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Discussion Starter · #1 ·
So I previously made a post about starting problems and got plenty of help and advice but in the end I've decided to completely rebuild of the engine. So my first question is about boring and honing my head out to 81 mm is there any really power gain as for cost it really doesnt matter much because I plan on doing this rebuild through fall winter and possibly some of spring. Also has anyone used wiseco 81 mm piston kit because I have a friend that purchased a blackbird a little after I did and was considering doing the same but decided against it after buying a wiseco kit and offered to sell me it for around 200 instead of dealing with the pain of shipping it back and all that jazz. My third question is fuel injection conversion or carb because I prefer fuel injection and can get what I need from a salvage yard and so on. Any input on these questions would be greatly appreciated.
 

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For your first two questions, I have no personal experience or expertise, but here's a thread I found with a quick search. There are more, too

http://www.cbrxx.com/engine-airbox-exhaust-fuel-delivery/16009-wiseco-kit-looking-for-feedback.html

For your last question, if you want FI that badly, do yourself a favor and sell the carbie to buy a FI Bird. Seriously. Unless you're a master mechanic who loves a challenge and has a ton of spare time, the conversion and operating kinks that would come with it are just not worth the effort.
 

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... So my first question is about boring and honing my head out to 81 mm is there any really power gain.......
by taking the engine out to 1195 there is a gain in torque but since HP =(torque x rpm) / 5252 (units omitted for clarity) the by product is more HP. How much the gain will be depends on the inlet / outlet the '1200 conversion' works best with cam and exhaust changes.

As for Carb or FI, either way set up on a rolling road will be necessary and it all depends on the operator. Decent carb tuners are thin on the ground now and FI will require a PCIII or similar.
 

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Discussion Starter · #5 ·
Fi doesn't seem like it'd be to much of a pain just have to get 99 parts and swap over but I'm fine with running carbs because I've also contemplated e85 conversion and carbs are far easier than fi. But I'm wanting to get the most out of the 81 mm piston tho their mostly just to replace the old ones because they're 54k on them and the old head had bent valves and eat up brackets from a poor valve adjustment. But if anyone has some recommended porting for the exhaust and intake love to get them because I'm going to run 4-1 exhaust and open the exhaust to 2 1/4 to help make up for the change from 4-2 plus I like the single side look. But yeah love to hear about any recommended upgrades or mods to the engine to the get the most out of the 81 mm pistons.
 

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So I previously made a post about starting problems and got plenty of help and advice but in the end I've decided to completely rebuild of the engine. So my first question is about boring and honing my head out to 81 mm is there any really power gain as for cost it really doesnt matter much because I plan on doing this rebuild through fall winter and possibly some of spring. Also has anyone used wiseco 81 mm piston kit because I have a friend that purchased a blackbird a little after I did and was considering doing the same but decided against it after buying a wiseco kit and offered to sell me it for around 200 instead of dealing with the pain of shipping it back and all that jazz. My third question is fuel injection conversion or carb because I prefer fuel injection and can get what I need from a salvage yard and so on. Any input on these questions would be greatly appreciated.

Please take no offense to what I'm about to say, but I have to say it to get you on the right track.

Seems you don't have the knowledge to do the job unless you have a good machinist/machine shop for the boring, honing and other things that need done. You do not bore and hone a head. It's basically impossible. You bore/hone the block. Which in this case is part of the engine case. You need to be very accurate in all your measurements and machining. This takes $$$$$$$ in bore gauges, mic's boring machine and a very good honing machine. You're working with measurements of no less than .0001, a half thousand. Many parts need checking and most likely reworked some or at least checked properly. ex resizing of rod ends, rod/piston balanced w/crank by good crank grinder shop.

The bore/hone should be done with the newer style equipment for the simple fact of accurately. These motors are super motors and will come apart very quick if not rebuilt properly. Do you know the stresses at 9-100000 rpms? As far as heads leave them stock, maybe clean the ports to the valve seats. I said clean not port! Not sure about the Honda valves. I don't think they can be reground, at least not by much. The stock openings will give you better low/mid range cause they should flow faster than with stock bore.

The Wisco kits are very good. The biggest bang for the buck is by boring an engine. You will need a good head gasket cause you are raising the compression just by boring it with stock head. The rings need to be end ground to fit the new bores with the proper end gap so they don't bind then break. There are many more little things that you must pay attention to when building a high performance engine and experience is one of them. What's yours and your knowledge of such? I'm sure you don't want a hand grenade after spending lots of money.

Personally unless you are or have a carb expert I would go FI for many reasons. The carbs are going to most likely need modifications to the new characteristics of the new motor besides jet change to get the power out that they are able to produce. FI is so much easier to tune and more forgiving than carbs.

Wish you good luck. The internet is a great place to get the knowledge needed as long as you don't get on some hokey sites that don't really know what they are talking about.
 
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