Could someone translate? I don't speak...

[K31Fan]

Please tell, what kind of bike / engine ?
However, it is not so simple. If you run the bike easy on city streets, have to be super lean mixture and some other problems if it boils.

Depending on engine and circumstances, blown head gasket does not always mean huge amount white smoke and "milk".

Its a 1995 zx7-L3. So far the motorcycle has only been overheating at idle, or slow speeds. It seems the air rushing around it at highway speeds cools it enough to keep it under correct temp...wait, wha-? How do I diagnose a head gasket leak then?

Bad Radiator Cap......... and a bad seal do to a crash from before I owned the bike the neck was messed up a bit.. smoothed that out and a new cap.. problem gone.

Sounds like a damn good idea. I'll bet my local Autozone would have one.

If its not at least a 50/50 mix, your boiling point will be too low, and youll have your problems.

The coolant came premixed 50/50. So I may be incorrectly assuming that the manufacturer mixed it correctly. But that seems a little out there to me. What else would you like to know about the bike? In terms of miles it has 13xxx on it, and it's a 1995 Kawasaki ZX7-L3 model.

What type of test did you do checking the water pump's function?

I saw the coolant get sucked back into the bike when I blipped the throttle (also makes me think it's not a head gasket problem). And I took the water pump cover off and saw the impeller turn while the engine was running. The impeller isn't loose, and it won't turn after the engine is off since it's gear-driven.

Timing. incorrect timing will cause over heating / lean running

Good idea! That's definitely a possibility. I haven't worked on the timing yet... Are you talking about ignition timing? Engine timing? Or are they both the same thing?

[Byte Stryke]

Are you talking about ignition timing? Engine timing? Or are they both the same thing?

yes,

correction... they are USUALLY the same thing, as long as your timing chain/Gear hasn't jumped

[Hannu]

If you want to be sure about head gasket and/or other internal mechanical problems, bring your bike to a place that has engine leakdown tester... and someone who knows how to use it
Side note; many Japanese motorcycle engines have adjustable cam wheels so you can actually adjust each cam separately.

If your bike ONLY boils while idling or driving slow and works nice when ur on I-25 going 80mph, do not worry about fuel mixture, ignition / cam timings etc. things that need pressure inside cylinder to heat up the engine.

You probably know you need lower temp thermostat at 5000 ft than at sea level ?

[K31Fan]

If your bike ONLY boils while idling or driving slow and works nice when ur on I-25 going 80mph, do not worry about fuel mixture, ignition / cam timings etc. things that need pressure inside cylinder to heat up the engine.

You probably know you need lower temp thermostat at 5000 ft than at sea level ?

...That really doesn't make sense to me - not contesting it, just saying I don't understand.

Anyway, there's only one type of thermostat available for the bike. And that's the 82 Centigrade (179 Fahrenheit) one.

Also, why would running lean not be a problem if the bike doesn't overheat at highway speeds? Doesn't that just mean the air is cooling it down faster?

[Hannu]

When pressure in cylinder is very low (like when engine is idling), ignition timing, mixture etc. things have very little to do how the engine heats up - you can adjust both pretty alot to any direction and as long as engine keeps running relatively smoothly it does not heat up anymore when engine is idling - but only if cooling system is working properly.

But because there is no cooling air flow, problems with cooling system have very much to do how engine heats up while idling.
+in order to make fan work properly, there must be proper cooling liquid flow in the engine. Pressure loss, air in cooling system etc. will make fan much less effective and that is specially visible when radiator does not have lots of airflow and water pump speed is low.
For example, if there is air blockage in cooling system near fan switch - engine will boil before fan even starts working because switch is getting wrong info. And when you test fan, switch etc. everything seems to be fine.

When driving faster engine / water pump rpm is higher, both coolant and air flow through radiator is much bigger - problems with pressurizing, local boiling etc. are usually much less visible... but only before you have white smoke coming out from tailpipes

When pressure cylinder is high, mixture has very much to do what kind of temperatures are happening and where exactly. When cylinder pressure is high, too lean mixture will cause engine to heat up _locally_ (cylinder head, valves, pistons etc) which is usually not possible to see in temp gauge, at least before it is too late. Too much ignition advance, too much boost and some other things cause pretty much the same.
When mixture is too lean - temp raises - uncontrolled mixture burning called knocking starts - ruined piston and usually lots of other broken things too.
Very sometimes you will get early warning if engine temp is rising when pushing the engine at high load rate for a long time.

Many engines (specially charged) use extra rich mixture up top to cool engine down. Some engines use toluene, water etc. and separate injectors to do the same etc.

Of course, this is all very much simplified and guessing - like gunsmith telling you why your pistol is not running by listening your shooting
Hope this will still clear at least something.

Those were the times, when I was drilling small holes to thermostats... Do not do this at home unless you know 110% what are you doin; thermostat also has a big effect on cooling system pressure @ high rpm

[K31Fan]

.....

Thanks for taking the time to explain Hannu; that makes total sense now! I hope Boulder County is still treating you well!

you are doing 1/2 ass guess work, asking for input then questioning their help. you say your knowledge is minimal ,so pay the piper now instead of having a motorcycle with a seized engine

Jim, some of the best mechanics I've known started out doing half-assed guess work at first. And yes, if I don't understand the advice that someone has kindly offered, I'll ask if they can explain it a little to aid my understanding; something that seems like a fairly normal process to me... As to the engine possibly running lean, I'm still working on that (and trying not to seize the engine! ha!) and while I definitely understand the loyalty to TFOGGER here on the forum, I'm actually trying to learn how to fix it myself! But thanks for the input!

Replace the radiator cap as this is most likely the issue. We see this problem every once in a while and it is always the cap.

I think I'm with you and clublights on this one. I'm going to rent a pressure testing tool from my local auto parts store this week, and see if its the cap!

Thanks for all the advice dudes!

Edit: 100 posts! F**K YEAH! I'll be a grand master know it all before you know it!

[K31Fan]

Has anybody here ever DIY'd it concerning radiator cap pressure tester adapters? I got one, but I don't have an adaption small enough to test the radiator cap. At first blush I'd say I just need a different sized adapter, but I'm hoping that there's a simpler way to test it, considering I have to return the pressure tester on Friday, and I really don't want to have to order special adapters for a rented tool.

Any brilliant ideas floatin' around with them naked girls in your heads?

Incidentally, I find I'm coming on here more and more often for advice. The help I get is really great; so far it's helped me fix a legion of stuff wrong with this bike! So thanks guys!

[Great-Kazoo]

...That really doesn't make sense to me - not contesting it, just saying I don't understand.

Anyway, there's only one type of thermostat available for the bike. And that's the 82 Centigrade (179 Fahrenheit) one.

Also, why would running lean not be a problem if the bike doesn't overheat at highway speeds? Doesn't that just mean the air is cooling it down faster?

this is why i have mentioned before take it to someone who actually does mc repair for a living. you are doing 1/2 ass guess work, asking for input then questioning their help. you say your knowledge is minimal ,so pay the piper now instead of having a motorcycle with a seized engine

[wctriumph]

Replace the radiator cap as this is most likely the issue. We see this problem every once in a while and it is always the cap.