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lixno

WR450F starting motor problem (burned)

19 posts in this topic

My bike is a 2003 WR450F. Bought it new back then and never had any of the e-starting problems these bikes had. About 3 years ago i changed the exhaust cam for a YZF one and the starter would spin but the bike couldn't fire up...so i took the battery off and kickstarted the bike since then.

now that i installed a BB ice cube kit with web cams the compression increased and the kickaster stiffened a lot. So i did put a battery again to see if with the web cams the problem would be solved.

Unfortunately with the stock 5Am battery just spinned the crank and then stopped. i thought that because of the compression maybe the stock battery didn't have the power to turn the motor.

So i tried with a car battery, trying to find out what was the problem, but the same thing happened again. The crank just spinned and then stuck again. After a few tries it wouldn't spin at all!

I removed the starting motor and found that the wires going to the one brush were cut! But the biggest problem was later to be found...the whole starting motor is "burned" (sorry but i can't find the right words to describe it).

So i have to buy a new very expensive starting motor or try to fit a YZF 1000 R1 street bike starting motor, which is very similar to the stock WRF's, as a friend told me.

Because i have no clue about these electric stuff, did anyone have similar problems with the starting motor? What could have caused such a problem?

the 3 years i didn't use the e-start had to to do something with that?

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My bike is a 2003 WR450F. Bought it new back then and never had any of the e-starting problems these bikes had. About 3 years ago i changed the exhaust cam for a YZF one and the starter would spin but the bike couldn't fire up...so i took the battery off and kickstarted the bike since then.

now that i installed a BB ice cube kit with web cams the compression increased and the kickaster stiffened a lot. So i did put a battery again to see if with the web cams the problem would be solved.

Unfortunately with the stock 5Am battery just spinned the crank and then stopped. i thought that because of the compression maybe the stock battery didn't have the power to turn the motor.

So i tried with a car battery, trying to find out what was the problem, but the same thing happened again. The crank just spinned and then stuck again. After a few tries it wouldn't spin at all!

I removed the starting motor and found that the wires going to the one brush were cut! But the biggest problem was later to be found...the whole starting motor is "burned" (sorry but i can't find the right words to describe it).

So i have to buy a new very expensive starting motor or try to fit a YZF 1000 R1 street bike starting motor, which is very similar to the stock WRF's, as a friend told me.

Because i have no clue about these electric stuff, did anyone have similar problems with the starting motor? What could have caused such a problem?

the 3 years i didn't use the e-start had to to do something with that?

You just need to re-build the starter, and make sure you have a cam with the decompression system that works.

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The starter is not rebuildable because Yamaha sells it as an assembled part.

the thing that worries me the most is why did this happen, since i never abused the starter trying to fire up the bike, and of course if i pay a lot of money to fix what to do to void such a damage again.

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Just because Yamaha doesn't split it out doesn't mean it's not rebuildable. Take it to an automotive repair shop and show them the broken parts, they should be able to match up something to work.

Starters are fairly simple and are all pretty "standard" between models and even makes. Do some digging, it's mostly gears and mounting flanges that are different.

And there is a reason you have ratings on bike batteries and car batteries are not recommended to try. You just found out why. The hard way.

Try a 6.5 ah battery maybe. Otherwise you may have to just strengthen your legs or get a stock cam in there to try.

Mike

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Thanks for the reply.

The problem is that the cost to repair the starter is quite big (a shop told me about 200$), so i will just try to find a used part.

So you think that the cause of the damage was the car battery? Doesn't the relay "control" the Ah going to the starter?

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Thanks for the reply.

The problem is that the cost to repair the starter is quite big (a shop told me about 200$), so i will just try to find a used part.

So you think that the cause of the damage was the car battery? Doesn't the relay "control" the Ah going to the starter?

Nope it doesn't , but it doesn't matter. If the draw off the battery was the starter, then the battery only delivers what the starter needs. It's when you jump with a running car that you run into problems.

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Nope it doesn't , but it doesn't matter. If the draw off the battery was the starter, then the battery only delivers what the starter needs. It's when you jump with a running car that you run into problems.

Well seems then that the running car was the cause of the problem...

I will try to repair the starter with parts from other bikes and hope it will spin the motor.

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It's the starter motor that is too weak to turn the engine, not the battery. They're good enough to start a well tuned stock engine and that's about it. I had arc spots across many of the commutator segments. I'm not sure how much it would have cost to have it re-built, but I suspected close to the cost of a new starter. I found a great deal on a used one off ebay and I haven't had any problems since. My engine is all stock, though.

