Since you just got the bike, I'd do a complete coolant change. Here's how it is done.
1. Start engine and warm it up, shut it off.
2. Remove drain plugs from radiator, bottom of engine by right footpeg, base of both cylinders.
3. Remove the 2 plastic pieces of the steering head cover, and remove the filler cap on right. Let all coolant drain.
4. Put all plugs back, finger tight.
5. Start engine, and SLOWLY fill with DISTILLED water through the coolant filler neck. Must be done slowly to let air out.
6. Let engine run a few minutes to circulate the DISTILLED water.
7. Shut off engine, remove all drain plugs. If the water looks clean, go to next step. If it looks dirty, repeat the above procedure until the water comes out clear.
8. Install all plugs and tighten them. You may want to use new copper washers to prevent leaks. They are very cheap compared to having to deal with a leak later on. Use only oem washers, not something from a hardware store.
9. Start engine, start filling cooling system with coolant through filler neck, again VERY SLOWLY, so air does not get trapped in the engine. Fill to top of filler neck, install filler cap. Do not install steering head covers yet.
10. Remove overflow reservoir on right side behind engine. Pour out old coolant, rinse good with DISTILLED water.
11. Install coolant reservoir and cover, making sure hoses are routed properly. Also make sure rear brake cable fits into the recess in the reservoir properly. Fill reservoir with coolant to lower level.
12. Ride the bike, keep an eye on the temp gauge. After a couple of heat/cool cycles, remove the filler cap by the steering head, the level should be full. If it is, reinstall the cap, and the plastic covers. If it isn't add coolant till it is full, replace the cap, and the plastic covers.
13. Check the level in the reservoir. It may have dropped. If so, add more coolant.
14. After a few days, check all the drains, make sure none are leaking. If you have a leak, you will have to remove the plug to fix it.
15. If no leaks and cooling system works ok, job is complete.
1. The manual makes reference to an "air bleed screw" that you have to remove the tank to get to. Don't bother. The bleed screw is only inches away from the filler. Just fill slowly, and all the air will come out through the filler.
2. Use ONLY distilled water to flush the system. Tap water and flushing chemicals contain corrosive elements that can start corrosion in the cooling system.
3. I recommend only premixed motorcycle specific coolant. I use Maxima brand, but any name brand is fine. Some people recommend using car coolant concentrate, and mixing it with water to save a couple $$. IMO, it isn't worth it. The coolant is good for 2-3 years. Over that amount of time, the savings is irrelevant. Do it right and it will work right.
4. I DO NOT recommend Engine Ice. Living in a HOT climate, I tried it. It took a lot longer for the engine to warm up, which meant it had to idle longer. When the engine was shut down, it cooled off a lot faster, sometimes requiring the engine to need to be warmed up again after sitting only a couple of hours. More unnecessary idling. Actual operating temperature, which is what I was trying to lower, remained the same. Ethylene glycol (the green stuff) is the coolant to use.
I am a motorcyclist, NOT a biker.
1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike