Revival of old thread, that I participated in previously, but I'm now tackling tunnel cooler install on my 2020 Yeti 129/2020 YZ450F. Can anyone confirm if the C3 thermostat outlet nipple and the Yamaha top radiator inlet nipple are both 3/4" I.D.?
When I ordered the tunnel cooler from C3 I also bought the C3 silicone double tunnel cooler hoses (5/8" I.D.) and plan to route my coolant lines like Snowscooter5 did in the above images. It looks like the C3 thermostat nipple is 3/4". Also looks like the radiators upper inlet is 3/4". I could pull the hose and check, but hoping to not pull it until I start the project. If both are 3/4", I'll use 3/4inch "HPS Silicone 180 Degree Elbow Coupler Hose" coming off the C3 thermostat to redirect hose backwards, then a 3/4" to 5/8" adapter into my 5/8" I.D. tunnel cooler line. On the 5/8" tunnel cooler return line, I'd use a 5/8" to 3/4" adapter to go into the cut, stock 3/4" upper radiator hose (or better yet, likely save and not cut the factory hose and just get a scrap of 3/4" I.D. coolant line to use). Mainly want to confirm that both the C3 thermostat nipple and the Yamaha upper radiator inlet nipple are both 3/4" so I order the right hoses and adapters the first time.
Regarding the two small bolts, that are part of the gas can/rack bracket, that will hold up the rear of the tunnel cooler, are the factory ones long enough or do I need to source longer ones? I saw one recommendation to use some type of sealant between the cooler and tunnel, but seems unnecessary if the two small rear bolts are loctited in place. How many have used sealant? How many have only used the bolts (with loctite) and had or not had bolts back out?
Also, how best to determine where the holes are drilled? Spacing between the holes I can get from measuring the tunnel cooler, but for placement top to bottom, looks like a guy just wants to drill below, but as close as possible to, the external cross brace, correct?
I'm gathering as much info as I can beforehand and hopefully make this go smoother and get it done in mostly one sitting rather than having to stop mid project and drive for parts or order parts.
I really thought about getting rid of the radiators all together, but having trouble finding an appropriate "coolant filler neck and cap" for the project. The ones from the late 90s Artic cats look perfect (picture attached), but can't find new versions and don't like the idea of 20+ year old plastic. There are some universal ones that seem reasonable (pictured) but not finding anything ideal. Any ideas there would be appreciated as I still might do radiator delete. Only reservation there is if I ever get into a situation where the tunnel cooler isn't enough (boiler plate trails in the spring where I can't dip off to the edge of the trail to cool). Or, if I ever damaged the tunnel cooler mid season and needed to temporarily have another form of cooling while I wait on parts or to finish out the season). In both cases, having left the radiators in place would give me options. I'm really drawn to the notion of removing them and all the associate plumbing, though. Lighter, simpler, cleaner, less failure points. I have radiator guards in place that would stay to support the bikes plastic shrouds and the filler neck, etc. I also have a radiator bib that covers them completely and could then stay in place full time, once I install the tunnel cooler, whether I delete the radiators or not.
I'm also using Evans waterless engine coolant, so don't need a pressurized system since it will never boil.
Example of old Arctic cat filler neck that are around, but old plastic. I can't find this part newly manufactured rather than old used or old stock, but maybe the plastic they used ages well and there is no issues with using 20+ year old plastic? Just makes me a bit nervous.
Universal filler:
Another (though this one has its drawbacks with nipple orientation and not much neck, but the the 3/4" barbed fittings are removable in case you need to install your own fittings in the 1/2" NPT Female threads so one could put in 5/8" 90degree elbow to more easily tie into the 5/8" tunnel cooler hose and then the 5/8" hose that drops down to the water pump.
![s-filler_cap.jpg s-filler_cap.jpg](https://www.snowest.com/forum/data/attachments/338/338140-c6b948e457362cb29b6e29651031cf98.jpg?hash=xrlI5Fc2LL)