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14mil cub or 4mil DM


JCSO605

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Hey guys I'm wanting to build another bike just about have one complete. It's fitted with a 10mil cub built by D&M Racing. I bought the engine from buckeyeshee here and he is a good one to do business with. My deal is I'm torn between going with a 14mil cub or 4 mil DM. This will be an 1/8 mile bike. It will also be ran on race fuel not alky. I will go with a&s, d&m, or k&t for the setup. Which would be best Thanks

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I think you might come out cheaper with the 4 dm case work ,but as far as hp goes its all in how fast you want to go and other things like weight,tuning etc.. don't get to big in the whole hp thing ,because there stock cylinders out there running 6.20s and faster

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so both would be close to 500cc if im thinking right. 68x68 on the cub and 72x58 on the dm ?  sqaure engines usually have the advantage with more port area assuming both are close to the same cubic capacity and similar port design. over sqaure is never a good idea if you can avoid it especially if its extremely over sqaure. 72x58 would be extreme imo

 

but you have to remember if the cub is originally cast as 64mmbore and you take it to 68 what is that gonna do to the trans and exh tunnels

 

likewise with 72. when you push the bore that far into the tunnels is not a ideal situation

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Thought dm are all 77-78bore. also transfer tunnel layout is different to help accomodate bore size. also wouldnt be concerned about bore size on a cub cylinder.64-68 no difference. You builder will do fine with either. also thought you wanted to build another bike meaning 2total. dont reuse what you have. I have a 14 cub that runs good. i think i would do a short stroke big bore when i do it again. like a 4 dmx maybe

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I do want two just finished a 10 mil cub bike now I'm wanting to build something a little different I just wanted to know if there was any difference in power between the 14 mil cub and the 4 mil dm. Also the one that made the best power for the money. 4 mil DMX. THAT IS A BEAST

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Thought dm are all 77-78bore. also transfer tunnel layout is different to help accomodate bore size. also wouldnt be concerned about bore size on a cub cylinder.64-68 no difference. You builder will do fine with either. also thought you wanted to build another bike meaning 2total. dont reuse what you have. I have a 14 cub that runs good. i think i would do a short stroke big bore when i do it again. like a 4 dmx maybe

 

large bore short stroke is not the best idea on a 2t. any builder worth a grain of salt will tell you this.

 

on a twin with cylinders close together the trans tunnels dont have the best of geometry to begin with. increasing the bore only adds to the problem. when they go almost straight up and make a 90* turn thats a poor performing duct

 

small bore cub close to sqaure with as long a rod as possible is likely to have the most power per cc.

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