I really want to go over 1250cc on 1200.
The problem of this mod is the cases reboring. Dismount the whole engine and enlarging the crankcase where the cylinders bolt can be very expensive.

Just few days ago I searched into my phone book for a great mechanic I've worked with long time ago.
He is an expert mechanic who worked for racing teams into national super sport 600cc championship and now the Kawasaki Ninja Trophy.
Told him about my problem to rebore the case but I don't want to spend so much for a complete engine dismanteling.

He told me that he's able to do this such a job without dismont it, but with the engine on the bike also!
The technique is the one I wrote some days ago into a post of mine.
Put some plastic and/or cotton and silicon to seal the flywheel housing, so nothing will enter inside the motor. Try to mount the cilinder thorough his rods till the round bottom side touch the cases and mark around with a undelable marker pen. Dismount the long rods, and start working with an hand tool like the one used for head works but bigger. Removing material till reaching the mark made with the pen. Smooth the housing contour making it the most circular possible...
Clen everything well and remove plastic and silicon.
Proceding assembling pistons and cylinders.
I saw this magician doing some jobs like this on some mono dirth bikes and to some 4 cylinders. If he can do it on my sportster for nothing (there's still a friendship between us) or for a very few bucks, I'll kiss his ass. :laugh

If I find a kit 1350 or 1400 (I don't want to go over 1400cc) that doesn't need flywheel re-balancing, I'll do it. Dont' search for high-end power, but for strong low and mid-range torque for a smooth and hi quality driving and overall power delivery.

I like very much the Sputhe 1400cc kit.
http://www.sputhe.com/SPORTSTERBUELL.html

I hate to say it but that sounds like a recipe for disaster -- misalignment -- stress risers -- crud in the engine -- these motors are very simple machines -- take it apart and do it right.

I hate to say it but that sounds like a recipe for disaster -- misalignment -- stress risers -- crud in the engine -- these motors are very simple machines -- take it apart and do it right.

I thought, but the cylinder is aligned by the long rods. There's only the problem of not sufficient housing space for the bottom side. The difference is only that dismounting the cases, the job will be done by a machine with water emulsion to cool the case and tool during cut job.
By the friend of mine, this job is hand made, with some stops, and with a different tool. It can be made is there's only 1cm diameter to cut.

I don't know if it'll be really possible to do it, till he will dismount cylinders and look how much case needs to be cut and what material they are made of.
If it's aluminium, it's more easy, it's a light and more fragile metal. But if it's cast iron, I think it'll be difficult.

It's time for a question... What metal the cases are made of?

How much time do you want to spend NOT riding your scoot because of a problem?

Common knowledge says the more you do, the more you'll be down....

My .02

The quickest way to do anything is the CORRECT way..

I've seen too many mistakes from things like that over the years.....

Now if ya don;t want the job done properly then I'll just tell ya ta F%^^K OFF and take it elsewhere.


I recall one years ago when I was working for another company.....

A Toyota 4WD had bent a conrod and damaged the bore.
The boss wanted us to remove the head and damaged conrod and bore the cylinder in situ...
I tryed to do this and then we ended up having to take the engine out anyway.
The boss wanted the crank left in it.
So it took a few of us to put it on the boring machine and it took longer because the main caps were still on.
When we went to assemble it the crank was tight.
So we ended up takin the crank out to chaeck it and it was bent.

By the time that "quick" job was done it had sucked up FOUR TIMES the man hours it would have taken to do the bloody thing properly...

A lesson well learned..

As my grandad used ta say "if the job is worth doin, it's worth doin right and if it ain't worth doin right, then it ain't worth doin"


Strippin a sporty motor is not difficult

Personally going through all the hassle and expense of case boring is a pretty high price for the sake of performance unless you are in it professionally. And I definately would not trust the work to anyone but a highly skilled machinist. I don't really know but I thought I read in another thread that Sportster engines don't really like being much over 1250cc. I think you would run into flywheel problems and would need have the engine ballanced and blueprinted as well. Couldn't the same thing be achieved with gearing? I would be very interested in hearing more on these radical conversions.

I'm goin 88" with case boring on mine..........

There's no dramas with flywheels but granted it's not the sort of build that should be attempted by someone who doesn't know what they are doin...

All my performance engines and most of my normal street engines are blueprinted anyway.... all blueprinting is, is making sure everything is measured and it's right...no guess work.

Balancing is not such a big deal either.... most 88" pistons are very similar weights to stock pistons..

When you bore XL cases for 88", you have very little margin for error.

The cylinder is located by a dowel pin. The spigot needs to be cut the correct size with the correct relationship to that dowel, within a few thou. It's also got to be straight and square to the case deck. Get any of this wrong and the cylinder won't fit. Force it and you'll hurt something.

The stock spigot hole is about 3.68" diameter. You've got to take it up to 4.010 to fit the 4" spigot of the new cylinder. This consumes ALL of the available room. You literally cut into the oil drain passages, the center bolt, and you cut right up to the dowel pin.

Speaking of the center bolt, since the boring operation eats into it's threads, we drill the hole all the way through, spot face it at the exit, and use a long bolt with a nut. We have the bolt in place during boring and the boring operation cuts it into a V shape where the new bigger spigot holes pass intrude on it. I recommend a carbide cutter.

Don't underestimate what a precise operation this is. I can't imagine a setup on an assembled engine that could do it properly. And if you mess it up, it can be expensive.

http://www.nrhsperformance.com/images/boringxl.jpg

This is how we do it, on a CNC machine. We used to do it on a mill with a boring head, but this setup does a more precise job. The coolant keeps the temp even, too.

I don't pretend to know anything about this operation, but look at the picture close metal shavings and filings flying everywhere. Even IF you could do it without disassembly, Just one small sliver of filling could spell major disaster down the road.

I don't pretend to know anything about this operation, but look at the picture close metal shavings and filings flying everywhere. Even IF you could do it without disassembly, Just one small sliver of filling could spell major disaster down the road.

I saw the mechanic I'm talking about working on 2 jobs like this and he obtained good results. The difference is that they where smaller displacement engine, aluminium crankcases and for no more that 1/4" of diameter enlargement.
The job has been made by hand and with air hand tool, sealing with silicon the flywheel side.

If there's lot of material to remove and the case is made of cast iron, an automated tool with emulsion cooling is necessary.

Actually if you want to get the hole centered -- which is somewhat important you need a boring tool -- hogging it out with a grinder -- is a little bit shade tree. Sometimes shadetree is good -- in this case it isn't. I don't see the point by the time you get it to the point that you have to to do it by hand you are probably only a half hour away from taking the whole engine apart and maybe an hour away from reassembling the engine to that point. I assume that they have machinists in italy -- after all you build Ferraris -- and Maseratis and Falcos -- but then come to think of it you also build Fiats ;)