400 with a 520 Piston/Cylinder

trewent

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May 26, 2000
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Have any KTM 400 owners replaced their piston/cylinder with that from the 520? Or better to just turn the 400 and get the 520? The displacement calcs out to 454 using the stock 400 stroke.
 

Shaw520

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The stock parts are not interchangable, the 520 cylinder has a longer stroke than the 400 crank, so it wont work.
Although, there are a few people on hear punching out there 400's to 450's.
Might want to do a search in this forum and find the thread, from there you will contact the person invloved via IM or e-mail.
 

OLD STROKER

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Feb 19, 2001
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The stock parts are interchangeable. You can use a 520 cylinder & piston with a 400 crank!
I just converted my 400 into a 540 ( KTM hard equipment ) but I had to install a 520 crankshaft. If it turns out I don't like that combination, I'm going to try that 454 combination by putting in the 400 crank. Sooo.... stay tuned:)

PS.. the 454 combo should be a revver!!
 
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trewent

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May 26, 2000
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Old Stroker,

Please let me know how it works!

What do figure the P/C & misc parts would run?

Thanks!

Trewent
 

Shaw520

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Stroker. With a 520 crank installed, you bsically have a 520, but with the 400 crank (64mm stroke) in a 520 cylinder that has a stroke of (72mm),....... Sounds like some major machining going on!!??:eek:
 
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OLD STROKER

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Feb 19, 2001
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Shaw520
All the cylinders, 400, 520, & 540, are the same in physical demensions. The bore is the only difference. No machining is necessary. You can run any combination of bore & stroke you want.
 

OLD STROKER

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Feb 19, 2001
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trewent

To convert your 400 into a 540 will cost you about $1800.
$1250 for the 540 kit
$350 for a 520 cranshaft
$110 for a 520 camshaft
$90 for gaskets & misc.
 

Shaw520

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Stroker, forgive me asking these 'stupid' questions but; installing a 520 piston/cylinder on a 400 crank, with the 400 stroke being 8mm shorter, wouldnt that reduce compression too much? :think
 

BCR-Bob

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Mar 8, 2001
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Old Stroker, I assume then that you have to put in a diff length rod then right?

The reason I ask is that KTM has different part numbers for the 400 and 520 rods.
 
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BCR-Bob

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Mar 8, 2001
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Never mind Old Stroker, I figured it out. Must have had my head somewhere else than my shoulders.

The 454 combo sounds very interesting.
 

OLD STROKER

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Feb 19, 2001
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BCR-Bob
I wouldn't replace the rod because I want the stroke of the 400.( they are different length rods ) But after thinking about it:think I would have to have a piston made. I checked the pin location on the 400 ( vs ) 520/540 and the 400 is 4mm lower ( measuring from the top of the piston to the center of the pin )
 

BCR-Bob

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Mar 8, 2001
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I was wondering about the pin locations but just figured that if they made two diff length rods that they would leave the pin locations the same between the two pistons. Would have made the whole thing a lot easier huh?
 

Shaw520

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Cylinder length being the same, w/different stroke, the pin location would have to be different to achieve proper compression.
 

BCR-Bob

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Mar 8, 2001
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Instead of changing the pin location why not just change the rod length? On a shorter stroke crank it would accomplish the same thing of moving the piston higher in the bore at the top of the stroke.
 

Bud-Man

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Dec 5, 2000
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KTM 450

Old Stroker,
You may want to give Eric Gorr a call. He's working on a 450 kit and even has purchased a bike to use as a test mule, if I understood him correctly. He already had the prototype pistons made for him. Out of curiousity, can you fit the 520 piston to the 400 con rod? I know the pin height is different, but I'm curious to know why they spec two different con rods if the lenght appears the same.
 

