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Discussion Starter · #1 ·
ok I'll admit it, I have never done a de-carb on my 446 tractors. Anyone up to the task of laying out a step by step procedure. I sure wouldn't want to tear apart a running Onan engine without a clue on what to do? :shock:
 

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Order new graphoil gaskets from ONANPARTS.
Sit down on a milkcrate.
Remove the side tins.
Remove the cyl heads.
Plastic or wooden "scraper" to remove carbon after rotating the piston to the "top"
Install new gaskets.
Torque head bolts per manual.
Replace tin. This is the only part requiring any finesse, it helps to pay attention during removal ( tab A, slot B etc)
 

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Discussion Starter · #4 ·
99flhr said:
Order new graphoil gaskets from ONANPARTS.
Sit down on a milkcrate.
Remove the side tins.
Remove the cyl heads.
Plastic or wooden "scraper" to remove carbon after rotating the piston to the "top"
Install new gaskets.
Torque head bolts per manual.
Replace tin. This is the only part requiring any finesse, it helps to pay attention during removal ( tab A, slot B etc)
Ok, after using a wooden / plastic scraper, how clean is clean enough? Do I dare to use emery or anything else to remove loose particles?
 

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I would not try to make it bare metal, just remove the "crustacations"


Perhaps run Seafoam before and after the decarb.
Prior will loosen the crud and after will get any thing left behind

I would NOT introduce anything with GRIT
JMO

EDIT: use your shop vac to remove particles as you clean.
 

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Discussion Starter · #7 ·
1. Order (2) new 110-3181 graphoil gaskets from
http://onanparts.com/index.php?main_pag ... ucts_id=17
2. Sit down on a milkcrate.
3. Remove the side tins.
4. Remove the cyl heads.
5. Use plastic or wooden "scraper" to remove carbon after rotating the piston to the "top"
(a) Do not try to make it bare metal, just remove the "crustacations"
(b) Perhaps run Seafoam before and after the decarb. Prior will loosen the crud and after will get any thing left behind
(c) DO NOT introduce anything with GRIT
(d) Use your shop vac to remove particles as you clean.
6. Install new gaskets.
7. Torque head bolts per manual. (16-18 ft/lbs)
8. Replace tin. This is the only part requiring any finesse, it helps to pay attention during removal ( tab A, slot B etc)
 

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Onan Master, new and used parts.
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O.K.
you guys ALL missed this.
valve grind/carbon removal gasket kit #168-0189 (from onan parts.com)

you have the tin off already, this is the time to adjust the valves.
(i actually remove and clean and lap mine,i have seen some valves SO
full of crud that the engine barley ran)
thank you. boomer
 

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One other thing that helps is to use spray on gasket remover on the carbon deposits. When I used that they almost wiped off with a damp rag, far easier to remove than just scraping. Caution I only did this on the heads so I could be sure I didn't get any of the solvent were it might contaminate the oil. Some autoparts stores still carry out but around here most don't but our local CASE IH dealer carries the stuff and I thought Napa did too.
 
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