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Discussion Starter #1
I'm looking do put a 440 stroker kit in the ol 400, along with vforce reeds a 42mm carb fmf gnarley exhaust, ported/ polished head. I first of all was wondering what else that list of parts would need to build it right. I was also wondering what this would do to the driveablility and if I would be able to run it on trails and put miles on it, I'd like something fast but don't want it to be a full on race quad, the goal is 70hp.
 

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What year and model 400 do you have? Two stroke or four stroke? What kits have you been looking at?

Boring and stroking both increase low end torque at the cost of high end performance - you cam up to regain the high end lost in boring and stroking at the cost of loosing some low end - you then change the exhaust to gain back some low end lost when the high lift cam is installed - to compliment the increased displacement, the combustion chamber needs to be reconfigured to match the bore and larger valves installed - to take advantage of the larger valves, the head needs to have the ports enlarged and finally a larger carburetor to compliment the rest of the changes - of course a larger carb results in reduced throttle response and low end torque, but gives you higher top end performance.

ENGINE BUILDING IS FUN!

If you want more bang for the buck, sell the 400 and get a 500, 600, 700 or.............
If you just want the thrill and experience of building your own engine, go for it!
 

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Discussion Starter #3
I'm looking do put a 440 stroker kit in the ol 400, along with vforce reeds a 42mm carb fmf gnarley exhaust, ported/ polished head. I first of all was wondering what else that list of parts would need to build it right. I was also wondering what this would do to the driveablility and if I would be able to run it on trails and put miles on it, I'd like something fast but don't want it to be a full on race quad, the goal is 70hp.
It's a 1997 scrambler 4x4
What year and model 400 do you have? Two stroke or four stroke? What kits have you been looking at?

Boring and stroking both increase low end torque at the cost of high end performance - you cam up to regain the high end lost in boring and stroking at the cost of loosing some low end - you then change the exhaust to gain back some low end lost when the high lift cam is installed - to compliment the increased displacement, the combustion chamber needs to be reconfigured to match the bore and larger valves installed - to take advantage of the larger valves, the head needs to have the ports enlarged and finally a larger carburetor to compliment the rest of the changes - of course a larger carb results in reduced throttle response and low end torque, but gives you higher top end performance.

ENGINE BUILDING IS FUN!

If you want more bang for the buck, sell the 400 and get a 500, 600, 700 or.............
If you just want the thrill and experience of building your own engine, go for it!
It's a 1997 scrambler 400 4x4, I wanted a two stroke 4x4 and this is what I found
 

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OK - well that changes things substantially.........

Boring a two stroke does not gain a lot beyond renewing the engine. I don't think anyone makes a stroker kit for a two stroke. Parts for a 97 are getting scarce and hop up parts are very hard to find.

Take the cylinder to an experienced two stroke mechanic and have him clean the ports - the best thing you can do as far as gaining performance is getting a tuned expansion chamber. Find a custom pipe builder and with a dyno and he can tweak the engine for maximum performance. The engine develops power comparable to an 800 cc four stroke - with a good pipe and tune it can be comparable to an 850 or 900 cc four stroke.

Have fun!
 

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Discussion Starter #5
I appreciate the reply, my dad is an experienced Harley technician, and he can do the posting and polishing, if I were do add a carb and reeds what company's shoudl I go with?
 

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I like Boyensen Reeds - I doubt if V-Force has a reed assembly for it, but they are good too and for a carb either Mikuni or Keihin
 
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