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Discussion Starter #1 (Edited)
Good Morning everyone. I am a part of a student racing team at the University of Western Ontario in Canada and I have a couple simple questions regarding engine cleaning/rebuilding. I have attached a picture showing a CBR600F4i engine that we have recently disassembled.

We found excessive carbon build-up in on the pistons, the tops of the cylinders, and in the exhaust ports. What is the cause of this carbon build up? From what i've read online it could be due to the previous owner running the bike at lower loads and not letting her ever see some high revs.

Also, what would be the best way to clean off the pistons without damaging the cylinder wall, and to clean the exhaust ports without disassembling the cylinder head? We tested some varsol on old pistons we had around the shop and it seemed to remove the carbon pretty well, but the concern is that the varsol will seep down past the rings in to the case. Also, I can't think of a way to clean the ports without causing varsol to get stuck in the valve seat.

Any help is appreciated.




Edit: some more pictures of piston carbon build up:


 

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I've had good luck with carb cleaner and a stuff brush (non metal) or you could try kerosene as well. It looks like an engine that was run at low loads for a long time or possibleit was run with poor quality fuel. It doesn't look like oil, but it's hard to tell from the pics.

I wouldn't worry too much about what you use as long as you try to contain it and flush the motor out a few times before starting.

I'd clean it up, run it and pull the head off after a while to see what it looks like. My guess is it'll look great.
 

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Probably ran 91octane causing incomplete combustion which is a great way to carbon up an engine. Use whatever you want then just change the oil if your worried about contamination.
 

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I seen and used standard Automatic transmission fluid to clean up carbon or stuck pieces, I had a older Honda Foreman that a older gent brought to me, this thing never saw past maybe a 1/16 more of a throttle opening, and he must have ran 89 or 91 in it, cause only after about 600 miles, the valves intake tract was so gummed up with carbon the valves would not seat right. Took the head off and with a stiff plastic brush and some ATF fluid the stuff started to come off almost dissolve off, then into the spirits tank to clean that off and it was 100X better then when I took it off. ATF is a detergent and a lucubration agent.
 

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Discussion Starter #6
I seen and used standard Automatic transmission fluid to clean up carbon or stuck pieces, I had a older Honda Foreman that a older gent brought to me, this thing never saw past maybe a 1/16 more of a throttle opening, and he must have ran 89 or 91 in it, cause only after about 600 miles, the valves intake tract was so gummed up with carbon the valves would not seat right. Took the head off and with a stiff plastic brush and some ATF fluid the stuff started to come off almost dissolve off, then into the spirits tank to clean that off and it was 100X better then when I took it off. ATF is a detergent and a lucubration agent.
Im curious about this one. Did you clean the head without disassembling it? What did the valve seats look like afterwards?
Or is the only way to clean out a head to disassemble it first?
 
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