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To rebuild or to No rebuild

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Old 04-16-2018, 01:15 PM
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I have a Reds R5 team motor. Before it lost it's pinch it was a great motor. I tried having it repinched but that is not working out so well. hard to tune, losing tune during the run, idol all over the place. Was thinking of just putting a new piston and sleeve and orings in it, maybe a new crank. It was measured and did show signs of wear but with in tolerance. What's the plus and minus besides cost? The piston and sleeve cost is a non issue. I already did new bearings, block is still nice, head is nice still, button is good. I was told to just paper weight it because it'll never be the same. I was thinking it would be at least a good practice/club race motor....
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Old 04-17-2018, 02:11 PM
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Originally Posted by tfrankito View Post
I have a Reds R5 team motor. Before it lost it's pinch it was a great motor. I tried having it repinched but that is not working out so well. hard to tune, losing tune during the run, idol all over the place. Was thinking of just putting a new piston and sleeve and orings in it, maybe a new crank. It was measured and did show signs of wear but with in tolerance. What's the plus and minus besides cost? The piston and sleeve cost is a non issue. I already did new bearings, block is still nice, head is nice still, button is good. I was told to just paper weight it because it'll never be the same. I was thinking it would be at least a good practice/club race motor....

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Old 04-17-2018, 02:55 PM
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Piston/sleeve replacement is already borderline. If you have to replace the crank, you're better off getting a new engine, if only for the peace-of-mind that comes with it.
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Old 04-18-2018, 06:37 AM
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If u need a new crank then no, donít rebuild it. Use it for spare parts (carb, head nuts bolts) or do as I like to do and learn how to properly tune an engine to its max and grenade it. I learned a lot in tuning just simply seeing where the max areas I was able to tune in without letting a bog accure and it was fun till it popped. Rule of thumb is if u plan on needing a rebuild make sure itís with an engine that has a dlc coated crank so itís worthy, the rest of the engines without that one important part are useless after the first sleeve wears out because the rod pins get so damaged within 6-8 gallons.
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Old 04-18-2018, 01:24 PM
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Originally Posted by Matt Piva View Post
Rule of thumb is if u plan on needing a rebuild make sure itís with an engine that has a dlc coated crank so itís worthy, the rest of the engines without that one important part are useless after the first sleeve wears out because the rod pins get so damaged within 6-8 gallons.
No offense but that's not a correct statement. DLC coating is something that was a necessity for specifically one Asian brand of engines in the past (OS) becuase they had issues with the materials they were using for their cranks and could not get them hard enough which resulted in the crank pins wearing out prematurely (as in before the piston and sleeve even wore out). This coating was initially offered by JP Racing on their modified version of that brand of engines and later (about 15 or so years ago) DLC coating as a fix (and the rest of the tuning mods that JP did too) was pretty much copied by the factory in a production model (the first Speed). The reality of the matter is that the Italian engine companies have metallurgy figured out and never had an issue with premature crank pin wear but because of this one Asian company DLC coating has become a "marketing trend" lately. So if you are using a fuel with quality lubricants, tuning the engine properly and most importantly not sucking in a bunch of dirt a non DLC coated crank from any of the Italian manufacturers should easily last you the life of several piston and sleeve sets too before needing to be replaced. In testing in the past we have regularly gotten 3+ rebuilds out of a crankshaft without seeing excessive crank pin wear.

If you feel that you need a crankshaft that will theoretically last forever (or you plan on rebuilding a engine for the rest of your life) then by all means make sure that you get a DLC coated crank, just realize that around $35-$50 of the cost of the engine that you are paying for is due to the cost of that coating alone and it results in zero performance increase, it just means that you crank pin will never wear out. With motors costing less nowadays than they did 15-20 years ago the cost of a replacement piston/sleeve and rod is often creeping up on 70% or so of the cost to just replace the entire engine! Because of that I have seen the trend changing from back in the day of people owning and rebuilding a single engine multiple times to nowadays at the most replacing the piston and sleeve maybe 1 time before just buying a new engine, in which case being candid having a DLC coated crank is basically a waste of money.
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Old 04-18-2018, 02:39 PM
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JP Racing was called Black Couting
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Old 04-18-2018, 05:25 PM
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Originally Posted by Pedro Jesus View Post
JP Racing was called Black Couting
It might have been what he (Jean Paul) called it for marketing purposes but it was DLC coating before anyone (in this industry at least) really knew what it was. At that time TiN coating with it's signature gold color was just about all that was really known about and it was being used in motorsports on stuff like GP bike shocks and front forks to reduce friction. Matter of fact I believe Losi also came out with some TiN coated shock shafts for thier vehicles right about then too. Bottom line though he (JP) was the only one to offer that coating for several years and he started using that coating to specifically address OS's premature crank pin wear issue that they seemingly could not figure out how to fix on their own which he did as one of the features in his line of JP Racing modified OS engines. Unfortunately they (OS) later pretty much just copied everything that he did including the coating, black case color and modifications that he made and called it the "OS Speed" engine and basically put him out of business.
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Old 04-18-2018, 06:05 PM
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I'm not sure if it's also due to some pretty crappy fuels that's out there too, the crank pin usually never lies on that matter, and it might be that some engine mfg is trying to cover their ass.
It might be to late for say OS to stop using it, even if they got the metallurgy figured out, people expect it now.
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Old 04-18-2018, 06:30 PM
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+1 on that.
Fuel quality (oil packages) make a massive difference to engine life expectancy.
We have had sponsored drivers using different fuel products to what we normally provide and their engines experienced far greater engine wear (loss of compression and crank pin / rod bushing wear) compared to everyone else ...... Stands out like a sore toe when you maintain team engines and can measure the difference between the various fuels being run.
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