Putty

Member
Oct 25, 2007
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Looking for a simple mod I can do to increase output. I did new reeds. Stock exhaust...not sure how much that would help. Have heard mixed reviews on exhaust upgrade. Going to go up one on the rear sprocket.....maybe two. I just want a good low end and midrange.....top end means nothing to me since all I do is track/trails.

CR
 

Rich Rohrich

Moderator / BioHazard
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Jul 27, 1999
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PROPER Jetting is the single most effective mod you can do to a bike, and oddly enough it's also the cheapest.

Go to any MX track and ask 100 riders if their jetting is sharp and 97 of them will say yes. More often then not 95 of them will be totally wrong and their bikes will be slugs as a result. Bolting on parts doesn't make bikes fast, tuning does. ;)
 

BSWIFT

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N. Texas SP
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Nov 25, 1999
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Rich Rohrich said:
PROPER Jetting is the single most effective mod you can do to a bike, and oddly enough it's also the cheapest.

Go to any MX track and ask 100 riders if their jetting is sharp and 97 of them will say yes. More often then not 95 of them will be totally wrong and their bikes will be slugs as a result. Bolting on parts doesn't make bikes fast, tuning does. ;)
Crisp clean throttle response will seem like a lot of ponies compared to a bolt on pipe. After getting my YZ jetted right, I haven't considered a pipe, I went for a flywheel weight.:)
 

D36-108A

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Dec 3, 2002
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What Rich said. Carburetion is everything.

As for paying a shop to "jet" your bike, only the guy twisting the throttle on the trails can jet the bike.

I have an 02 CR250 and when I couldn't get it to run consistently with the Mikuni I put on a Keihin. Then I applied the same basic carb tuning and got it running sweet and crisp. I later added a V-Force reed cage, which gave slightly better throttle response, maybe a little more low end. Race gas also helps with throttle response.
 
Oct 24, 2007
4
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Easy Fix

Jetting the Cr's is simple.
First go one size down on the main.
Next the air screw on these bikes is , I believe , two turns out.
If you need more than two turns go to the next smallest pilot.
If you need less than two go up one size.
Before you buy a pipe just try a Power core 2 on the stock pipe.
It will work and if it isn't enough it will still work on the pipe you buy.
 

Putty

Member
Oct 25, 2007
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CANADIAN BACON said:
Jetting the Cr's is simple.
First go one size down on the main.
Next the air screw on these bikes is , I believe , two turns out.
If you need more than two turns go to the next smallest pilot.
If you need less than two go up one size.
Before you buy a pipe just try a Power core 2 on the stock pipe.
It will work and if it isn't enough it will still work on the pipe you buy.

It is simple, if you know how to do it....If not, you need to rely on a dealer.....which is the position I am in. A gear, Pro182 reeds, and a jet should wake it up quite a bit
 

SQUIRLEYMOFO

Member
Jun 11, 2002
310
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CANADIAN BACON said:
Jetting the Cr's is simple.
First go one size down on the main.
Next the air screw on these bikes is , I believe , two turns out.
If you need more than two turns go to the next smallest pilot.
If you need less than two go up one size.
Before you buy a pipe just try a Power core 2 on the stock pipe.
It will work and if it isn't enough it will still work on the pipe you buy.
I tried way more jets than that.............and finally got close. And no the other carb didn't fix my problem. The S4 nozzle really helps the 2002-2003 CR 250's........
 
Oct 24, 2007
4
0
Needle Jet

I forgot to mention that when switching out the needle jets note that the "27" series needles are 1/2 position richer than the standard 26 series needles.
Jetting is a time consuming and frustrating activity.
However the Honda reliability is worth it.
The newer CR's have a smaller crankcase volume and are easier to tune. I'll find out soon as I have one on order .
The nice thing about these bikes.
If they aren't happy they just foul the plug and we know they come from the factory fat.
 
May 10, 2007
957
0
you cant go with what he has. there is no PERFECT jetting for every condition cuz it is affected by temp. altitude, fuel, and what premix you use. and like a billion other things.

as for if you dont know how to do it.... it really isnt that hard. im sure you could find someone to help you do it the first time. thats what i did. i got my dad to help. now if i need to rejet i know how to do it.

also i believe sending the engine to eric gorr and having him port it for bottom end has good results for the money spent.

also getting your suspension set up is a great way to be faster.
 
Oct 24, 2007
4
0
For Sure

flyingfuzzball said:
you cant go with what he has. there is no PERFECT jetting for every condition cuz it is affected by temp. altitude, fuel, and what premix you use. and like a billion other things.

as for if you dont know how to do it.... it really isnt that hard. im sure you could find someone to help you do it the first time. thats what i did. i got my dad to help. now if i need to rejet i know how to do it.

also i believe sending the engine to eric gorr and having him port it for bottom end has good results for the money spent.

also getting your suspension set up is a great way to be faster.

Porting is the way to go. Something you can also do your self.
On the vintage bikes we also cut the piston skirt on the intake side. Any serious 2 stroke rider will have their motor ported and polished.
However after all is said and done modern two stroke motors need constant jetting attention. If you don't like to jet buy a 4 stroke.
Once you get your main , needle and pilot sorted out adjustments can be made with the air screw.
Half a turn makes a big difference.
Good talking with you/all
 
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