When I had an 88" motor I punched it to 95". Didn't want to split the cases for a 103" or bigger. Now I have a 103", I want to know how much I can punch this motor out without splitting the cases. This will give me a starting point for engine mods. Looking for a strong combination that will be reliable yet capable of hauling the mail. I realize this may be an over simple question.

 

107 is as big as you can go without machining the cases

 

Hmmm, that makes me wonder what is the best way to get the most out of the motor.

 

i can't see 4 cubic inches making that big of a difference. i'd go after the top end with ported heads, bigger valves, and bigger cams, maybe bump up the compression a bit, etc.

 

All things being equal, about 3-5 hp/tq difference upping the displacement 4 cubic inches.

 

There are a few threads around where people post HP/TQ graphs of a stage one on a 103. Th end results were pretty damn close to my 107 if not more. That of course depends on what you do such as heads, etc. If I were you I would stick with your current displacement and go stage 1/2. You'll be up around 95 HP and 110 TQ easily.

If you want more than that might as well sell off the 103 and get a crate 120.

 

Intake, exhaust and cams. Race tuner and dyno. Head work will help but not much bang for the buck.

 

Yeah, that.

 

Cmon you think pulling and selling the 103 and buying, installing, adding needed add ons is better than modding whats there is the best way to go???? Let me know when you want to sell the 103's and I'll take them all day. There is an awful lot of power left on the table with the factory motors. Get up with Fuel Moto or any reputable engine builder and you can end up with a 115/115 or more motor very easily. Just sayen...

 

I agree for the most part and I didn't say it was the best way to go. I would do a stage 1 or 2 on the 103 and be happy with 90+ HP on that bike.

My point is after that you start to hit the law of diminishing returns. Especially when you get to 110 ci or bigger. I'm just saying that by the time you spend money on a case split and subsequent modifications you might want to do the math on selling the 103 and doing a crate 120 for about $7k. My guess is it wouldn't add too much to the tab.