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ART-ADS
Nova Slayer



Joined: 09 Feb 2018
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PostPosted: 11:16 - 01 Mar 2019    Post subject: valve snapped Reply with quote

intake valve snapped in the head, near the top where it holds the spring on.

is it easier to just buy a new valve and do a top end or try and use a spare engine i have lying around, i dont know if the second engine runs

caused by cam chain gear bolts breaking off and cam chain falling out of its place
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MarJay
But it's British!



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PostPosted: 11:30 - 01 Mar 2019    Post subject: Reply with quote

Spare engine. You don't know what bits are now floating around in the oilways of that engine. The only way to be sure would be to do a nut and bolt rebuild...
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Riejufixing
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PostPosted: 12:22 - 01 Mar 2019    Post subject: Re: valve snapped Reply with quote

ART-ADS wrote:
intake valve snapped in the head, near the top where it holds the spring on.

is it easier to just buy a new valve and do a top end or try and use a spare engine i have lying around, i dont know if the second engine runs


"valve stem ... valve collets"

Anyway, the only way to tell what's happened to your engine is to take the head off and have a look. Further dismantling may be needed. You may as well do that straight away, 'cos unless you know what the damage is, you won't know whether you need to investigate your other engine, which may in itself be unserviceable...
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Teflon-Mike
tl;dr



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PostPosted: 12:56 - 01 Mar 2019    Post subject: Re: valve snapped Reply with quote

ART-ADS wrote:
intake valve snapped in the head, near the top where it holds the spring on.

is it easier to just buy a new valve and do a top end or try and use a spare engine i have lying around, i dont know if the second engine runs

caused by cam chain gear bolts breaking off and cam chain falling out of its place


A brand new valve, is likely only a tenner or so... so what do you think you might 'save' trying to take one from a scrapper, when that will likely double the work to get at the dang thing!

Meanwhile, as said.... valves don't tend to just break... they tend to get broken.

Cam chain gear bolts breaking? Ugh? I think the suggestion there is that the cam-chain slipped.... other wise called a 'timing chain'... the usual consequence is that the piston comes up on an open valve and lamps it one.

Consequent carnage, tends to be rather dire. And the first port of call is to look at the piston, which quite likely has had a hole punched in it by the valve.... piston 'soft' alloy... valve, hardened high grade steel... hmmm....

If piston smacks the valve, it will likely bend the valve stem, and you will likely have a devils job to get the thing out of the head, because the bent stem will be stuck in the valve guide... which it most often cracks along the way, cos its a soft porous iron.. and if piston-valve interference didn't crack it... trying to pull a bent valve out probably will.

Next up, and suggestion that the valve stem crack at the collets.... collets sit in a groove in the top of the valve stem, this is then a natural weak-spot, BUT, for it to actually 'snap' something has had to hit it pretty hard, and it's not shoved it some-where else, so the piston coming 'up' has met valve coming 'down', valve pushed by cam via probably a rocker... so if the valve has taken a smack, so have they...

What state is the rocker in? What state the cam? This sort of catastrophe can bend or break rockers, and re-using them can be daft, cos the stress they suffered, IF it isn't apparent when you take them out, can see them bend or break in later use. Meanwhile, the smack that the valve took, it would shove back at the cam, frequently denting or 'flatting' it.. a flat-spot on the cam, will then cock-up the timing, but the profile will have been changed, and if you think, of the acceleration that the cam is causing from the change in height over 1/4 turn, put a ding in that, and even though the change in height may be fractions of a mm, rather than whole mm... as the follower rides over the ding, in only a few degrees, the 'acceleration' it will cause is enormous, and even if the 'ding' hasn't broken through the surface hardening of the cam... the accelerated wear of further use will.

In short?

Theres FAR more and far bigger fish to fry here, than 'just' whether its easier to buy a new valve or try and salvage one from another engine!

Answer is its easier to buy a new valve..... BUT there's so much else to be looking at, ans so much else likely to have been damaged, and so much that could need replacing whilst in there.... IF you have a take-out engine to pillage... it MAY be as easy/cheap to cannibalise that for ALL that is in question... and have fewer question marks that just trying to swap out one obviously broken bit, and thinking that's that!

But WHY did the cam-chain slip? Bolts dont usually just 'break' either, and it's as likely that the piston smacking open valve whilst cam trying to push valve down, it was the head-on collision of this two that put the force on the bolts to make'em break, so your suggested cause could actually be 'effect' and you STILL need to find out, and fix what caused timing chain to slip......
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A100man
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PostPosted: 13:34 - 01 Mar 2019    Post subject: Re: valve snapped Reply with quote

Teflon-Mike wrote:
..Bolts dont usually just 'break' either, and it's as likely that the piston smacking open valve whilst cam trying to push valve down, it was the head-on collision of this two that put the force on the bolts to make'em break, so your suggested cause could actually be 'effect' and you STILL need to find out, and fix what caused timing chain to slip......


