Yamaha C3 - Radiator fluid issue

[rideslikenacho]

Having a small amount of radiator fluid drip down the engine case underneath the engine only after riding. Idling it will not do it. I’ve checked all the hoses, radiator and nothing wrong. Is there a weep hole or something under the engine case that would let excess fluid out?

[GrumpyUnk]

It makes no sense to build in a leak. There may be a weep hole on the pump. Getting an adapter to fit the tiny radiator cap may prove difficult. I think I might go to a lab supply and get a rubber cone stopper. Using that, a length of tubing, a Mityvac pump and a metal tube stuck in the stopper, pressurize the system while not running. Then look closely for seepage. Most likely spots are the head gasket(not good.), banjo fittings, and posslbly any sensors that screw into the head or cylinder. If you get enough to get droplets reach the ground, you have a leak. A hot engine will tend to evaporate small seeps before they can trickle enough to form a droplet and make their way down the hot metal.
tom

[rideslikenacho]

Aug 24, 2023 7:57:47 GMT -5 GrumpyUnk said:

It makes no sense to build in a leak. There may be a weep hole on the pump. Getting an adapter to fit the tiny radiator cap may prove difficult. I think I might go to a lab supply and get a rubber cone stopper. Using that, a length of tubing, a Mityvac pump and a metal tube stuck in the stopper, pressurize the system while not running. Then look closely for seepage. Most likely spots are the head gasket(not good.), banjo fittings, and posslbly any sensors that screw into the head or cylinder. If you get enough to get droplets reach the ground, you have a leak. A hot engine will tend to evaporate small seeps before they can trickle enough to form a droplet and make their way down the hot metal.
tom

Yep good idea on pressurizing it. It’s definitely not a lot coming out. Not coming from the cylinder gasket, checked that first. There’s a rectangular section on the bottom of the cylinder right beside where the input line for the water pump enters the cylinder. Its got a gap with what looks like two holes. Have a picture but not sure how to load to this forum. Seems like the only place it could be coming out.

[aeroxbud]

How to post pictures 49ccscoot.proboards.com/post/7984

[rideslikenacho]

Excellent thank you! Below is the area Im curious what it is and whether there should be a cover for it. Seems like this is where it could be leaking from and there is a tiny hole on one side. That said I can find nothing in the manual about it nor on parts diagrams but it sits on the bottom of the cylinder body just beside the input line from the water pump.

[GrumpyUnk]

If it is missing, it has been missing long enough to get about the same coverage of dirt as the rest of the engine. If leakage started recently, I doubt it has anything to do with the rectangular recess.
Bottom looks as if you have removed the cylinder head. The ferrule in the lower left threaded hole must have gone with the cylinder head. If missing, you must be sure to line up the head properly when you re-install it. The ferrules are there for alignment.
It is kind of difficult to get the context of the images without owning a similar bike. The arrow in the bottom picture is pointing to something, but I have no clue what.
tom

[rideslikenacho]

So I bought this bike and rebuilt the engine, split the cases, replaced the broken crankshaft and piston and put everything back together to spec using new gaskets etc on everything. Not sure how it was prior since I bought it broken.

That second image is just pointing out the location of the recessed area on the bottom of the cylinder. Just isn’t clear exactly what that is for and why radiator fluid could be coming out of it. Quick search of C3 cylindera shows its not missing a cap or anything for that. Cylinder was lined up correctly with those ferrules as mentioned.

[GrumpyUnk]

Do the two(apparently) holes in the box in the top picture lead anywhere? Is the hole at the very top in the corner of the sqare tapped and threaded for a bolt?
As a very ignorant guess, it looks as if the holes lead to a passage(bump in the outer surface) that points to the lower end of the water(coolant) jacket on the cylinder. It is possible that some versions have a cover that bolts on and seals, with a fitting in the cover for connecting a hose that leads to other parts of the cooling system.
tom

[rideslikenacho]

Aug 26, 2023 8:39:00 GMT -5 GrumpyUnk said:

Do the two(apparently) holes in the box in the top picture lead anywhere? Is the hole at the very top in the corner of the sqare tapped and threaded for a bolt?
As a very ignorant guess, it looks as if the holes lead to a passage(bump in the outer surface) that points to the lower end of the water(coolant) jacket on the cylinder. It is possible that some versions have a cover that bolts on and seals, with a fitting in the cover for connecting a hose that leads to other parts of the cooling system.
tom

Very hard to tell if they actually go anywhere but all the cylinders I have seen on ebay etc are open like this one. That hole doesn’t appear to be threaded either. I’m going to take it for another ride tomorrow then lean it on its side and see if I can catch any actually coming out. Have to check the level and see if its lost any substantial amount first. Only so many place that radiator fluid goes on one of these.

