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SuperDave
17th November 2004, 13:41
I'm new to this and was wondering if those who were more knowledgable could help me out. I have come to the understanding that there isn't much more I can do to increase the HP of my FXR150, well, I've been told that spending a couple of grand will gain me about an extra 6HP but there isn't much point in that.

So, I was wondering if there are any set rules as such as to what bikes can have their factory performance ratings increased? I mean, what factors go into wether they can or cannot, such as engine displacement etc. I was also wondering for the 250cc and under if 2 strokes accept performance upgrades more readily and effectively than say 4 strokes 250cc and under?

FlyingDutchMan
17th November 2004, 14:30
There is an interesting site you should read about turboing engines. Especially read the bit about "Pushing it too far". http://www.sdsefi.com/tech.html

There have been numerous attempts at getting more power out of 4 stroke 250cc engines, but the only one I heard of made 92hp (up from 45hp), but only lasted 50km or so. BIG waste of money IMHO.

Warren
17th November 2004, 14:50
I generally trust the manufacturer. They try to get the most power out of the engine while keeping it reliable and affordable.

Coldkiwi
18th November 2004, 14:04
I generally trust the manufacturer. They try to get the most power out of the engine while keeping it reliable and affordable.

that depends very much on the focus of the bike.

Hayabusa engines for example happen to be ripe for turbocharging because they're not highly stressed.. despite being pretty powerful to start with and even then not a bad price.

FXR's on the other hand have almost certainly been developed with cost at the forefront of the design criteria and I would think have got very little potential to unleash more horses out of them without rooting them.

having said that, if you want more engine performance you could try
1) get a more open exhaust system (full exhaust pipes etc much more expensive but obviously make more progress)
2) lightening the flywheel - get this done by someone who knows what they're doing - (try F1 engineering, they're in the phonebook)
3) any number of clever tricks to the engine to raise compression, adjust cam profiles etc etc but I doubt it'd be worth the hassle.

If you're dead set on the FXR and want more performance else where, start looking into lightweight wheels and upgrading your suspension/brakes because they really are designed as a commuter/learner machine and are naturally pretty soft and smooth - but in all honesty, if you wanta small cc machine that goes, save your cash on FXR mods and get an Aprilia RS125 or 250

vifferman
18th November 2004, 14:10
No-one's mentioned NOS yet... :shutup:

Devil
18th November 2004, 14:20
No-one's mentioned NOS yet... :shutup:
Or maybe an underseat JATO bottle...

Mr Skid
18th November 2004, 16:29
Cut back the subframe - you aren't *really* going to want to carry pillions are ya?

Skip breakfast in the morning and keep the tank under 1/2 full.

At ~19hp the frame looks over engineered as well. Drill some holes in it to reduce sprung weight.
:niceone:

SuperDave
18th November 2004, 18:04
Well, I wasn't wanting to try and increase the power of the FXR, want to buy new tyres but thats it. I was thinking more along the lines of what bike to upgrade to once I've saved enough money. But I guess its just buy the bike with the most HP as it comes out of the factory.

FROSTY
20th November 2004, 13:41
dude -Dont bother . Its a big deep pit to pour your money into.
Im told with some minor jetting changes you will unleash the full unruley 20 horses in your mighty FXR There is no point in doing more.
Don't sweat HP--better to invest ya money in some really soft sticky tyres-Theyll last forever on a lil bike like yours.
Go Out and learn to ride your bike. I mean really ride it not flat out in a straight line. Pick a set of corners and practice riding on em.
When ya tink you're too good for ya bike.Lend it to MR for a few minutes and He'll show ya what it can really do.
The american military have trained chimps that can ride a motorbike in a straight line. :scooter:
That said -Um if you're actually a bucket racer trolling for ideas to hot up ya race fxr -well then do I have some Ideas for you. :Punk:
Throw the carb into the bin and fit a GN250 carbie.-its identical to look at but has a 3mm(AS I recall) bigger throttle body. Throw away the air box and fit a single pod filter Throw away the exhaust system and fit a reverse cone megaphone -Itll now run like shit but sound meaty as
Sort out your jetting so you have a good spread of power.
There is room for a SMALL amount of porting but I'd be bloody carefull
OOPs dribbling on--its just a project I've had in mind for awile.
To be totally honest if you are a learner rider -spend a few months on ya fxr then buy a 250 twin or multi. -Theyre putting out double the power and aren't a heck of a lot bigger.

jasonu
24th January 2010, 18:08
Read the Buckets forum. A lot of those guys mod and race (and blow up) the FXR.
Don't go too far though, I am certain they are made in Thailand and are not nearly as good quality (cranks, rods pistons especially) as Japan manufactured models.
If you want more power, sell it stock and get a bigger bike, cheaper in the long run.

Kendog
24th January 2010, 21:33
Read the Buckets forum. A lot of those guys mod and race (and blow up) the FXR.
Don't go too far though, I am certain they are made in Thailand and are not nearly as good quality (cranks, rods pistons especially) as Japan manufactured models.
If you want more power, sell it stock and get a bigger bike, cheaper in the long run.
How did you find this 5 year old thread? :lol:
But more importantly, do you think FXR's will catch on in buckets?

Autech
24th January 2010, 21:37
The GN250 carb is said to make her a bit more peppy, but I'd say keep it as it is. The FXR is a great bike to learn to ride on and doesn't lack power considering what it is

FROSTY
25th January 2010, 16:07
-This has to be one of the biggest thread dredges known. 6 years or so on I'd be interested to hear from the bucket guys doing well if i was right in my theorising.

quickbuck
25th January 2010, 16:16
-This has to be one of the biggest thread dredges known. 6 years or so on I'd be interested to hear from the bucket guys doing well if i was right in my theorising.

Got to be some sort of record!

I see the OP has fixed the whole problem by buying an RS250....
Yup, that will do it. A bit more than a 6hp gain ;)

Autech
25th January 2010, 22:02
-This has to be one of the biggest thread dredges known. 6 years or so on I'd be interested to hear from the bucket guys doing well if i was right in my theorising.

Damn, never even noticed the original date, props to jasonu lol