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05 CRF 50 Carb not tuning well

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I purchased this bike a few months ago for my kids. It sat for a few years. So much in fact that the carb was dirty. I pulled it appart cleaned it the main jet looks good. I can see through it. I pulled the gas tank and had to remove what was left of the fuel screen. I cleaned the tank put in a new fuel screen and also a filter before the carb just to make sure. I put the carb back on and I am having trouble tuning it. The fuel screw is 1 1/2 turns out. The idle screw I have no idea. I can start the bike. It runs however when I twist the throttle practicaly dies then revs up. It also seems to take a little while for the idle to come back down. Anyone have any ideas?

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Have you tried adjusting the air screw? 1.5 turns out is just a starting point. Also, have you checked for intake leaks?

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I have practically the same situation! Bike refused to run after working great for years, then all it took was one tank of gas that sat for a month. I got a rebuilt kit and removed, cleaned, and reassembled the carb. These are 18mm Keihin's correct?

Now it will start and run, but has no or very little throttle response. The main jet is clean and cleared. I've blown air compressed air through all the passages. My concern is the pilot jet on these. They aren't removable correct? The passage is so small, that even a very thin wire will not pass through, should it?

On the side of the carb I have to screws, the top one, closed to the tank is for idle, correct? What's it default or starting position? The lower one is the air screw that adjusts the air/fuel mixture, yes? Is the default position on this 1 3/4 turns out?

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I'm still working on mine. The little brass tube that is pressed into the carb body. Is that supposed to have a passage to the carb body. If you are not sure what I am talking about. I'll post pictures. I can't seem to get anything small enough to put in the hole of the tube to find out if it is blocked or not. I definately don't see light. And it is pressed in the carb body so I can't remove it.

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There are two holes in the intake at the rear of the carb where the air filter goes, one of them is connected to the pilot jet tube. Squirt contact cleaner into that hole and you should see it come out the pilot jet tube. If it doesn't, its clogged. The other hole goes to the main jet circuit, the contact cleaner should come out at the main jet itself.

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Thanks, I'll give that a try. Here is a picture out of my book of what I am talking about. It is the brass tube next to the one with the arrow. It is the one with a tiny hole. Should that be clear. I would think so, because it would have to serve some kind of purpose. Thanks

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Thank you for this the hint of how to check that the pilot circuit isn't clogged. That is what has always been missing from any thread that I tracked down. Finally I understand that the pilot jet can't be removed like every other carb Honda uses. That's to bad, as this seems to be a problem prone area. I've had the carb pieces soaking in parts dip overnight and will now do the spray test to check.

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yep that seems to be my problem as well. The pilot jet. This should be interesting to get cleared

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the pilot will come out with some tactful use of pliers....grab and twist slightly while pulling straight out.....clean jet and tap it back in

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Damn... It did't work. The tube seperated at the base of the carb. Guess. I need to look at a new carb. Ohh well. At least I tried.

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Sorry to hear that. I cleaned my carb by taking it apart and using a gallon can of Berrymann chem dip. It's a product specifically used to clean carbs, carbon covered valves. It's very strong, so you need to use gloves and remove any rubber of plastic pieces.

Edited by iwonder8
misspelled word

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I pulled a piece of wire out of one of my wire brushes with a needle nose pair of vise grips.

I used that to clear out my pilot jet in my sons 50. when i blow cleaner through the holes in the back of the carb. i get fluid coming out of the passages. yet i still have the problems you are decribing. i have replaced all the gaskets on the intake manifold on the engine side, and the carb and isolater. I still have hte problems our describing. have you had any success. Any helop would be great.

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I got luck and found a used carb on Ebay. The guy said it was good and guaranteed it. So I bought it. Put it on and had to tune it a little other than that. I was good to go.

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Glad to hear you got a replacement carb and your off and running again.

I on the other hand, was successfull. I got all the passages flowing with carb cleaner after another thorough cleaning. I put everthing back together and bolted it back up to the manifold. I also got rid of the after market air cleaner and put the stock air cleaner back on (cleaned and lightly oiled) along with the engine crankcase breather setup that attaches to the stock air cleaner. Set the air screw at the the factory recommended turns and fired it up. It idles and revs up with out a stumble off the bottom end. I rode it down the street to put a load on the motor. It. pulled well through all the gears and when I did a plug check. I got a light tan plug readiing. I guess I got lucky.

Lesson learned on my part. Shut fuel off and let motor run out of gas before putting away. Leaving old fuel in the tank and carb was not good.

Any advice on what to do over the off season to eliminate my nigthmare??

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Your lesson learned is a good one..........as I learned it as well. The blended fuels are to blame as the alcohol attracts water. The gas and alcohol start to separate and the alcohol, water is what creates the compounds that gunk and corrode things up I've been using a product recommended by the Honda Dealer "Startron". They are now using it in every gas machine they sell, as they has no start issues with brand new power-craft, that got traced back to fuel problems. An example is someone buys a water jet and they use is. Then don't go to the lake for a 2-3 week period, and now the new expensive jet boat won't start.

Use a product like this and run and carb dry, then open the bowel drain screw as well and you should be all set for winter storage. This is what the Honda dealer is recommending to me.

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I'm running into the same problem on my sons xr50. Any advice on purchasing a carb off ebay? Are the aftermarket mikuni carbs as good as the OEM?

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I was lucky and found a used OEM. The other stuff I have no idea. All I know is I bought an supermarket one new off ebay for my sons Polaris ATV and it was junk. It wasn't a mikuni though. I would think that would be fine. Hopefully someone will chime in.

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