Question about 2001 Honda CMX 250 Rebel
CMX250 starts and idles well. Has hesitation and looses power at low RPM, but recovers power after throttle increased. Start the 2001 Honda Rebel 250 (CMX250C) with the choke. Starts very easy and ildes well to warm up. Idles fine after taking choke off as well. There is a hesitation/loss of power at low throttle, but it recovers very well after increasing the throttle. This an air cleaner issue or carb? Just bought the bike. Changed plugs, gapped 0.025". Don't know when the air cleaner was last replaced. @
Hi, Greg love that name, engine "BOG" is mainly caused by a rich air and lean fuel condition but it can also be caused by a lean air and rich fuel condition this situation rarely occurs and is only caused by the misinformed weekend warrior that owns a toolbox. If the bike has been sitting for months or years you will have to completely disassemble the carburetor and submerge the parts (except rubber parts) in "Carburetor Dip" It usually comes in a gallon bucket with a wire mesh basket that can be purchased at any automotive store. If it is not the above scenario then the following explanation will apply.
The more you open your throttle the more vacuum you are creating in your carburetor venturi and your intake manifold. When you are operating at higher RPM any unmetered air that leaks into your system can become more obvious.
Unmetered air is the air that is getting into your system after the fuel has been delivered. If you have unmetered air getting into your system between the butterfly/slide of the carburetor and the cylinder head this will create a lean condition.
All of the rubber components of the fuel system like vacuum hoses and intake manifold that you mount the carburetor to are made of rubber. If none of these components has been changed they are more than likely highly degraded and probably cracked in places to allow unwanted-unmetered-contaminated air into the combustion chamber. Check all of your vacuum lines and vacuum plugs for carburetor synchronization. The vacuum plugs are in the head just after the rubber intake manifolds. The petcock has a vacuum line as well as part of the emission system.
1. Check the intake manifold for fissures.
2. Ensure the bands used to tighten the manifolds down on the intake are secure and have not bound up the manifold.
3. Make sure air box fittings are not warped and fit completely over the carburetor.
Your airbox is metering air and is the first step in the process of consuming air and fuel. The system requires the resistance of the air filter in order to get the proper vacuum to "SUCK" the fuel out of the float bowl and create the proper venturi effect.
Improper mounting and sealing of the airbox will create a small lean effect. This might seem like no big deal but you are inviting dust and debris in your engine that is doing slow damage by not having proper fitment. Fix it so you know it's not contributing to your issue. Pick the low-hanging fruit first.
Do not go and start adjusting anything at this point. It ran fine before. There is something wrong with the assembly or a component. Do not adjust your floats. Get it back to where it was. The moment you start tweaking everything is the moment you lose OEM settings which are a must-have for fine-tuning and maximum performance.
Fine-tuning your carburetor and multi carb syncing come at the very end following the proper procedure established by the Carburetor Gods.
For more information about your issue and valuable "FREE" downloads that you will need for viewing or printing please click on the blue links below. Good luck and have a wonderful day.
Why is my motorcycle losing power when accelerating
Honda rebel 250 Service Manual
Posted on May 12, 2019
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Posted on Jan 02, 2017
First thing I would try is some sea foam, you can get it pretty much at any auto parts store...put it in the tank per instructions on the bottle, if the carbs are gummed/dirty... seafoam is you best hope at getting them clean without pulling them.
If sea foam doesnt work, you'll have to yank the carbs, but before you do... pull the tank, set it backwards where the seat was, get about a two foot fuel line (air line works just fine) run it ti the tank and start the bike, take a can of starting fluid (WD 40 works too but stinks when it starts to burn off afterwards) and spray around the base of the outside of the carbs where the boots connect it to the intake, if the engibe revs, you have a leak...cracked boot probably.
If no leaks are detected... then yank the carbs, pull the bowl covers and start cleaning....also, while you have them off pull the slide covers off and check the diaphrams on the needle for rips or cracks as well.
Check/clean.. put everything back together... if it still isnt running right then I have no other suggestions... certainly sounds like an air/fuel problem... if were anything else choking it wouldn't make it better.
Posted on Jul 10, 2009
It sounds like your bike has been sitting in storage for an extended period of time (a year or more) - and the carburetors are plugged up. If this is the case, they will need to be completely disassembled and cleaned out.
If it hasn't been sitting (and the carbs aren't plugged up) then check that all of the normal tune-up items have been performed, especially valve adjustment, oil and filters, spark plugs, etc. If this fails to produce positive results, perform a compression check on the engine. Each cylinder must be able to produce at least 140 psi of compression in order to run and idle properly.
Posted on Nov 07, 2009
Has the bike been stored for any long length of time?
old fuel in the carburetor will turn to a varnish like residue blocking the jets,or possibly water in the carburetor.
Posted on May 03, 2010
Testimonial: "The bike was not stored and was ridden regularly, but it still sounds like it could be the carburetor. Thanks for your insight."
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