Radiator overflow leakage

[Gerard De Ruyter (Twistandshout)]

I've noticed I lose a certain amount of coolant during each race day on my '86 250.  I've never really worried about it, but just read an article in MXA which said it could be a symptom of either blocked hose, bad radiator cap, faulty impellor, coolant passageway blockage, lean jetting, water pump seal leakage, thrashed top end, contaminated coolant, or blown head gasket.  gearbox oil is not milky (and i've done the devcon fix of a previous corrosion leak to gearbox plus new seals), lots of compression so top end good (and no reason to suspect blown head gasket), impellor looked fine - so any tips on quick way to try to locate the reason why it loses coolant?  maybe try swapping radiator caps with someone for a race, see if different (watch out young pup and snowy)?  i do notice sometimes when i top up the radiator, some fluid comes straight out of a hose underneath the bike...

our races are never long enough to make overheating a real risk (ie only loses a third to half a cup of coolant at most).

[cyclegod]

Buy a new cap and ensure the rim inside the radiator is free from corrosion and contaminates, the spring and seals on caps don't last forever a new one every two or three years plus an annual flush always helps.

[Gerard De Ruyter (Twistandshout)]

yeah, good idea cyclegod....god know how old existing one is....local honda shop has one there, will grab and try.

[Hoony]

..........................  i do notice sometimes when i top up the radiator, some fluid comes straight out of a hose underneath the bike...

G'day Twisty, this will be from the overflow hose near the radiator filler, hose is on frame side of filler and runs down frame rail and exits under the engine usually, nothing to worry about if it comes out only when topping up.

[cyclegod]

http://cgi.ebay.com/ebaymotors/CRF-YZF-RMZ-KXF-KTM-Husky-250-450-COOLANT-TANK-SYSTEM_W0QQcmdZViewItemQQcategoryZ35580QQihZ021QQitemZ310082408610QQrdZ1QQsspagenameZWDVW

[fsc]

Don't worry about it they all do it and I've done everything trying to stop it, you won't. The honda owners manaul and the honda workshop manauls all say that you will lose between 25- 50ml as normal. I 've had the problem with my CR125 82, CR250 81, CR250 83, my friends CR250 84 and CR125 84. I just take coolant to the races and add some after each race. 

[STW996]

Twisty, you will get all types of advise on this and the article you ready was right but where to start, if it is not loosing a lot of coolant they ok it is not a problem (yet) pressurised systems will leak from time to time but there is always a reason, try the simple things like caps and alike first then look into the other areas as you need to (if the problem gets worse). We have 2, 84 CR 250 and neither "leak" coolant but one a one stage did and we did all the things to fix it turned out to be the barrel (new head gasket, seals, hoses etc), then had it re-bored and at the same time had the top "lapped" and have not had a problem since.

The other thing I found was do not over fill the radiators in the first place, about half way from the core to (top of)the top tank is about right (for me anyway) anymore and it will spit out via the overflow.

This is one problem were I prefer the 79 250 and the 84 500 no water leaks in these baby's

Shane

[holeshot buddy]

just gearboxes

[STW996]

I will give you that one Holeshot

Hey you doing tambo?? Hope to have the 5hundy going (with new gearbox ) for it.

Shane

[holeshot buddy]

yeah i will be there
you can eat my roost

[STW996]

Roast?? Are you cooking? oooh Roost like as in dust nice oh Holly one

[utsman]

Hey Here's my thoughts,

If you fill the radiator right to the top it will leak on the next ride. The bike doesn't have an expansion chamber like a car. So when the coolant expands (when hot) and the release valve in the cap opens to prevent too much pressure, a bit of  coolant goes out the overflow and onto the ground. When you next  check it (cold) the coolant has contracted again and the level is  lower than when you filled it to the top. I've worked out that if you fill it to just cover the top of the cores ( almost full), this gives it the required room to expand so when it's hot it is full but not overflowing (like 996 said) Otherwise you may as well just pour that top up bit straight on the ground.

Twisty, sounds like thats about the amount you are losing?

[Gerard De Ruyter (Twistandshout)]

that makes a lot of sense utsman.  i'm not sure whether i lose a bit more than that or not - will make a few observations at race day this sunday to see whether its just the expanded topup going out the overflow or more than that.  it wouldn't be much more than that anyway.  reassuring info tho.

[STW996]

Racing this Sunday? where to you ride Twisty?

[Gerard De Ruyter (Twistandshout)]

i'm part of the ACT old bikes' crew - we've had a good relationship with the local club for some years now and they're willing to indulge our low overall numbers (mainly cause they have to keep mr amazing, dennis myers, onside as the club's track maintenance guru).  this year we been running a 'new' class, 'Old School', for any bike not with upside down forks or disc rear brake (and that was mainly to indulge me, who for 'various' reasons, runs an '86 CR250.....).  anyway, we get seven or eight bikes each club event, and muck in with the womens' class, and lotsa fun.  all welcome!