i've changed a new cap twice. the first one was the similar 1.1 then i changed it to 1.3, both didnt help with the problem. just now i rode it, coolant was leaking out of the coolant reservoir tank. it was leaking at the bottom hose where it connects to the reservoir. since i have been adding coolant into the radiator directly each time the level drops, now the level in the reservoir tank have gone above the Full level.

seems to me when the engine heats up, the coolant travels to the reservoir but when it cools, something is preventing the coolant from traveling back to the radiator and due to the high pressure the hose that connects to the bottom of the reservoir is leaking.

when i open the radiator cap after each ride, i get an "air pressure sound", like opening a can of beer.

im not sure how a cracked cylinder can cause this problem but if its a cracked cylinder then my luck is certainly bad.

i will check the hose again tomorrow, maybe take it off and run of stream of water through it to make sure no blockage then put it back on. if the problem is not solved by next week, i will change the cylinder head gasket.

And if the problem is still there, i will get rid of the big bore and install back the stock cylinder head and piston.

 

Lots of others on the internet with overflow bottle problems on their bikes and cars etc.

Answer range from a leak in the hose going to the bottle, radiator cap seal, to a head gasket.

Maybe try moving your bottle right next to the radiator cap with a short extra piece of new hose connecting it to the overflow spout and see if you can eliminate the long hose going back to the bottle now as part of the problem.

The air pressure 'pop' when you take off the cap could be from a head gasket leak pressurizing your cooling system. What happens if you idle the engine with the cap off? Can you see bubbles in the coolant? (sorry if you answered that earlier)

I had head gaskets leak on two cars back in 2010; my worst year ever for buying used cars . Overheating and bubbles in the coolant as you look into the cap opening were common symptoms

 

I think i have eliminated radiator cap as a source of the problem since i replaced 2 new ones and the problem is still not solved. i will remove the hose today and blow air and water into it to make sure no blockage or leakage. if all else fails, the gasket will be replaced.

yeah i do have bubbles when the cap is off and the engine is on, is it possible for combustion pressure to enter the radiator while no coolant enter the engine? like i mentioned earlier, i wish i had a clearer sign on what is wrong.

One more thing, after the big bore, when i look at the gasket for the big bore, the water channel holes are pretty close to the bore itself chances of leaks are quite high.

 

You might want to do a pressure test of the cooling system at the radiator cap. The cooling system should hold pressure. If it bleeds down you have a leak. Testing at the cap is independent of the recovery system.
Pull the spark plug during the pressure test. See if any coolant leaks into the cylinder. If not then the head gasket to cylinder seal is fine, but you could still have a coolant leak into the crankcase.
If your oil is milky or has a yellowish in color then there is water in your oil. Oil and water plus heat make the oil acidic and can do bad things to crank bearings over time.

I have not done a big bore kit yet but plenty of experience with infernal combustion powered transportation.

I am seriously considering a BB 331 kit as my next improvement so....
Good Luck and keep us posted

 

If you do end up replacing the head gasket, I'd strongly recommend going all the way down and replacing the cylinder base gasket as well, while you're in there. It shouldn't be that much extra work and you don't want to replace your head gasket and put everything back together, only to still have problems due to a bad base gasket. Good luck. I've got a thousand miles racked up on my big bore and so far it's been all smiles. I'll probably keep my fingers crossed til the day it dies lol. I'm planning on (hoping for) at least 30,000 miles out of this machine before I need to do another top end. If I get 50k+, as some reportedly have, then that'd be awesome, but I'm not counting on that much, especially since a lot of the miles I put on my dual sports are very rough, low speed off road use, which can amount to two or even three times more engine-run-time than cruising along at 60 mph on smooth highway. I'll do 4 to 6 hour day rides where I only put 30 to 50 miles on the bike! Think about how many miles I'd have on the odometer if those six hours were spent slabbing it down Interstate 10 lol... My DR200 has 20,000 miles, but if all its run-time were only highway commuting, it'd probably show more like 35,000!

 

I think some of the early BB 331 kits commonly had gasket problems, but Bill has changed the gaskets since then, so this type of issue (if in fact this guy here does have a gasket problem) should be pretty unlikely, particularly if you check the gaskets for ANY sings of damage before approving them for use, and obviously make sure to install them properly (no damage during installation). With the 331, even with bone stock exhaust, carb (only re-jetted), and gearing, you can shift at 5,000 RPM all day and still have more than enough smooth rolling torque to get you up a steep mountain road, even at half throttle or less in top gear! The only reason I ever rev the motor above 5k RPM on the street anymore, is if I want to go a little bit faster, never because I need more power. It's freakin great man, lol! By the way feel free to PM me if you ever have any questions about any aspect of the big bore, or anything about the KLX for that matter! I've been meaning to do a write about my build, since I have a TON of mods, including the big bore, and over 40 hours of work and a couple grand into the finished product! SO worth every penny and drop of sweat, and the occasional extreme-frustration-induced headache lol!

 

KJ7687 - Thanks for the feedback Just curious, what altitude to you generally ride?

The main reason for thinking BB331 is last weekend I went on a ride with a substantial climb at high altitude. The section I failed on was the last of 3 switch backs which totaled over 1000 ft climb in less than a mile. The climb topped out at about 10,500ft. In the last section the bike began to drop power until I stalled it. The stall occurred fairly quickly once the rpm dropped below 4K rpm. The engine felt like it was running out of steam. Once stalled I got it restarted it did not initially want to rev over 5K. I ended up slipping the clutch to keep the RPMs high enough to keep it running and get up the last section of the climb. I am correctly jetted for ideally about 7000ft.

My riding companions recommended getting a bigger bike like they we on: DRZ400, KTM500, XR650 etc. I was the only little bike (250) at the event; a fund raiser for the New Mexico Off Highway Vehicle Association (NMOHVA) . The group was really supportive in keeping me from turning around an going back down. This is the first time I felt let down on my KLX. Other than the last 100 yards of that climb the other 65 to 70 miles of mud holes, short rocky climbs, snow drifts and water crossing the bike performed flawlessly; even if the rider didn't.

Thanks

 

Capt, I'm assuming this high altitude ride was on dirt of some kind. At that altitude you would most likely have needed one notch of needle drop and probably a main jet drop of one size. It's just usually a requirement when you tackle those kinds of altitudes. It will likely be necessary regardless of having more displacement. The actual stall was probably just a result of the idle needing to be turned up a bit as you were climbing. Displacement will certainly help, but high altitude riding...especially on trail or gravel...improves by a ton with proper jetting. If you're just going over an occasional pass with most riding done at noticeably lower levels, you can suffer through. However, when I go to CO or such, I go for the high country riding, so a rejet is more than worth the trouble...even with a bigger bore.

 

Yes i will definitely replace the base gasket as well, since it comes in a set of top and base, i will definitely replace both. The brand of gasket used by Bill is Cometic, i believe this should be good quality gaskets. However the top gasket looks like it has flashes at the side, im not sure if this is normal. But one thing which stands out is the proximity of the water channels to the bore, installation of the gasket has to be very careful and tidy. i will watch the tech install it this time, also gives me a good chance to have a look if the other parts are ok.

i checked the hose that connects the radiator to the reservoir and it seems ok, but i re-lay the hose to see if there is any difference. i flushed the radiator again and put in new coolant. i will run it again this week and it there is still problem, i will replace the gaskets. i also ordered Engine Cool but have not arrived yet, hope that will help too.

 

My normal day-to-day riding is at about 3,000 to 3,500 feet ASL. However, I'm fairly confident my bike will run at least well enough to be usable up to pretty much as high as I'll ever ride. The thing is, if you jet a bit on the lean (smaller jet - less fuel) side, which I believe my bike is for my altitude, it will still work okay at lower elevations (albeit with slightly less power than you might get with "perfect" jetting for a given elevation), but you shouldn't have to mess around with your carb settings just to get by at higher elevations. This is great for someone like me who is super lazy when it comes to having to change or adjust something that's supposed to be DONE. For example I'm also way too lazy to switch CS sprockets in the middle of a dual sport ride (as some people will) just to have better street and better off road gearing. I'd rather just pick one that works and leave it be. Same concept applies to the carbs in my bikes. I'd rather have some power loss than have to turn fuel screws or remove air box lids or any of that crap. That stuff works for some, but it's not my cup of tea. As for your friends' recommendation for a bigger bike, they do have a point to some degree, as a more powerful motor will be better able to cope with an elevation-induced power loss (since it will have more power to start with...). That being said, leaner jetting and lower gearing will help (since the RPM will be higher at any given speed in a given gear), if you think you might want to go that route... That's definitely a lot cheaper and easier than doing a big bore. I've found my DR 200 is a bit of a dog above about 8,000 feet. I found I needed to keep it in first gear a lot more and really keep the thing reving quite high for it not to bog down. For the record, I really didn't mind that lol. To me it just adds to the adventure, which is what these bikes are all about anyway right, lol? As long as I do keep the revs up, it works just fine up to probably 9k feet or so... If you go big bore on your KLX, you'll have a bigger motor (obviously...), and therefor as I said, you shouldn't have to worry as much about power loss from high elevation. I've not actually taken the KLX to higher elevations yet, but I'm quite confident it'll do just fine with the current setup.

EDIT: I just read exactly how high you were talking about. If memory serves, some of the mountains surrounding Death Valley, CA may get up that high. I've ridden there on the Suzuki and it did okay. That is indeed quite high, but I still think with a 331 and on-the-lean-side jetting like mine (DJ 124 main with air box snorkel removed), you should be okay. Next time you're in that situation by the way, pull off your airbox snorkel and lid (if you had them on). That should help the engine breath a little easier when it's suffocating like that.