Let me start by making a point very clear:

This is not an indictment of big-bore kits, the suppliers of such kits, or even bikes that run these kits successfully.

Recently I bought the standard 1250 big-bore kit from Hammer Performance.My experience could have happened with the NHRS kit, teh S&S kit or any other kit. Hammer performance is a stand-up company with good products and excellent customer service. I would buy from them again. So don't take this as a slam on these guys. In fact, probably the opposite.

So, I bought the standard kit.
Cylinders
Pistons (installed in cylinders for a small fee.)
Wrist pins and clips
Cometic gasket set

I did not opt for headwork or cams. I used my stock heads and cams.

The HP site has a LOT of detail about the kit and tells you EVERYTHING you need to know.

The kit was installed. Fairly easy as major engine work goes. No surprises; about 5 hours total labor.

The bike started instantly (with a 1200 map from Fuel Moto.)
The static heat cycles went fine.
The short test rides (as prescribed by HP) went fine. 1 mile, full cool-down, 2 miles, full cool-down.

Here is where it went bad.

I sent out to put about 25 miles of the prescribed 50 miles/3200rpm limit. I got about 1/2 block from my house and i heard a "clank" and immediately saw the oil light.

Note that the engine never stalled or even made a hiccup. I knew what happended immediately.

Rewind to the Hammer Performance "EVERYTHING you need to know" information.

The Hammer performance page recommends the replacement of the oil-pump worm-gear for people doing high powered upgrades. In my infiniate wisdom, I decided that the basic kit wasn't powerful enough to warrant such an upgrade.

Wrong.

So, being a brand new bike and being that I made the mods that likely created the issue, I decided to take my bike to the dealer. I've bought a few bikes from them and know them well. I figured I'd pay for the worm-gear replacement rather than screw something up.

Damn good thing.

The worm-gear disentigrated and spewed metal bits into the cam bearings. Although the engine still runs, it wouldn't have lasted long.

Finally, some good news (believe it or not.)

The dealer, is going to reaseemble my motor to the 883 (luckily I still had the old parts.) Then, they are going to send it to HD for warranty. HD is already in process of sending a brand new 883 motor to my dealer.

I will of course be charged for the re-assembly of the 883 parts, then the re-re-assembly of my 1250 kit onto the new motor.

My opinuion? I dodged a bullet. I'll end up paying 10-15 hours of labor, but the warranty saves me a couple to a few thousand dollars.

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The lesson here is this.

If you do the big bore kit, spend the extra $70 on the bronze worm-gear sold by Hammer Performance.

 

Wow, somebody who takes responsibility for his own mistake. Refreshing!

 

I do not think your failure had anything to do with your performance upgrade, unless there was some bad wrenching involved.

 

I'm a fair wrench. Aerospace mechanic turned engineer. Also, I never touched the bottom end. Not even one fastener.

 

Wow Bud, bummer, but sounds like it could have been worse, sounds like the dealership is being very hospitable.

Glad it's going to turn out alright!

 

Thanks Blue Suede Dude. I found the response fair. I hope it sticks.

 

Good, then you can understand even if your oil flow maybe wasn't sufficient for higher output engine (I doubt that), there is still no way the 1250 kit would damage the oil pump.

 

It didn't damage the oil pump. It shattered the worm gear that's pressed onto the end of the crankshaft. The worm gear drives the oil pump shaft, which then turns the oil pump.

It's also a known weak point in high powered Sportster engines. Buell replaced the worm gear with a bronze version for this very reason. Hammer Performance recommends the Buell part (and sells it.) I didn't take their recommendation, but should have.

In reality, crank runout causes the worm gear to wear and eventually fail, higher powered engines cause it to wear and fail quicker due to larger, harder hitting pulses from larger displacement and higher compression.

Runout in a gear system acts on the gear with a repetitive impact each time the high spot is forced against the mating part. When that impact changes due to larger pulses (higher compression, larger displacement), the stress points drive the pulses deeper into the substrate. This causes a crack. Think about a series of light taps, then a hard whack when breaking ice or rocks. Same principle.

Yes, I understand exactly what happened.

 

Thanks for your post, very informative. Looking forward to a successful outcome with your new 883/1250 engine!

 

did you not read the original post. smh