Cooling system

Just filled the radiator, reserve was already full, on my '84 vf500 not more then a week and a half ago and just yesterday i found that the reserve was completely empty. I've been looking for any kind of leak but haven't had any signs. The bike seems to be functioning just fine except the coolant seems to be all but disappearing! I'm new to bikes so i'm not even sure what kind of problem or signs to look for so any help would be much appreciated.

 

well...

there are tools out there for cars to pressurize the coolant system and highlight where the leaks are. I'm not sure about the availability of those tools for motorcycles though. (kind of like a bike pump that connects to the radiators.) you could ask your local motorcycle shop if they have one.

or, hoses (cheapest possible problem) can develop cracks that leak once the coolant is hot. massage the hoses when the engine is COOL (IMPORTANT) you may find a leak.

 

Hows your oil lookin'?

 

Oil seems to be just fine, checked it today and it seemed okay, no odd colored exhaust or anything either.

 

My '82 VF750S (Sabre) lost coolant too. I unfortunately found it in the oil. I haven't torn it down yet, but I fear it's a head gasket.

 

It's possible that you just had an air bubble in your cooling system if it was low before. But I would deffinatly give it a once over.

 

If it was a head gasket, you'd either be low on power or it would be in your oil. I like the air bubble idea.

You might try flushing the line and refilling. If you bike has a few years and/or a few miles, it may be time for that anyway.

 

Not necessarily. On my '85 VF700F, my rear headgasket blew. The coolant leaked into the combustion chamber and was flung out the exhaust - but no white smoke - the leak was so slow.

Then my front headgasket blew.

Do a compression test on the cylinders. Harbor Freight has a universal compression tester for $16 that worked fine. http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92720

Doing the compression test will probably take 2 people.
- kill switch in the "off" (not run) position,
- hold the throttle wide open
- firmly hold the compression tester in the sparkplug hole of the cylinder you're testing.
- Thumb the starter until the compression stops rising.
a. Do not run it for more than 3 or 4 seconds as you can damage electrical components.

Do this for each cylinder. When my rear headgasket blew, I saw PSI around 50 - while the others were above 150.

When my front headgasket blew, I did this test on my front cylinders and saw 180 psi. This was because the coolant in the headgasket was sealing the combustion chamber. I also had significant coolant leaking into the exhaust.

Note: When I tested my front cylinders, the compression test caused my radiator system to pressurize. When I loosened the drain plug on the radiator bottom, coolant sprayed in a 4' circle around my bike .

 

for the tool to pressure test your radiator, you might also try a local auto parts store, some of them rent tools like that, which are nice to have, but used so rarely for most people, that it doesn't make sense for the average shade-tree mechanic to buy one
Of course, it may not fit, but who knows, worth a shot.
There is also dyes you can buy and introduce into the system that when they leak leave a stain, or appear under ultraviolet lights.
The cheap simple solution is to follow a service manual about how to full and burp the radiator, you said you just got it, so the prior owner may have serviced it before selling it, and didn't do it correctly. Don't know about your model and year, but I know on the 98, if you just fill the radiator directly, you end up with a BIG air bubble int he system. Under heat and pressure, the air moves and shows up elsewhere, and the cavity is filled with that coolant.
You also may be leaking it somewhere, where it leaks onto a part that is so hot during normal operation, that it burns the coolant off. Run it hot in your driveway or vented garage, as it would be easier to find that way then when under way.

 

Hey thanks for the info and advice guys, I was riding today and the bike made a clunking sound. Now there is an odd almost popping noise coming from the exhaust area? I will have to do more investigation into where exactly its coming from. Bike seems to be idling low now and struggles to start, does this provide any more insight into what the problem is?

Again, any input is appreciated.

 

Yeah . . . stop riding and pull the plugs - how do they look. Look down the sparkplug hole and see if the piston looks wet. Do a compression test ASAP.

Keep ridin' it with problems and it "can" get progressively more expensive to fix.

 

You might take a LITTLE sniff of the exhaust. If it smells like antifreeze or a little sweet, I would lean toward a cracked head or blown head gasket. Also check the oil. See if it if it looks like a chocolate milkshake.:frown:

 

It appears to be a blown head gasket.. can anyone give me an idea of what the repair costs might be?

 

Local Honda place won't even work on the bike... it seems to be missing on a cylinder. Thanks for the help guys, looks like i'll have to find a good mechanic to get it fixed up all nice.

 

most shops will only work on a bike that is less than 10yrs old. you might find a mom & pop shop to do it for you, or do it yourself... just use zip locks and label everything.

 

Call Honda Customer Service. They'll find a dealer who'll work on it. The dealers in East Tennessee don't seem to have a problem working on even the oldest Hondas, as long as they think the bike is worth what the bill will be (in case the owner never picks it up and they have to sell it for the bill). Be sure to find someone who knows these bikes. They are a little complicated for the average joe.

 

Head Gasket . . . about $36 + shipping.
Manual . . . about $20 + shipping.

Time well spent to understand your bike . . . priceless.

Just replaced the rear and am now in the process of replacing the front headgasket on my VF700F.

Doing it myself, because I don't trust a dealer to care as much about my bike as I do. Plus - why pay someone to learn how to change a headgasket on a Honda V4 engine when I can learn how to do it for free.

 

Let me know how hard the job is. My 83 VF750S needs the same thing. Was it hard to put the cams back in time? Did you have to pull the engine from the frame? This Sabre looks like the engine will have to come out.

 

The job is not hard - just tedious. Use labeled zip lock bags for your parts.

If you've already done a valve adjust and removed your carbs before - You've already done 2/3 of the job. The most laborious part is cleaning the block and head of gasket material.

I can only say that for my VF700F, the rear head requires the engine be dropped. The front head does not.

Still working on getting the front cams back in with correct timing. The firing order is different between the SabMags and the Ceptors.

I believe the Ceptor's firing sequence is 1-4-3-2 while the SabMag's are 1-2-3-4.

Can anyone confirm the 1st Gen's Ceptor's firing sequence?

 

I have a book for my 1983 Interceptor, and was going to use that to do the headgaskets on my Sabre. Thanks for letting me know that there may be a difference. I'll go ahead and buy the correct book for the Sabre. Keep us informed on your progress. If successful, Intrested in doing another one?:decision: