Sp1 overheating - Honda RC51 Forum : RC51 Motorcycle Forums
 
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post #1 of 9 (permalink) Old 01-25-2015, 10:59 PM Thread Starter
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Sp1 overheating

My SP1 is overheating. Getting up to 240F on the freeway under light throttle, used to settle down around 202F up until about 2 weeks ago. The right side radiator is really hot. The left side radiator is cold. The fan will come on for a few minutes if I sit still at those temps, but temp only goes down to about 236F. I assume that the thermostat is not opening and preventing flow through the cooling system. I don't think the water pump is at fault because the temps should be the same, if that was the case. How difficult is it to get to the thermostat? Does the throttle body have to come off? Any other thoughts?
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post #2 of 9 (permalink) Old 01-26-2015, 01:31 PM
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Try burping the cooling system.
When was the last time you flushed the cooling system, removed rads and inspect all hoses?

John, 2000 RC51 #000100

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post #3 of 9 (permalink) Old 01-26-2015, 02:42 PM Thread Starter
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Had the bike for almost a year now, never had the cooling system apart. I just ordered a thermostat. Looks like I have to dive down pretty deep into this thing to get at it.
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post #4 of 9 (permalink) Old 01-26-2015, 04:10 PM
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I have an idea before you tear into the thermostat. (Which is under the throttlebodies.)

First, make sure your small hose from the rad neck to the overflow bottle is clear and unblocked.
Second, make sure your rad cap is healthy. Or just buy a new one. They're cheap - like $10-15. Any auto parts store, ask for a 1.1 bar rating. (I would replace the cap before even thinking about going into the thermostat)

Take your fairings off, and with the bike cold, and on it's sidestand, remove the radiator cap (and fill if necessary) and start the bike up. Watch the temp gauge and watch the coolant in the rad. It should be very still, no circulating movement. By 167F degrees, you should see a little movement. By 172F, it should be obviously swirling around. That's the sign that your thermostat is opening. If your bike does this, and you can see that the coolant is circulating, if you gently roll the throttle several times, that will help expel any air bubbles that may be causing your problem. Keep rolling the throttle till the bubbles stop coming out.

The coolant should continue swirling around and by about 190F it will swell up and over the filler neck just a little. That's when I shut the bike off and replace the rad cap.

After you replace the rad cap, start it back up again and let the bike continue to warm up. Watch what temp your fan kicks on. It should kick on at 219F and then off at 209F. If it does, than your fan thermoswitch is working properly.

If the bike keeps climbing above 220 -225F before cooling back down, then you have a problem which could be one or more of the following: blocked hoses, inadequate coolant level, bad thermoswitch or connection or fan fuse, air bubbles, Rad cap not allowing excess pressure to be relieved to overflow bottle, or even a bad thermostat.

Hope that helps...

John, 2000 RC51 #000100

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post #5 of 9 (permalink) Old 01-27-2015, 01:17 AM Thread Starter
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I'll make those checks before swapping out the thermostat.
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post #6 of 9 (permalink) Old 01-28-2015, 05:04 PM
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240° is getting up around head warpage and you could even have a blown head gasket where exhaust gasses are pushing their way into the cooling system and vice-versa.

As mentioned make sure the systems is full and burped first as that is an obvious culprit. If the system continues to run hot or lose coolant then definitely be looking at other issues like the head gasket...
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post #7 of 9 (permalink) Old 02-01-2015, 02:52 PM Thread Starter
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Finally got a chance to look at the bike, I was low on coolant. I have a leak at the Y pipe. One of the clamps was a little loose, I tightened it up but we still have the leak. Hoses and a new Y pipe need to be ordered.
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post #8 of 9 (permalink) Old 02-01-2015, 03:10 PM
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Hope that's all you need to get it sorted
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post #9 of 9 (permalink) Old 02-02-2015, 10:37 PM Thread Starter
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Amazing what having coolant in your bike does. Took her out for a ride today and the temps stayed in the 178-190 range. BOSS.
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