Missing expansion tank cap

[kalbo]

My bike is missing its original radiator (overflow)expansion tank cap. The previous owner had been using a regular plastic screw cap, that has come from a 1 liter bottle of engine oil. The screw thread matches, but it obviously doesn't seal the system, which should be pressurized. I am never going to find another original part, but can anybody recommend something more suitable than what i have now. I don't know if this is a common sized cap shared by other water-cooled bikes.

 

[[email protected]]

$4 for the whole tank w/cap on ebay
http://www.ebay.com/itm/94-Yamaha-V...ash=item3f64db8295:g:~6EAAOSwNuxXYVP1&vxp=mtr

Or, drop Sean Morley an email. I'd bet he has one laying around

 

[fbnewell]

Those caps are still available. Bought one last week online from MR Cycles. Mine was split, and fell apart first time I tried to tighten it. I ordered cap only, reused my old rubber seal. Make sure to order that seal also, if starting over. Doesn't come with it.

 

[kalbo]

Thanks....I usually have a problem with getting things sent to me from the U.S. as I am in the Philippines and the cost of shipping is usually very high. Plus customs usually like to hold everything for a month before they will release it, then they add a ridiculously high customs import tax to it. It might cost me $100 by the time I get it. I have ordered before from japan and it takes around 2 months to get here.

 

[one2dmax]

Iv'e got new on hand.

 

[kalbo]

I think it will be best to get an original cap, but in the meantime can someone tell me whether it should be airtight. I can find a cap with a rubber seal that would make it airtight, but I'm thinking that a proper expansion tank cap must be airtight, but at the same time must have some kind of pressure release. Otherwise, in the event of the pressure becoming to high it would cause the tank to explode? right or wrong?

 

[caseyjones955]

It seems to function like a conventional automotive overflow reservoir. No pressure but its made stout to hold the scalding hot coolant. When the engine is hot some coolant is pushed into the reservior and when the engine cools it is drawn back into the cooling system through a cool little check valve built into the radiator cap. I'm not sure how much coolant it moves per cooling/heating cycle but I would be surprised if it were more than an oz or two. I think I got that about right. The bottle is vented, there is one inlet that comes from the coolant neck and another that should be vented via hose toward the ground.

I think your bottle cap may work in the short term but my guess is it will eventually break down as it is not designed to handle the heat. I would be on the lookout for a replacement. If no ebay sellers ship to where you are maybe its worth a trip to the tech to see what he has laying around that may work.

We ship giant boxes of goodies to the PI from the states here, it is expensive and sometimes all the boxes contents do not make it.

 

[one2dmax]

You are correct. The bottle is not sealed. The fluid comes in from the radiator overflow neck into the top of the bottle but a tube actually pushes it to the bottom where when the system reverses it also sucks it back in. The bottle does not have to be air tight.

 

[besit]

It seems to function like a conventional automotive overflow reservoir.

This is it - overflow reservoir cap. I drove over 60000 km on my previous bike (91) with a cap from chemical bottle with 'РЕАХИМ' written on it. Sold it with this cap.

 

[vmaxed1989]

Check out eBay as there's a tank and screw cap going cheap


Sent from my iPhone using Tapatalk