Author Topic: 125H runs for 5 minutes then dies  (Read 29737 times)

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Offline Hoony

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Re: 125H runs for 5 minutes then dies
« Reply #60 on: October 20, 2007, 07:32:57 pm »
YZ250H,

you need to check all around the water pump housing for any pin holes to oil side of case. i am by no means a yamaha expert (that's Hilly, Nathan & the Bonester) but i do know Honda's and they all have a problem with electrolysis in this area, also check the water pump shaft for wear where the seal sits as the seals do wear the shaft (on honda's anyway). good luck mate, i have been following this thread with interest and want to know the final outcome.
Long time Honda Fan, but all bike nut in general, Big Bore 2 stroke fan.    http://www.youtube.com/watch?v=XJoKP6MawYI
1985 Honda CR500RF "Big Red"
1986 Honda CR250RG
2005 KTM 300EXC "The GruntMeister" ( I love that engine)

Offline DJRacing

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Re: 125H runs for 5 minutes then dies
« Reply #61 on: October 22, 2007, 08:19:49 pm »
YZ250H
  Dont use any sealant between the head and barrel, the O-rings do a good job. But replace the water pump seal (93103-12119).
Good luck
If at first you dont succeed, give up and drink beer

Offline YZ250H

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Re: 125H runs for 5 minutes then dies
« Reply #62 on: October 23, 2007, 09:54:50 am »
A couple of things I have checked.
Reed block looks OK to me.  They seem to close nice and tightly.  Maybe you can identify it from the photo  ???


Pokey,
Is this good enough - note a couple of minor pits remain.  How good do they need to be ?


My major concern is the clutch basket at the moment.  The other one was eaten out the same.  The gears don't seem to be meshing properly and I can't see from the parts book that there is a washer added (or missing).  Any ideas.


I've ordred the new water pump seal and priced a new impellor with shaft $65.60  :o :o  Do you think it wise to just try the seal first ??
Cheers
T.J.B.
Looking for YZ250C parts NOS if possible

"My inability to use emoticins in the right context is really getting me down :)
The only triple jumps he would have been doing are the hop, skip & jump.

Offline DJRacing

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Re: 125H runs for 5 minutes then dies
« Reply #63 on: October 23, 2007, 10:17:21 am »
Try the seal, unless you think you really need the new impellor shaft. The mating surfacers for the head and barrel look ok. Has the clutch basket come loose at some time? There are 2 washers on the clutch, one between the bearing and the basket and then one between the basket and the clutch boss. (90201-174E1). Make sure you have a lock-tab washer on so the main nut doesnt come loose.
If at first you dont succeed, give up and drink beer

Offline Hoony

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Re: 125H runs for 5 minutes then dies
« Reply #64 on: October 23, 2007, 10:44:08 am »
water pump impellar shaft may be ok , did you check if it is worn where the seal (seals) runs on it ?

question for DJ Racing do the yamaha's YZ125 H's run 2 seals or one ?
Long time Honda Fan, but all bike nut in general, Big Bore 2 stroke fan.    http://www.youtube.com/watch?v=XJoKP6MawYI
1985 Honda CR500RF "Big Red"
1986 Honda CR250RG
2005 KTM 300EXC "The GruntMeister" ( I love that engine)

Offline DJRacing

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Re: 125H runs for 5 minutes then dies
« Reply #65 on: October 23, 2007, 10:51:55 am »
The YZ125H/J run one waterpump seal (93103-12119) which is ID-12mm OD-31mm W-13.5mm.
If at first you dont succeed, give up and drink beer

Offline pokey

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Re: 125H runs for 5 minutes then dies
« Reply #66 on: October 23, 2007, 12:05:24 pm »
Bit hard for a picture to convey truness of surfaces. thats what engineering ink is for.  Can also check with a straight edge and feeler gauges  but the ink is best and easiest. It does look like you have done an okay job on them.
as long as you have a decent  surface around all journals  and no high points she should be right but do check with the ink.

 I can i believe see one pit on the head that may be on the combustion/water sealing surface, rub it out if you can. If its pretty deep fill it with sealant like stag or a hi temp ceramic epoxy then a rub after it hardens and finishes shrinking.

 looks like its coming along fine

BONEHEAD

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Re: 125H runs for 5 minutes then dies
« Reply #67 on: October 23, 2007, 06:16:39 pm »
im back from holidays ;D ;D and looks like you have possibly found the concern with the bike, like i suggested before if the gearbox oil is milky you have a coolant leak from the waterpump seal and possibly a worn shaft on the impeller, this inturn creates pressure build up in the crankcase due to the extra fluid entering but should expell via the crankcase breather unless the crankseals are worn when then it will enter the combustion chamber causing it to not run, rust in the bore suggests this ,as when left sitting the electolisis process starts, DO NOT USE STAG, this is only used for putting in welsh plugs in V8 1970 - on vehicles , as far as the clutch basket goes , looks like it has run loose, anyway im keen to see this bitch run ,its good to be back on board, CHEERS ;D ;D

