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martinfan30

720cc XRL

18 posts in this topic

Any one know anything about this? What mods need to be done to the engine to get it to work? Saw it on another site and now it has my interest.:thumbsup::eek:

http://cgi.ebay.com/ebaymotors/xr650l-honda-big-bore-kit-720cc-1993-to-2005-FREE-SHIP_W0QQitemZ200200109249QQcmdZViewItem

Found it at SMJ. The case's have to be clearanced. I wonder if the 700cc kit has to be done the same way. I'm pretty sure the 675cc doesnt.

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I love the water-cooled 2stroke kit they use in the picture!

Dave

Yeah, I thought that piston didnt look right!:thumbsup:

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If I remember correctly a 102 or a 103mm piston will fit into the cases, but after that you have to machine the cases for it to fit at BDC.

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the sleeve will definatly not fit if the piston is over 104. Of course you will probably have to balance your crankshaft for the different piston weight and such. We have noticed that we can tell a vibration difference on ten grams beleve it or not.

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Off hand, do you know the approx. weight difference between the 100 and 103?

Will the 103's weight affect revability?

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not sure about the weights of the 100 and the 103. We make our own pistons so we are on a different path. our 104.8 weighs 379 grams. trust me reving is not really the answer. we were breaking springs and squaring off camshafts in 5000 miles reving to 8750. we focused on the torque which is the biggest atribute to this motor not the rpm and hp. we had some cams made that we decreased the rpm to 8200 and now we have just a beast that has three more ft lbs and one less hp and it out performs the previous style engine configuration. it still makes our bike go 140 so its plenty fast on top as well.:thumbsup:

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All that I can say is WOW. Stepho you get to play with the cool toys. I'm just a lowly wrench turner who happens to have an engineering degree. I've known a lot of hardcore engine builders, but none of them ever attempted making a piston. There is a ton of detail in making a long lived piston.

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trust me reving is not really the answer.

Especially as the reciprocating assembly gets heavier from bigger pistons and even worse if the stroke is increased at the expense of rod length. You know what they say about RPM; it Ruins Peoples' Motors. Totally different field, but a lot of people are pushing stock Mustang 5.0 blocks pretty far now by keeping the rpm low with the cylinder pressures high.

I'm just a lowly wrench turner who happens to have an engineering degree.

You don't work at HPD, do you? :thumbsup: It's the only place I can think of that would need wrench-turners with engineering degrees. :eek:

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You don't work at HPD, do you? :thumbsup: It's the only place I can think of that would need wrench-turners with engineering degrees. :eek:

All my wrenching is done on my own time. At work I'm a desk/keyboard jockey. Kind of ironic as the name of the company that I work for is Wrenchead.

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damn keyboard jockeys LOL guess ill take a look at the ebay link you had on first thread tonight when i first saw the topic i was thinking a 720cc L motor was kinda out of place and prolly a hoax. Interesting post there stepho about the motors, where do you guys test for top speed? you come out to El Mirage or anything?

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the 73 freeway, the 405 freeway, the 5 freeway and cycleworld guys took it somewhere in the dezert a few years ago.

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As I recall Back in the late 90's Dirt Bike or Dirt rider did a story on a 720"L".

additional cooling fins were needed and the cases bored out and I think it was L.A. sleeve that did it ...you may want to ask them if your curious MF...

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that was in january 98 dirtbike mag and it was a LA sleeve kit the bore on the 720 is a 105mm bore they did a dyno with that kit all stock but the big bore and aftermarket pipe the hosepower at the wheels were 41 my xr600 bore to a 630 white bros cam and port and polish made 43 on the dyno and would wheel up in 4 gear with a 42 tooth spocket at about 65mph an animal.i'll tell you about the 720 kit when its done installed in my bike..

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