Question about 2005 Yamaha Road Star Midnight

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Diagram of mikuni carbs

Bike sat for a season and now the carb has problems. It is a Mikuni BSR 40 - fuel is pouring out of the overflow tube into the air filter box. Thinking that the float chamber has issues as the floats are not closing off the overflow. What are some of the steps that I can take before pulling the carb and having it rebuilt, also had problems at higher altitude or in hot temp areas with full running out at when filling up. Is there a replacement Carb that would work better then the original?

Posted by Anonymous on

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  • Yamaha Master
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Hi, Anonymous the BSR 40 is a great carburetor if your bike has been sitting idle for months or years and you did not do any pre-storage maintenance I feel your pain it will probably have a dead battery and not want to start or if it starts it will idle and run poorly then stall, here are the following steps necessary to complete in order to get your bike back to an acceptable running condition.
1. If your battery was 2-3 years old when you last had the bike running you should replace it.
2. If you believe your battery might still be serviceable remove it from the bike and put it on a 1 or 2 amp trickle charger for 24 hours. If it is the old lead acid type with visible cells and acid levels fill each cell to the top line with distilled water and replace the caps, run the vent tube into a plastic or styrofoam cup, any cells that are cloudy/milky replace the battery.
3. After charging remove the leads and let the battery sit for a couple of hours then check the battery voltage with a volt meter, you should have 12.5 volts or better, any readings in the 11 volt range you need to do a proper load test on the battery and replace as necessary, any readings in the 10 volt range you have a dead cell and the battery needs to be replaced.
4. Drain and flush fuel tank, google " how to clean a motorcycle gas tank" find a couple forums to view the different options available.
5. Remove and inspect your air cleaner paper elements that are not oil soaked can be cleaned with a soft brush and low pressure compressed air, oil soaked elements must be replaced. Gause mesh and foam elements can be cleaned by soaking them in a container big enough to completely cover them with a solution of 1 gallon of water and 1 oz. of Dawn dishwashing liquid for small and medium size elements, for monster size double the formula and let soak for at least one hour then rinse with warm water shake off excess and let air dry, "WARNING" do not use compressed air as this will embed micro-sized dirt and road grime and destroy the mesh pattern and stretch foam elements out of shape just squeeze it like a sponge and let air dry, use a fan if you're in a hurry. When completely dry spray a very fine mist of air filter oil evenly around the whole element.
6. Remove the carburetors, disassemble and decontaminate with a carb dip or if you have EFI remove injectors and clean with carb spray and compressed air
7. Remove fuel valve and filter disassemble and clean as necessary, remove, clean, and inspect fuel and vacuum lines and replace as necessary.
8. Replace spark plugs with new ones and check for spark.
For more information about your issue and valuable "FREE" downloads that you will need please click on the links below. Good luck and have a nice day.
http://www.mikuni.com/pdf/sbn_manual.pdf
MikuniPower com Mikuni Carburetor Tuning and Maintaince Manuals
http://www.rswarriordocs.com/manuals/WarriorServiceManual-WO3646.pdf
OEM parts for Yamaha
Yamaha XV17ATMV Road Star Owner Manual

Posted on Nov 24, 2016

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SOURCE: yamaha yz 125 1994

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Can I get a “very helpful” rating on this answer? Thanks!

Posted on Jul 06, 2009

dmsr63
  • 2050 Answers

SOURCE: Mixture screw on Carb

I believe it is near the bottom, around where the float bowl meets the carb body.. You need a straight small screwdriver (Short) facing upward.

Posted on Jul 29, 2009

SOURCE: Carb (Mikuni) flooding on Yamaha Vmax motor cycle

You will have to adjust the float pin of tht particular carb and don't remove them off the rack..just pull them out of the engine and work on the one tht needs attention.
Hope this helps!

Posted on Sep 06, 2009

ollie reece
  • 1167 Answers

SOURCE: wr400 2000yr hard starting & won't idle

buddy change the plug also on the carb there will be a idle screw turn this in 1/4 of a turn with the machine running and get back to me 724a8c7.jpg

Posted on Sep 17, 2009

  • 32 Answers

SOURCE: carbs leaking

all carbs have floats.it a cv type carb,with a big diaphram for the slide.real easy carb.to work on.if you have any mechanical knowledge.get a manual if not go on internet,and plenty of vendors for *** bikes that sell factory parts look up yours,and the carb will give you a breakdown of it.harley does not have any parts look up like *** bikes.sound like the carb needs cleaning or needle and seat is wore out

Posted on Mar 27, 2010

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