250sx top speed

[peco250sx]

i was riding my new 250sx and i opened it up and it didnt have the top speed i expected, my 200m was going faster and in top gear it seemed to stay at a low rpm and wouldnt go faster than 75-80km? i did some work on it recently and havent opened it up since before the repairs so i just wanted to compare speeds

[Tri-ZNate]

55mph is the gennerally accepted speed.

[peco250sx]

k thats about 90kms so im looking for an increase of 10kms/6.25 mph so ill do valves and stuff until i get there. i might even shoot for 62mph/100kms

[Tri-ZNate]

get an after market pipe (I used bassani), lighten it up with a 200x front end, 350x carb, and an air filter and you'll probably see what you want. i had mine clocked on a gps with a high speed of 62mph

[honda250sx]

Mine runs about the same nate mid 60's. Thats 350x carb. Full SuperTrapp. 20 inch wheels. Open air box. Full 85 200x front end. She rips!

[userj8670]

Are you guys serious?! 60's with a 250sx? Mine is all stock, i think it tops around 45 - 50 sound right? Honda250sx, lets see some pics of your bad boy!!

Jim

[Dirtcrasher]

IDK, I didn't think mine does 60 and she's heavily modded.

Mods don't do crap anyhow, they just get you there faster. The SX has built in limiter as the early 85's were snapping crankshafts. So with the top RPM's being equal and the rear differential gearing unchangeable. I'd imagine being on a 2 mile road, we'd ALL be going the top speed in time with tire diameter or weight reduction being the only factors.......

I thought I'd need 22" tires to approach 60mph.....??

[Yamada]

Tires sizes and rider's weight have a lot to do with the top speed. On my ytm-225dx with 20 inch tires it was ridiculous running it WOT in fifth gear, it felt so slow. But I'm sure with 22 inch tire it would be perfect. Concerning the rider's weight when my cousin and I swith from the ytm-200e and the big red when drag racing, the lighter rider (my cousin 145 lbs) always win because I weight 100 pound more than him.

[honda250sx]

i have seen it on my speedo on my trike. Never matched against another speedo. Plan to test my new GPS on it though.

http://i71.photobucket.com/albums/i151/brauerpower/DSCN3320.jpg

http://i71.photobucket.com/albums/i151/brauerpower/DSCN3319.jpg

[Dirtcrasher]

That thing looks real nice Jeffro!! I honestly like the ES motor color BETTER than the stock SX black. I forget why you had to put an ES motor in there or if it came that way.... That was about 500 conversations ago :lol:

I'm just surprised they hit 60mph? I guess my 3fiddy must be about 70 then?? And hopefully the 86 200X will hit 80MPH :D - J/K

[ChrisD]

I had my 86SX clocked by radar at 49 MPH with 20" tires and the snowplow on the front. The bike is stock. 55 stock is about right.

[userj8670]

Nice trike!! Do you ever get it muddy? ChrisD - do you have any pics of yours? I agree with DC, i would think mods would get you there faster but not equal more top end? However i am always willing to give anything a try at least once. Honda250sx, what are you running for rims and rear tires. I really like the stance of your trike. How much would it cost to get mine set up like yours? I am really considering it!

Jim

[honda250sx]

USER:

Front end is 85 200x. Cost me 99 cents plus shipping on ebay.
Completely rebuilt forks with Progressive suspension. $100
Rear rims 9x8 3+5 offset douglas red label wheels. $75
PRM desert bar $60
YFZ450 L.E.D. Tailight $45
Supertrapp Exhaust $150
350x headlight $65
New Maier fenders $150
Speedo kit $200
Pro Taper fat bars $60
NOS Seat $85
1" billet wheel spacers made by me
Repainted gas tank with tank sealer / new petcock
350x carb
Fully rebuilt with OEM parts brakes
Powdercoat all done by myself


This trike has been buried on several occasions, snow, mud etc. its seen it all. I keep it clean and looking nice always. I'm pretty damn meticulous. You gotta pay to play.

[userj8670]

Wow. She is a great looking trike. Does adding a supertrapp make that much of a noticable difference? Also since i am not the greatest with trike linguo, what was the progressive suspension you spoke of? I am soon to be tearing my SX down and if i have the money i am going to try and come up with something like yours.

Jim


p.s. Is powder coating really worth it? I have heard its alot of money and i dont know anyone in my neck of the woods that does it. :(

[honda250sx]

The supertrapp makes a world of difference. They are tough to come by.

Progressive suspension is a kit for the forks. It improves the front suspension tremendously.

Powdercoating it definetly worth it. I do all my own. There are plenty of good coaters in western ny just do a search.

[honda250sx]

I do all my own coating at my other home in Lockport,NY. Were practically neighbors. Thats where my SX is.

[userj8670]

I could have sworn i used to see you listed as lockport ny back in the day but why are you in PA? Are you coming back anytime soon? Perhaps i could give you a call and stop by sometime and check out your sx.:beer I have heard numerous things about a super trapp exhaust and would like to get one but again have heard they are hard to come by. I assume just type in supertrapp on ebay and wait til i see one for a three wheeler? The exhaust on my trike looks origional but i know it is not. Its waaay louder and has a different tone from alot of the sx's and big reds i have seen. I also think its got more oomph than normal. Where abouts in lockport are you located my friend? Finally, someone somewhat local who i can call on for help :)

Jim

[Name Brand]

I was next to a truck reading its own speedometer; I was told 63mph.

