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Old 10-14-2008, 06:24 AM   #151
rickf
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Quote:
Originally Posted by gaspipe
I wasn't going to go into this until later on.

But, for what I am expecting to do with the bike, longevity and reliability are more important than peak HP. A 75HP 613cc monster does me no good when I'm looking at a holed crankcase in the middle of the Vizcaino Desert.

The stock bore 525 (510cc) motor with a stroker crank (78mm) gives a swept volume of 552cc. That is, IMHO, the magic compromise of power/torque and reliability that I am looking for in this bike.
Watch your peak piston speed with that one.
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Old 10-14-2008, 01:47 PM   #152
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Quote:
Originally Posted by rickf
Watch your peak piston speed with that one.
The TRPA guys have tons of miles on all iterations of the motor (510, 540, 552, 576) and assure us that the 552 is both the preferred engine character and durable.

fingerscrossed
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Old 10-14-2008, 01:49 PM   #153
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Quote:
Originally Posted by neduro
The TRPA guys have tons of miles on all iterations of the motor (510, 540, 552, 576) and assure us that the 552 is both the preferred engine character and durable.

fingerscrossed
Wot he said. :alsofingerscrossed
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Old 10-14-2008, 02:02 PM   #154
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Don't tel me this I have the 570 kit that should be delivered, any tick of the clock ,

So what do your sorces say about relieablity of 570 kit with stock crank ?


My set will be 570 kit+ jetting stock crank
15 -50 or 48 gearing
RS concept fairing ( due to land next week )

and one hell of a build thread ( made harder as i lost my camera on the weekend )
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Old 10-14-2008, 04:29 PM   #155
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Quote:
Originally Posted by Mudguts
Don't tel me this I have the 570 kit that should be delivered, any tick of the clock ,

So what do your sorces say about relieablity of 570 kit with stock crank ?


My set will be 570 kit+ jetting stock crank
15 -50 or 48 gearing
RS concept fairing ( due to land next week )

and one hell of a build thread ( made harder as i lost my camera on the weekend )
He's talking about the stroker crank.
The longer the stroke, the more peak piston velocity (middle of the stroke)you have for a given rpm.
That is the main reason high rpm engines are very short stroke. Not the only reason but the main one.
You can actually see it on old steam locomotives, eh GP?
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Old 10-14-2008, 07:18 PM   #156
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I was acually asking about reliability , of the stroker V's big bore

not what a stroker kit is ,

Eg,
510cc w\stroker kit ( 552cc lightend crank) will X amount of hours

V's

570 kit will last X amount of hours ( standard crank )
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Old 10-14-2008, 07:59 PM   #157
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mudguts,

I have zero experience with the 570. A little with the 540, and plenty with the 510 and 450. Rickf is right on about piston speed - that's part of what we're working to avoid on the 552 stroker.

The basic problem with the heavy wheels on the OE stroker crank put an enormous side load on the crank roller bearings. And they can fail. High RPM actually spreads the crank wheels, and puts that side load on the roller bearing. SuMo guys have been swapping to a ball bearing, which handles the side loads much better. But that's not what I'm looking for. I don't want nor need a 8000+ rpm motor. What I'm after is longevity.

How do we get that?

The bigger swept volume per stroke with the 78mm vs 74mm crank speeds gas velocity through the ports, all other things being equal. There are also other things happening (leverage, for instance), but I'm going to ignore that for now. Another thing is that a 510cc cam will feel more 'mild' in a 552cc because of the velocity in the port and the filling ability of the duration and lift of the cam, etc.

So the net of it is, with the stock 450/510 cam, the stock 510 bore, and the extra 4mm of stroke make a really nice pulling motor that does not want to be revved real high to make the torque we're looking for.

You can gear it up a little now. I plan to run a 14/48 to start, and see how it feels. Maybe even close ratio MXC 1st through 4th, and EXC 5th and 6th for cruise?

Anyway, the net result we're looking for is a motor that doesn't need to be wrung out to generate the torque to pull the silt, sand and such. It becomes more XR650R like in the power delivery, rather than SX like. Hope that makes sense.

In my very limited experience with the 540 motor, it wants to rev more than I want to rev it for this type of machine. RPM's are what kills these RFS motors.

As I mentioned, I have zero experience with the 570 variant, but I have heard that they are not super long lasting motors compared to the OE 510 and 552 stroker. That may be due to the cams and compression ratios run with that bore size, as well as the cylinder mods needed to achieve that bore size.

I wish I could quantify the time before failure of each, but I just don't know.

The good news is I might run a huge motor in my 450, maybe as big as a 613cc, so I reckon I'll find out more soon than later how the bigger bores hold up.
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Old 10-14-2008, 08:29 PM   #158
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What you just discribed is the Berg setup.

