Monster big bore kits
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Joined: May 2011
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From: Glendora
Monster big bore kits
Hey guys i am wondering if any one has tried the 88in and 90in conversion kits that are sold for the sportster? Also if you have tried these or know about them does it make the motor less reliable? And what kinds power would you get from these kits? And lastly are they just straight bolt on or do you have to do a ton of work to the cases and trans and stuff.
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From: Bedford UK
If you are talking about NHRS there is nobody I would chose above them! Pal of mine has a 1250 conversion in his Buell. As for reliability you are talking of a serious upgrade with those, so engine life is likely to be shorter than a stock motor. They make a bolt-on 1250 kit (76"), but the 88" and 90" require case machining, in other words a complete strip-down.
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Absolutely, NRHS is the way to go. However, I would shy away from anything larger than 88", as they are fairly problematic. The 88" is known to be quite reliable, and will offer nearly stage one longevity. As mentioned, going larger than 76" is a major undertaking, and must be approached with caution. I would suggest using a commercial machine shop and perhaps even a top-drawer mechanic for this job, as opposed to trying it yourself.
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From: Glendora
Hey guys thanx for the info. I wasnt really thinking about trying it ya know. To much money for me right now. But i was curious about it. With the 88 inch are you looking at a good amount of hp and tq?
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From: Landrum, SC , elevation 986'
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From: Glendora
Hey guys thanx again. Freebird I love that site alot. Its b/c of you that i found that site. I was thinking about the 1250 kit. Is it a huge improvement over my stock 1200? As always i can count on you to be some to to turn to when needing advice or questions answered.
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Joined: Jun 2011
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From: So. Cal.
With the two kits you mentioned you would have to bore your cases also. You're talking a good chunk of change for those two kits. 1250cc is the largest you can go without boring the cases.
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The 1250 is a huge improvement over your 1200. Of course, you can get much of the benefit with just swapping slugs for more compression, doing a good valve job, and programmer. On the other hand, by the time you do all that, you may as well get the 1250, which is still a noticeable improvement.
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