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Lilgrebel
I learned to ride on my 2005 Honda 250 Rebel and although fellow riders stated over and over “you will want a bigger bike after you ride for a year” it was not the case. I love this bike! It fits me perfectly. All I wanted was a little more power and a bit more “cool” factor. After searching the internet we came to a few conclusions in the aftermarket. You could go the bobber route or the full dress touring style however nothing in between. Also after looking virtually everywhere in the world we could not find a big bore kit to fit the bike. We decided to do some customization on our own and to build a big bore kit from scratch. Here is the list of what modifications have been made:
- We had pistons custom made to 2.5mm overbore and with compression of 10:1 vs stock of 9.2:1. (Note we had to have multiple sets made up for this and will probably sell our extras on ebay as Lilgrebel big bore kits.)
- Main jet to 112 from 108
- Drilled holes in air box.
- Installed shorty mufflers from Blue Collar Bobber. Nice units, good value and good service from Blue Collar Bobber.
- Powder coated the Blue Collar Bobber mufflers black.
- Chopped and customized the rear fender, tail light and turn signals.
- CRG bar end mirrors.
- Painted rims black
- Removed all decals and repainted bike black.
- Black bars, lower with less pull back. Almost a drag style bar.
- Seat upholstered with side to side stitching to give it a bit of an old school look.
- Larger front sprocket. (Bike was now strong enough to pull it)
What I ended up with was a pretty cool Rebel that is as close to a “one of a kind” as can be imagined. Displacement was increased approximately 10% and compression about 9%. Our rear wheel dyno tested performance gains showed horsepower went from 15.9 to 16.67 and torque from 11.7 to 13.79. 5% gain in hp and 17.9% gain in torque. The big story however was in what happened to the power in the lower rpm range. At 5500 rpm where most people would be riding the hp went from 12 to 14.5 and torque from 11.25 to 13.5. That is a 20.8% increase in hp and 20% in torque at 5500 rpm. It made the bike much more fun to ride and allowed us to gear the bike up by downsizing the front sprocket. My little Rebel will cruise all day at 60 mph and although I have not run a top speed test expect that it should be able to top out at close to 80 mph.
 

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Very nice work. The engine work is impressive and the cosmetics look great! I'd love to see more detailed photos of the seat. Regards, Chef
 

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Welcome aboard.

I've got a question for you though.
How did you get a 250mm overbore from a 53mm standard?
That would make the new bore 303mm.
 

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My understanding is - when you put on a smaller front sprocket you've Lowered the gear ratio.
 

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Discussion Starter · #5 ·
Sorry gang. A couple mistakes in typing my post. 2.5mm overbore not 250 and one tooth bigger on the front sprocket not smaller.
 

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Discussion Starter · #6 ·
Will edit my original post once I can figure out how to do so. Any tips on that would be appreciated. I can't find an edit button and wonder if my opportunity to edit has expired?
 

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Took care of the original post edits for you. After a certain amount of time you won;t be able to edit them. Contact a mod to do so.
 

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Really like the look. Great job on the upgrade and HP and Torque increases were impressive for the 250, really nice.
Where did you get the pistons made and were you able to find the rings for the upgrade.
I have a 450 and something like that would be a interesting thing to look into.
Again nice subtle modifications.
 

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Welcome. Did you keep track of how much the engine mods cost?
 

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Wow.. awesome.. and thank you so much for sharing the information with us.. I have a 450 and had toyed with the idea..but as you pointed out never really came across a big bore kit..

I would be interested in knowing how much it all cost you as well..

I just had a conversation with a guy who though it was a waste of time and money to do all what I have done with my Rebel and suggested I just get a bigger bike... Then I told him I do have a couple of bigger bikes.. but I love my Rebel and it is well worth my time and money...

after a bit of back and forth this lady came over to see if I would play darts with them they needed another female.. I did because it was a great out to get away from that idiot..

Later I found out that he does not and never has ridden a bike.. he is always just trying to drum up business for his son who sells used Harleys...
 

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Discussion Starter · #12 ·
Horsepower went from 15.9 to 16.67 and torque from 11.7 to 13.79. 5% gain in hp and 17.9% gain in torque.

250 Honda Rebel
 

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Discussion Starter · #13 ·
It cost me approximately $600.00 for my mechanic to overbore, remove engine and install with new pistons. So with this and the cost of the big bore kit it would be $1200.00.

The big bore kit for the Rebel 250 includes pistons, rings and gaskets.

Sorry guys, but I don't have any pistons for the 450, just the 250. You could research piston manufacturers and see if they will custom make you some pistons, as I did. A word to the wise though, they may want you to order up to 20 sets to make it worth their while.

Rebel 250
 

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Wow... $600 that is awesome...

Hmmm I guess if you have to order 20 sets you will just need to be a little entrepreneurial and put together 450 big bore gets to sell...
 

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I have done a bit of checking around.. I think the 450's have a few more options in big bore kits and there are a couple that I found that would work for around $400 to $800....

Again I do appreciate you sharing all the information with us... I will do some more checking around and post more details for a 450 big bore job...
 

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That big bore kit sounds nice. Is that the most you can bore out the 250? I want to build a 250 Nighthawk (same engine) cafe racer with a polished and matched head, intake,and carb. With a big bore kit and tuned exhaust it could be a sweet engine. No hot rod for sure but a sweet running motorcycle.
 

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$600 for pistons, rings and gaskets seems outlandish!
 

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your bike looks kinda like mine... i melted one of the pistons in my first engine running open pipes and stock jets. since then i've put the original 86 motor back in it and i've been playing with the jetting... just about got it right since you've made so many changes i would keep an eye on the plugs if i were you... just a thought... Spark plug reading chart
 

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I beg to differ. The pistons would be a lot cheaper if the person having them made ordered a few thousand and knew she could sell most of them. Its a crapshoot as to if she can even sell the 20 sets that were made. Sorry 19. One for her bike. Sorry 18 need a spare. If I can find a 250 Nighthawk on the cheap I will order one and do the engine work myself. See post #17.
My wife will not let me do anything but clean and gas up HER 85 250 Rebel. Oh yeah, I am allowed to change the oil too. The upside is its ok with her to do the Nighthawk project if it keeps me from doing mods. to HER motorcycle. :) I can live with that :biggrin::biggrin:
 
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