The 650 pulls hard from way down low. The power is very linear. And stops revin around 8 or 9 k.

A very low first. With 2nd through 6th being closer than the EXC.

This setup really does make for a great trail bike. Or an open space bike that just needs to carry a nearly costant speed not retake time that was lost in a corner.
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Old 10-14-2008, 09:06 PM   #159
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Had no idea this thread was here

Glad to see those bikes rolling again.

For the 2006 Dakar, they implemented a 100mph speed limit. I was teamed up with Mike Krynock and Pedro de Uriarte from Mexico then. We were discussing bike choice with Mike Kiley of PAi in June: Pedro had 2 hammered 660 Rallys and I had one. With the new rule and the available 660 parts, we thought the best plan was to make these frankenbikes. I went into the garage and held some 660 tanks up next to a 525 and that's where it started.

We had some money back then. This year, nada.

Before I forget, use ICW radiator on these bikes rather than the fluidyne ones. Brett will make some cool radiators cheap and you can use wider rather than thicker ones on the rally bikes because you have the room. Wider will cool better. www.icwbikestands.com
And, try a front disc and carrier from a pre-2000 640 Adventure, which was 300mm. Works well on these bikes. The larger discs are too vulnerable to rocks. (You could order the 660 disc and carrier too, same parts, higher price.)

Pedro's first ride:

Pedro broke his kneecap in November before the Rally. I called Jonah, and you probably know the rest.


At the finish, Jonah, Mikey and team.

I'll try to dig up the photos from the original build.

fun fun
Charlie

neduro screwed with this post 10-17-2008 at 06:44 AM
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Old 10-14-2008, 09:25 PM   #160
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Gaspipe

there is a guy in thailand on a 2006 525/ 570exc whom i under stand had a pretty good run apart from the balancer coming lose ( i think ) but the was more adventure riding not racing ,

As i believe the Stock CDI for an EXC tops out at 7250RPM and SX around 8500+rpm

I don't see this as a problem for the 570BB but I'm no machanic, I guess I'll have to wait and see , Hoping i don't punch the con rod throgh the casings

just waiting on Thumper Racing to send me the kit ,
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Old 10-14-2008, 09:52 PM   #161
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RFS bikes hate high revs. We found that the main bearings fail. I think Jonah held it wide open in top gear in the sand for over an hour and the bearings failed soon after that in Mauritania in 07. Several of our other early motors showed signs of the same failure. The 06 Dakar bikes were stock motors. The 07 Dakar bikes were 540cc big-bores, but we have since tested 552 strokers and used them in many customer engines. Best to balance your crank and weld the little pin in the side of it. Supermoto guys tell us the pins sometimes come out but we've never seen it. Also, use very high quality oil and keep the motor as cool as possible. For long desert races, up the oil capacity with a cooler or external tank. Use big radiators and a fan. We also researched some higher quality bearings from a German company called Schubert (I think) but never used them. Last year we switched to the 690 Rally because it solves most of the 660's problems and because the Dakar stopped enforcing the speed limit rule.

fun fun
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Old 10-15-2008, 12:03 AM   #162
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The piston speed is only half the problem with stroker cranks. The other is the rod ratio. More stroke with a stock rod= more side loading on the piston. In really poor examples of strokers they actually put on a shorter rod so that a new piston with a shorter pin height is not required.

Where you get your mid range torque from is the short rod produces a lot higher piston acceleration speeds from TDC, this in turn speeds up your port velocity's. This in conjunction with the extra mechanical advantage gives the extra torque. Short rod motors also like a little less timing advance......

Also, anything you can do to lighten the piston, pin and rod before you balance the crank will do wonders. A few onces goes a long way in motor longevity.
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Old 10-15-2008, 07:44 PM   #163
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new KTM 565cc engine (a la Berg '09 FE570)

Interestingly the new KTM 565cc engine (a la Husaberg '09 FE570) is 100 x 72 so a lot more oversquare than the 510cc 525 motor with the same stroke.

Any thoughts on how it may hold up for long distance rallyes ??

Seems like it will be more rev happy, but torque ??

I love the current Husaberg FE650 motor with its 100 x 80 confguration, lots of grunt, but will also rev, it makes a fantastic rallye motor and will hum along all day at 100-140kph and do that for 7,000-10,000 km no probs, also it will run easy up to 175kph when you want it to.
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Old 10-15-2008, 08:03 PM   #164
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Any more pics, GP and Ned? Not the holding hands ones, of the bikes.

Jim.
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Old 10-16-2008, 08:52 PM   #165
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I'm sure you guys have seen plenty of factory rally bike pic's, but I ran across a 660 factory bike in Denver today and snapped some pictures with some of the details I liked (pretty weak iphone pic's though). Posted a thread in thumpers here.
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