Full Tilt CR250 Build - MXA Two Stroke Hall of Fame

CamP
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CamP 8/19/2016 7:39am
8/19/2016 7:39am
Steely Dan wrote:
The carburetion of the Lectron is far and away better than a standard carb. That's why it gets better fuel economy. It atomizes the fuel so...
The carburetion of the Lectron is far and away better than a standard carb. That's why it gets better fuel economy. It atomizes the fuel so much better that it uses less to achieve the same air/fuel ratio.

The trick with those is to set the metering rod so that it will only idle with the idle screw turned all the way in as far as it will go. So basically, turn your idle screw clockwise until it stops, then set your metering rod so the bike will idle at about 1,800-2,000 rpms (sounds high, but two-strokes idle differently). That is the "sweet spot" that gets rid of the partial throttle hiccup.
I have a Lectron gathering dust in my garage. It's a decent carb, but I think a well tuned Keihin PWK is better. That being said, I have a relatively stock 05 CR250 with a 2015 YZ250 carb. I thought it was a big improvement over the stock Mikuni, and didn't think there was much room for any additional gains until I tested a new PWK metering block that a fella in Wisconson has developed. He sent me one to dyno test and everyone in the dyno room was blown away by the results. None of us have ever seen a bolt-on mod perform this well.

Green line is stock YZ250 carb with 175 main, 48 pilot, CEJ needle #3 clip.
Blue line is mod carb with 188 main
Red line is mod carb with 185 main



cslacker
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cslacker 8/19/2016 7:47am
8/19/2016 7:47am
The Rock wrote:
What a cool project. Interesting comment about liking the Lecfron due to gas mileage. Are you trying to run as little fuel as possible? When I...
What a cool project. Interesting comment about liking the Lecfron due to gas mileage. Are you trying to run as little fuel as possible?

When I raced a lot it always bugged me I ran with too much fuel. Thought of ways to calculate required fuel load to minimize weight but never progressed past the thought stage.
I go desert and mountain riding quite a bit with my bike and have occasionally gotten lost... I also hate the feeling of desert tanks so getting good economy is just an added benefit. It isn't necessarily the priority. When racing moto I tend to do what you are talking about and limit the fuel to what I estimate I will need.
cslacker
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cslacker 8/19/2016 7:51am
8/19/2016 7:51am
CamP wrote:
I have a Lectron gathering dust in my garage. It's a decent carb, but I think a well tuned Keihin PWK is better. That being said...
I have a Lectron gathering dust in my garage. It's a decent carb, but I think a well tuned Keihin PWK is better. That being said, I have a relatively stock 05 CR250 with a 2015 YZ250 carb. I thought it was a big improvement over the stock Mikuni, and didn't think there was much room for any additional gains until I tested a new PWK metering block that a fella in Wisconson has developed. He sent me one to dyno test and everyone in the dyno room was blown away by the results. None of us have ever seen a bolt-on mod perform this well.

Green line is stock YZ250 carb with 175 main, 48 pilot, CEJ needle #3 clip.
Blue line is mod carb with 188 main
Red line is mod carb with 185 main



I saw this on TT yesterday. IT has me really considering this for my pwk. If nothing else I will be adding it to my cr500 carb. Thanks for putting in the work on that as I was really skeptical.
Steely Dan
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Steely Dan 8/19/2016 8:04am
8/19/2016 8:04am
Steely Dan wrote:
The carburetion of the Lectron is far and away better than a standard carb. That's why it gets better fuel economy. It atomizes the fuel so...
The carburetion of the Lectron is far and away better than a standard carb. That's why it gets better fuel economy. It atomizes the fuel so much better that it uses less to achieve the same air/fuel ratio.

The trick with those is to set the metering rod so that it will only idle with the idle screw turned all the way in as far as it will go. So basically, turn your idle screw clockwise until it stops, then set your metering rod so the bike will idle at about 1,800-2,000 rpms (sounds high, but two-strokes idle differently). That is the "sweet spot" that gets rid of the partial throttle hiccup.
CamP wrote:
I have a Lectron gathering dust in my garage. It's a decent carb, but I think a well tuned Keihin PWK is better. That being said...
I have a Lectron gathering dust in my garage. It's a decent carb, but I think a well tuned Keihin PWK is better. That being said, I have a relatively stock 05 CR250 with a 2015 YZ250 carb. I thought it was a big improvement over the stock Mikuni, and didn't think there was much room for any additional gains until I tested a new PWK metering block that a fella in Wisconson has developed. He sent me one to dyno test and everyone in the dyno room was blown away by the results. None of us have ever seen a bolt-on mod perform this well.

Green line is stock YZ250 carb with 175 main, 48 pilot, CEJ needle #3 clip.
Blue line is mod carb with 188 main
Red line is mod carb with 185 main



Thunder Products? Is the "fella's " name Lon?

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CamP
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CamP 8/19/2016 8:11am
8/19/2016 8:11am
cslacker wrote:
I saw this on TT yesterday. IT has me really considering this for my pwk. If nothing else I will be adding it to my cr500...
I saw this on TT yesterday. IT has me really considering this for my pwk. If nothing else I will be adding it to my cr500 carb. Thanks for putting in the work on that as I was really skeptical.
Yeah, it was pretty amazing. The part added power everywhere on the curve and at 7600rpm it was +3hp, from 7700-8300rpm it was +4hp, and at 8500rpm it was +5hp.
CamP
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CamP 8/19/2016 8:13am
8/19/2016 8:13am
Steely Dan wrote:
Thunder Products? Is the "fella's " name Lon?
No, it's a guy named Keith Peterson. He goes by KPRacing on TT.
seth505
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seth505 8/19/2016 8:28am
8/19/2016 8:28am
CamP wrote:
Yeah, it was pretty amazing. The part added power everywhere on the curve and at 7600rpm it was +3hp, from 7700-8300rpm it was +4hp, and at...
Yeah, it was pretty amazing. The part added power everywhere on the curve and at 7600rpm it was +3hp, from 7700-8300rpm it was +4hp, and at 8500rpm it was +5hp.
That's bonkers, I'm intrigued!
blackdiamond
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blackdiamond 8/19/2016 10:57am
8/19/2016 10:57am
Energyrail wrote:
What's your setup otherwise?
blackdiamond wrote:
The 14/51 works really well IMO.
Travis_Hudson wrote:
I'm sorry I can't remember, did you modify the chain guide? I seem to remember there being not much room for anything over a 50t on...
I'm sorry I can't remember, did you modify the chain guide? I seem to remember there being not much room for anything over a 50t on this scoot.
The 51T seems to work fine, the changes on the guide were primarily cosmetic and to aid cleaning the mud out.
blackdiamond
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blackdiamond 8/19/2016 10:59am
8/19/2016 10:59am
ocscottie wrote:
Good stuff bro, just finished reading the article, they did a good job and explaining almost everything (ive followed this thread since the beginning) This pic...
Good stuff bro, just finished reading the article, they did a good job and explaining almost everything (ive followed this thread since the beginning)

This pic is so rad Cool

I agree, I was pretty stoked on the article to say the least. It was a lot more detailed than I thought it would be.
Steely Dan
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Steely Dan 8/19/2016 11:05am
8/19/2016 11:05am
CamP, when was your lectron manufactured?
H4L
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H4L 8/19/2016 11:15am
8/19/2016 11:15am Edited Date/Time 8/19/2016 11:16am
Odd that MXA didn't mention the HGS exhaust. Good article & thanks for posting.

I couldn't help but laugh when they wrote about the stock 03 motor test run they did back then. I do remember MXA being the worst of the mags really talking negative about the case reed motor. I basically took a stock bike with heavier suspension springs, jetted carb & vf2 block & did very well at a few local mx races. After the cyl & head were modified I had no problems pulling 450's & other 250 2 strokes off the line & straights.

The 1 tooth in the rear was hilarious as I lost count how many times I've read that comment through the years in the mags... I think Jody is the worst offender. LOL !
CamP
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CamP 8/19/2016 11:37am
8/19/2016 11:37am
Steely Dan wrote:
CamP, when was your lectron manufactured?
Late 90's. Appears identical to what they are still producing today. They were in Waco then and now they are down by Austin.
CamP
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CamP 8/19/2016 11:56am
8/19/2016 11:56am Edited Date/Time 8/19/2016 12:00pm
H4L wrote:
Odd that MXA didn't mention the HGS exhaust. Good article & thanks for posting. I couldn't help but laugh when they wrote about the stock 03...
Odd that MXA didn't mention the HGS exhaust. Good article & thanks for posting.

I couldn't help but laugh when they wrote about the stock 03 motor test run they did back then. I do remember MXA being the worst of the mags really talking negative about the case reed motor. I basically took a stock bike with heavier suspension springs, jetted carb & vf2 block & did very well at a few local mx races. After the cyl & head were modified I had no problems pulling 450's & other 250 2 strokes off the line & straights.

The 1 tooth in the rear was hilarious as I lost count how many times I've read that comment through the years in the mags... I think Jody is the worst offender. LOL !
MXA's description of the 03 engine was spot on in my experience. A friend of mine has a bone stock garage queen 03 with about 10 hours on it. I rode it and it feels just like MXA said their 03 ran.

“The CR250’s powerband is its biggest handicap. It’s mellow, linear and smooth down low. It takes its good old time building revs..."
H4L
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H4L 8/19/2016 12:31pm
8/19/2016 12:31pm Edited Date/Time 8/19/2016 2:13pm
CamP wrote:
MXA's description of the 03 engine was spot on in my experience. A friend of mine has a bone stock garage queen 03 with about 10...
MXA's description of the 03 engine was spot on in my experience. A friend of mine has a bone stock garage queen 03 with about 10 hours on it. I rode it and it feels just like MXA said their 03 ran.

“The CR250’s powerband is its biggest handicap. It’s mellow, linear and smooth down low. It takes its good old time building revs..."
Has your friend done any jetting ? The stock jetting is way off & isn't even close from the showroom floor in my experience. The 02 & 03 models owned in stock form ran night & day different after getting the jetting sorted out. I also found by adding a tooth or two it made a big difference as well.

I'm in the minority & prefer the 02-03 motors over the 05-07 models. I've also read about a few reputable tuners that say the 03 cyl. is very good to work with. Chad Watts RC's mechanic at that time is one of those tuners that likes the 02-03 engines. Once set up right after mods they have a very good broad powerband like BD's 03 motor. MXA compared it to a KTM450sxf & that's high praise considering they really dissed the stock motor.

CamP
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CamP 8/19/2016 12:50pm
8/19/2016 12:50pm
H4L wrote:
Has your friend done any jetting ? The stock jetting is way off & isn't even close from the showroom floor in my experience. The 02...
Has your friend done any jetting ? The stock jetting is way off & isn't even close from the showroom floor in my experience. The 02 & 03 models owned in stock form ran night & day different after getting the jetting sorted out. I also found by adding a tooth or two it made a big difference as well.

I'm in the minority & prefer the 02-03 motors over the 05-07 models. I've also read about a few reputable tuners that say the 03 cyl. is very good to work with. Chad Watts RC's mechanic at that time is one of those tuners that likes the 02-03 engines. Once set up right after mods they have a very good broad powerband like BD's 03 motor. MXA compared it to a KTM450sxf & that's high praise considering they really dissed the stock motor.

We installed Pro Circuit's recommended jetting, but it was still slow revving and anemic feeling. Just felt gutless, like a huge flywheel weight was installed.

I've heard they can be improved, but I haven't personally been down that road.
H4L
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H4L 8/19/2016 1:14pm
8/19/2016 1:14pm Edited Date/Time 8/19/2016 1:21pm
CamP wrote:
We installed Pro Circuit's recommended jetting, but it was still slow revving and anemic feeling. Just felt gutless, like a huge flywheel weight was installed. I've...
We installed Pro Circuit's recommended jetting, but it was still slow revving and anemic feeling. Just felt gutless, like a huge flywheel weight was installed.

I've heard they can be improved, but I haven't personally been down that road.
PC's specs are good for the 03 engine. Is he running the S8 nozzle as well ? The oem S9 is to rich & the S8 will clean up the 1/4 - 3/4 throttle range. The 03 motor will run much better & have better snap as the oem jetting specs are fat rich. Don't know what Honda was thinking with the jetting specs on the 02-07's from the showroom floor.

Texas has hotter heat ranges than here in CA where the PC jetting specs were tested. He might also need to go a tad leaner & experiment with an S7 & leaner jets. A makes a big difference on getting the jetting sorted out as you probably already have experienced with the case reed motor & mikuni tmx carb..
CamP
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CamP 8/19/2016 1:37pm
8/19/2016 1:37pm
H4L wrote:
PC's specs are good for the 03 engine. Is he running the S8 nozzle as well ? The oem S9 is to rich & the S8...
PC's specs are good for the 03 engine. Is he running the S8 nozzle as well ? The oem S9 is to rich & the S8 will clean up the 1/4 - 3/4 throttle range. The 03 motor will run much better & have better snap as the oem jetting specs are fat rich. Don't know what Honda was thinking with the jetting specs on the 02-07's from the showroom floor.

Texas has hotter heat ranges than here in CA where the PC jetting specs were tested. He might also need to go a tad leaner & experiment with an S7 & leaner jets. A makes a big difference on getting the jetting sorted out as you probably already have experienced with the case reed motor & mikuni tmx carb..
I'm sure it could be improved, but it's just a garage queen, and he never rides.

I have two other friends that race 03's with our vintage club. The have both gone to Gorr engines with PWK carbs and they look like they work well, although I haven't ridden their bikes.
emifrancy 8/19/2016 1:40pm
8/19/2016 1:40pm
Hi guys, I'm a cr 250 2007 that you see in the picture, I installed the complete boyesen rad valve, One special "messico" exhaust, special cylinder head, and similar cylinder of "Varner" modify. with Mikuny carburator (420 max, 26/64 needle in second, 40 min.) I always too rich and my motorbike consumes to
much petrol, but as final performance is the carburetor that does go the strongest bike. three weeks ago I got the lectron but unfortunately when I testing it, I have not had the desired results, the bike consumes less petrol, for how I use it: "woods" the boost is smaller at low revs, and I am fine. (though I have done many tests with this carburetor). instead with the keihin (max:180 , NECJ at the second, 45 min.)I a good yield, but at high rpm does not go as the mikuni, I wish it were not the fault of TPS: I hooked up correctly, but the maximum value in ohms that I can find by adjusting the potentiometer is 3, and I wouldn't want that wasn't enough, because I read in the manual that must be from 4 to 5. let me know if you have some
suggestions with Lectron or keihin.
many thanks



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H4L
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H4L 8/19/2016 2:05pm
8/19/2016 2:05pm
emifrancy - Something to consider is the 05-07 engines don't rev as well as the 02-04 models in stock form. If you have had the base milled .030" combined with the Keihin it will have even less topend. Not familiar with the messico exhaust (here in the US ) & what part of the rpm range it's suppose help ? I would experiment with different needles on the Keihin as it sounds like that's what your asking (or lectron) . Have read on Thumper Talk from members that have had good results with the suzuki Keihin needles for woods application.

If you like the topend power the Mikuni provides you can also experiment with different needles & jetting specs. Best case scenario is to reach out to your local moto community about jetting specs. They will have a better understanding of the terrain, temps, altitude etc..

Also suggest reaching out to the company Messico exhausts to see if they've done some testing with jetting & can provide a good starting base platform on the oem mikuni.
emifrancy 8/20/2016 10:37am
8/20/2016 10:37am
thank you very much for your reply, I live in Italy, but we don't
have the special forum like this....
emifrancy 8/20/2016 10:48am
8/20/2016 10:48am
thank you very much for your reply, I live in Italy, but we don't
have one special forum like this....
luckynino
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luckynino 8/20/2016 12:37pm
8/20/2016 12:37pm
emifrancy wrote:
thank you very much for your reply, I live in Italy, but we don't
have one special forum like this....
Sorry for a little italian offtopic:

Certo che c'é !

Vai su MxBars sul forum Tecnica MX:
http://forum.mxbars.net/viewforum.php?f=5

saluti
Nino
emifrancy 8/20/2016 11:39pm
8/20/2016 11:39pm Edited Date/Time 8/20/2016 11:54pm
emifrancy wrote:
thank you very much for your reply, I live in Italy, but we don't
have the special forum like this....
Hi, thanks a lot for the answer,
for now I have not changed the height of the cylinde: is original ... I would keep the mikuni because it has more high rpm and more low rpm with my exhaust (Messico pipe). I suppose that the keihin problem
is the value of TPS, I have maximum 3,5 ohm but in the manual there is write that the correct value is 4,5 or more..I would like to use the keihin because consumes much less gasoline, but I would like it more at high rpm..

for Nino:
thank you very much, but in the bars forum there are not so many people with cr 250
modify
emifrancy 8/20/2016 11:52pm
8/20/2016 11:52pm
H4L wrote:
emifrancy - Something to consider is the 05-07 engines don't rev as well as the 02-04 models in stock form. If you have had the base...
emifrancy - Something to consider is the 05-07 engines don't rev as well as the 02-04 models in stock form. If you have had the base milled .030" combined with the Keihin it will have even less topend. Not familiar with the messico exhaust (here in the US ) & what part of the rpm range it's suppose help ? I would experiment with different needles on the Keihin as it sounds like that's what your asking (or lectron) . Have read on Thumper Talk from members that have had good results with the suzuki Keihin needles for woods application.

If you like the topend power the Mikuni provides you can also experiment with different needles & jetting specs. Best case scenario is to reach out to your local moto community about jetting specs. They will have a better understanding of the terrain, temps, altitude etc..

Also suggest reaching out to the company Messico exhausts to see if they've done some testing with jetting & can provide a good starting base platform on the oem mikuni.
please, another question, do you have the link about thumpertalk forum that they speak about the Suzuki needle? many thanks in advance
H4L
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H4L 8/21/2016 8:48am
8/21/2016 8:48am Edited Date/Time 8/21/2016 9:19am
emifrancy wrote:
please, another question, do you have the link about thumpertalk forum that they speak about the Suzuki needle? many thanks in advance
Below is just one link I found of many on Thumper Talk putting in a search in the Honda 2 stroke section. I'd suggest becoming a member if your not one already & starting a thread (Honda 2 stroke forum) to help with your jetting. There are a few members ( like rtv & hallsy) who are good with jetting specs & recommendations with Keihin equipped 3rd gen (02-07) AF CR250r's. Rtv is the member I've seen post on the recommended Suzuki needles.

http://www.thumpertalk.com/topic/1158530-keihin-pwk-number-8-slide/?vie…

There are other factors to consider like what has been done to the cyl port work, cyl head, gearing & exhaust. Was the work performed on the cyl. done to concentrate in the low-mid rpm range. Is the exhaust designed to concentrate in the low-mid like a (US) FMF Gnarly pipe ? Is it geared to low ?
dbrunski125 8/25/2016 11:03pm
8/25/2016 11:03pm
blackdiamond wrote:
The front caliper is a slightly modified Ride Engineering billet caliper with lightened pistons and the rear is a 2015 CRF 450 caliper that has been...
The front caliper is a slightly modified Ride Engineering billet caliper with lightened pistons and the rear is a 2015 CRF 450 caliper that has been machined to reduce the weight slightly and help with cooling. The rear brake piston has flutes machined into it like some of the braking systems frequently used on race cars and GP bikes. This mod greatly reduces the heat transfer from the brake pad to the piston by allowing it to vent. After the piston modification it was DLC coated for less friction and drag. All of the caliper pins, brake pad pins and bleed nipples are specialty parts from Racetech Titanium. The caliper pins are DLC coated as well for less friction.

The pics below show the calipers in various stages with these mods.















Any long term issues happened machining off the ride engineering logo off of the caliper? I really like the look of thay compared to what the caliper looks like normally. Looks lot closer to the factory Nissan billit calipers.
blackdiamond
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blackdiamond 8/26/2016 2:55am
8/26/2016 2:55am
No probs at this time. Keep in mind it only tales approx .060" to clean it up in the first place.
emifrancy 8/26/2016 11:16am
8/26/2016 11:16am
emifrancy wrote:
please, another question, do you have the link about thumpertalk forum that they speak about the Suzuki needle? many thanks in advance
H4L wrote:
Below is just one link I found of many on Thumper Talk putting in a search in the Honda 2 stroke section. I'd suggest becoming a...
Below is just one link I found of many on Thumper Talk putting in a search in the Honda 2 stroke section. I'd suggest becoming a member if your not one already & starting a thread (Honda 2 stroke forum) to help with your jetting. There are a few members ( like rtv & hallsy) who are good with jetting specs & recommendations with Keihin equipped 3rd gen (02-07) AF CR250r's. Rtv is the member I've seen post on the recommended Suzuki needles.

http://www.thumpertalk.com/topic/1158530-keihin-pwk-number-8-slide/?vie…

There are other factors to consider like what has been done to the cyl port work, cyl head, gearing & exhaust. Was the work performed on the cyl. done to concentrate in the low-mid rpm range. Is the exhaust designed to concentrate in the low-mid like a (US) FMF Gnarly pipe ? Is it geared to low ?
thank you very much, I read some post about the keihin carb.. Did you test with Yamaha yz needle N3EW??

another thanks!
Mr. Robinson 8/27/2016 6:21am
8/27/2016 6:21am Edited Date/Time 8/27/2016 6:22am
CamP wrote:
Yeah, it was pretty amazing. The part added power everywhere on the curve and at 7600rpm it was +3hp, from 7700-8300rpm it was +4hp, and at...
Yeah, it was pretty amazing. The part added power everywhere on the curve and at 7600rpm it was +3hp, from 7700-8300rpm it was +4hp, and at 8500rpm it was +5hp.
seth505 wrote:
That's bonkers, I'm intrigued!
It's the real deal. I have one on my YZ250 and it's the shit ! Feels like I installed a big bore kit.
H4L
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H4L 8/27/2016 7:27am
8/27/2016 7:27am
emifrancy wrote:
thank you very much, I read some post about the keihin carb.. Did you test with Yamaha yz needle N3EW??

another thanks!
I have not.

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