I know that most people on here are sportbike riders but for those who are mechanically knowledgeable i have a question about Harleys. It seems that a lot of people have bought the 883 Sporty and wanted to improve the bikes performance so they got their 883 bored out to 1200 or bought new 1200 or 1250 cylinders with big pistons etc. My question is, don't you have to re-balance the crankshaft when you make a major change like this or is the rpm range of a Harley so low that it doesn't matter?
Harley Davidsons
- Thread starter Basketcase
- Start date
I doubt the crank gets modified when installing a big bore kit on an 883, it would at least double the cost of the installation. I'll bet the bottom ends of the stock 883 and 1200 motors are the same. Yeah, the Sporty motor redlines around 6000 rpm so maybe larger pistons don't affect the crank enough.
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I don't know but the big bore kit is sold and installed at the dealer for the 883.You can also buy a kit for the v rod as well and I don't think they balance the crank on it either(9000rpm red line).I will be a the dealership later to day so I can ask for you so I would agree with^^^^^
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My understanding was its a bolt on kit, same crank, new barrels and pistons.
Also, if the crank needed modification, the bike would sit on the bench far longer. A top end swap can be done within a day and I'm assuming without needing to the remove the motor from the frame. If the crank needed to be sent out for balancing, the motor would be removed and cases split, way too much work to be cost effective.
HD's kit is simply jugs and pistons. Everything else is left stock. Heads, bottom end etc. It's a quick upgrade that bring the best bang for the buck.
If considering the 1250 kit, the price is higher and you should have the intent to do some more motor work to reap the benefits. And it gets real spendy, real quick. Head work, valves, crank, cam, etc. Not to mention beefing up the clutch and tranny to deal with the extra power too.
The 883 is geared lower for a quicker jump off the line so, if you do get a 1200 kit, they generally are quicker than a stock 1200.
Exhaust, high flow air cleaner and a power commander or jetting upgrade is the cheapest and most common power upgrades.
The crank was balanced when the bike was first built by Harley. No need to re-balance it again unless you wanted every last bit of performance. Then you would be tearing the motor down and replacing things like the rods, pistons, cams and balancing everything at the same time.
Tripletrouble
Well-known member
The crank is balanced so that the weight of the pistons/rods is offset by the counterweights. Changing the pistons will change the balance however this is quite a complicated subject. If "balancing" was the answer then it would be possible to have a smooth idling V-twin motor . The reality is that motors are balanced to keep the worst of the vibrations away from the rev range commonly used which is why a motor balanced for racing will have a different factor than a street motor where the worst of the vibes occur away from the top end where the motor spends most of its time.
Let's be real clear about something right off the start.
EVERY crankshaft in EVERY motor is/was balanced BEFORE the engine was built/assembled.
If it wasn't balanced, the bearings wouldn't last 10mins.
Making changes to the top end has absolutely no effect on the operation of the crankshaft.
Harleys have cranks like small tractors anyways, so feel free to add all the horsepower you want.
As for max rpms, the only thing holding it back is the stock top end and cams.
The motor is quite happy and able to run at 9000rpms providing you have the correct heads, pistons, cams, ignition, rods etc..
Another myth is the belief that displacement is the only answer for speed and power.
If that were true, a small honda car engine wouldn't be able to make 300hp.
The larger displacement will give you more torque, thats what you are paying for, the HP gain is minimal.
An 883 with Buell lightning heads, pistons, new cams, ignition module and small carb mods will kill any 1200, 1250, and all stock softails Harley makes.
Take it a step further and custom port polish the heads, big twin valves, and have them shaved, you can spank most sportbikes down the quarter mile.
If you doubt any of the above, make sure you never bet your bike slip against me.
EVERY crankshaft in EVERY motor is/was balanced BEFORE the engine was built/assembled.
If it wasn't balanced, the bearings wouldn't last 10mins.
Making changes to the top end has absolutely no effect on the operation of the crankshaft.
Harleys have cranks like small tractors anyways, so feel free to add all the horsepower you want.
As for max rpms, the only thing holding it back is the stock top end and cams.
The motor is quite happy and able to run at 9000rpms providing you have the correct heads, pistons, cams, ignition, rods etc..
Another myth is the belief that displacement is the only answer for speed and power.
If that were true, a small honda car engine wouldn't be able to make 300hp.
The larger displacement will give you more torque, thats what you are paying for, the HP gain is minimal.
An 883 with Buell lightning heads, pistons, new cams, ignition module and small carb mods will kill any 1200, 1250, and all stock softails Harley makes.
Take it a step further and custom port polish the heads, big twin valves, and have them shaved, you can spank most sportbikes down the quarter mile.
If you doubt any of the above, make sure you never bet your bike slip against me.
Is there a place in the Toronto area that could do this type of work?
The 883 souped up would make more sense to me as I would expect it to vibrate less with the smaller pistons and be able to rev a bit higher.
Then of course one might as well buy the small engined Buell I guess?
If you are worried about vibration, go buy a Honda.
