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07 crf250 in the pacfic north west what jetting to run ?

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new bike to me and I,m about to rip into the carb it 's timing was off a tooth and it don't start well. I put an r&d remote fuel screw on it and get no change when turning it, the bike appears stock I have stuff sitting around like #50 leek jets ncvs needles,42/45 pilots and a shit load of mains, throtle plate seals, acc pump update kits-I know the drill but I'm looking for a little guidance as to what might work well.

The bike will be used for single track mainly, I don't know what needle is in it now or what jets are in it, I,m thinking of putting in ncvs 2nd 50 leek, 42 pilot 175 main, throttle plate gasket o-ring mod acc pump update kit .

I checked the 250r stickeys for a jetting thread but if anyone has any better ideas than what I posted let's hear them? I'm going out to tear into this thing and i'll report back whats in the thing for jets and check for responses

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I found a 70 leek jet

               42 pilot

               175 main

               NKBT 3rd clip position

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First, do not go changing the jetting. See what is in the cvarb first. Then ensure the carb is clena, all parts in good contition and properly adjusted per the manual. One of the biggest mistakes people make is they change things and make a small problem huge. Get a baseline. Stock jetting, clean and properly adjusted. Then ride the bike, testing and noting very carefully any problems.

 

You must first get the idle and fuel screw right BEFORE you attempt to change anything else. Put a NEW stock pilot jet in. Make sure the oring/washer and sping are on the fuel screw. Make sure the float is adjusted EXACTLY per the manual. Make sure the passage ways are clean. Make sure the slide release plate is installed properly. Make sure the idle speed is low while setting the fuel screw. You can increase the idle speed once the bike idles properly.

 

 

Once that is done and the idle is perfect, then and only then, can and should you experiment with needle changes. After that, the main jet and finally, the AP.

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thank you, I found the pilot jet was plugged, I am cleaning the carb now and will put in a new pilot jet of the same size to start

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Elevation? For 6500 feet I went from a 162 main to 155 made It run perfect the local shop recommends 10 percent drop from stock at this elevation. Really wished someone could have made it that simple for me.

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so after cleaning up the carb cold starting was only good some times but crappy most of the time, warm starting allways easy

I could bump start it if I could not kick it when cold

I  found after pulling the cam and blowing air in the plug hole I could hear the air in the intake and hear the slide rattling, all the valve guides are loose,

I know this is a jetting thread but that's the news

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so after cleaning up the carb cold starting was only good some times but crappy most of the time, warm starting allways easy

I could bump start it if I could not kick it when cold

I  found after pulling the cam and blowing air in the plug hole I could hear the air in the intake and hear the slide rattling, all the valve guides are loose,

I know this is a jetting thread but that's the news

 

What???

Who did you head work??

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settle down krannie nobody has done any head work that I know of. I have checked clearances  then confirmed  the timing was off by one tooth and set it right but it jumped again. now it has a new tensioner and cam chain in it and cold starting is awfull.

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 I have new guides here and am waiting for the new valves to arrive, in the past on Honda heads that I had done I could see the margins on the valve or valves wear pattern cupped  . these look to have wide margins no cup worn into them but the guides shure let the valves flop around, I'm not detecting a wear line wore into the valve stem. I just got the bike so its a possibility that some one tried a cheap fix like threw in new valves without doing guides or not cutting the seats? I really am not sure what to think but it sure seems like classic intake valve problems but no trench wore into the narrow edge of the valve. I don't see valve marks on the top of the piston but they are not sealing and I know this because before teardown I welded a small pipe onto a spark plug carcas and installed it and blew air into it with the cam removed and air was coming out the intake side of the head - poor mans leek down tester.

if the valves are bent from bad guides and slaming into the seats un centred should I be able to spot this from rolling them on a flat table? the seats don appear to be damaged to my old eyes

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I know that it's going to need to go to the shop for work, I have the guides and seals here and the valves will be here latter this week. I'm just trying to see what I can before it goes to the machine shop, putting the valves in the cordless drill and spinning them was a joke that chuck is no ware near true.

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Elevation? For 6500 feet I went from a 162 main to 155 made It run perfect the local shop recommends 10 percent drop from stock at this elevation. Really wished someone could have made it that simple for me.

 

I'm not sure what  a 10% drop would be in terms of jetting size....and it is an erronous statement anyway.

 

Jetting is about AIR DENSITY, not altitude.

Altitude is one way that air density changes, along with moisture level, and dust, and air filter maintenece.

So, at 0ft elevation in a heavy down pour, you need leaner jetting just like at 7500 ft elevation on a clear day, maybe.

Just putting in a brand new air filter may solve your problems at high altitude. Bring exta clean/oiled ones.

Does that help you understand why you change the jetting?

 

The rule of thumb is go down one size on the pilot and main for every 5000 ft of elevation change.

The problem with that is, are you starting from the correct jetting to begin with?

 

Copying a similarly tuned bike of the same make and model and year that runs at the altitude in question, is the fastest way to determine ball park jetting

So, you ask this question in the brand/model forum, where the owners will see your question.

 

Now, you are assuming that your bike has exactly the same carb wear as yours, not to mention valve lash, and fuel and everything else.

 

 

 

Otherwise, you have to just go off of the rule of thumb knowing your current jetting is spot on.

 

I personally run from 0-8500 feet with the same jetting with no issues.

Can it run better up there? Maybe, but I don't ride at that elevation all the time.....so.....

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Sorry it's a 6 percent drop a 6 percent drop in size takes a 162 and sets it at about 152. But it's erroneous I guess

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So what ever you are jetted for at sea level you would drop 6 percent on the main jet for 6500 feet. The local shops do this to every single bike that hits the floor.

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