Oil weight VS Clearances

level600a

Member
I brought a new honda GX390 crankshaft for this new engine build and I checked the clearances between crankshaft and rod bearing, got .0025-.0028 tight, so I am wondering what weight oil to run in this engine?...Last years crankshaft had .0035-.0038 clearances ran Thor heavy worked great, so should I use the same weight or a lighter one.
 
.0025 is right on the lower side of acceptable for me. Ive had better luck with a smidge more. I am sure your using a billet rod with inserts. They are much more forgiving. I run 5w-20 in "stockish" builds. You know, just mild upgrades. As the build gets more intense, I go to 10w-30. I run Amsoil Dominator racing oil. How does this equate to the light, medium, heavy kart weights? I have no idea. It needs to be thin to flow good in a splash oiler but thick enough to provide a film and protection. I know I didnt help, just telling what Ive done. good luck.
 
Most kart oils are in the 20 viscosity range, the multi grade 5-20 10-30 only perform well at their average which would be right around 20 most of us do not operate these engines in temp where they act like the lower viscosity so it is irrelavent.
 
.0025 is right on the lower side of acceptable for me. Ive had better luck with a smidge more. I am sure your using a billet rod with inserts. They are much more forgiving. I run 5w-20 in "stockish" builds. You know, just mild upgrades. As the build gets more intense, I go to 10w-30. I run Amsoil Dominator racing oil. How does this equate to the light, medium, heavy kart weights? I have no idea. It needs to be thin to flow good in a splash oiler but thick enough to provide a film and protection. I know I didnt help, just telling what Ive done. good luck.

jsstump why use Dominator and not there 4T oil? Will it work with meth.
 
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jsstump why use Dominator and not there 4T oil? Will it work with meth.
Never really understood the Amsoil marketing ploy. Seems like the easier they could make it to get, the more they could sell. Getting Amsoil is a pain. Sure I know several dealers, but it takes them a day or two to get what i need. If I need it i want it. With that said, I get Dominator several cases at a time. I would use the 4T but the dealer i normally use had no idea what i was talking about. I showed him a page I printed from the internet and he said he would order it but it would take a while to get. I dont know what the real story may be. He could get the Dominator in a day so thats what i got. There is even a "Amsoil" store in Roanoke. On Plantation rd I believe. I stopped by one day and asked about the Dominator and 4T. He had Dominator but had to go to his catalogue to see what 4T was. He had never seen it. My buddys dealer price was better on the Dominator so I just stuck with him.
As far as viscosity and "thicknesses" go, listen to Kart43. He seems to have it going on in the minutia of detail on most stuff. Gives accurate advice. Good luck

I wonder if the Dominator and 4T are maybe the same in different containers? Oil choice can yield a heated debate sometimes. As hard as getting Amsoil is, its still easier than getting certain kart oils. I think CoolPower, Thor, FHS, Red-E are good oils (to name a few) but No where I know of convenient to "stop in" and get a gallon. Usually have to order it and that takes days. Good luck. Let me know what you decide on. If you have good luck I will gladly take credit, if its bad luck, its all on you. I had nothing to do with it. LOL


PS: I rarely run meth. Only once or twice in these engines. I ran it back in my Kohler days. I feel confident Amsoil is fine with Meth.
 
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