Ok. So next winters project is doing the Hammer Performance 1275 kit. What other mods did you do? Has anyone just installed the bigger jugs and pistons and call it a day? I want to start saving now for what I'll need. Not looking to build an unrideable monster but something with a little more oomph! Thanks!!

We get asked this basic question literally every day, usually multiple times a day. Guys do a basic conversion and they're thrilled with it, but after awhile they get used to the power and want more and they ask us how to get there. I wish I had a good answer for them, but without changing the pistons, there just isn't a good answer.

The complete reason behind that is kind of long and obscure and gets into a bunch of detail about how the heads and cams and pistons play together. The short version is that you can't put big valves into the heads, along with much overlap into the cams, without making the chambers bigger. You just physically can't do it without creating issues with valve-to-valve and valve-to-piston clearance. And bigger valves along with more overlap is exactly what the motor needs to make more power.

The issue is that making the chambers bigger drops the compression. Meanwhile, your new cams probably require more compression, not less. And you can't get your lost compression back with decking. Decking a head that far causes a whole new set of issues. You have to change the pistons.

At the end of the day, you have to think of piston and cams and heads as a matched set. You can't move any of those things very far without bringing the other two along. They're matched in numerous ways. Your reverse dome conversion pistons are well matched to the stock 883 heads and cams. They're not well matched to high overlap cams and big valve heads.

Doing a hop-up project incrementally over time is tough. You end up either buying some parts twice, or you compromise your result, or you push clearances much tighter than you should.

You can do a mild hop-up without changing the pistons, don't get me wrong. But we hate having disappointed customers, so we try to avoid that. Generally speaking that path leads to disappointment.

Not the answer I want to give, believe me. If I could bend the laws of physics and solve this problem, we could really help sales.__________________
Click Here to Contact Me

What is an unrideable monster?

I probably should have written that differently. I don't want something that isn't reliable. I know too many people who build up bikes and are very temperamental. Then again they probably didn't know what they were doing and how they were gonna use their bikes. I know you did this recently. What all did you do is what I'm asking.

Basically I want to know if l have to go with new cams and headwork or if just adding the bigger jugs and pistons will wake up my engine. Guess I should talk to the guys at Hammer! Thanks for the replies! I'm a newbe to these new fangled engines!

Basic conversion is A ok!!! I’m just obsessed so I have a 120 plus hp street 1250 and race 1275

This is for my 2007 1200 Low. I'm thinking about the 90hp kit.

Let me know how it goes, I have a 2007 1200 Low as well.