[bbrins]

That passage does go through the casting, and there is a hole through the head gasket for it. The only reason that I know this much is because I still have my old cylinder from when I did the BBK on my 2007 C3. I do not know if there is a passage in the head for it as well or not since my head was reinstalled in the engine. I snapped a couple of pictures of the passage through the cylinder casting, which also shows the hole in the gasket.

Those holes are not threaded on mine either.

My guess that this is a secondary cooling passage that is either meant for another application, or Yamaha decided that it wasn't necessary.

I also took a look at my Spare Malossi cylinder, that flange, or whatever you wanna call it is in the casting, but it does not go through.

If you are getting coolant coming out of that passage, your head gasket may be leaking, or possibly something is cracked. But, just because you see coolant dripping off of one part, does not necessarily mean that that is where it is leaking, it could be running along other things until it gets to the lowest spot, or the spot with the least surface tension.

I have a 2018 Zuma engine(same as the C3) that isn't installed at the moment, I'll take a look and see if there is any kind of weep hole on the water pump tomorrow. I have plans to do a BBK on this engine in the near future, I'll have to try to remember to figure out where all that passage goes.

[rideslikenacho]

Thanks for the follow up! Curious what the bbk is you refer too? Also whether you know of any good YouTube channels etc with good videos on the C3.

So I am an idiot, it IS leaking from the base gasket and it IS oil not radiator fluid. It’s coming from the bottom left cylinder bolt side if looking at the front if the engine. What Im trying to figure out now is whether the engine has to be dropped to tighten the cylinder head nuts that are under the cylinder head cover. It has a tightening sequence that I probably need to go back through again and retighten since I rebuilt the engine and replaced the crank and piston. Would be great if I can do it without dropping the engine again. I think it probably just needs retightened.

Also seems like the steering nut needs to be tightened too. Makes a clunk sound when I hit a bump or stop fast.

[rideslikenacho]

Tightened the cylinder nuts and it leaks more now than before. Safe to assume it needs another new base gasket? Should I use a gasket maker on top of a new gasket? I’ve done lots of base gaskets and this is the first to ever leak.

[bbrins]

I guess it's moot at this point, but I did not see a weep hole on the water pump. My 70cc Big Bore Kit is the Malossi one that scootertuning.ca offers with the tuner. I can't think of much off the top of my head as far as YouTube channels go, there is one called "Mike's Mini Motors" that has some C3 content, plus some Ruckus and mini bike stuff. Going from memory, I think with the plastics and floor board removed, that you can get that cover off, whether there is room for a torque wrench in there, I couldn't say. There's also a couple of head bolts that are obscured by the water pump, so you may need to remove that too. If you need to replace the gaskets, you will definitely need to remove the engine.

[rideslikenacho]

Yeah when I rebuilt it, I added all new gaskets to everything including base gasket. I’m still not real sure why it leaked. I’ll order a new one but considering a layer of gasket stuff with it too just in case. Any thoughts on that?

[bbrins]

Sometimes, even when you do everything correctly, stuff still happens.

I usually only use sealant along with a gasket when I need something to keep it in place during assembly, or a little dab where the gasket crosses a seam in a case or something like that. It is also sometimes necessary if one, or both surfaces have imperfections deep enough that a gasket alone can't make up for it.

Thinking about it a bit more, the crankcase splits in half right behind that gasket, if I remember right. Maybe the case halves aren't sitting perfectly level with each other there? In my non-professional opinion, I don't think that a bit of sealant would be inappropriate on the side of the gasket that faces the crankcase, either a thin layer all the way around, or a thin layer just where the seams are.

Hopefully you've been using one, but I highly recommend using a torque wrench for this job.