Wr dad with sons YZ issues (OK'd by WR Mod)


24 replies to this topic
  • bluebike1999

Posted December 18, 2008 - 02:46 PM

#1

I know this isnt the YZ forum, but i have posted there. This forum has the most concentrated knowledge base so i thought id ask here and if it gets moved, well so be it.

http://www.thumperta...075#post7369075

My sons YZ 85 is farting out once its been in the band for a couple of gears.
It dies, then a big pop.
Its been fully rebuilt, new stator, and now i suspect the CDI or coil..
How do i tell and what are the symptoms of a stuffed CDI?
Im about to take a whizz to town to get the CDI tested, but im not sure who can or how.

Any suggestions.?
Clark, please leave it a day or so before either moving or binning it as there is possibly only 5000 dads with WR's who kids have yz 85's on here..thanks
a

  • Charles De Mar

Posted December 18, 2008 - 03:03 PM

#2

I know this isnt the YZ forum, but i have posted there. This forum has the most concentrated knowledge base so i thought id ask here and if it gets moved, well so be it.

http://www.thumperta...075#post7369075

My sons YZ 85 is farting out once its been in the band for a couple of gears.
It dies, then a big pop.
Its been fully rebuilt, new stator, and now i suspect the CDI or coil..
How do i tell and what are the symptoms of a stuffed CDI?
Im about to take a whizz to town to get the CDI tested, but im not sure who can or how.

Any suggestions.?
Clark, please leave it a day or so before either moving or binning it as there is possibly only 5000 dads with WR's who kids have yz 85's on here..thanks
a


check with TT member yzman400. He works on his son's 85 all the time. He loves it:busted:

  • GCannon

Posted December 18, 2008 - 04:29 PM

#3

Boy the manual is no help! It says test everything else and then replace the CDI . The Spark Gap test could be help full the wider gap will load the system and may help duplicate the problem in the shop.

Give a careful check of the sparkplug boot and wire between the coil and the plug it need a goood mechanical as well as electrical connection and can break down from being pulled on for service.

I can send you the manual if you need one. or you can download off the Yamaha of "OZ" site

Do all the Stater tests check out?

  • mercier24

Posted December 18, 2008 - 04:48 PM

#4

The timing could be off, or maybe the carb? Unless you already had that straightend out in the rebuild.

  • PumpkinHumper

Posted December 18, 2008 - 04:55 PM

#5

I know this isnt the YZ forum, but i have posted there. This forum has the most concentrated knowledge base so i thought id ask here and if it gets moved, well so be it.

http://www.thumperta...075#post7369075

My sons YZ 85 is farting out once its been in the band for a couple of gears.
It dies, then a big pop.
Its been fully rebuilt, new stator, and now i suspect the CDI or coil..
How do i tell and what are the symptoms of a stuffed CDI?
Im about to take a whizz to town to get the CDI tested, but im not sure who can or how.

Any suggestions.?
Clark, please leave it a day or so before either moving or binning it as there is possibly only 5000 dads with WR's who kids have yz 85's on here..thanks
a



You say fully rebuilt...How fully. Top end of top end and crank?

Is it fowling the plug when it dies? My 1st thought is crank seals. If you have a leaky crank seal it will let tranny oil into the cylinder making it run rich and fowl a plug. Usualy when you replace a crank you replace the crank seals also which is why I was wondering how complete you rebuilt it.

How do the reeds look? Are they chipped or starting to bend away from the cage?

What year is this bike? When is the last time that it ran good and what has changed since then?

Have you had the carb apart and cleaned. All the jets are clear? Float level set correctly?

It could be about anything. Gonna need more info to narrow it down. CDI's rarely go out. Id be suprised if that was it.

Why did you replace the stator?


As CDM said I have a 03 YZ85 that my son races and I have had that thing apart every which way so Im fairly intimate with these little bikes.

  • PumpkinHumper

Posted December 18, 2008 - 04:57 PM

#6

Oops just clicked on your link...You powdercoated the frame. Did you grind away the powdercoat where the coil mounts. The coil grounds to the frame I believe. Maybe your not getting a good ground. Also possible that the motor needs to be grounded as well. Stator mounts to the motor motor mounts to the frame. Motor might not be getting a good ground.

  • bluebike1999

Posted December 18, 2008 - 06:14 PM

#7

thanks heaps so far for your input

Fully rebuilt was
new crank pin, rod, (and seals) piston, rings, barrel, bottom and top end bearings, main bearings.

I'll try and answer questions in order
I just took the coil and CDI to an auto electrician (said he couldnt check CDI without a book and numbers) and yes there was an issue with the spark plug boot, apparently the coil is two coils, a low and high speed one and we got inconsistent readings back from it, so i raced home and grabbed another coil of another bike (pw80) and tried it, the bike runs prefectly, in fact goes like a bloody hammer, then its just like the kill swith is pressed then a pop then it goes again, and thats what it was doing when i first took it get checked out.

Havent done any stator tests seeing its brand new, what would you suggest i test as far as the stator goes?

not sure about timing as it goes perfect, idles perfect, and i have had this carb apart so many times, it all appears ok and clean. the 1st mystery to me is that it runs so well until its been in the band 3 maybe 4 times then the farts begin

no, not fouling plug, unless they can be only fouled for a second or two, i put a new one in last week and i have had the boy out to test it so many times too, that he rides off, holds it flat up the paddock, and just when we think its fixed, dies for about 3-5 seconds, pops and fires back up again.
Coil / powder coat. I made sure it had good contact there when we reassembled it, but again, the bike runs perfectly

Reeds are fine, barely even looks used. It has a v force reed block, it was one of those special deal ones here in Oz comes with pro tapers, race tech suspension, FMF fatty and a shorty pipe, holeshot button and the reed block and some other stuff

I replaced stator cause the fella who rebuilt it said (over the phone) "sounds like the stator" and seeing I sell genuine Yamaha parts from my sites www.dirtbikestuff.com.au and www.trailriderz.com.au and cause i get it cheap, I just grabbed one, but no difference. but a CDI is still a fair amount of money ($200) auso im just checking before i keep spending.

carb, floats and jets all fine

thanks all very much for your help so far. me and the boy put it on its stand and walked off (again) , he says "thanks for trying Dad" everytime and i'd love to get it all fixed for a ride we are going on over summer, he's 10 and hangin to go.
heres some pics of it
Posted Image
Posted Image

  • PumpkinHumper

Posted December 18, 2008 - 06:58 PM

#8

Ok that helps. Motor sounds like it is solid. Carb and reeds are probably ok. Plug isn't fowling. Its gotta be electrical.

1st thing to check is pull the tank and unplug the kill switch and try running it again. Could be that the kill switch is grounding to the bar.

Coils usualy either work or dont. No middle ground. Same with the CDI. I assume you have but have you looked at every electrical connection and check for corosion or loose connections.

If you can find someone that has a YZ85 see if you can con them to let you swap out the entire electrical system to see if that fixes the problem. Sounds like all that is left is the coil and cdi anyways.

Just another thought the Stator has slots in where it bolts to the motor. You did bolt on the new stator in the exact same place as the old one. You can advance and retard the timing by turning the stator one way or the other. That can cause bad things I would think if its not set right.

  • madmaxter39

Posted December 18, 2008 - 06:58 PM

#9

Blue, I've been there and done that too. My son's bike was only the spark plug boot, I ran it in the dark and noticed blue spark would jump out from the boot, where it connects to the plug, and just go wild sparking all around the engine and frame and the engine would die. Put a new spark plug boot on it and the problem was gone. YZ's seem to have this issue for some reason. Hope this helps

  • bluebike1999

Posted December 18, 2008 - 08:17 PM

#10

yep, the boot actually tested a bit dodgy at the auto electrician so i have another one on its way
yzman, i see what you mean about intimate...i know this little bugger inside out...the boy is hopeful every time we wheel it out to 'try this'...and each time it farts and dies out i can see he's dissappointed...he loves this bike, cant even touch the ground but we'll forge on.

and we have tried disconnecting the kill switch. the mechanic we go to does that to almost every bike as a first check...

yep stator went on the exact same spot. the most puzzling thing is that it goes so well...when it goes.

spark plug boot is on its way, wife will be home from town with it soon, so we'll give that a shot....but the other coil complete with plug boot didnt change anything...

might just drain the carb again while im waiting and have some more thinks

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  • Matt James

Posted December 18, 2008 - 08:24 PM

#11

It could be the coil. When the start to fail it begins like your symptom. They get got and break down. See if you can borrow a coil and try it.

