2002 cr250 motor mod suggestions

Sipes #412
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Sipes #412
Sitting here at Sheppard airforce base bored out of my mind wont be getting home till end of July so decided to get some suggestions on motor mods for my 02 cr250. Been going back and forth on if I want to keep my cr or get a 17-19 250sx or tc250. I've heard these motors have potential but not sure where to start. I love the chassis on this bike but would like to get more out of the motor without running race gas.
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H4L
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H4L 5/18/2019 12:31pm
5/18/2019 12:31pm Edited Date/Time 5/18/2019 5:34pm
Have an 03 CR2 model & had similiar thoughts like you in 2017. Have never owned KTM's, but have ridden some of their 250 2t's dating back to a 92 model from fellow riders. Rode on some PDS / 4CS bikes in the past & couldn't get off of them fast enough to give them back to the owners. Fast forward to 2017 I was looking to upgrade to a new 250 2t after reading & hearing all the rave about the white & orange bikes. The new 48mm AER WP air forks were supposedly the cats meow according to many on social media & mx mags. 2 yrs. later most are doing spring conversions or going to cone valve & ohlins forks.
After test riding a 17 250SX & 250TC I have to say I was thoroughly disappointed after all hype on the bikes. Needless to say I didn't think the modern bikes would have been an upgrade IMHO so I stayed on the old CR.
The 02-07 CR2 have basically the same case reed engine design as the modern KTM, Huskies or TM's. With some minor engine tweaks they make very good power & respond really well to mods.. About 5-7 hp more than the traditional reed intake cyl. induction engine mod vs. mod.
In about 2005 I had PC perform their cyl. / head mods for about $300 & was blown away on how much of a difference it made. You can get them to run good on pump fuel, but if you're looking for a very fast engine having the head reshaped for race fuel puts the engine into a whole different level.
The 3rd gen 02-07 AF chassis is as good as it gets.
H4L
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H4L 5/18/2019 5:53pm
5/18/2019 5:53pm Edited Date/Time 5/18/2019 6:27pm
Just to give you an idea of how good these CR2 bikes still are. The link below is to a 2017 mx race in Europe with a past racer on a basically stock 02 model with a Dep pipe. He is competing against a current champ on a 2017 KTM that more than likely has engine mods done to it. Mind you this is at a high level pro race in their country & is impressive to say the least.
Even though these bikes still get a bad rap in the engine dept., it's good to see proof of how severely underrated these engines were & still are.

https://youtu.be/A4eNJop_KC8?t=596
Sipes #412
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Sipes #412 5/18/2019 6:10pm
5/18/2019 6:10pm
They are good on the top end if I could get a little more on the bottom like my yz's had this bike would be perfect. The chassis on these bikes are really good definitely one of my favorite I feel like I can control the bike where sometimes on other bikes I feel they control you. Have you had any experience with vhm heads?
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H4L
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H4L 5/18/2019 6:23pm
5/18/2019 6:23pm
Sipes #412 wrote:
They are good on the top end if I could get a little more on the bottom like my yz's had this bike would be perfect...
They are good on the top end if I could get a little more on the bottom like my yz's had this bike would be perfect. The chassis on these bikes are really good definitely one of my favorite I feel like I can control the bike where sometimes on other bikes I feel they control you. Have you had any experience with vhm heads?
I don't have any experience with a vhm head. What exhaust are you running ? Carb & jetting ? Gear ratio ?
Sipes #412
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Sipes #412 5/18/2019 6:43pm
5/18/2019 6:43pm
Sipes #412 wrote:
They are good on the top end if I could get a little more on the bottom like my yz's had this bike would be perfect...
They are good on the top end if I could get a little more on the bottom like my yz's had this bike would be perfect. The chassis on these bikes are really good definitely one of my favorite I feel like I can control the bike where sometimes on other bikes I feel they control you. Have you had any experience with vhm heads?
H4L wrote:
I don't have any experience with a vhm head. What exhaust are you running ? Carb & jetting ? Gear ratio ?
I bought the bike with Stock expansion chamber and fmf turbinecore 2 silencer and with 14/50 gearing. I added Keihin pwk 38 airstryker carb from jd jetting haven't got much time on it before I had to leave for texas which is where I'm at now so right now. When I get home I'm tearing the bike down to clean and restore it.
H4L
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H4L 5/18/2019 7:03pm
5/18/2019 7:03pm Edited Date/Time 5/19/2019 8:34am
Sipes #412 wrote:
I bought the bike with Stock expansion chamber and fmf turbinecore 2 silencer and with 14/50 gearing. I added Keihin pwk 38 airstryker carb from jd...
I bought the bike with Stock expansion chamber and fmf turbinecore 2 silencer and with 14/50 gearing. I added Keihin pwk 38 airstryker carb from jd jetting haven't got much time on it before I had to leave for texas which is where I'm at now so right now. When I get home I'm tearing the bike down to clean and restore it.
Try a 13T frt. sprocket with an HGS pipe & an a 05-07 oem base gasket for starters. The base gasket is .010" thinner & will bump up the comp. slightly to give the engine better lowend snap. You won't have to run race fuel, but I'd recommend running a comp. test if you go this route to be on the safe side.
I'd also suggest getting in contact with Terry Varner & discuss engine mods if you want more power. He can mod the engine to run on pump fuel.
BTW - The 03 CR2 with PC mods has similiar power down low to an 04 YZ250 owned with PC engine mods done as well. So I know it can be done. Mid-top the CR would out run the YZ.
Sipes #412
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Sipes #412 5/18/2019 7:20pm
5/18/2019 7:20pm
Sipes #412 wrote:
I bought the bike with Stock expansion chamber and fmf turbinecore 2 silencer and with 14/50 gearing. I added Keihin pwk 38 airstryker carb from jd...
I bought the bike with Stock expansion chamber and fmf turbinecore 2 silencer and with 14/50 gearing. I added Keihin pwk 38 airstryker carb from jd jetting haven't got much time on it before I had to leave for texas which is where I'm at now so right now. When I get home I'm tearing the bike down to clean and restore it.
H4L wrote:
Try a 13T frt. sprocket with an HGS pipe & an a 05-07 oem base gasket for starters. The base gasket is .010" thinner & will...
Try a 13T frt. sprocket with an HGS pipe & an a 05-07 oem base gasket for starters. The base gasket is .010" thinner & will bump up the comp. slightly to give the engine better lowend snap. You won't have to run race fuel, but I'd recommend running a comp. test if you go this route to be on the safe side.
I'd also suggest getting in contact with Terry Varner & discuss engine mods if you want more power. He can mod the engine to run on pump fuel.
BTW - The 03 CR2 with PC mods has similiar power down low to an 04 YZ250 owned with PC engine mods done as well. So I know it can be done. Mid-top the CR would out run the YZ.
I will try the hgs and .10 gasket first and see how I like it. I appreciate your help. Now I just have to wait till I get home to try these mods out lol. July couldn't come soon enough.
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Sipes #412
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Sipes #412 5/18/2019 8:54pm
5/18/2019 8:54pm
I'm definitely going to upgrade the stock clutch with a rekluse or hinson. Im going to start with the hgs pipe and silencer and .10 gasket. I already have the boysen rad valve. Can you run pump gas with the vhm head?
adam8781
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adam8781 5/22/2019 11:08pm
5/22/2019 11:08pm
lectron carb, 05 cylinder base gasket, rework the head, boyesen reeds

if you want toget serious, send it to terry varner

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