Here is the stroker plan, what you ya think??

[KawieKX125]

Here is the stroker plan, what do ya think??

As my topic below said, I am going to build a spare engine to my bike using the plethora of parts I have collected over the years, including 1.5 complete extra engines. I have a 144 big bore from way back in the day for my bike that is in awesome shape and have enough engine parts to make a good complete engine with carb ready to drop in at any time.

I have called quite a few crankshaft places and the prices are more than reasonable (200-250 for stroking and case mods) for me to do this mod over the summer when I have some more money.

With no stroke, the 144 is well, a 144, with the stroke it is a 154. Will the power gained be worth the porting and head mods as well as the bottom end mods needed to accomidate the longer stroke? I am looking at what I would guess to be about 600 or so dollars total for gaskets and parts to make this happen and it would be alot less expensive without the crank work and associated modifications. Should I bother doing it?

Next question is for Eric Gorr. Eric, when the time comes that I have to have the cylinder and head modified, will you be willing to work on an existing big bore that was done by max power (Jim Neupert's old KX cylinder)? At the moment it is unported and only had the base cut a little bit. If not, what would it cost for me to have the mods done to a spare top end that is trashed over the price of the big bore?

What kind of power do you think this engine would produce? Right now I have a fully built TMR engine in the bike and it is unbelievable fast so I don't really know what to expect from a big bore stroker engine.


Thanks!

 

[marcusgunby]

The 154 will have a higher torque at a lower rev than a 144. IMO it will ride less like a 125 than the 144 does and it will be a half way house between a 125 and a 250, not neccessirily a good thing.I doubt it will have more peak power than a 144.Do you like the way a 250 rides or the way a 125 rides?-thats the question.

 

[KawieKX125]

I like both. 250 type power is nice, to be lazy, but I am light and tall 6 feet 145 lbs on a heavy day so 250's are too much for me. I love 250f's though and I am hoping that the stroker will be more like that than a 125. Sometimes it is fun to ride a 125, it makes you feel like a hero since you are WFo all the time.

 

[bclapham]

it might make me a hypocrite since i am considering doing it, but doing the stroker think is a bit of a can of worms- so many different things need to be played around with- most importantly the port timing, but i am sure Eric has programs for that etc. the next thing is cost- motosportoutlet are selling a new complete crank, bearings and seals for $180- now theres a cheap rebuild- sorry to Eric if i am raining on this "stroking" parade a bit, but he already knows i am cheap, LOL :)

the 144 certainly is a fun bike and with some clutch and gas will go very fast, i shocked a couple of guys on 450s the other week as well :yeehaw:

 

[marcusgunby]

it might suit you kawi but now the cost would put me off-so much money for little return in extra power.

 

[MikeT]

I'd take the $600 and buy a late '80s 250 and transplant that engine It will cost the same $$, get the power you want and get a whole parts bike. Personally I think the money spent on boring out a 125 doesn't yeild the power that you think you might get. You will get some more power but very little (seat of the pants feel) more. JMO

 

[KawieKX125]

The point of the stroker is that I would have a whole extra engine that I could bolt in to my bike. I would have the built 125 for racing and the 155 stroker for play riding and sand riding. There is no way in hell I would hack a 250 engine into my 01kx frame. I don't want a 250 either. I dont like them, they hit too hard for my tiny size(140 lbs or so!). Also, as an engineering student, the idea of customizing my engine is very attractive to me. :p

 

[MikeeeP]

The 155s are awesome from what I have studied. They seem to be the ultimate even surpassing the 167 in many areas especially in keeping the 125 like rev (to an extent) and powerband.

The 155 kitted 125 is supposed to be unbelievable. After talking with Eric and RPM, it sounds like the stroked and 144cc cylindered 125s (now 155s as they are called) will make more horsepower, still rev and absolutely romp on any of the 144 kitted bikes.

The number I have heard from both Eric and RPM are almost unbelievable. From the crack of the throttle to peak HP (not peak RPM) the 155 with correct pipe, porting, jetting, fuel can push 45 legit horsepower - easy according to one of the above mentioned tuners!

RPM mentioned that the longer stroke causes higher velocity intake, Eric mentioned that the longer stroke causes more dwell time (did I get that right EG?) so the fuel is burnt more completely before blowing the piston back down. Both resulting in MORE MORE MORE (sorta like Eric's MO'Betta porting) haha

Is it worth it? Basically after talking to these two companies, our next race bike will probably be sent to Eric for the full 155cc big bore/stroker kit. Over the choice of a new 250 thumper because the 2 stroke still feels light and handles much better than the thumpers in my opinion. The alternative for us is starting with a KTM200 which already makes around 36-38hp from what I have read. I wish I had some legit numbers from someone that has had them a 200SX on a dyno.

Just my thoughts on your question.
Mike Patrick

 

[bclapham]

Originally posted by MikeeeP
The number I have heard from both Eric and RPM are almost unbelievable. From the crack of the throttle to peak HP (not peak RPM) the 155 with correct pipe, porting, jetting, fuel can push 45 legit horsepower - easy according to one of the above mentioned tuners!

sorry Mikey, but unless we are measuring hP from the crank, then i dont beleive it, however i admire your optimism :) it just seems unrealistic in a mX engine to me- we have seen people on here build 144's, spend hours behind a dyno and the best yet was around 38rear wheel HP- is that extra 11cc's really going to give an extra 7HP?????

however, i am willing to put my money where my mouth is- I know Eric has all the parts to build up his own RM155- and i am almost tempted to send my engine to Eric and have him do a clone for me and have him prove me wrong. :worship:

 

[marcusgunby]

Some 250s dont have that at the wheel - i will believe when i see:)