Shaw520

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Bob, Thats what he did, he had to install a 520 crank/rod in the 400 to get it to work, basically, you end up with a 520.
But I think what he is trying to achieve is a 454 with the shorter stroke of the 400 for a higher rever.
To get 520 plus displacement from a 400 crank would require a much larger bore than the 520 cyl will allow.
So, you can install a 520 cyl on a 400 crank with a custom made piston but your displacement will be somewhere 463. :think
 

trewent

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May 26, 2000
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WOW, thanks for the posts fellas. What I wanted to do was put the 520 p/c on my 400, being a dimbulb in the mechanics dept, I thought it would be a no brain big bore kit, how wrong I was! I would like to get more bottom end from the 400, without the "gyro" feel the Husaberg 500's Ive ridden have. Does anyone notice this on the KTM 520 in the woods or tight tracks? For the 454 I took the 520 piston diameter, the 400 stroke and applied the pi*Radius squared to get the volume of the cylinder. From the sound of things, I am thinking, just buy the 520. As mentioned I'm not much good at wrenching other than maintaining.
 

Bud-Man

Member
Dec 5, 2000
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Shaw520,
I'm confused on your comment about the 463cc displacement. Are you assuming that the custom piston will be larger in diameter than a 520's? It sounds like KTM is using the same con rod in both bikes, does anybody know if this is true? I'm guessing here, but the wrist pin to top of piston dimension is 4mm shorter on the 520 piston, which would make sense if the stroke is 8mm longer (con rod's big end is 4mm farther out on the crankshaft) and the cylinders are the same height. Sounds like the only way to get a 454 would be a custom "520" piston with same wrist pin to piston top dimension as the 400's or to use a 4mm longer con rod with a stock 520 piston.
 

Shaw520

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Bud-Man, you are correct, but the crank/rod assemblies are different, which is the reason KTM located the 400 wrist pin 4mm lower on the piston to create the proper compression at TDC.
As for your confusion; the stock 520 bore (95mm) X the stock 400 stroke (64mm) will leave you with 463cc.
Assuming we're installing a stock 520 cylinder/piston on a stock 400 crank, the rod OR the wrist pin will have be lengthened OR moved 4mm to achieve proper compression. Which brings us back to my first post. These parts are not interchangable without some machining.

Now,.... if Weisco comes out with a piston that'll do just that! :cool:
 
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EricGorr

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Aug 24, 2000
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Hi fellow KTM Guys,

Yes its true I commisioned J&E to make a small batch of 95mm pistons to bump the displacement of a 400 to 454 just by boring and NICOM plating the stock cylinder, or by using a 520 cylinder. The first machine is used for dirt track in District 16, rcaed by Joe Barr or Barr's Kawasaki KTM The head had to be matched with some minor adjustments to accomodate the larger piston's squishband and to set the compression ratio to 13.2:1

The second test bike is owned and raced by Dave Antolak of TUF Racing. On that bike head will be modified by raising the floor of the intake port to increase the short side radius. Because KTM uses so many common parts for the LC4 engine series, I think that the cylinder head's ports are way too big for the little 400 making the overall powerband a bit boring. Some could argue that its traditional European but lots of riders beg for the thrill of a YZF from the smaller LC4. We're going to run the squish clearance tight and set the compression ratio up near 14, then use Phillips B37 fuel.
Dave's bike is unique in that Ohlins has built him a set of forks and shock for his KTM400

Apparently Thumper has a 95mm piston kit for the KTM. Inquiring at Wiseco they reffered us to Thumper but when we called them nobody working the phones knew anything about the kit. Perhaps they didn't want to sell just a piston kit to us knowing that we'd handle the cylinder and head ourselves. We finally gave up on trying to buy a piston kit from them and opted for the J&E prototype batch. I figure that this model will be around for a lot of years and that for many riders, a 520 is just a bit more bike than they really need but a 454 with some head work and a choice of compression ratios would be just perfect.

I'll be ready to sell kits this winter. The kits will be in stages. You can buy a piston kit and 95mm head gasket $200, or the top end parts with overboring/NICOM plating/diamond honing, and instructions for modifying the head for $350, or a kit with complete porting and valve service with the big bore for $500

For you guys thinking of buying a 400 and spending another $1800 to make it a 540 consider this, Barr's Kawasaki/KTM has 2001 model 400s and 520s on sales for under $6,000 and Wiseco makes a 540cc kit that runs about $325 to bore and plate with the top end parts. Barr's will even sell you the new bike with the big bore kit installed for a modest labor charge. For anyone interested, Barr's is located in Madison Wisconsin and the telephone number is 1-608-222-6800
 

Shaw520

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Eric, Thanks for the front-line info, the 540 kits sounds interesting, is that done with a 400 crank, or the 520 crank?
 

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