I was thinking that. My suggestion
1) Check compression of spare engine - if good fit.
2) Pull apart nadgered motor for fun if you can be bothered.
3) post pics of what you find.
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ART-ADS
Nova Slayer



Joined: 09 Feb 2018
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PostPosted: 14:20 - 01 Mar 2019    Post subject: Reply with quote

i was told when i bought the engine that it runs perfect 5k miles on it. the guy added me on social media etc so doesnt seem like he's lying

im gunna swap in the new motor, then pull apart the old one and try and see the damage

did i say the other bolt that holds in the cam chain sprocket is still inside the engine somewhere? lol
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Grubscrew
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PostPosted: 19:47 - 01 Mar 2019    Post subject: Reply with quote

If you did buy a new valve and with some engines you may have to ream the internal diameter guide to match the new valve.

If the bike is your baby treat it with new.

If the older valve out of the wrecked engine is in good shape, try it in the guide. I have changed internal engine parts from other units provided they are in good order and are withinn manufacturers spec and not had any problems.
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WD Forte
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PostPosted: 19:54 - 01 Mar 2019    Post subject: Reply with quote

Anyone else wondering what feckin bike hes talking about?
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Grubscrew
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PostPosted: 20:01 - 01 Mar 2019    Post subject: Reply with quote

Probably an Aerial Rolling Eyes
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P.
Red Rocket



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PostPosted: 01:29 - 02 Mar 2019    Post subject: Reply with quote

Probably his faggy chop VT with a handmade exhaust which has allowed the valve to heat itself to oblivion.
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Bhud
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PostPosted: 01:43 - 02 Mar 2019    Post subject: Re: valve snapped Reply with quote

Teflon-Mike wrote:

A brand new valve, is likely only a tenner or so...


Don't know what that guy is riding, but a brand new (old stock) intake valve on my bike can cost £80+ (cheapest I've seen is £35 plus p&p), and a new exhaust valve is simply unavailable.
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bikenut
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PostPosted: 11:43 - 02 Mar 2019    Post subject: jub Reply with quote

Hows the Jubilee??
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redeem ouzzer
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PostPosted: 13:41 - 02 Mar 2019    Post subject: Reply with quote

Paddy. wrote:
Probably his faggy chop VT with a handmade exhaust which has allowed the valve to heat itself to oblivion.


This. I doubt the thick twat is bright enough to use a dyno.
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ART-ADS
Nova Slayer



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PostPosted: 14:12 - 04 Mar 2019    Post subject: Reply with quote

Paddy. wrote:
Probably his faggy chop VT with a handmade exhaust which has allowed the valve to heat itself to oblivion.


was the intake not the exhaust valve that snapped. bud,
also get out of your own ATGATT ass
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ART-ADS
Nova Slayer



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PostPosted: 14:14 - 04 Mar 2019    Post subject: Re: jub Reply with quote

bikenut wrote:
Hows the Jubilee??


coming along slowly but surely. was told not to bother with a thread so i wont
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P.
Red Rocket



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PostPosted: 17:54 - 04 Mar 2019    Post subject: Reply with quote

ART-ADS wrote:
also get out of your own ATGATT ass


I wear trainers and trackies mate, calm your vagina.
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ART-ADS
Nova Slayer



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PostPosted: 11:49 - 05 Mar 2019    Post subject: Reply with quote

Paddy. wrote:


I wear trainers and trackies mate, calm your vagina.


?
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P.
Red Rocket



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PostPosted: 11:55 - 05 Mar 2019    Post subject: Reply with quote

Dense.
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ART-ADS
Nova Slayer



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PostPosted: 10:52 - 15 Mar 2019    Post subject: Reply with quote

wanted to post an update

engine went in fine, had issues with the starter and had to replace the bushings inside the starter motor.

running sweet as a nut Smile

i'll pull the cylinder off the front when i can and show you guys the valves, someone asked about it.

also see if the exhaust valve got burnt, as it should have according to a few people here, we'll see

and see if the intake valve got bent / damaged the piston or whatever
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Riejufixing
World Chat Champion



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PostPosted: 13:51 - 15 Mar 2019    Post subject: Reply with quote

ART-ADS wrote:
i'll pull the cylinder off the front when i can and show you guys the valves, someone asked about it.

also see if the exhaust valve got burnt, as it should have according to a few people here, we'll see

and see if the intake valve got bent / damaged the piston or whatever


It's always interesting to see what's happened....
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