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Old 26 June 2014, 18:02   #1
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Tohatsu 50 cylinder

Opened up the engine today to give it a bit of a clean & the intention of getting 1mm taken of the head soon.

Is there anyway of telling if the head has already been skimmed? Engines already had some work so maybe have already been done but I don't know.

Also I knew it wasn't going to be spotless but is this normal amount of carbon build up?

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Old 26 June 2014, 18:26   #2
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Originally Posted by lukewhiting View Post
Opened up the engine today to give it a bit of a clean & the intention of getting 1mm taken of the head soon.

Is there anyway of telling if the head has already been skimmed? Engines already had some work so maybe have already been done but I don't know.

Also I knew it wasn't going to be spotless but is this normal amount of carbon build up?

Attachment 96142

Attachment 96143
Hi

My way of telling if it's been skimmed,1 how old is the engine,2 what was it before the head was taken off 3 what should it be in rhe manual.Also read in a previous thread I think it may have been rolfhat or whatever there name, 1mm skimmed is approx 30psi but don't quote me on this.Have a word with the tunning guy.pretty sure this was mentioned a couple of weeks ago.
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Old 27 June 2014, 04:09   #3
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Cleaned all the carbon off now & going to polish it later. Would the carbon suggest I'm running the mixture wrong? Too much fuel? Or too much 2 stroke oil? I run it 50:1 on fully synthetic rock oil.
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Old 27 June 2014, 04:58   #4
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That carbon build up is normal. Mine had more than that anyway. Get a set of vernier calipers, the standard head is 33.6mm or thereabouts. You want to take it down 1mm. Yes I believe 30psi increase is what you should expect, although mine remained the same due to raising the exhaust ports.
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Old 27 June 2014, 05:00   #5
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Also if you polish the head and pistons enough it prevents carbon build up in the future
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Old 27 June 2014, 05:04   #6
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Okay cheers I'll try find out later. Going to polish them right down & get it all gleaming!
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Old 27 June 2014, 06:01   #7
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Okay cheers I'll try find out later. Going to polish them right down & get it all gleaming!
1200 wet and dry should give the finish after going through most grades of abrasive paper!
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Old 29 June 2014, 17:33   #8
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Finally got round to giving it a bit of clean! Already looking much better

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Old 02 July 2014, 18:00   #9
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Higher octane fuels supposetly forms less carbon build up. Years back made an experiment with 2 same 2 stroke Tohatsu 30 HP engines. One used regular 90 octane fuel, the other premium 95 octane fuel, both engines were run at constant 3/4 to wot speed on trasport ribs.

After 1.5 K meterd working hours, the engine using regular fuel had near double carbon built up than the one using 95 octane. Besides 95 had better throttle response with bit less fuel consumption.

Good to polish pistons & cylinder head interior to baby's arse soft condition, will form less carbon buil up. 2 strokes engines needs to be decarboned at min each 100 worked hours.

Buy a can of carbon guard, follow instructions, engine must be on while spraying product though carbs, cleans fantastic well all combustion chamber carbon deposits, engine runs smooth, with top power and rejuvenated glow.

Happy Boating
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