Overheating Viva

[Gary]

With all the other posts about overheating I didn't want to be left out. My Viva had been running nice and cool, then all of a sudden started running hot. I changed the coolant, but that didn't help. I looked around and found that a small port on the plastic radiator fill piece had cracked:



I'm not sure what the purpose of the port that broke off is. The hose that attaches to it goes off to the engine somewhere around the head I think. The other small port leads to the oveflow tank, and the big port at the bottom goes to the radiator.

Allnewsports has a replacement on order they say. In the meantime, I used some fiberglass reinforced putty used for boats to make a temporary repair:



This seems to be holding up so far.

While I was at it I noticed that one of the frame bolts was missing:



Seems like the holes didn't line up quite right so they didn't put the bolt in.... I installed the missing bolt, but can't say I notice any difference.

[monty57]

Gary,

The small, lower port should go to the bottom of the coolant tank. The upper small port should go to the top of the coolant tank. The upper port is for letting hot coolant that over flows when the system overheats go to the tank. The lower port allows the coolant to return when the system cools.

[scooterollie]

If you want a slightly better made replacement for that broken filler neck, go to a Honda dealer and order this part #:

19039-KM1-004

It was $17.50 from my local Honda dealer. As they say, don't tell them it is for a Chinese scoot. The quality is slightly better.

As for the lower port that broke off, it does not have anything to do with the overflow tank. It goes to the carb. and is a preheater of some sort. The upper port is the only one associated with the overflow tank - coolant goes both ways through this hose (if things work properly, unlike my scoot!), the direction being controlled by the presence or absence of pressure in the system and the radiator cap.

With the lower port cracked, coolant would leak out through the crack each time the scoot's coolant began to heat up and expand. You would not build up the pressure in the system to prevent the coolant from boiling.

[Gary]

Thanks guys. I think the original fitting would have been OK, but due to limited clearance when it was assembled at the factory there was sideways pressure on the nozzle. It was just a matter of time (not much in my case) before the nozzle cracked.

I was able to install my temporary fitting so that there wasn't sideways pressure on either of the small nozzles. But that Honda part sounds good if allnew doesn't come through with a replacement.

[monty57]

Scooterollie,

I don't know what type of scoot you have, but on the RR TLX the lower port goes to a the bottom of the coolant tank and the top hose goes to the top of the coolant tank. I s this hooked up wrong? Everything seems to be working ok.

[scooterollie]

monty57;
My answer is based on the CFMoto Honda-cloned design as found on Tank, Roketa and many other "Brand" name 250 scoots made this way. There is only one hose to the coolant recovery tank and that hose goes into the top of the tank. You may have an entirely different coolant system design.

ps: Monty, just remembered you have the scoot with the radiator up front and the filler cap under the front panel. Apparently, even with the same engine as ours, your cooling system is designed differently.

[Gary]

Monty -
Have to agree with Ollie. The second hose on my scoot goes off to the engine somewhere, definately not to the overflow tank. Its purpose is certainly intriguing, perhaps some sort of preheater as Ollie suggested.

[monty57]

Yep, you guys are right and I apologize for any misinformation or problems my info may have caused. I had come to my conclusion by tugging on the second hose and watching what moved. This obviously is not the best way to check things out. I have since removed the bottom pan on the scoot and traced the hose and it does not go to tank but to the motor. Once again I hope my jumping to conclusions did cause you any issues. I will check things out more thoroughly in the future!