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Thread: 450xc-w RFS 2007 top end help

  1. #1
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    Default 450xc-w RFS 2007 top end help

    Hi All,

    New to the forum and hoping to get some advice/opinions on how to proceed on a top end rebuild of my bike. This would be the first time for me A little history: I bought the bike used and for the most part it has performed great. However a couple weeks ago it was becoming really hard to start and would bog at the top end. Thought it was carb issues so throughly went through that. No difference. Anyway, I'll spare you all the details - went to look at the valves and discovered one of the valve adjuster nuts was missing! Wasn't sure if the previous owner had just lost it or worse it had worked it's way down and damaged the engine. So started taking things apart and eventually did find it stuck to the ignition pickup magnet. The nut was a little beat up, but everything else that I can see so far looks okay. But now that I have everything apart I figured I should have a look at the cylinder and piston and perhaps get a new piston etc.

    One challenge is that I don't know how many hours are on this bike. Also I'm not having much luck finding pictures of pistons/cylinders to try and assess what condition mine are in. Was planning on ordering a wiseco piston and tusk top end gasket kit from Rocky mountain MC. Before that I was oping to get some opinions/advice from others who have done this before. I'm attaching some pictures - any help would be greatly appreciated. Thanks guys!
    Attached Thumbnails Attached Thumbnails IMG_0040.jpg   IMG_0042.jpg   IMG_0037.jpg   IMG_0044.jpg   IMG_0045.jpg  


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  3. #2
    Lifetime Team KTMTalk TravisD37's Avatar
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    Default Re: 450xc-w RFS 2007 top end help

    Piston actually looks ok. Probably just a new set of rings would be all you need.
    Have you checked ring gap?

    The cylinder looks like it has some decent ring grooving going on and should be replated. There is no way to tell a cylinders condition without using a micrometer. They can look fine with good cross hatching and still be out of round and/or have a taper.

    Your intake valves are sunk into the head. They need replacing. New valves should stand 1mm proud of the combustion chamber. Because of how deep the valves are you will probably have worn out seats as well. Rather than replace the worn seats you can do +1mm kibblewhite valves and recut the seats this will bring the valve hight back into the correct spec.

    Check the sealing surface of the exhaust valves as well I'll bet they are very pitted and will need replacing as well.
    Last edited by TravisD37; 10-18-2020 at 09:30 AM.
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    Default Re: 450xc-w RFS 2007 top end help

    Thanks for the reply - really appreciate it! Haven't checked the ring gap but will look into that. On taking a closer look the exhaust valves are sitting almost flush with the head and intake are about 1mm proud. What are people using to clean the build up off? Contact cleaner okay? Will have to look into where I can get the cylinder replated and also how hard replacing the valves will be Thanks again for your help!

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    KTMTalk Member dirtbikeace's Avatar
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    Default Re: 450xc-w RFS 2007 top end help

    Get the Kibble whites I was adjusting all the stock valves every 3 months, the KB intakes once and exhausts were fine in a 1 year.
    present bikes
    2006 KTM 450 EXC
    2006 KTM 400 EXC
    1999 Kawasaki Concours
    1983 Husqvarna 250WR
    1968 Honda CT90 trail 90
    1971 Suzuki RV90
    1964 Honda CT200 Trail 90
    member Great Lakes dual sporters
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    Default Re: 450xc-w RFS 2007 top end help

    Thanks for the tip - appreciate it.

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    Default Re: 450xc-w RFS 2007 top end help

    Kibblewhite black diamond valves okay?
    https://www.rockymountainatvmc.com/p...lve-p?s=135694

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    KTMTalk Member DJH's Avatar
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    Default Re: 450xc-w RFS 2007 top end help

    the first thing to wear out is the valves, 2nd is the bore, 3rd is the rings, 4th is the piston
    [URL=http://www.djhcyclesport.com
    Former Husky Dealer in the '70's, currently Sell Real Estate, Seattle area and as a hobby business I manufactor cam chain tensioners for the KTMs, do Carburetor modification & setup and valve work on KTM & Husky 4 strokes. Full stock of parts for the KTM's. My rides are; Cadillac Escalade (the 1/2 pickup version), 72 ElCamino 454SS, and Triumph 1050 Sprint ST, Iron Butt member

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    KTMTalk Member dirtbikeace's Avatar
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    Default Re: 450xc-w RFS 2007 top end help

    Markus, DJH did my 400's valve job, highly recommend him.
    present bikes
    2006 KTM 450 EXC
    2006 KTM 400 EXC
    1999 Kawasaki Concours
    1983 Husqvarna 250WR
    1968 Honda CT90 trail 90
    1971 Suzuki RV90
    1964 Honda CT200 Trail 90
    member Great Lakes dual sporters
    www.gldsmc.org
    AMA charter life member-663466A

    District 14 ama- #0025

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    Default Re: 450xc-w RFS 2007 top end help

    Thanks for this - I'm in Toronto so will try and find something a bit closer if possible. So would you guys leave the piston for now and just concentrate on new rings, valves and re-plate the cylinder if possible? I know it's difficult to comment on these things without seeing in person, but could save a bit of money leaving the piston alone for now if it's okay. On the other hand, don't mind getting a new one while it's all apart if you guys think it's the thing to do?

  11. #10
    KTMTalk Member DJH's Avatar
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    Default Re: 450xc-w RFS 2007 top end help

    Shipping from me to you is easy, we use mail, UPS send it to customs. Not certain going you to me? may be the same but its not a big deal
    [URL=http://www.djhcyclesport.com
    Former Husky Dealer in the '70's, currently Sell Real Estate, Seattle area and as a hobby business I manufactor cam chain tensioners for the KTMs, do Carburetor modification & setup and valve work on KTM & Husky 4 strokes. Full stock of parts for the KTM's. My rides are; Cadillac Escalade (the 1/2 pickup version), 72 ElCamino 454SS, and Triumph 1050 Sprint ST, Iron Butt member

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