Stock engine; TRX diff, 25 inch tires, 145lb rider...

[peco250sx]

nice trike i did the same with the frontend i just didnt finish it with paint and plastics i ran out of money

[peco250sx]

i wanted to keep going but i ran out of time and money. :(

[DixiePlowboy]

I agree with DC, i would think mods would get you there faster but not equal more top end?

I disagree(strongly) that mods alone cannot equal more top speed.

For example:
Jump on....let's say a stock 200X, and get a radar verified top speed. Pull it down for a high-comp piston, a good higher-rpm camshaft, and good exhaust. When broken in and jetted correctly, using the same tires and gears with the same rider and get a new verified radar top speed.

If it was assembled and broken in correctly, I guarantee you'll have gained a few mph, if for no other reason than that you now have more power at higher RPM, and more useable RPM to work with up top. You'll still have some steam left where your X was falling on it's face.

If this principle were not true, my '85 200E Yamahauler(Kerker exhaust and an unknown brand-cam) wouldn't have been walking off and leaving my buddies' 200X's with aftermarket exhaust on topend.....but it was.

[SCRAMCHARGER318]

you can build up the top end all you want, and still will not gain mph, simply becuase the cdi box wont let it, when it's redline thats it, but where talking about a 250sx not a 200x, i know the sx has a built in rev limiter, i don't know about the 200x. but anyway unless you can figure a way to increase the redline on a sx or put bigger tires on, you will not go any faster, BUT there is such a thing as not having enough power to use all of your gears, for example the atc 90 stock in low range you can use all 4 gears, but in high range you can only go up through maybe 3rd, same story with the 185s 5 speed, if it's a stock bike you can't top it out becuase you don't have enough power

[Dirtcrasher]

My line of thinking was different -

There is a rev limiter, lets call it 10000RPM's for discussion purposes.

The output shaft drive and ring and pinion are fixed at whatever ratio they may be, call it 5:1 or whatever.

SX #1 has no mods, bone stock.

SX#2 has a 10.5:1, Webcam, performance springs, Cobra exhaust, no airbox lid and a 350X carb (Mine :D)

Of course SX#2 will get there faster but if they both go 3 miles, How can the top speed of either SX be different if you've reached the rev limiter and the gearings are fixed.....??

I'm a heck of a mechanic, but not an engineer - although I do dabble in my rockets science :lol:

Just curious what peoples thoughts are......

[DixiePlowboy]

Admittedly, I did not have rev-limiters in mind. I wasn't aware that the SX had one, but then it has been 20+ years since I've had an SX.

My argument is to the idea that top speed cannot change without a change of gearing.....which is false. Horsepower, torque, reduced weight, and increased useable RPM can change top speed. It doesn't ALWAYS change with mods, but the right mods CAN change top speed.

Edited to add:

I've got to thinking about the SX I had, and I can't ever remember it ever hitting a rev-limiter and dropping out ignition like say a 300EX does.

The one I had in '87 or '88 was bought new by a friend of mine. He and I raced each other several times a week. I can remember that he and I were almost equal top speed between his stock SX and my stock ''85 230 Q'Sport, until he had a Wiseco high compression piston put in it, bolted on a chrome Sand Scorcher exhaust, and put a clamp on K&N filter on it. He could then pull away from me.

When the racing bug bit him, he actually bolted on Dura Blue wheel spacers, number plate, twist throttle, and 18" flat track tires and flattracked it because he couldn't talk his mother into buying him something more raceable. Needless to say, it no longer had any top speed, but the tight/short track we raced didn't require top speed. He and I were in the same class(200-250 4-stroke auto clutch class) for a whole season. I raced the yamahauler and a 225DX with 18's in that class(without better than a 2nd place behind him).

I can't remember once hearing a rev-limiter on his, before or after I later bought it with those short tires on it.

[peco250sx]

the reason i thought mods would increase my top speed is because there wasnt enough power to use all of 5th gear and it could have gone faster with more torque

[userj8670]

I have a 85 sx and its been bored .020 over. I has balls and it will use all of 5th but i cant remember ever hitting a rev limited now that i mention it. I just can tell by listening to the sound 'you open this throttle up any more and im gonna blow!' To me its like trying to pedal in the biggest gear on your bike...there will come a point where you just cant go any faster. The sx seams to me ...well in my case to be more 'gearing-limited' versus 'engine-limited'. Just my two cents worth...however if there is a rev limiter, which again i knew nothing about nor the fact that my sx has one, maybe there is a way to bypass it ...Come on DC time to get them wheeels in your trailprotrailpro head turnin...

[piroguedog]

55mph 220lbs, super trap w 14 plates, 20s, 200x front end, works shock, 155 main jet, open air k&N. WOuld like to try the 350x carb swap but it seems that I may be maxed out due to gearing. I would think that if a lighter rider could get more out of it then the carb would work. Its amazing how we can take a perfectly good machine that goes faster than we need to go and probably blow it up trying to get 5 more mph out of it..........idiots we are.