144cc stroker

[burn1986]

If you modify a 125, I have heard that just boring the cylinder, replating, and getting a larger piston is not enough since the bigger piston will create more work on the engine. Does having a stroker crank/ motor take care of this? Is this the reason the Athena YZ144 is not as fast as the KTM 150? What about the pipe? Should you get different pipe since the original is made for the 125?

[Coop]

Eric Gorr has some good info on his site. Even if you go with someone else you can read and learn more about it.

[ford832]

The KTM is entirely set up to be a 144-not just a bore/stroke job on a 125.That's the difference.

[redrider611]

When I built my RM144. I kept the stock crank. I did machine the cases so I was certain there was enough skirt clearance (A must on CR 144 builds)

I also filled cases for volume and ported cylinder. I did NOT mill the head or clyinder due to clearance. Instead, I went back to my old school days and played different thickness's of base gaskets. I ran a fairly thin one. Once the motor was where I was I wanted it, I clayed the piston and measure the clearance. If I raced up north or cooler weather, I would switch to a thicker base gasket. Just remember that if you run a thin base gasket you may run into detonation issues on pump gas. I always ran 50% C12 and 50% 93 pump gas.

I did require top end jobs on a regular basis. I also went through clutches like crazy. However, I rode a lot of tracks with deep loam so it was hard on all the 2 strokes.

I can honestly say, I LOVED that way the RM ran when it was all done. It was a 250F killer. HAHA 

[Dirt Addict]

yeah the ktm is built to be a 144.  the pipe is the same as a 125 though.   the ktm has some excellent engineering.  the air tract from the filter to the carb is built straighter for better / greater flow.  more air equals more power....

[Super Trucker]

If you modify a 125, I have heard that just boring the cylinder, replating, and getting a larger piston is not enough since the bigger piston will create more work on the engine. Does having a stroker crank/ motor take care of this? Is this the reason the Athena YZ144 is not as fast as the KTM 150? What about the pipe? Should you get different pipe since the original is made for the 125?

   My  04 cr125  is 2mm overborred,with 2mm  longer crank, 1mm  taken  out  of  the head, so it,s  1mm up  and 1mm down  if  that  makes any sense.  HGS  makes  144  pipes  for  YZ,KX  maybe  more  makes, I  havn,t  been  on there  website  for along time. I  custom  fit a  HGS  BUD  racing  pipe  for a 03 KX125  onto  my   04 cr125. There,s  nothing  cut out  for  the  crank, on my  cases. There,s  engine  builders  that  off  center  overbore, a  stroker crank  puts  more  pressure  on  the exhaust port bridge, not  a  good  thing  for  a  honda.  I  have  to  drill  3  lube holes  on  the  piston,lined up with  the  exhaust bridge, I  didn,t  want it  overborred. I  would  rather  have a  ported  cylinder  and  run  a  stock size 54mm  SRS piston, with  the  stroker crank.

[redrider611]

If you modify a 125, I have heard that just boring the cylinder, replating, and getting a larger piston is not enough since the bigger piston will create more work on the engine. Does having a stroker crank/ motor take care of this? Is this the reason the Athena YZ144 is not as fast as the KTM 150? What about the pipe? Should you get different pipe since the original is made for the 125?

   My  04 cr125  is 2mm overborred,with 2mm  longer crank, 1mm  taken  out  of  the head, so it,s  1mm up  and 1mm down  if  that  makes any sense.  HGS  makes  144  pipes  for  YZ,KX  maybe  more  makes, I  havn,t  been  on there  website  for along time. I  custom  fit a  HGS  BUD  racing  pipe  for a 03 KX125  onto  my   04 cr125. There,s  nothing  cut out  for  the  crank, on my  cases. There,s  engine  builders  that  off  center  overbore, a  stroker crank  puts  more  pressure  on  the exhaust port bridge, not  a  good  thing  for  a  honda.  I  have  to  drill  3  lube holes  on  the  piston,lined up with  the  exhaust bridge, I  didn,t  want it  overborred. I  would  rather  have a  ported  cylinder  and  run  a  stock size 54mm  SRS piston, with  the  stroker crank.

The reason you your cases are not "cut" or machined out for clearance is because your bike a 134 @ +2mm. It is required to machine the cases to build a 144 out of a CR. If you dont, the skirt will hit and well, the rest is history.

