tlmark
Drag-strip hero
Posts: 203
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Post by tlmark on Jul 23, 2020 19:32:54 GMT 1
So this happened 
less than a thousand miles after her restoration she seized on me.
well she nipped up to be fair. I guess it wouldn't be the true LC experance with out it 
10mins later she started and got me home with out fuss, all be it a little rough. I'm hoping to pull the top end off this weekend I'm guessing a nicely smeared piston on the bore.
Ho Hum  |
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Post by Gitram on Jul 23, 2020 19:47:43 GMT 1
that's a blow.. but, best of luck
marti
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Post by stusco on Jul 23, 2020 19:53:04 GMT 1
Bummer were you giving it some welly?
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Damn it!
Jul 23, 2020 19:55:28 GMT 1
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Post by doohanno1 on Jul 23, 2020 19:55:28 GMT 1
Ah bummer, hopefully you get away lightly..wonder what contributed to that.🤔
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Post by midlifecrisisrd on Jul 23, 2020 19:56:29 GMT 1
Unusual it lasted 1k miles 🤔
Steve
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Damn it!
Jul 23, 2020 19:57:39 GMT 1
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Post by midlifecrisisrd on Jul 23, 2020 19:57:39 GMT 1
Sorry, should have said - bummer
Hopefully something not too serious (if a seizure isn't bad enough)
Steve
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Post by tony2stroke on Jul 23, 2020 21:40:25 GMT 1
Such is the life of a 2 stroke owner, never goes as planned.
Hope its nothing bad.
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Post by arrow on Jul 23, 2020 21:48:45 GMT 1
Sorry to hear this, nice looking bike.
According to my memory banks, I've not seen your oil pump.
Although, other reasons are possible of course.
How fast were you going when it seized?
I'll put my rep. on the line and say 50~60mph?
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Post by chrisg on Jul 23, 2020 22:31:27 GMT 1
My first thought is oil pump, followed by jetting/timing.
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Post by shaunthe2nd on Jul 23, 2020 22:38:27 GMT 1
Oh no, it looks a beauty too.
Hope you get to the bottom of it and not too expensive to resolve.
The strewn clothing looks like you stripped and stropped off!
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Post by JonW on Jul 24, 2020 1:07:08 GMT 1
deceleration rather than being on-it?
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Post by dusty350 on Jul 24, 2020 7:05:02 GMT 1
Sorry to hear that  I bet all of us here have an image like your pic - staring back at a broken bike Mine was on the M25 ! Still, they are rebuildable, and I'm sure you'll still see a fair bit of summer riding when it's sorted. Hope you find the reason for the seize first though  Good luck Dusty  |
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Damn it!
Jul 24, 2020 7:34:44 GMT 1
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Post by flames on Jul 24, 2020 7:34:44 GMT 1
Bugger!
They are rebuildable but make sure you find the cause 1st. It's worth sending oil pump to Arrow whilst you are re building just for peace of mind. Hope you get sorted soon. Bike looks lush btw.
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tlmark
Drag-strip hero
Posts: 203
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Damn it!
Jul 24, 2020 8:07:55 GMT 1
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Post by tlmark on Jul 24, 2020 8:07:55 GMT 1
Sorry to hear this, nice looking bike. According to my memory banks, I've not seen your oil pump. Although, other reasons are possible of course. How fast were you going when it seized? I'll put my rep. on the line and say 50~60mph? Wow yup bang on! It was a new pump from Norbo as wen I started the rebuild I found it was a 250 pump |
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Post by arrow on Jul 24, 2020 8:13:55 GMT 1
Did you fit the correct 350 wormshaft also?
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Damn it!
Jul 24, 2020 8:21:35 GMT 1
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Post by beardy on Jul 24, 2020 8:21:35 GMT 1
Sorry to hear this, nice looking bike. According to my memory banks, I've not seen your oil pump. Although, other reasons are possible of course. How fast were you going when it seized? I'll put my rep. on the line and say 50~60mph? Wow yup bang on! It was a new pump from Norbo as wen I started the rebuild I found it was a 250 pump That’s certainly not the sort of speed I’d expect a seizure. Hopefully Arrow will give some pointers as to why it happened. |
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Damn it!
