should i bore it or bore and put a top end in it?

[CamDayKX125(4)]

hey guys, were going to do a compression test tonight and my dad said that probably either way were going to put a new top end in it. he also said that he thinks that, if the compression is right, itll be about 150 psi. is this the right estimate?( by the way, this is on a 00' kx 125) were the third owners of my bike,( the first owner, i dont know who he was) and, for all you TNT riders who know rick( hes the track mechanic from wednesday-friday at TNT he has a son named will and hes on a hyped-up 04' kx250f( if you call $16,000 in its engine hyped-up :p ) i bought it from rick. ive also heard that boring my kx to about 130-135cc. would solve it but it probably needs at least another piston ring. when( very soon) i get a top end, my and my dad want a Boyesen top end. is there another brand that can hype it up more but isnt super expensive?

 

[robwbright]

$16,000 in the motor??!! Geez. That's ridiculous.

If I recall, I think 150 would be on the low end of the compression spectrum.

Why don't you have Eric Gorr put a 134 cc or 144cc kit in it. Last I checked it was $475 for 144 bore, cylinder plating, porting, polishing, head mods, new piston, ring, reassembly, case modifications, etc. . .

http://www.ericgorr.com

He will do mo betta everywhere porting or mid-top porting at your request. He will set the compression for race fuel or pump fuel at your request.

The 144 kits are AWESOME. My first ride review is here:

http://www.dirtrider.net/forums3/showthread.php?t=126800

You might want to read this thread as well:

http://www.dirtrider.net/forums3/showthread.php?t=127695

 

[kawicam125]

ive only ridden a 125 since last november( in other words, i dont have that much experience on a full-size bike) i owned a cr 80 but blew its engine because the previous owner didnt do proper maintenence. ive heard that a 144 can compete with a 250f in torque. is this true? i ride at TNT (only tracks) and mainly the intermediate track. if i got my kx 125 to a 144( how much would this cost with a EG kit and a Boyesen top end. whats the best engine or does EG make their own[ i dont know to much about them]), it would push me to the expert tracks more often. how much harder is a 144 to handle over a 125(considereng that im going to be 14 y/o in august, im 5'4'' - 5'5'', and 105-110lbs.)? what are the main engine differences in a 144 compared to a 125? thanx



no longer CamDayKX125(4)!

 

[Chili]

If it needs a fresh top end, change it then keep the rest of your money for lessons, practice fee's, fresh tires and regular maintenance items, I guarantee that bike bone stock can go faster than you can.

 

[robwbright]

If it needs a fresh top end, change it then keep the rest of your money for lessons, practice fee's, fresh tires and regular maintenance items, I guarantee that bike bone stock can go faster than you can.

Undoubtedly true, but I guarantee you the 144 is more fun! And, I am definitely quicker on starts and exiting the corners. That's going to be worth half second a lap, at least.

 

[robwbright]

ive only ridden a 125 since last november( in other words, i dont have that much experience on a full-size bike) i owned a cr 80 but blew its engine because the previous owner didnt do proper maintenence. ive heard that a 144 can compete with a 250f in torque. is this true? i ride at TNT (only tracks) and mainly the intermediate track. if i got my kx 125 to a 144( how much would this cost with a EG kit and a Boyesen top end. whats the best engine or does EG make their own[ i dont know to much about them]), it would push me to the expert tracks more often. how much harder is a 144 to handle over a 125(considereng that im going to be 14 y/o in august, im 5'4'' - 5'5'', and 105-110lbs.)? what are the main engine differences in a 144 compared to a 125? thanx



no longer CamDayKX125(4)!

Did you read my post above and the links I posted?

Eric does EVERYTHING you need for $475 - bore, plating, porting, polishing, head mods, case mods, piston, ring, reassembly, etc. . . He'll even pay for the shipping back to you if you prepay the order. He designed the 144 pistons for Wiseco, so he pretty much is a/the expert on 144's.

Is there some reason you want a Boyesen top end as opposed to an Eric Gorr? Unless Boyesen is similarly priced, I'd go with Eric. Very professional and exceptional gain is performance. But I'd go one way or the other - don't try to mix the work of two builders.

A 144 will NOT stay with a 250f on torque. There's 250cc's there to work with on the 4 stroke.

However, my personal opinion is that the 144 has an advantage on a stock or lightly modified 250f (assuming a rider who knows how to ride a modded 2 stroke). A highly modified 250f is still going to have the advantage.

A stock 125 peaks at maybe 30-33 HP. A properly set up 144 peaks at 36-39+. A stock 250f is about the same HP as a stock 125, but the 250f has a much broader powerband and more low/mid torque.

Of course, if you blow the 250f motor, you might as well buy a new bike cause you'll have $2000 in fixing it. If I blow mine, I can buy a new 144 cylinder from Eric for for about $325. :laugh:

By the way, I'm 140 lbs. The last time I really got into the 144 on the street in front of the house, I nearly wheelied out in 4th gear - only using throttle and not leaning back.