[Super Trucker]

Yeah I  know about  that Redrider611, hell  I  didn,t  even  want  the  overborre, just  the  stoker crank and some more porting. The shop has  your creditcard #  and  they go to town. The shop called me when I  was in Cali. trucking  80 days straight, when  I  found out  they  ran the bill up and  overborred it. It,s  bad enough  that I,m in and out of Cali. for weeks, and  now I have a 1,700 dollar bill  for work that I  don,t  even need. A  stoker crank  carries  the  power  further, just  overborring  the  motors  are  flat on top, short shift motor.

[Coop]

That's illegal, a shop cannot do work without your approval. You could have disputed that. If all you wanted was the crank and porting, that's all you should have paid for. I used to be a motorcycle mechanic, heck if we couldn't produce the old parts, the customer didn't have to pay even.

[Super Trucker]

Yeah COOP  I  told him  that, and I  told  him  that I  every incoming  call when I,m in the truck is recorded, because of  the corruption  in the trucking industy. He  blamed the  plater  for  the  1st  exhaust port bridge break, he  said  the  chamfering  was done wrong, he,s  the  engine builder and can,t  tell  it,s done wrong. The  plater  did a  crap job, welding  and  plating, it  broke  the bridge again. So  last  year  was 3 months  of  bs, heat cycles and  2 minutes  of riding  by my storage,I  never made it to a track, and  more than 10 k  in dedt. After that  I  never  wanted to see a bike again, to top it off  there  wasn,t  nothing for a driver job. I  had  to get on with a  mega co., and run the railyards of Chicago, 6 driving test, 2 drug test,1 is where they cut  hair from 5 parts of your head, 6 day orientation, 2 days of rail yard training,supposed to be 4 or 5 days. I had  19 break downs in the 1st 60 days, I  stop counting after that, after 8 months I  drove 9 different trucks,freightliner junk,broke down all the time. I  knew  the country was  doing bad, in  orientation  there,s  owner operators  with  6 trucks, he laid the drivers off and parked the trucks,alot  of  25 yr. exp. teamsters, now  working for peanuts.

[Super Trucker]

Sorry  about  the last post. I  sent the cylinder to Millenium Technologies  in Plymouth Wi., I  heard  they do great work, and it,s true. They  built the bridge up-thicker,chamfered  all  the ports,resessed the bridge, it should be bullet proof. If  anyones  having  plating problems,check them out, they  do work for team Suzuki, and 2-st. roadracers, so I,ll  have to ride it and see.

[burn1986]

Wow, that's a lot of stuff into a 125/ 144. Would a Stroked 125 with a port job run like a 144? Would it run better than a 144?

[SubTexel]

Wow, that's a lot of stuff into a 125/ 144. Would a Stroked 125 with a port job run like a 144? Would it run better than a 144?

Yes.

From my understanding the KTM 150 (144) is just a stroked and bored 125... Cases and everything else are off a 125 (same with the pipe, CDI, etc...). So honestly, people saying it is a purpose built 144 isn't too correct.

Big bores give you the low end power but don't rev like the stock 125, stroked 125s give you the revs at the sake of low end a big bore only gives you, bored and stroked give you the best of both worlds (this is true in 2 strokes as it is in 4 strokes).

A stroked 144 with porting would be just like the KTM, which is already a Mid - Top bike (it has more low end than the 125 it replaced but not much more). This is why the GYTR and Athena kits and some other 144 kits for the Yamaha/CRs/KXs/RMs don't have similar power outputs the KTM has (big bore only kits).

[Super Trucker]

Wow, that's a lot of stuff into a 125/ 144. Would a Stroked 125 with a port job run like a 144? Would it run better than a 144?

On a ported motor with a stoker crank,the powerband would carry further, more mid also,that,s what my engine guy told me.

[mrhp]

The ktm 150 IS purpose built, and yes its pipe is different.

The athena 144 kit is horrible as delivered.  It's merely their 125 offering bored out.

A quick glance reveals that the ports are untouched after boring, the boost port is very easy to spot this even if you dont know much about porting.

There is a lot that goes into what stroke should be run...etc.  But at the end of the day, a well built purely bored 144 can run awesome.

The athena kit, modified, can eclipse the 40hp mark fairly easily.