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ART-ADS |
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ART-ADS Nova Slayer
Joined: 09 Feb 2018 Karma :
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MarJay |
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MarJay But it's British!
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Riejufixing |
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Riejufixing World Chat Champion
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Teflon-Mike |
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Teflon-Mike tl;dr
Joined: 01 Jun 2010 Karma :
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Posted: 12:56 - 01 Mar 2019 Post subject: Re: valve snapped |
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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...... ____________________ My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?' |
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A100man |
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A100man World Chat Champion
Joined: 19 Aug 2013 Karma :
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Posted: 13:34 - 01 Mar 2019 Post subject: Re: valve snapped |
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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. ____________________ Now: A100, GT250A, XJ598, FZ750
Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600 |
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ART-ADS |
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ART-ADS Nova Slayer
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Grubscrew |
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Grubscrew Scooby Slapper
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WD Forte |
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WD Forte World Chat Champion
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Grubscrew |
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Grubscrew Scooby Slapper
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Posted: 20:01 - 01 Mar 2019 Post subject: |
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Probably an Aerial ____________________ FJR1300/CBR1000F |
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P. |
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P. Red Rocket
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Bhud |
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Bhud World Chat Champion
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bikenut |
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bikenut World Chat Champion
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redeem ouzzer |
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redeem ouzzer World Chat Champion
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ART-ADS |
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ART-ADS Nova Slayer
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ART-ADS |
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ART-ADS Nova Slayer
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P. |
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P. Red Rocket
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ART-ADS |
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ART-ADS Nova Slayer
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P. |
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P. Red Rocket
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ART-ADS |
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ART-ADS Nova Slayer
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Posted: 10:52 - 15 Mar 2019 Post subject: |
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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
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 ____________________ 98' RZ50, 92' H100S2, 03' VT125, 59' Jubilee 250, 05' varadero chop, |
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Riejufixing |
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Riejufixing World Chat Champion
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Old Thread Alert!
The last post was made 5 years, 47 days ago. Instead of replying here, would creating a new thread be more useful? |
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