FYI, YFZ450 (quad) starters are also the same.

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Nope it doesn't , but it doesn't matter. If the draw off the battery was the starter, then the battery only delivers what the starter needs. It's when you jump with a running car that you run into problems.

Correct, and I didn't spell that out in my original post, and you are far safer to try a car battery when it is unhook or on a non-running vehicle.

But also remember that a starter can only safely crank an engine for 5-10 second bursts with 10-20 second pauses in between them to cool down the windings. If you hit the starter and leave it spinning for a long period of time (30-40 seconds repeatedly) you can damage the windings. With a car battery you can spin and spin the engine far longer without drawing down the battery like you would with a bike battery, another reason you MUST be careful with a car battery jump, even out of the car.

My buddy had a couple split apart starters at his shop with burnt windings to show people what a car running jump start and car batteries being used can do.

Al lot of people bitch about WR starters being so bad, but with proper battery and starter maintenance it will actually be VERY reliable and works great with a stock, or stock compression released cam. My 04 starts hot or cold EVERY time I hit the button, even after a long Minnesota winter. Doesn't take much to keep it good and working and I even have a 3 or 4 year old cheap ass battery in it.

Mike

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My 03 had simular problem, but it turned out to be the starter clutch was falling apart. I replaced the starter clutch and its still working great. Never had issues with the key either.

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Thanks for the replies everyone. They will be a useful guide in the future.

I found many used YFZ 450 starters on ebay but i am not sure if they will fit because they seem slightly different from the pics. Anybody knows for sure?

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I went through this darn starter problem. When you heat up the starter the springs will compress and the brushes wont get good contact. I have already done this. I replaced the springs and brushes and the starter didnt work well. Buying another starter was my best choice. 350 bucks new. I did parts searches and couldnt ever find a cheap alternitive. Good luck these starters... threads have been covered tons of times. I really think these starters are barely strong enough for the motor. I use my starter only after the motor is warm.

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I found many used YFZ 450 starters on ebay but i am not sure if they will fit because they seem slightly different from the pics. Anybody knows for sure?
Sorry, I'm not certain, however, based on the following link that explains Yamaha part numbers, the starter motor, damper assy, idler gear and starter gear will interchange between 04 WR and 04 YFZ. There was no YFZ in 03 and some of the 03 WR starter parts were upgraded in 04, but the 03 and 04 WR starters are the same, as are most of the other starter system parts.

YFZ450 starter - 5TG-81890-00-00 -vs- WR450 starter - 5TJ-81890-20-00

http://www.thumpertalk.com/forum/showthread.php?t=871275&highlight=yamaha+part+numbers

Edited by bg10459

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Well some upgrades with the problem.

I took my starter to a shop and repaired it for 50$, so now it works again as a new one.

But i had again the same problems with the webcams. It is impossible for the starter to spin the motor.

So i took the webcams off and installed the OEM cams to find out that the starter works great with them...

Web cams increase the compression of the motor a lot.

So, the #963 grind at web cams catalogue is recommended for YZF's and YFZ's, but not for WRF's, because it is a race spec grind.

YFZ's have a different starter compared with the one of the WRF's. It seems bigger. I beleive that a YFZ starter will have the power to spin the motor, but i am not sure if it will fit my WRF.

So any help will be highly appreciated!

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Nope it doesn't , but it doesn't matter. If the draw off the battery was the starter, then the battery only delivers what the starter needs. It's when you jump with a running car that you run into problems.
Oh my lord someone that gets it!!!!!!! Thank you!

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When the starter motor didn't turn because the engine's compression load was too high, the starter motor acted like a dead short and all the amps the battery could give went right into the starter windings. Since no work was being done, all those amps generated a lot of heat and it sounds like it didn't take long to cook the motor.

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Good news! I found the solution finally (after a burned starter and many hours of searching)...

I had to retard the exhaust cam! Now the bike fires up just fine:ride:

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Hello, I am sorry, my english IS bad

I have the same issue on the same bike upgraded, i installed a new starter motor, i only used it 2 times and nothing after. Engine takes more time to run (more than 4 revolutions), i noticed it. I test starter motor directly with an other battery, nothing happens. I think it dies.

I tested the kick starter, and i heard a noise like cracked gears by the stator side. Starter motor gear teeth were damaged. I pulled the assy damper limiter out and i can start again my bike. No more noise. I reinstalled the damper limiter, same issue.

Someone met this problem. I ordered a new starter motor, I think receive or next week. I would not damage a new one. Someone knows How to control the starter clutch and the damper assy ?

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