Offline YZ250H

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Re: 125H runs for 5 minutes then dies
« Reply #68 on: October 24, 2007, 09:58:46 am »
Boney, I thought a sniper had got ya or something  ;D
I have since learnt from Hilly that stag is only good for filling plumbers cracks (which we get around our house occasionally  :D)
Knowing what I know now I'm pretty sure there was water leaking in everywhere (at the head and at the impellor seal).  I haven't looked at the shaft, but will this week-end.
I will have another crack at the head lapping.  I used the Nikko pen and it seemed to be flat as a tack, so should be OK.  That pit you see on the head is on the outside of the sealing area of the inner O'ring, but I will do some more lapping and see if I can get it out.  It took me a long time to get it to this and I basically got the sh1ts with it by the end.  I was having a beer while I was doing it and there was quite a few empties hanging around by the time I finished :-[.  For some reason the number 8 keeps coming into my head  ;D
Hopefully new head O rings and flat surfaces, new crank seals, SEALED case halves and impellor seal will solve the bigger problems and then I can get onto the smaller stuff.
The clutch basket was done up with the impact wrench and has a locking tab.  I will have another look at the washers as I may have overlooked something.  I may have one of the washers in the wrong place.  I'll make certain on reassembly.  I put everything back together as I found it, so maybe the "mechanic" that put it back together before me got it wrong.  Time will tell (not too much time Hilly ;D)
Looking for YZ250C parts NOS if possible

"My inability to use emoticins in the right context is really getting me down :)
The only triple jumps he would have been doing are the hop, skip & jump.

Offline DJRacing

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Re: 125H runs for 5 minutes then dies
« Reply #69 on: October 24, 2007, 02:57:26 pm »
Yeah lapping heads is a boring bastard of a job and the closer you get to having all the pits/dents removed the longer it seems to take ;) ;D
If at first you dont succeed, give up and drink beer

Offline YZ250H

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Re: 125H runs for 5 minutes then dies
« Reply #70 on: October 24, 2007, 03:01:17 pm »
I actually have to confess to starting the second piece (barrel) with coarser paper than 1500  :-[
Patience is a virtue I don't have a lot of.
Looking for YZ250C parts NOS if possible

"My inability to use emoticins in the right context is really getting me down :)
The only triple jumps he would have been doing are the hop, skip & jump.

BONEHEAD

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Re: 125H runs for 5 minutes then dies
« Reply #71 on: October 24, 2007, 08:05:08 pm »
YOU NEED TO DRINK MORE BEER , as you work, you also may require to use your imagination, for example what could you do with the latest pin up girl from the magazine you just bought ;D or do the lawns need mowing  ???or am i paying enough attention to my wife  ::)or WILL THIS THING EVER RUN ;D cheers  ;D oh the joys ,lets hope its all ok  ;)

Offline YZ250H

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Re: 125H runs for 5 minutes then dies
« Reply #72 on: October 29, 2007, 09:52:12 am »
Sorry Dudes,
Mr Yamaha did not come through with his promise of having the case halves ready by Friday  >:( so it's next monday for the video.
Looking for YZ250C parts NOS if possible

"My inability to use emoticins in the right context is really getting me down :)
The only triple jumps he would have been doing are the hop, skip & jump.

Offline DJRacing

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Re: 125H runs for 5 minutes then dies
« Reply #73 on: October 29, 2007, 03:55:49 pm »
Dont worry YZ250H, it has been good trying to figure out the problem, but I'm sure by now you wish you had the bike up and running ;D ;)
If at first you dont succeed, give up and drink beer

Offline YZ250H

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Re: 125H runs for 5 minutes then dies
« Reply #74 on: October 29, 2007, 05:04:04 pm »
You're not wrong there DJ.  Talk about trial by ordeal on my first VMXer  :o ;D
I had a brain wave (rare for me) over the week-end that I think will definitely confirm it is water related.  When I first got the bike it hadn't been started for a long, long time.  I just mixed up some fuel, literally 3 kicks and away she went  8).  I could only ride it around for a few minutes at a time 'cause the water pump cover was missing and no water in a watercooled bike I'm guessing is a no no.  SOOOO I put a new cover on and filled her up with water.  That's when the trouble started.  It amazing what 20/20 hindsight can do.  I'm still not counting my chickens yet, but I reckon we are most of the way there  8)  I still have a long way to go before I have the knowledge of you blokes, but believe me I have learn't a hell of a lot about this bike and now feel quite comfortable delving into splitting cases etc.  Thanks once again to all you guys for your tips and ideas.  Should set me up well for the other restos I have to do.  Next comes the 250 8) 8) (now that I have something going to ride) and Nathan's 125H 8) - then the others.
It seems like forever ago that this whole saga started with a wayward bolt jamming in the clutch gears.
Looking for YZ250C parts NOS if possible

"My inability to use emoticins in the right context is really getting me down :)
The only triple jumps he would have been doing are the hop, skip & jump.