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Need some advice

596 Views 11 Replies 6 Participants Last post by  Hudson 1975
So long story shortish. I have a 98 bird. Bike sat for along time befor I got to it. I got it a few months ago but haven't really taken it out much. It runs great but something I noticed was I'd warm the bike up till the fan kicks on and take off with it. The gauge would drop to the bottom mark while riding and warm back up to normal sitting at a light. It'll never go over the fan does its job. So he comes my issue. The other day was the first hot day of summer here where I'm at. About 100f and when I got home I could hear boiling from the reservoir. I assumed it was a air pocket with how the gauge read and the bubbling sound. I've been trying to bleed it but it just keeps pushing out coolant when the tstat opens. What am I doing wrong? Bike runs great bit with the brutal summers we have here I wanna make sure I have no issues. Thanks and sorry for the lengthy question.
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Is the fan still cycling on
Then chances are the radiator cap has lost it's ability to hold pressure. Replace it and when you refill the system have it on the sidestand.
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That was another thing I noticed was it felt like the hoses had no pressure when I would get back from riding. Thanks I'll try and track one down. Will post an update
Cbr radiator caps.
95 Honda Accord rad cap will work.
Here is the NAPA part# 703-1712.
While I was reading your shortish problem I was thinking it was most likely the cap too. Good luck.

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Cbr radiator caps.
95 Honda Accord rad cap will work.
Here is the NAPA part# 703-1712.
While I was reading your shortish problem I was thinking it was most likely the cap too. Good luck.

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Yeah sorry about the lengthy question lol but I appreciate it ima go grab one this morning and go take the bike for a spin.
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That was said with laughter in my writing... just ask the forum members as my writings often wax long and eloquent!

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Yeah sorry about the lengthy question lol but I appreciate it ima go grab one this morning and go take the bike for a spin.
Your good I figured so
Then chances are the radiator cap has lost it's ability to hold pressure. Replace it and when you refill the system have it on the sidestand.
Also make sure reservoir tank cap is fastening securely with a good seal!
G'day purple reign,

Do a full system check. You should not need to warm up until the fan comes on. This is odd. I suspect more than an airbubble. I'm tempted to say stuck thermostat. The fan should take a long time to activate, so if it's coming on quickly, like a normal warm up time, then the coolant is likely not circulating freely. Check the workshop manual in the forum library resources section.

One way to check.......ensure coolant is full with no air bubble (requires a lot of burping) and new cap in place. Set catch tank to the max mark.

Start from cold and watch the temp gauge. Our FI's are digital, your BB is a dial gauge I think?

Anyway, the temp should rise until the thermostat opens, then it should go cooler for a minute or so as the cold radiator fluid circulates, then it should start to climb up to 103C where the fan should cut in. If it doesn"t do the little back flip, it could mean the thermostat is stuck and not fully closing or opening when it should. Might be stuck half way too?

The catch tank should rise when hot, and drop to the set level when cold as per all water cooled bikes.

Boiling kettle noises mean it's chronically overheating due air - or maybe due a closed thermostat stopping the rad from doing it's job.

Make sure you drain the system from 2 points - one at the coolant pump, the other at the cyl head, and squeeze and burp till your wrist aches (I disconnect the lower hose from the rad and syphon the old fluid out, then flush with boiling water to open the thermo). It's simple enough but it's a bitch to get right - test ride it before putting the fairings back on. Incorrect coolant change procedure is very common and the BB runs pretty warm normally so it needs the cooling system to be in A1 condition.

Good luck, let us know how you go.

(y)
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