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  1. #1

    Default What is a big flathead engine worth

    Hey there guys,

    I hope these questions are even allowed here, so if not just point me in the right direction here.

    I always wanted to get my hands on a bigtwin flathead, and I got offered some parts.
    Its basically an empty motor meaning that we have matching 39U cases, cylinders, cylinder heads, feed pump valves, generator and the ignition timing device everything original except genny this one is new, the case seems to be already cleaned and isn't damaged or welded or something. No title

    The person asks for 7000 bucks for the whole thing, what do you think?

    thanks guys

  2. #2

    Join Date
    Sep 2017


    I think its high. Several questions, belly numbers match? Vin number and boss OK? Prewar is good. Should have cast iron heads. Gonna cost some to fill up the empty space. The rods are special and used to be kinda hard to get. Not sure how now. Flywheels are different than regular bigtwin. Are the barrels 13 fins, do they need sleeved, seats and guides,? Lifter bases, valve covers,valves, pistons, all the cam chest stuff, headbolts, case bolts,cam and lifter screws all cost bucks. then ya still gotta rebuild the thing. Big twin flatty parts are kinda thin on the ground, If you are contemplating its purchase, save some more bucks and buy a running one. Buying a frame and all the parts to make a motorcycle would far exceed its value. I would pass and keep shopping unless its a gotta have type thing. If its your ultimate dream go for it its only money.

  3. #3


    hey flatman thanks for your answer,

    I also thought the price is a little steep. The cases look just beautiful, from what I can tell those will require the least amount of work, they are pretty much in mint condition. Belly numbers match the cases would a decent buy, the rest...lets say it needs work. That being said I am pretty aware, that it will be a ton of work to get it running. My estimate is, that you can add at least an additional 7k bucks until the engine runs. I have put together engines before but never a HD flathead so I am really looking forward to all the challanges that might come with buying one. I am pretty obsessed with flatheads in general, the whole sidevalve thing is just so cool, they are such heavy dinosaur tech, i would say its not so much about owning a big flathead for me, I just figured the extra displacement wouldn't hurt. My plan is to build a flathead that I can take anywhere I wanna go and i know you can wake up those 45s in many ways to make them decent as far as power goes. With a big flathead you wouldn't have to do that really because of the bigger displacement, so the real question is going cost effective by tuning a 45 to fit my needs or spend extra to get the more powerfull engine. Either way I think you are right saving some extra and buy a comlete engine makes more sense.

    As far as parts go w&w cycles offers everyting to build a brand new big flathead, you can literally buy the whole engine in parts on their webside, tho it would cost a fortune...w&w is pretty expensive not gonna lie. I live in germany like 15 miles away from where they are situated so I could just pick up a brand new set of UL cases in 30 minutes whenever I wanted. And if I think about it now I could get the same ammount of parts for 7k from w&w and would have brand new stuff, sure it is not original HD but if you only cared about owning one who cares. I am honestly torn, kinda want to get the best for my money, kinda want the origianl stuff, but 7k idk man. I think I will change plans and get a decent 45 and tune it up, If I'm not satisfied I can always get a bigtwin flatty, like you said its only money.

    Also I think it would be better to start of small and really get to know the flathead first.

    Last edited by Norrimichlson; 10-25-2022 at 3:41 AM.

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