Jul 24, 2020 8:51:57 GMT 1
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Post by chrisg on Jul 24, 2020 8:51:57 GMT 1
Wow yup bang on! It was a new pump from Norbo as wen I started the rebuild I found it was a 250 pump That’s certainly not the sort of speed I’d expect a seizure. Hopefully Arrow will give some pointers as to why it happened. On deceleration the bike is getting very little fuel and hence not carrying the oil to the cylinders, just thinking out load 😕 |
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Post by arrow on Jul 24, 2020 9:14:17 GMT 1
The Yamaha engineers developed the pump to deliver the correct amount of oil in every given scenario, including off throttle deceleration.
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Post by midlifecrisisrd on Jul 24, 2020 9:35:47 GMT 1
I would guess that arrow's 50-60mph premonition would be down to the crucial point where an undershimmed pump has a small throttle opening, a decent amount of revs and very little oil
Am I right in thinking new pumps only have the one same shim fitted so should be checked at fitting
May not be the issue though
Small throttle openings are probably the leanest point
Steve
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Post by arrow on Jul 24, 2020 9:38:11 GMT 1
Totally correct Steve, and we also need to establish if the wormshaft was swapped for the correct one.
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tlmark
Drag-strip hero
Posts: 203
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Damn it!
Jul 24, 2020 10:00:30 GMT 1
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Post by tlmark on Jul 24, 2020 10:00:30 GMT 1
Yup bought the worm shaft at the same time
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Post by oldbritguy on Jul 24, 2020 10:07:05 GMT 1
Sh*t, that is bad news indeed. You will be gutted after all that work getting the bike finished and looking like she is.
Still, on a plus, it can be fixed and there are no big expensive bits of metal sticking out the front of the motor.
Hopefully a quick and straightforward fix.
Let us know what you find
John
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Post by arrow on Jul 24, 2020 10:11:05 GMT 1
A small minimum stroke on the pump should not have caused this on its own. It could have been slightly advanced/lean/hot as well.
You need to investigate this.
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Post by 4l04ever on Jul 24, 2020 10:19:28 GMT 1
If not stripped yet, I would perform a leak down test to check for any contributory air leaks. Once that is determined, get some pics of the piston on the side that seized and post up. There are some good two stroke piston diagnosis reference pics available on the internet.
Good luck with the rebuild.
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Post by 4l04ever on Jul 24, 2020 10:28:32 GMT 1
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Post by 4l04ever on Jul 24, 2020 10:36:12 GMT 1
If pump was new, it is probably not that.
If timing was set correctly, it is unlikely to change, so probably unlikely to be the cause.
Most likely to have gone lean. Could be an air leak, maybe crank seal or elsewhere. A leak down test will confirm if it has an air leak or not. It could be that the jets are not made to spec, so could be undersized, or that your bike actually needs bigger than standard jets.
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tlmark
Drag-strip hero
Posts: 203
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Damn it!
Jul 24, 2020 10:51:14 GMT 1
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Post by tlmark on Jul 24, 2020 10:51:14 GMT 1
With seeing inside yet I wouldn’t mind guessing it’s the right hand pot
That didn’t smoke as much as the left
Not sure the piston will tell to much as I wound the pump cable adjuster
To pump more before I rode home a good 15 miles
I also put my spare plugs in as well
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Damn it!
Jul 24, 2020 10:51:33 GMT 1
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Post by midlifecrisisrd on Jul 24, 2020 10:51:33 GMT 1
Hopefully not a Yambits crank seal scenario 😬
As has been said do a leak down to prove no leaks then have a look inside the top end
Steve
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Damn it!
Jul 24, 2020 10:53:30 GMT 1
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Post by midlifecrisisrd on Jul 24, 2020 10:53:30 GMT 1
Oh and what size bore is it on?
Just wondering if 2mm or over can that not affect chamber volume/compression
Steve
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tlmark
Drag-strip hero
Posts: 203
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Post by tlmark on Jul 24, 2020 11:55:21 GMT 1
Hopefully not a Yambits crank seal scenario 😬 As has been said do a leak down to prove no leaks then have a look inside the top end Steve No Mate gen Yam from fowlers |
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