Big Bore LC4, 660, 700?

Discussion in 'Thumpers' started by Donkey Hotey, Dec 28, 2005.

  1. Donkey Hotey

    Donkey Hotey De Jo Momma

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    I've searched the Bleeping Index and the archives and can't come up with an answer to this, so....

    I am going to need to rebuild a 640 engine here pretty soon. Does anybody have any idea how the KTM Baja bikes arrived at or near 700cc? Here's the breakdown of bores and strokes that I've collected:

    <TABLE cellSpacing=0 cellPadding=2 width=195 border=0><TBODY><TR><TD width="24%" height=16>
    Model​
    </TD><TD width="24%" height=16>
    Actual​
    </TD><TD width="26%" height=16>
    Bore​
    </TD><TD width="26%" height=16>
    Stroke​
    </TD></TR><TR><TD width="24%" height=16>
    620​
    </TD><TD width="24%" height=16>
    609​
    </TD><TD width="26%" height=16>
    101​
    </TD><TD width="26%" height=16>
    76​
    </TD></TR><TR><TD width="24%" height=16>
    640​
    </TD><TD width="24%" height=16>
    629​
    </TD><TD width="26%" height=16>
    101​
    </TD><TD width="26%" height=16>
    78.5​
    </TD></TR><TR><TD width="24%" height=16>
    660​
    </TD><TD width="24%" height=16>
    654​
    </TD><TD width="26%" height=16>
    102​
    </TD><TD width="26%" height=16>
    80​
    </TD></TR></TBODY></TABLE>

    Was the Baja engine a bore, stroker or both?

    Also, does anybody know if the 640 and 660 share the same balancer or will that need to be changed with the 660 crank?
    #1
  2. cross-country

    cross-country .

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    The 660's and 710's are all longer stroke motors. They use different case halves and do not support counterbalancers. I have ordered a 660 crank to see if there is a way to make it work with the 640 cases. If you want to put a 660 piston in your bike you could bore it, replate it and run it but a millimeter and a half won't do much IMO.
    #2
  3. dirtrider

    dirtrider Dusty Adventurer

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    The Dakar bikes are:

    660 (654) 102x80
    700 (692) 105x80

    Both are big bore and longer stroke than the 640 (625)

    If you have to go through the engine, but the crank is fine, why not consider a 675. We've built 2 so far and they have been awesome. It is a 105x78 engine. It builds a lot of torque and due to the stock stroke, is still a quick reving engine and with the stock crank, the counter balancer is still used. Also the piston, even though bigger in diameter, is as light as the stock piston. With a BST carb, KTM airbox screen, Pro Curcuit silencer, and no other changes, this engine puts down 54-55hp at the REAR TIRE.
    #3
  4. meat popsicle

    meat popsicle Ignostic

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    You might want to mention if "price is no object" or you are just dreaming.

    I can imagine that the parts for the racing engines (660 on up) are very expensive, due to economies of scale if nothing else. Just a courtesy on your part since dirtrider is offering his services.
    #4
  5. dirtrider

    dirtrider Dusty Adventurer

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    Any time you do a big bore or stroker engine, it's expensive so most people do dream about it.

    I just did a big bore on my Yamaha 700cc triple snowmobile turning it into an 800cc. I did all of my own work and bought the parts at cost, and it still cost over 1K but I went from 143hp to 168!:evil It went from being an antique to a sled that can run with or better than the new ones and the big bore was much cheaper than a new or newer sled saving me money in the long run.

    We can do the LC4 675 kit for what I feel is a realistic price.

    1: You send in the cylinder and head to us and we will send it back with all the parts to install yourself $1250.00

    2: You send the complete engine and we will send you back a complete engine $1575.00

    3: You bring in the complete bike and we will do all the work including Dyno tuning it $1900.00

    If you research big bore kits, you will find that the above prices are very reasonable.
    #5
  6. Donkey Hotey

    Donkey Hotey De Jo Momma

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    Well, I'm not dreaming. Here's the deal: I bought a 99 Adventure with a rod knock. I knew what I was getting into (thanks to Mr Creeper). I estimated that the rod, main bearings and likely the piston and liner were damaged. The difference that I can see between a 625 rod kit and whole 660 crank assy is about $250. A pistion is a piston, ditto for a replate. The difference is about $40 to punch out the bore before replating.

    The strategy is this: tear down the engine. If the cylinder is okay, rebuild the crank, new seals, gaskets, maybe some clutch plates and call it good. If the cylinder is NOT okay, go for it.

    This news about the 660 not using a counterbalancer is surprising. Hey Dirtrider, does your option #2 include a bottom end teardown or just top end? What do you do to the head? Overheating? I realize we're talking about significantly thicker aluminum walls here so the percentage of material removed is less. Still, I plan to operate this bike in some severe heat conditions (100+F in Death Valley).
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  7. dirtrider

    dirtrider Dusty Adventurer

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    None of the options include a bottom end teardown as it's not required to install the big bore kit. On the cylinder, we don't bore it. We actually press in a new sleeve and machine the sleeve for case clearance. The head is machined for the larger bore and piston to head clearances are checked and machined if necessary. We also do a MILD! porting job.

    We have not had a chance to test it in severe heat as we did the first one in October. So far there have not been any overheating problems or crankcase venting problems as some riders have had on Monomaniacs.com.

