Then precisely torquing the head. Milling the head slightly at a machine shop would be better but considerably more expensive. To test flatness before ruining a new "gasket kit" lay a steel straight edge across the gasket surface in several directions while holding it up to the light looking for light to show through under the straight edge. A couple of thousanths is acceptable, no more. Good luck my friend and thanks for your help over the years. | ||
| Oldog |
Reep: can you verify that the water pump is working, the foop - foop sure sounds like the coolant in the engine over heats in pockets those pockets flash to steam and blow the coolant out, the steam removes some coolant and heats the rest. the remaining coolant gravities to the hot areas and the process repeats foop-foop this seems to also make the "vacuum" bit make some sense until the liquid begins to vaporise you would have no additional pressure. My 0.000002$ check the water pump output. Err and make sure that ALL of the passages are clean and devoid of air, If you dont have a hand held vacuum pump call me at home tonight I will fetch my cheepie outa storage | ||
| Oldog |
Reepi: Your earlier description shure sounds like no flow / low flow allowing hot spots to form, if the coolant pump is air bound / or damaged the coolant would not flow or not flow sufficently to cool the hot spot. this would lead to hot spots in locations like say on top of the combustion chamber, the coolant would be expelled in "gouts" as that area got hot enough to flash the coolant to steam. also you may be aware of this but if the system is intended to be pressurized and is not the coolant will boil over at a lower temp as its boiling point is lowered. BTW you are a fine mechanic, its a 23 year old bike and well $hit happens! my 0.0000002$ FWIW. | ||
| Reepicheep |
I have a lot to learn as a mechanic, but the price is right Good advice Bob, if that head comes off, it won't go back on without being checked for warping. I was thinking along the same lines you were thinking, with some valve grinding compound and a plate of glass I can see some coolant flow when the bike is running by looking down into the radiator (with the cap off). It has enough flow to raise a bump on the surface, and I pulled apart the water pump and it has no obvious damage. I can flush the radiator of coolant and rig up some hoses to circulate water in a bucket. That would be almost as much fun as the balloon trick . And you may be on to something. I didn't post this, to try and limit mental pictures of me looking as silly as I looked, but I took the inflated balloon off the hose, and "sniffed" it as it deflated. This as like the 4th or 5th time the balloon had been inflated and deflated, so if there was air in the system it was long since purged. I expected to smell the same exhaust smell that is all over my cloths every time I ride this bike... if it was a gasket leak or a cracked head, it should be exhaust or fuel in there. But it didn't. It smelled, well, like antifreeze. Not a hint of fuel (burnt or raw). So you might be on to something... Hmmmm.... Maybe I'll rig up some hoses and a bucket tonight. 250cc 17 HP super soaker, anyone? | ||
| Reepicheep |
+1 for OldDog! Thanks Jim! I broke the line between the radiator and the water pump and inserted some hoses into a bucket of water, and it wasn't moving squat. The water pump intake was going right to the bucket, and it was not moving a thing. So off to figure out why the water pump ain't pumping... more updates to come. | ||
| Ceejay |
damn archaic pushrod air-co....hey wait a minute... | ||
| Reepicheep |
Hmmm. Further inspection did indeed reveal a missing shim on the water pump impeller. But even after putting that in, the thing still barely moves any water, and of course the bike is still burping and overheating. How much water should that water pump move? I'm loving that Buell. No valve adjustments, no liquid cooling, no chain to lube (or replace, the Kawk broke one of those also). 2x the milage of the Kawasaki and NONE of the problems. | ||
| Oldog |
Reepi: the water pump may be air bound, if you have air trapped in the impeller housing and/or the inlet line the pump will not move liquid a request, if i may, please post pix either of the engine in the water pump area or from the FSM so I can see the system more clearly perhaps more sets of eyes, ( Henriks signal switch =) ) I'm out of the house over the weekend the AC system is whizzing on the floor =( so off to FLA to see mom =) | ||
| Oldog |
 one last thought ( I don't like to leave friends in the lurch ) try feeding it with the garden hose and try to flush out the air as you fill the motor / bucket leaving the outlet out of the bucket when the air is purged then try the pump flow test, BTW what are the pressure and flow specs? | ||
| Reepicheep |
I'm gone for vacation all next week, so no hurry. I have a nice reliable Buell to ride, so the fact that I have an unreliable Japanese motorcycle in the garage is not a big deal. It's a nice hobby The water pump is well located to purge air. The inlet and the outlet point almost straight up, as soon as you put any fluid in the radiator it falls down into those inlet and outlet tubes. Here are some pictures from the shop manual..     If I understand that last diagram correctly, I measured out at about 6.2 mm, so I should have needed a .8 mm shim. There was no such shim on my motor (making me wonder how the heck the thing ever ran without overheating). On my parts motor though, it did indeed already have the .8 mm shim, so I brought it over and installed it. It still pumps really anemically. I can crank the thing over with the kick starter easily by hand, so I am tempted to shim a little bigger and just watch for interference. Before I do that, I will probably "test in a bucket" one more time... I was trying to test the whole system, and that was really hard to do without just draining things. So I think I will pull both hoses, fill up the system so the head has at least some non circulating water in there for a short run, and just put the input and output to the water pump into a bucket and see what it moves that way (carefully priming it first). That will be the authoritative test. I should have done that last night, but I let myself get wrapped around the axle on the path I was on. I wish I knew how much water that pump is supposed to be able to pump a minute at idle... I'll go back through the manual again and see if it's hiding in there somewhere. | ||
| Bob_thompson |
Couple of things to remember Bill; a water pump does not have to pump much volumn or have much pressure, it is merely a circulation pump and if I remember correctly you do not have a thermostat for it. Also the coolant has to remain in the radiator long enough to have the air through the fins cool it and the reason for the stat. It is also a flow restriction even when open. Some people have used a proper size washer in its place to act as a flow restriction when a thermostat was not available. Also as I believe the engine was not overheating before your work so try and determine what you might have missed in your rebuild. Just might be something simple. | ||
| Reepicheep |
Thanks Bob, thats good info. I could not get a good test the way I was set up last night, so I need to re-test with a clearer objective. The way it was last night, it could not even pull water out of a bucket... but like I said the test was a mess of crossed tubing and leaking water. I would think it should at least be able to pump something like a .5 to 1.5 gallons of water in a minute. The head gasket is the only other suspect at this point (and a new gasket is on the way in the mail now). I'm not sure about the original failure. The terminal effect was an oil starved cam journal, but the "vanishing oil" was never explained. The symptom I saw before the failure was... overheating... So I can't rule out the possibility that the initial failure was cooling system related, and I overheated the thing, which caused it to consume oil at extreme rates, which ultimately lead to the head failure. Slower flow makes sense... I'll try and get a thermostat. | ||
| Ceejay |
There's some complex formula for figuring out head pressure, but not knowing your tubing size the pump may not be able to over come it and thus even if it were brand new wouldn't be able to pull water from a bucket that's a foot and half below it-especially if you've got a decent length of hose. I'd try an upside down 2 liter hanging from the handlebar. That may or may not help. |
