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Post by spooch63 on Dec 27, 2023 21:26:51 GMT 1
I've asked a mate to help me build an engine with a bit more horse power, possibly a 370 with associated carbs, electrics etc. First thing he suggested was to use an RD250dx crank centre as they were a lot stronger than the standard LC. He's a good mate and appears to know his stuff, he helped me with my previous engine build and set up on the dyno. So the question is, is the dx centre a common modification?
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Post by 4l04ever on Dec 27, 2023 21:30:59 GMT 1
It used to be common. I have a crank built that way, as it means the big end pins can be replaced without changing the webs.
On the negative side, it is heavier, so may not rev up as quickly as a 4L0 OEM crank.
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Post by chrisg on Dec 27, 2023 21:33:35 GMT 1
Im told that after 3 refurbishments to the LC crankshaft its no longer any good. Unless you buy a new crank, you will never know. The AC cranks have splines between the 2 webs. Speak to a known racing shop, maybe NK racing, to see what they can do. TZ bigend bearings is a common upgrade, as well.
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Post by spooch63 on Dec 27, 2023 22:47:06 GMT 1
Im told that after 3 refurbishments to the LC crankshaft its no longer any good. Unless you buy a new crank, you will never know. The AC cranks have splines between the 2 webs. Speak to a known racing shop, maybe NK racing, to see what they can do. TZ bigend bearings is a common upgrade, as well. TZ bearings were also mentioned along with the splines on the dx centres. It was just an idea Iwas toying with. |
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Post by spooch63 on Dec 27, 2023 22:58:57 GMT 1
The extra weight of the dx centres would hopoefully be offset by the bigger cc and tune. I was thinking of a tune for midrange/ torque if thats possible or maybe thats a 4 stroke type of tune. Failing that maybe a fast roadtune. Many ideas were bandied about, flatslide carbs, different ignition, as weall know it's where do you stop, it's usually budget related !
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Post by ferox100 on Dec 28, 2023 8:28:33 GMT 1
Great idea, makes it much easier to rebuild the crank and also it can't slip and put the timing out, never knew they fitted!
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Post by steeley on Dec 28, 2023 8:40:29 GMT 1
It used to be common. I have a crank built that way, as it means the big end pins can be replaced without changing the webs. On the negative side, it is heavier, so may not rev up as quickly as a 4L0 OEM crank. As 4l0 says the webs are heavier , on the plus side the center shaft is splined so wont twist and you can change the big end pins . I stripped an air cooled crank some time back to be a crank for a big bore motor i had plans for . |
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Post by muttsnuts on Dec 28, 2023 19:28:54 GMT 1
was a common thing back with the proddy racer boys and still a good mod to do if you have the parts, certainly doesn't harm the LC crank, had a good few engines in like this over the years, not really noticed any difference in performance etc
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Post by reedpete on Dec 28, 2023 22:29:05 GMT 1
Mine was/is lightened , so don’t think weight is a negative. A good solution if built up with TZ rods, big ends etc…
But for the cost involved, probably just best to buy an off the shelf upgraded one.
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