What Mods to do to a 4 stroke?

[wr250f95]

First off exhaust's get a big from me, on a race bike (unless its a wr or crfx, those come plugged up and even then you dont have to replace the pipe) offer little performance gain, are very expensive, and some will make the bike obnoxiously loud, not good for keeping riding areas open.
For a wr I would recommend the GYTR muffler insert, it will keep the bike fairly quiet and will not cost you much, if anything in performance.

Now onto general mods.
A great place to start is with the carb, the power now is a great mod for the money, and a JD jet kit will give you spot on jetting equaling good performance F2 Racing also makes a kit for this called the power back (not sure will have too look it up)
If you have a trail bike version you probably have an airbox lid, trash it.

In the engine I would start with a set of hotcams, they will help unleash the beast!!!! reports are of a higher reving engine, that gets there much quicker.
You may also want to look into a high compression piston, many including myself like the idea of 13.5:1, I would highly recommend one from wiseco. for reliablity, you may want to go with a set of Kibblewhite Stainless Steel valves, they offer improved valve life, but beware as they also put more strain on the timing chain and the motor will rev slower.

Ignition mapping can make a good improvement, an aftermarket cdi box will result in being able to reach higher rpm's thus tapping more of a power range from your engine.

Suspension, really a plus on any bike, getting the supsension set up for your weight and skill level will make the bike the handle better, and it will probably save you from a few falls.

This is just a general guide, I hope you find it useful.

[tigmaster]

well, i would like to represent the exhaust... there is a reason people get them. offering a gain of 3-5hp is huge!!! also, let that bike breath with a new filter. exhaust and filter should just come natural. also, with cams?? what is all this about a higher revving engine? rev limiter??? however cams are great because in most cases you somehow dont lose power, you only gain it which is a strange phenomenon. usually you will lose power somewhere but not with hotcams.

[wr250f95]

Originally Posted by tigmaster

well, i would like to represent the exhaust... there is a reason people get them. offering a gain of 3-5hp is huge!!! also, let that bike breath with a new filter. exhaust and filter should just come natural. also, with cams?? what is all this about a higher revving engine? rev limiter??? however cams are great because in most cases you somehow dont lose power, you only gain it which is a strange phenomenon. usually you will lose power somewhere but not with hotcams.

I just think that for the cost there is better ways to get more power out of an engine, while keeping it quiet.

[tigmaster]

well, most pipes are able to meet the ama requirements and what more could you ask for? full exhaust systems not only can produce a significant boost of hp, but they have the ability to shape your power output as well. they are actually one of the cheapest cost per hp mods out there.

[wr250f95]

Originally Posted by tigmaster

well, most pipes are able to meet the ama requirements and what more could you ask for? full exhaust systems not only can produce a significant boost of hp, but they have the ability to shape your power output as well. they are actually one of the cheapest cost per hp mods out there.

the ama shoots itself in the foot, people dont like loud bikes, its as simple as that. cams are a far better mod for the money, running about the same price.
as far the revving with the cams, a hot cam is lighter than the stock unit, thefore will be able to rotate quicker and freeer.

[tigmaster]

u sure about the weight??? most aftermarket cams are actually heavier. however cams are a great mod to COMPLIMENT an exhaust system. just a cam on a stock bike is almost a waste. you need to get things flowing better before you go and slap a cam in there. also some cams can actually cause faster wear to the "lifters". this is because some profiles boast a further opening valve but to not destroy timing they have to use a steeper slope on the lobe. however cams are great and like i said you usually can get free hp out of them but an exhaust is almost necessary with a cam.

[wr250f95]

Originally Posted by tigmaster

u sure about the weight??? most aftermarket cams are actually heavier. however cams are a great mod to COMPLIMENT an exhaust system. just a cam on a stock bike is almost a waste. you need to get things flowing better before you go and slap a cam in there. also some cams can actually cause faster wear to the "lifters". this is because some profiles boast a further opening valve but to not destroy timing they have to use a steeper slope on the lobe. however cams are great and like i said you usually can get free hp out of them but an exhaust is almost necessary with a cam.

most stock systems found on the motocross series bikes are pretty free flowing anyway.

[tigmaster]

them why do so so so many people buy them? there is an obvious reason manufactures make new systems for bikes. granted now weight is a huge issue as well but people get more power from exhaust systems period.

[gscx]

yea its pretty big that you have to get a new a aftermarket exhaust. even more so with a trail bike when you get new cam. if you look in the magazines most of them have a recomendation to get a aftermarket exhaust. its the same for big bore kits also

[wr250f95]

Originally Posted by tigmaster

them why do so so so many people buy them? there is an obvious reason manufactures make new systems for bikes. granted now weight is a huge issue as well but people get more power from exhaust systems period.

hype, the average exhaust is 3-500 dollars right? well if your only releasing 3-5 more horsepower that 100 for 1 hp.