Jump to content
Sign in to follow this  

getting more power of a 2-stroke

Recommended Posts

hey everybody i have a yz125 and i was wondering what there is outhere to get more power out of it.. for 4 strokes theres all sorts of things. for smokers all i can come up with is pipe and reeds??? unless that is i want to send my engine off to get it ported and polished.. eric gorr.. how good are you :D

Share this post


Link to post
Share on other sites

Fresh top-end (Sized if possible).

Fresh reeds.

"Corrected" compression and porting.

FMF pipe and silencer (Have pipe checked and matched to exhaust spigot).

Ignition if deemed necessary...

Have all this work done by TMR.

You won't believe the results.

Share this post


Link to post
Share on other sites

MAtch crank cases at intake, port/polish-cylinder/head, pipes, some boyeson pro series reeds help quite a bit. The bigest power gaining mod will be an ignition box, vortex make one that can add 5-10 horspower on a 200sx.

Share this post


Link to post
Share on other sites

I've played around with modifying two strokes quite a bit. Definitely fun to add new parts and see what happens. Unfortunately, sometimes not much an improvement is seen. Here is the best bang for the buck, from best to worst, if your bike's top end is still relatively fresh and has good compression, has good tires, fresh suspension, etc. I'd recommend making changes to the motor in this order.

1. Jetting. Two strokes are particularly sensitive to jetting. If you have it jetted in properly, it will make a big difference in throttle response, power, and lack of "spooge" out the exhaust. It's inexpensive and makes a big difference to get it right.

2. Porting. On a two stroke, there is no cam shaft. The functions normally performed by the cam on a four stroke are adjusted on a two stroke by altering the "heights" of the ports on the cylinder. By changing them, the bike can be adjusted for more top end, more bottom end, etc. When the bike is being ported, the compression ratio can also be increased for more power. I've used Eric Gorr at Forward Motion in the past, and have been very pleased with the results and the price. He's every bit as good as the big names, but can charge a reasonable price because he doesn't spend a ton on advertising like PC, FMF, etc. I think you could get cylinder and head work done for less than the price of a pipe, and it will make a much bigger difference.

3. Boyesen power reeds. These are not that expensive, and will make a noticable improvement. Truthfully, I can't really tell from the seat of the pants a power difference between just reeds on a stock cage and a complete set up like a rad valve or v-force. I've done the complete cage set up, and don't think I'd do it again. Not enough improvement to justify the price and alters the jetting significantly enough to be a real headache.

4. Pipe and silencer- these tend to move the power around more than anything else. Most stock setups are better than you would think.

5. Everything else. I've tried aftermarket ignitions (FMF) which added a little (and I mean little bit of extra overrev), power valve spacers, complete reed cage set ups, etc. In my opinion, if any of these made a difference they didn't make enough difference to justify the price.

Make sure the rings are fresh, get the jetting sorted out, and send the cylinder and head out when you get the money.

Share this post


Link to post
Share on other sites

sell it to a 15-yr old girl and get a 250. if you need more power than a 250 2-stroke has, turn pro.

mw

Share this post


Link to post
Share on other sites

Without engine work...pipe, reeds, bored carb. Thats about it.

I would port and polish as well. Your gonna need all you can to compete with the four-strokes out on the track. Good thing is, engine work is alot cheaper on two-strokes. And, if its reliability your scared about, dont be.

Share this post


Link to post
Share on other sites

suspension helps if you want to be more competitive with the 4 strokes...wont give you more power, but helps....racers edge suspension,racers edge port + polished, bored carburator, milled head, v-force reeds,FMF fatty, FMF shorty, renthal bars, renthal chain + sprockets, fast line converted front brake line, troy lee design graphics

thats all what's on my bike, and while some of it doesnt affect performance, i would say my bike is pretty fast compared to a stock yz125

Share this post


Link to post
Share on other sites

whats boring the carburator.. ive never heard of any company offering that or is it simple enough to do at home

Share this post


Link to post
Share on other sites
hey everybody i have a yz125 and i was wondering what there is outhere to get more power out of it.. for 4 strokes theres all sorts of things. for smokers all i can come up with is pipe and reeds??? unless that is i want to send my engine off to get it ported and polished.. eric gorr.. how good are you :D

twist the throttle and hold on :D

Share this post


Link to post
Share on other sites
whats boring the carburator.. ive never heard of any company offering that or is it simple enough to do at home

i wouldnt try this at home. but its increasing the diameter of the throat of the carb. like everything with engines there are tradeoffs

you will get more HP on the top end --> good for MX

you loose horsepower on the bottom--> bad for trail riding

when you increase the diameter of the carb you can flow more air, but you loose intake velocity/vacuum, so you have to really be sucking in a lot of air (high RPMS) to really make this work

conversely a smaller carb will have a higher air intake velocity any RPM range. but as the RPMs increase, your engine's desire for air increases, and this is where a smaller carb fails at supplying the engine with more air.

auto manufactures solved this by using 4 barrel carbs. under normal driving you would only use 2 barrels, when the engine demanded more air, the butterfly valves opened, allowing air to enter into the secondary barrels.

and then there are CV (constant velocity carbs)...

Share this post


Link to post
Share on other sites

well for the trails i ride im pretty much in the powerband the entire ride anyways.. or try to be.. but ill start with the 2 bolt on mods then when winter rolls around and i do my first top end i might send my cylinder and head out to get modded...well see

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Reply with:

Sign in to follow this  

×