I'm contemplating about getting rid of my TB250 although I do not want to upgrade to a bigger engine. The Z seems top choice but are there lots of upgrades like a big bore kit?

 

Keep dreaming, I wish they had a big bore hit for it. The 250EX has been out for a while and I don't know of a big bore kit available for that yet. If you wanted a big bore kit, I think you would have to get a custom one. A guy was going to do one for me a while back to make it around 300cc, but he kept changing his guarentee's so I didnt want to risk having my brand new toy messed up.

 

There are big bore kits for a 250ex Proell (sp), the people who built that nitrous raptor in dirtwheels a while back, its not worth it if you want more power just get a z400, 400ex or 1 of the new 450's...

 

you could get the crankshaft pin offset ground to stroke it a little, but you'll have to get custom pistons made or pirate some from another engine, but that's tricky with 4 strokes because of the valve reliefs and domes. Being a compact engine that's already a little undersquare, the motor's geometry might not like it and the stroke:rod ratio could stress things out when the engine is revved high and put under sudden loading. Does anyone know what the stock rod length is? Then you could calculate the ratio and find out if the motor would like a longer stroke.

Seems like a lot of work for... oh, I better watch my mouth!

 

Ok Ok I did catch that. I didnt mean to sound like I was singleing u out or anything so dont act like that. I was just a little revved about how people put down the Z250 all of the time I dont want to start any problems I already think that there are too many fights on here so I dont want to be the reason for another. So sorry if I vented on you too much...

 

you should really change that signature of yours... hehehe.

 

y should I it is true. not downing two strokes but those are more like 4 strokes gone crazy and on a path to destruction if you know what I mean[img]i/expressions/face-icon-small-wink.gif[/img] and dont tell me that ua re saying that all motors have valves because they dont. Reed valves and powervalves are not true cam/pushrod actuated valves found in a four stroke.

 

well, first off 2 strokes are nothing to be taken lightly. they are the best option for ultimate performance in all motorsports. Two strokes are the only option for weight-to power ratio where every last pound or horsepower counts. 4 strokes are great for not polluting the environment, forms of racing where it's hard to keep the motor in the powerband and for softcore riders that can't read a plug or consider rebuilding their engine, but two strokes will always win. 200hp/liter is possible in stock trim on many MX engines no problem. Try to say that about any 4 stroke MX engine!

And second, a piston is a valve. a rotor in a wankel is a valve. a butterfly or slide in a carb or throttle body is a valve.

Thirdly, pushrods are very low-tech in 4 strokes. If pushrods make an engine a 4 stroke like you suggest, then I guess OHC engines aren't 4 strokes? wow, in that case then 4 strokes really do SUCK!

even many 2 strokes have poppet valves. and some 4 strokes do not have poppet valves!

in the end, all motors have valves!!

 

well just to let you know I did say CAM/pushrod operated valves and i never downed two strokes so u jumped the gun on that one bud. o and you really pissed me off and would prolly **** a lot of others off if they read that you said 4 strokes are only great for softcore riders and people that cant read a plug or consider rebuilding an engine. I for one dont have any problem wrenching apart and rebuilding any four stroke motor and not a whole lot af people are scared to do so. Oh and if 2 strokes are the all time greatest thing for powersports and power-to-wheight ratios the y dont they use two stokes in the NHRA drag bikes. but i am not going to diss on 2 strokes like u did four strokes because I give credit where credit is due and you are right that 2 strokes have a power per liter advantage against four strokes but most of that power doesnt come in until the rpms reach the powerband.

P.S How do you figure a piston is a valve???

 

GTFZ250, just wait. JustinJones time will come when he pisses of the wrong people in these forums and then he gets b****ed out. He's just in here to annoy the h*ll out of people. 4-strokes are great of tight trail riding and mud and 2-strokes are great for dunes, desert, flat track riding etc... Just because people own 4-strokes doesn't mean they are idiots. I have two 2-stroke snowmobiles, and I do all the maintanance on them by myself. One of them is a 20 year old Arctic Cat Lynx that runs like new, and the other one is a modified Arctic Cat Thundercat 1000cc and can run over 180mph. Now I don't think an idiot would be able to maintain and run 2-stroke engines like that[img]i/expressions/face-icon-small-wink.gif[/img].