KACR catastrophic failure
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Junior Member
Joined: Sep 2019
Posts: 1
From: United Kingdom
KACR catastrophic failure
Hi all, new here so bare with!
I've got a 1995 KLX250 ... Whilst riding to a friend's house recently, I accelerated up his road (quite quickly) and heard a "Ping" from the engine, instantly cutting it out.... Pushed it to his place and having just replaced the cam chain and fitting a Krieger CCT I thought the problem was a snapped cam chain. I wound the Krieger chain tensioner in and it kept going... Brilliant.
Removed the head cover and observed an absolute grenade had gone off inside.
The chain had indeed been torn to bits, luckily I was able to remove it out the top ... Moving round to the other side, I noticed that the KACR had basically exploded, with half the mechanism bent round at 90 degrees and wedged into the side of the head, bits of KACR everywhere but worst of all, the hole where the left hand exhaust valve lives had been chewed up on the outside (where the KACR exploded into it) this made removing the valve bucket near impossible. We eventually got it out with molegrips and a lot of swearing.. basically that hole isn't a perfect circle now so the bucket won't go back in...
Long story short I'm now looking for a new cylinder head complete with valves and potentially an exhaust camshaft with KACR, cam chain ect...
Anyone on here got a cylinder head going? Cheapest ones are about 800 dollars (plus 22.5 percent import tax to UK) and 150 dollars postage 🤢 and would I be able to salvage that exhaust camshaft by removing the KACR? (No other damages to that camshaft)
Thanks
I've got a 1995 KLX250 ... Whilst riding to a friend's house recently, I accelerated up his road (quite quickly) and heard a "Ping" from the engine, instantly cutting it out.... Pushed it to his place and having just replaced the cam chain and fitting a Krieger CCT I thought the problem was a snapped cam chain. I wound the Krieger chain tensioner in and it kept going... Brilliant.
Removed the head cover and observed an absolute grenade had gone off inside.
The chain had indeed been torn to bits, luckily I was able to remove it out the top ... Moving round to the other side, I noticed that the KACR had basically exploded, with half the mechanism bent round at 90 degrees and wedged into the side of the head, bits of KACR everywhere but worst of all, the hole where the left hand exhaust valve lives had been chewed up on the outside (where the KACR exploded into it) this made removing the valve bucket near impossible. We eventually got it out with molegrips and a lot of swearing.. basically that hole isn't a perfect circle now so the bucket won't go back in...
Long story short I'm now looking for a new cylinder head complete with valves and potentially an exhaust camshaft with KACR, cam chain ect...
Anyone on here got a cylinder head going? Cheapest ones are about 800 dollars (plus 22.5 percent import tax to UK) and 150 dollars postage 🤢 and would I be able to salvage that exhaust camshaft by removing the KACR? (No other damages to that camshaft)
Thanks
Senior Member
Joined: Aug 2009
Posts: 4,652
From: Delaware, Ohio
1st Gear Member
You only know about the cam if you remove it. No scarring of the bearing journals and you're good. That type of thing happened on a number of KLX650s over the years I've been a member at the Yahoo KLX650 Group. Problem with the older bike if you remove the KACR is the kick start only. But the trick is to bring the piston to TDC compression and ease it just over then kick with some authority, no slap kicking like a two stroke.
On the KLX650s one thing we did on my 650 was to restake the rivets on the tensioner shoes. They were sloppy loose. 50,000 miles and no KACR problems.
On the KLX650s one thing we did on my 650 was to restake the rivets on the tensioner shoes. They were sloppy loose. 50,000 miles and no KACR problems.
Member
Joined: Aug 2018
Posts: 95
1st Gear Member
as above on the cam... it'll work without the flyweights
as for the bucket bore... you got the bucket out, there couldn't be much preventing it from going back in. so, is that damage on the kacr side of the bore? and how much damage is there? you should be able to grind off the bad part.... or is there other damage that makes the head unserviceable
in older designs with no bucket, the cam lobes put a rocking motion on the valve stem, that eventually wears out the guides. bucket takes that motion and transfers it to the head, making the valve motion vertical in the guide instead of rocking. where I'm going with this is the main loading is fore and aft, and not so much left and right
got pictures?
as for the bucket bore... you got the bucket out, there couldn't be much preventing it from going back in. so, is that damage on the kacr side of the bore? and how much damage is there? you should be able to grind off the bad part.... or is there other damage that makes the head unserviceable
in older designs with no bucket, the cam lobes put a rocking motion on the valve stem, that eventually wears out the guides. bucket takes that motion and transfers it to the head, making the valve motion vertical in the guide instead of rocking. where I'm going with this is the main loading is fore and aft, and not so much left and right
got pictures?
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