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Old 27 August 2018, 09:44   #1
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Tohatsu 60

Hi there can anyone tell me why my tohatsu 60 is backfiring through the exhaust when idling? Idles fine runs fine. Just makes popping noise when sat there ticking over. Thanks
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Old 27 August 2018, 10:56   #2
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I suspect nobody can say for certain without seeing it, BUT backfiring is unburnt fuel hitting the hot exhaust. Is it 2 stroke or 4 stroke? Carbs or injectors? How often is it backfiring? What revs is it doing on tickover?
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Old 27 August 2018, 11:23   #3
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It’s 2 Stoke with carbs. Does it every 10 seconds I’d say. Doesn’t have rev counter so I can’t tell. Other than the popping it runs sweet, only notable when run on muffs
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Old 27 August 2018, 11:35   #4
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Rule out the simple stuff first. Assuming it's a 2-stroke (model M60C). Check the spark-plugs and replace them. They're relatively inexpensive. Use NGK BR8HS-10 or BR8HS-10.

HT leads can cause backfires if they are faulty. Lastly the carbs. Are they spotless? Quick check is to remove the fuel bowls (hex-nut) and see there's absolutely no contamination. Anything in there, then you're looking at a strip-down.

Does the backfire go once the engine is up to temperature? These engines are fairly solid, but aren't great from cold. The butterfly choke valve on the top air intake is known to seize, so something else to rule out. Take the air-box off to check. Press the key in the ignition and it should click open.
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Old 27 August 2018, 11:47   #5
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Yes it’s a m60c 2 Stoke. I’ve stripped down the carbs and cleaned, replaced the spark plugs with the correct ones. Even when the engine is up to temp the popping still accurs. How can you tell if it’s faulty leads? I’ll check the butterfly choke. Thanks
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Old 27 August 2018, 11:50   #6
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Quote:
Originally Posted by Jacklowe View Post
Itís 2 Stoke with carbs. Does it every 10 seconds Iíd say. Doesnít have rev counter so I canít tell. Other than the popping it runs sweet, only notable when run on muffs
Simple answer - don't run it on muffs!
Slightly more serious answer - the back pressure and temperature when running in water is different from the muffs so I wouldn't loose too much sleep over it.
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Old 27 August 2018, 15:00   #7
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The only way I can discribe it it's more a burble than a backfire a two stroke caratistic more evident when the through prop exhaust is out of water as poly says no water muffeling the exhaust gases no silencer straight through.
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Old 28 August 2018, 02:50   #8
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Quote:
Originally Posted by Poly View Post
Simple answer - don't run it on muffs!
Slightly more serious answer - the back pressure and temperature when running in water is different from the muffs so I wouldn't loose too much sleep over it.
Inclined to agree with Poly. If it idles fine, and there's no loss of power on the water, then leave it as it is.

Regards faulty HT leads, there are videos on Youtube that you can test with a multi-meter. The other option is to extract spark-plug and ground to engine block to test spark. I'd be inclined to check the HT wiring to see there's no insulation breakdown, clean contacts, etc.

Tohatsu in their wisdom didn't use tinned wiring, so if you haven't had issues to date you're one of the lucky ones. I had to splice in wiring to the remote that had disintegrated, replace wiring to the trim, etc.
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Old 01 September 2018, 06:46   #9
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Thanks guys, I swapped the 3 coil leads with a spare set I had and the backfiring has gone. Faulty lead was the answer. Thanks for your help
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Old 01 September 2018, 14:05   #10
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Good news regards fix.
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