  • bluebike1999

Posted December 18, 2008 - 10:03 PM

#12

just got the new boot and tried it, worse wont even get into the band..which is good somehow...the plug cap its got is a real big blue hammer head style one, so i pulled the new one off, and as i did, i noticed the wire out of the coil lead was hanging out a bit and i pulled it and the wire came out, about half an inch worth, so i cut the rubber back about 10mm and cut the wires neat, plugged the original cap in, same thing, not even into the band, new cap, even worse....:thumbsup: i have suspicions along coil wire..so digging up yet another coil to try....


and i have, my wifes ttr 230 one, the one out of my wr 400 and yz 250 are too big, put the ttr 230 one in...FIXED.... i thought that maybe the one out of the pw 80 wasnt enough to run it flat out, so its the 230's for now
it is going harder than ever, has given the boy a bit of a fright already, but all i can hear from in here is the 85 on the band...neighbours will be stoked its fixed....he is absolutely rapt, and we are just about to go for ride to see how it goes

thanks everyone for their assistance.

  • bluebike1999

Posted December 18, 2008 - 10:36 PM

#13

spoke too soon...we went for a ride and it was going prefect for over twenty minutes...we even had a drag up the road (gravel) in which i narrowly won, and went on a celebration run further in the bush, and on a big hill he powered all the way up then it did it again,...bluuuuuuurrrrrrrrr ffffftt

looks like its a CDI after all....run out of low dollar fixes

thanks and i'll keep you updated

  • PumpkinHumper

Posted December 19, 2008 - 07:34 AM

#14

I have another idea.... And you (and I) are going to kick ourselves if this is it.

Check your gas cap vent line. Is it venting? Does it have one of those one way check valve's in the vent line? sometimes those dont vent or get stuck. If it has one of those check valves in take it off. Heck take the entire vent line off and see if that helps. Can you blow into the end of he line and blow air thru the gas cap into the tank?

It could be creating a vauume in the tank and not allowing fuel to flow to the engine. Ive had it happen to me before on my Honda. Worth checking out.

  • grayracer513

Posted December 19, 2008 - 09:06 AM

#15

I have another idea.... And you (and I) are going to kick ourselves if this is it.

Check your gas cap vent line. Is it venting? Does it have one of those one way check valve's in the vent line? sometimes those dont vent or get stuck. If it has one of those check valves in take it off. Heck take the entire vent line off and see if that helps. Can you blow into the end of he line and blow air thru the gas cap into the tank?

It could be creating a vauume in the tank and not allowing fuel to flow to the engine. Ive had it happen to me before on my Honda. Worth checking out.

That's where I was going with this. :thumbsup:

  • clark4131

Posted December 19, 2008 - 11:39 PM

#16

It looks like you guys are getting the problem nailed down. I'm gonna let it slide for a few more days, but them I need to merge it over to the 2-stroke area. If you get it all squared away in the next day or two, shoot me a PM. Best of luck...SC

  • tunefx

Posted December 20, 2008 - 08:51 AM

#17

Clark, thanks for keeping it here a bit. This is a great thread. It's like a good movie. We are all pulling for the kid because we can feel his pain! Hoping it's fixed before Christmas!

  • bluebike1999

Posted December 21, 2008 - 02:09 AM

#18

well, it did it again yesterday after putting in the new coil, but it was only when we went flat out up the road. Tonight, me and the 8yo (pw80) and 10yo (yz85) hve been racing around a small oval track we have here in the paddock, and he kicked us and it never missed a beat. we did possibly 30 40 laps and the thing went like a rocket the whole time. it really is a weapon

Posted Image
(little bloke has a shorter circuit but produces same laps times)
So i think i'll go for a new coil, even though the cDI is in the back of my mind.
he says if he doesnt hold it flat to the end of the throttle it doesnt do it and the wife will want a ride on her ttr 230 over summer so i better get a yz coil in for now.
thanks very much for all your input, i did check the hose going into the tank as about the 15th free fix/ check, but will check it again.

so in summary..the symptoms that have still occured are that it will die once its been in the power band in 1st 2nd 3rd flat, then a farty pop then starts again. If you have any ideas, please feel free to let me know

We are planning a ride together, last one was 115 km and they both did that on the pw80's and it was a big day, so hoping for a trouble free run
thanks again and thanks Clark for allowing access to the brains trust

  • clark4131

Posted December 21, 2008 - 08:29 PM

#19

It'll stick around for a while if you need some more help. I feel your pain. It took me forever to get the carb on my kid's TTR50 dialed in and he really wanted to ride it. Merry Merry...SC

  • grayracer513

Posted December 28, 2008 - 09:55 AM

#20

Are you just going to ignore the advice regarding the gas tank ventilation, or have you checked that and I missed it?

Very poor fuel delivery due to a clogged screen in the petcock or needle seat is another possibility.




 
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