    #7
  8. Hudman

    Hudman Adventurer

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    What's your shops phone number? I live in Spokane and would like to see aobut having you do a couple of 05 640's
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  9. Donkey Hotey

    Donkey Hotey De Jo Momma

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    Okay, so I'm still in for a bottom end teardown...uhhh...I mean the BIKE is in for a bottom end teardown :rofl

    A new sleeve? I thought these were nikasil on aluminum. Hmmm...this could change things. With a thinner, pressed in liner, I'm more curious about overheating and what gets done to the head. The prices seem very reasonable. It's good to know that you do this because all my Google's for "lc4 big bore" etc, etc, came up dry. Is compression ratio optional? I'd still like to run it on pump 91 in the heat.
    #9
  10. dirtrider

    dirtrider Dusty Adventurer

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    Sorry, I didn't clarify that. Yes I work at a Yamaha/KTM dealership.
    http://www.pencoadventures.com/service.asp

    The prices for the big bore packages are listed in my first post. As you live close to us, I would recommend doing the last package which includes the dyno tuning. That way we can get your jetting dialed in.
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  11. dirtrider

    dirtrider Dusty Adventurer

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    :lol3 You changed your post while I was typing. The number is 406-755-6229 at the shop. Give me a call and we'll get the ball rolling. Steve
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  12. dirtrider

    dirtrider Dusty Adventurer

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    You guys are asking too many questions. I don't want to give away too many trade secrets!:lol3

    The originals are nik'ed aluminum. We remove it and bore the naked cylinder larger to accept a new cast sleeve. The new sleeve is thicker than the original and disappates heat very well. This same sleeve is used in another OEM application at these specs with no overheating problems.

    Compression ratio is very optional. It's only a little machining away. On any of our big bores, we generally keep the compression reasonably low to run on pump gas and deter any detonation problems.
    #12
  13. Donkey Hotey

    Donkey Hotey De Jo Momma

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    Hey, I've got no shortage of machining capacity but a mill is like a paint brush. Just because somebody has paint and a brush doesn't make them an artist. It's not worth $1200 to figure out all the variables, make a sleeve, source a piston, machine it, check for valve clearance, calculate compression ratios, etc, etc, THEN actually do the machine work. I know when to pay for experience.

    As Creeper puts it so eloquetly on his website, there are variables involved and there is no single, 'right' solution. I'm trying to understand the variables to make the right choices for this bike.

    The LC4 is already way over-square and KTM's decision to go longer stroke despite the high RPM Baja running says something about that. Does anybody know if those were one-off cranks or KTM hard parts?
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  14. dirtrider

    dirtrider Dusty Adventurer

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    You certainly know your shit. We researched this project for 3 months before getting around to building it. We have to get the pistons from Europe, the sleeve we flat got lucky on, and the machining on the first one took a lot of our time after hours in Dave's machine shop.

    Check your PM's!
    #14
  15. Surly

    Surly surly adventurer

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    How much to make mine run smooth?
    I think they put rocks in it at the factory:wink:

    #15
  16. Donkey Hotey

    Donkey Hotey De Jo Momma

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    If you're feeling vibration, you're slabbing or riding too slowly. Ride it like you stole it and any vibration magically disappears :jump :ricky :jump

    Saying an LC4 vibrates too much is like rejecting Cindy Crawford over her mole. Yeah, it's there but if that's what your focusing on, you're really missing out :wink: :lol3
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  17. Surly

    Surly surly adventurer

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    I dont mind it 'cept when I get back on it after riding something else

    Youre right. The 1200 miles from MT to Baja is where it sucked. But thats not why I got it!

    This is why...
    [​IMG]
    #17
  18. pitbull doug

    pitbull doug Been here awhile

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    Hey gregcifu/dakar you sound like you know your 640 well.Maybe you can help me out regarding vibration issue which Ive read so much about on this site.I'm on the fence about buying a 06 640, but all the talk got me a little leary.I have a 03 525 mxc plated street legal,but dont like to put alot of highway miles on her.What I'd like the 640Advs for is riding from my primary residence in ventura co. to my desert property in the rosamond area apprx 105 mi one way, 70mi street and 40mi or so dirt to property. Question ? will I notice the vibration more than my 525mxc, are lc4s worse.Am I going to be shaking like a leaf with 640 adv when I arrive at my place.Your're opinion would be appreciated. Or maybe I'm better off with the beast 950adv?

    Thanks pitbull doug

    03 525mxc
    00 300 exc
    #18
  19. Donkey Hotey

    Donkey Hotey De Jo Momma

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    You're giving me too much credit. I have never ridden a 640 but I have two 620s (640 was bought DOA). I have ridden from Palmdale to Oxnard and THAT is 100 miles so something is off on the mileage or you know a shortcut I don't.

    I can tell you that a thumper is no fun on 126 but more fun than you can imagine on 23. Yeah, it's a little buzzy at sustained highway speeds. It's a little underpowered above 75 MPH on the Escondido grade. Then again, I would imagine that lighter is better for off-road. A friend has a 950 and he can go anywhere I dare take the 620. If I had to do that trip often and planned to use the bike, I'd buy the 950. But then you may have other factors that will sway you the other way.

    Above all, buy the bike that you like. Sounds like a cop-out I know, but a friend of mine told me that if I would give him any bike in the garage, there isn't ONE he'd want. Motorcycles are like that. I would be happier riding my 620 Adventure on the route you described than on a Gold Wing.
    #19
  20. Donkey Hotey

    Donkey Hotey De Jo Momma

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    Holy cow! That is some serious mileage! Yeah, you've got some right to whine there. I've put 425 miles on mine in a day but more than half was off road. I can't imagine slabbing that far on a thumper. I'm not worthy! :bow

    Sweet picture! I hope to hook up with one of the Baja-bound groups from here. Never been. Want to go. I should have known you were baiting me :lol3
    #20