Sounds like you aren't gonna be very happy riding a Harley, so i'd suggest you save your money for when you buy a new smoother ride.
The work i've mentioned won't be cheap unless you do most of it yourself.
A Buell xb9, xb12, and a couple others use the Sportster engine platform, but don't tell everyone or you'll make the Buell owners cry.
Better off buying a Buell engine and swapping it over unless you have 3k min for motor work and parts.
Like most guys, you are concerned about speed, but you should be focused on making the bike handle and stop properly first.
Stock HD is a piece o crap, i highly recommend better tires, progressive suspension, fork brace, and braided brake lines before you get to playing with the motor.
If you still love riding it in a year, then you can spend some dough on it.
I probably just saved you 4k, so you owe me a sammich.
SXE MX6
Well-known member
umm.....buy one with one already done! lol
And you might loose 200rpm with the bigger slugs if that. Lots of other factors are to deal with if you want more rpm.
The buell is a completely different breed of bike compared to a sporty.
Seems to me you need to figure out what kind of bike you want first, and then decide on the power you want.......
Let's be real clear about something right off the start.
EVERY crankshaft in EVERY motor is/was balanced BEFORE the engine was built/assembled.
If it wasn't balanced, the bearings wouldn't last 10mins.
Making changes to the top end has absolutely no effect on the operation of the crankshaft.
Harleys have cranks like small tractors anyways, so feel free to add all the horsepower you want.
As for max rpms, the only thing holding it back is the stock top end and cams.
The motor is quite happy and able to run at 9000rpms providing you have the correct heads, pistons, cams, ignition, rods etc..
Another myth is the belief that displacement is the only answer for speed and power.
If that were true, a small honda car engine wouldn't be able to make 300hp.
The larger displacement will give you more torque, thats what you are paying for, the HP gain is minimal.
An 883 with Buell lightning heads, pistons, new cams, ignition module and small carb mods will kill any 1200, 1250, and all stock softails Harley makes.
Take it a step further and custom port polish the heads, big twin valves, and have them shaved, you can spank most sportbikes down the quarter mile.
If you doubt any of the above, make sure you never bet your bike slip against me.
What kind of numbers do they make after all that?
Out the door a Canadian dealer will do 88ci (1200)for less than $2500 The bore difference is only 3" to 3.5.There are 4 different 1250 kits so the hp varies greatly but all 1250's are far quicker than a stock 1200 and aftermarket.The 883 needs nothing more than whats included the kit.This is what the dealer tells me so if you want to do it you have to go see someone.I don't like Harley's much either but I would never call some else's bike crap to each there own.Everybody hates my Porsche even the dealer so...
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Tripletrouble
Well-known member
You obviously have no idea about the why's and wherefores of crank balancing.
I understand just fine thanks, but i can see where you are going with this statement.
The guy isn't re-building an NHRA engine here, it isn't necessary to pull out the flywheel assembly for a simple conversion on an XL motor.
If he decides to get real serious, then he can rebuild himself a nice 1250 like this guy> http://www.streetchopperweb.com/tech/0704_stcp_crankshaft_balancing/viewall.html
Here's another decent article on heads. > http://www.streetchopperweb.com/tech/0706_stcp_sportster_cylinder_head_upgrade/index.html
There must be over a hundred different options available, you basically pay for what you get when it comes to power.
I'm assuming you just want some extra ooompff when you twist the throttle, so you want to keep the motor as low stress as possible so that it lasts too.
More power = more stress = more part failures = more money.
Go try someones 1200cc bike first, if that makes you happy, you can get a simple conversion done by HD, or someone else as mentioned.
This guy does great work, but hes usually busy, might have to book ahead quite awhile.
Brian Olsen Racing Services 12318 Highway 7, GEORGETOWN, ON L7G 4S4 905-873-1283
I doubt it will only cost 2500 if done at dealership, it's well over 1500 in parts alone at their retail Deeley rip off prices, but you can ask them.
Some conversion kits I have seen use the same weight pistons, so no re-balancing neccessary. Also, you're going from OEM cast pistons to forged.
Do it yourself and save a fortune. Some kit's are only $500 CDN. http://www.heritagecycleworks.com/Product_View.cfm?int_ProductID=839&ID=4&SubMenu=43
Do it yourself and save a fortune. Some kit's are only $500 CDN. http://www.heritagecycleworks.com/Product_View.cfm?int_ProductID=839&ID=4&SubMenu=43
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I don't think any of 'em commenting here do.
Typical GTAM FAIL!
To the OP:
If you want to do it, take your jugs AND HEADS to Gordie Bush. Use Keith Black pistons. It will be less than $1500. You don't need to rebalance the crank.
Tripletrouble
Well-known member
Here is a link for those that are curious about crankshaft balancing; http://www.enginebuildermag.com/Article/48121/understanding_crankshaft_balancing.aspx
It is likely that factory big bore kits address the balance question by keeping the new piston weights in line with the stockers as mentioned in the post above.
It is likely that factory big bore kits address the balance question by keeping the new piston weights in line with the stockers as mentioned in the post above.