 

[FoxDirtRacer111]

Hey im about to bore mine so hopefully it goes alot faster for me

 

[kawicam125]

Did you read my post above and the links I posted?

Eric does EVERYTHING you need for $475 - bore, plating, porting, polishing, head mods, case mods, piston, ring, reassembly, etc. . . He'll even pay for the shipping back to you if you prepay the order. He designed the 144 pistons for Wiseco, so he pretty much is a/the expert on 144's.

Is there some reason you want a Boyesen top end as opposed to an Eric Gorr? Unless Boyesen is similarly priced, I'd go with Eric. Very professional and exceptional gain is performance. But I'd go one way or the other - don't try to mix the work of two builders.

A 144 will NOT stay with a 250f on torque. There's 250cc's there to work with on the 4 stroke.

However, my personal opinion is that the 144 has an advantage on a stock or lightly modified 250f (assuming a rider who knows how to ride a modded 2 stroke). A highly modified 250f is still going to have the advantage.

A stock 125 peaks at maybe 30-33 HP. A properly set up 144 peaks at 36-39+. A stock 250f is about the same HP as a stock 125, but the 250f has a much broader powerband and more low/mid torque.

Of course, if you blow the 250f motor, you might as well buy a new bike cause you'll have $2000 in fixing it. If I blow mine, I can buy a new 144 cylinder from Eric for for about $325. :laugh:

By the way, I'm 140 lbs. The last time I really got into the 144 on the street in front of the house, I nearly wheelied out in 4th gear - only using throttle and not leaning back.

to answer your question, i read all the links. i was just thinking that EG could do different brands of motors( guess not). im just not sure i want to do this because id take some getting used to :think: . question: does having EG boring my engine add any weight? if so, how much? also, i was planning on getting a 250f around my 15th BD. not that i dont like 125s, its just it wouldnt have the torque (but then theres expense on repairs :think: ) that a 250f does. im also not sure my dad would want me too. my dad is going to get a 04'-06' kx250f this year and he might let me ride it at TNT. that would be two bikes i could ride at TNT. plus, my dad is going to try to call rick( TNT track mechanic) about bringing my bike down there and getting a top end. so, it would take lots of presuading. hed probably say something like " why would you wont to bore it? that bike has plenty of power for you." anyway, do you think boring it is a good idea? thanx

 

[robwbright]

i was just thinking that EG could do different brands of motors( guess not). im just not sure i want to do this because id take some getting used to :think: . question: does having EG boring my engine add any weight? if so, how much? so, it would take lots of presuading. hed probably say something like " why would you wont to bore it? that bike has plenty of power for you." anyway, do you think boring it is a good idea? thanx

I think maybe I misunderstand what you mean by a "Boyesen" top end. . . etc. . .

What do you mean by "different brands of motors". What Eric does on the 144 will be the same thing Boyesen will do on a 144 - the porting and head mods might be a little different, but the kit will be the same as far everything that is done to the motor.

No tuner prefers to work on a motor that another tuner has built. Better to stick with the same guy.

The 144cc kit will add about 1/2 an ounce (the 144 piston weighs 16 grams more than the 125 piston) - in other words, nothing you will notice in any way. Of course, he takes metal out with the porting and head mods, so you probably lose weight in the long run. . .

It will take some getting used to. When I took mine woods riding, there was so much power that it was very easy to spin out when cornering. The 144 requires very good throttle control - which is never a bad thing to learn, anyway. My bro (2000 KX 250) was riding my 144 the other day and nearly crashed because when he rolled on the throttle in a turn in the woods, it spun out and nearly put him down. (I do have a new rear tire on the way). Other than that, you just hang on!

And yes, I think boring is a good idea. :aj:

 

[Chili]

hed probably say something like " why would you wont to bore it? that bike has plenty of power for you."

Sounds like a wise man. I know Rob loves his 144 but I would suggest you two are at different stages. You are running a 6 year old 125 that it sounds like you don't plan to keep as soon as you could feasibly upgrade. If so why dump more money into a bike that could already outperform your ability? I see guys all the time at the track with all the latest "bling" on their bike and a bike tire that they have been riding on for 1/2 a season and they can't figure out why they get their ass handed to them all the time by bikes that aren't "tricked" out.

 

[robwbright]

Sounds like a wise man. I know Rob loves his 144 but I would suggest you two are at different stages. You are running a 6 year old 125 that it sounds like you don't plan to keep as soon as you could feasibly upgrade. If so why dump more money into a bike that could already outperform your ability? I see guys all the time at the track with all the latest "bling" on their bike and a bike tire that they have been riding on for 1/2 a season and they can't figure out why they get their ass handed to them all the time by bikes that aren't "tricked" out.

Agreed, Chili. However, he asked about boring it and about having a motor built, so I gave him the info . . . :laugh: