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Modest power mod suggestions?

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I am thinking of making some minor modifications to my daughters crf230. I do NOT want to install the power up kit, because I don't want to increase the noise level that much. My daughters aren't power hungry, but I want the bike to run well at our altitude.

We ride in Utah, mostly between 5000' and 9000'. I would like the bike to run well at 7500' and still be acceptable between 5000' and 9000'.

I don't want to modify the exhaust due to noise concerns, but I may be willing to drill one or two holes if that will make a significant difference without increasing the noise much. But I won't remove the baffle - I tried it and it is way too loud for my liking.

Given those constraints, what modifications should I perform?

Remove the airbox snorkle?

Change the main jet? If so, to what?

Change the fuel mixture screw? If so, to what?

Any other carb changes?

I would appreciate your advice.

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Drilling a couple of holes will help a little and with very little increase in sound level. You will probably need to get a jetting kit and play around to get the perfect set up. Also get a better filter the factory is very restrictive. Other mods that you may consider that wouldn't effect the sould level would be going to an alum. CR250 sprocket and a non o-ring chain "if your type of ridding permits". The bike will rev much quicker. :cry:

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I ran with a modified baffle for a while but did the "power up needle" at the same time. Same as Rick Ramsy http://rickramsey.net/CRF230F.htm

Since your conditions are rather unique you're going to have to do some fine tuning yourself. Here's where I'd start & expect to make some changes depending on it's symptoms:

Pull intake baffle

Drill exhaust baffle

Stock (42)slow jet should be fine

Will have to turn fuel screw out some; 1/2 turn for starters

Needle leave where it is, if it bogs then start raising it.

Main jet 112 for starters. When I did mine I bought 5 jets so I wouldn't have to go back if I needed a different size. You'll need larger main jets for when you come down in altitude anyway.

Your altitude cancels some of the improved breathing but not all of it. Cold temperatures cancel some of the elevation gain. I think this should get you close.

Happy jetting! :cry:

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Toast - thanks for your suggestions. I like your plan.

What size is the stock main jet?

I assume I will need to go up at least one step size with the opened up intake and exhaust. Is the 112 that you suggest up one step size?

I have two 230s, so I will do one first so I have something to compare it with. Once I get it dialed in I can upgrade the second one.

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Stock mainjet is 102. 112 is 4 sizes up. Removing the intake baffle increases the intake area by a factor of 4. So, when your wide open throttle it can gulp air a lot easier. With the baffle mod too one jet size would not be close to enough even with your altitude gain.

Good move doing just one first!

:cry:

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OK, here is what I did:

- Checked the plug - it was white (too lean)

- Removed the airbox snorkle

- Drilled eight 3/8" holes in the side of the exhaust baffle

- Replaced the 102 stock main jet with a 110 (they didn't have the 112 in stock)

- Adjusted the fuel mixture screw as best I could (I am not sure how many turns, but in the 2-3 range)

- Test ride in the neighborhood, compared with a stock 230. It was slightly louder and seemed to have a little more power. Seemed to run pretty well.

- Checked the plug - looked tan

- Upgraded the other bike.

Now I need to give them a good test on the trail and then check the plug again.

Did I miss anything?

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