Well I was looking at this kit for my 2003 450 foreman. The change in perforemance are said to be substantial.

The changes that are made by resleeving the cylinder and replacing the piston are ...

stock displacement = 433 cc
Big Bore = 475 cc

Stock compression ratio = 8.5:1
Big Bore = 10.25:1

I would assume that minor jetting and carb adjustments need to be made.

I love the Chassis of the 450, very rugged, and even though it has enough power I wouldn't mind a little more!

So I was wondering if any of you out there Has done this or has known someone who has and if it is worth it. Or will I just be opening a "Can of Worms" were I will plague myself with repair issues and hassles?

Thanks for any shared experiences

 

IMO, there is a reason Honda left the stock displacement at 433cc, and the compression at a very mild ratio. I would never attempt a big bore kit in a machine like this, basically an air & oil cooled workhorse. Keep it reliable and live happily ever after.

 

Like steady freddie said, what you'll gain is probably marginal in this kind of engine. Boosting displacement and compression ratio usually yields dramatic power gains in a high output kind of engine, and ours simply aren't that kind of engine. Easy to get along with, tons of bottom end torque, and reliable as hell, but not screamers. Hmm, come to think of it, I kind of like it that way.. must be a result of too many years of shifting to stay in the powerband..lol

 

I have discovered that the honda 450 has same engine as the 400 it is just bored out thats all. It was the fact that honda didn't have to make too many changes to it's tooling line is the reason why it is only 36 cc larger then the 400.
They just bored out an exsisting cylinder instead of resleeving, Cheaper to manufacture.

 

I agree with everyone.
I think that you would be screwing yourself by changing it. Adventually down the road you will have problems. You should probably go to a dealership and ask them what they think. I think that most of the stuff like that that is out on the market is a scam. I mean it might work for a while, but nothings as good as the original. It's a Honda that's the reason that there the "best on earth".
I own a Honda Foreman 450s and love it. I never had a problem with the amount of power it has. It does everything I want it to do, and more.

 

If you want to sqeeze some more power out of your 450 put on a good quality after market air filter and a white bros slip on pipe
do the jetting with facotry jets. you be surpised of the power gain you get with just doing that. I work as a honda tech and have them come in with these things gone and there a blast to run and the motor is still stock. I would buy a twin air air filter just cause I not a big fan of K&N in real dusty conditions. so good luck

 

Keep it stock. Substantial changes cause substantial problems.

 

I use my quad for trail riding, towing, Hunting, and farm work. A louder exhaust does not really appeal to me.

Well I Found a new big bore kit which is not as radical as the highlifter.

I have learned that when power is increased (with things like jetting and pipes) without increasing the displacement of the engine more heat is generated and it is harder to cool. This is due to more power and an unchanged surface area to dissipate the heat load.

The changes that are made by resleeving the cylinder and replacing the piston are ...

stock displacement = 433 cc
Big Bore = 452 cc

Stock compression ratio = 8.5:1
Big Bore = 9.5:1

I would assume that minor jetting and carb adjustments need to be made.

I do not think that this is too much for the engine to handle.

This is a forged piston which offers better cooling properties and it is also stronger and lighter then stock. I will also be adding an extra cooling fan for the cylinder, Aux. Heat sinks, exhaust wrap and a larger oil cooler to compensate for any increase in heat. Heat as we all know is the one thing that will kill an engine most often.

What do you think about this set up?

Thanks for any shared experiences

 

Sounds like you're doing your homework, glad to hear that instead of just tearing into it. This setup does sound better, but you're still going to sacrifice durability in the long run.

 

Where did you find the less aggresive BBK for the Foreman 450? The only one I have been able to find is at High Lifter.