battery or start engine brushes issue?

My WR450F has over 220 hours on it, but still runs strong, yet now I have starting issues. One year ago I replaced the original YUASA battery 6.3 Ah for another one (also Yuasa 6.3aH). I always connect it to a battery tender but it seemed that the battery lately has lost substantial energy, whic surprised me as the battery was fairly new. The cost for a new one OEM battrey in Brazil is ($300) believe it or not. Friends of mine that ride Honda 450s has successfully changed their batteries for OEM 5Ah, batteries so I followed their advise and bought an OEM Honda battery, that has the same size, but only slightly less power 5.0Ah vs 6.3Ah. The battery was activated yestyerday, but when I connected it, unfortunately the bike continues almost impossible to start (clearly lacking power to turn the cranckshaft at sufficient rpm) not as a result of poor jetting, my bike kickstarts easily.

QUESTION: does anyone have experience with a good 5Ah on a WR450F? Does this work? Or are my brushes of the starting engine worn? Please help, I have a race this weekend and would like to get my bike ready.

Ive been playing this battery and starter issue for years with my 03 450. I am convinced the starter is best as a starter-assist; like out on the side of a mountain with the kickstarter on the wrong side, haha! And, the battery MUST be fully-charged and able to hold a load, if its under a low voltage situation, the aperture in the starter will expire; I've been through 2 starter motors, and need a 3rd but am scoffing at the 300 bucks for a new one! OUCH! As Dr. Smith used to say; "The Pain, Oh, the pain"

The battery is brand-new and of good make (OEM manufacturer) yet 5Ah. If the start-engine needs to be overhauled, is this not just a matter of buying a set of new brushes on the OEM ThumperTalk site $20 isn't it . What are typical sympthoms if the brushes are worn? Anyone?

Couldn't tell you much about the starter part, but had lots of troubles with the stock battery. Spend some money and order a lithium battery. I built one myself and will never go back to a lead-acid battery. JLow

I am assuming your bike will turn over, but not start. Then you kick it and it fires right up. JLow

Actually when I add the start-cables from my car on top of the battery. it continues weak and will only turn weak and slow, and after 4 revolutions its exhausted, than I wait a bit and do again, but the revolution speed is not sufficient high to get the bike started (and it's not a jetting or spark plug issue, those are perfect) its really the rpm speed of the start engine that is too low.

I am considering checking my start-engine and take it apart. QUESTION what do I need to remove to get it out or at least check the carbon brushes. The pipe, the carb what else? Do I need to remove the engine out of the frame? Please assist me what I need to take off the bike and also if any special tools are required. Should the specific carbon brushes for the WRF are not for sale here in Brazil, has anyone tried using the brushes of any other more popular bike - Hints and suggestions are most welcomed!

If the starter motor can rotate then the brushes can still work, IMO.

I have changed the brushes once, when the motor could not move and just made the "tack...tack" sound when I hit the start button.

The brushes are quite popular and easy to find, even I'm in Vietnam.

To get the motor out, you need to get the carb. away.

Thanks! Other than the brushes could there be other parts that drain crank power from the start-engine? I wil check the cable connections, I am asking because there is no effective gain in rpm speed when I add starter cables connected to my car's battery with engine running. The bike itself kinckstarts easily.

If you are jump-starting from a car battery and the starter is still turning over slowly, and then stopping, you have a starter/connection problem. I never had issues with the starter so I can't help you much there. Jlow

I don't know how long the brushes from these starter motors typically last, but under normal operation I would expect more life. However, brushes can be damaged if the armature winding coils are shorted or if one of the coils is open. This creates severe arcing and will eat away the brush material quickly. You will be able to tell if there is a bad coil as it will typically be burnt or darker in color. Based on the starter not having enough torque to properly crank the engine, this would be my guess. If this is the case, a new starter is in order. Also, one of the commutator segments could have shifted slightly which will also eat brushes. This will be apparent as a dark or burned copper segment. The commutator needs to be close to perfectly round (.003" -.005" TIR) in order to maintain good connection to the brushes. If a bad segment, then a new starter as well. If the brushes are worn too short due to normal wear, replacing with the correct brushes is critical as the proper fit (.005" - .010" gap between brush and brush holder) and brush material is needed. I would recommend taking it apart and inspecting it for bad coils and commutator first then trying to either get new brushes or a new started based on the results of the inspection.

Hi,I had a similar problem with my wr450 it turned out to be my starter button on the handlebar.I took it apart and cleaned the contacts now it works great!

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