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Old 12-26-2012, 09:41 PM   #72181
Phreaky Phil
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Quote:
Originally Posted by procycle View Post
Maybe this will liven up the party a bit.

That my friends is a 10mm over stroker DR650 crankshaft with custom made Carillo rod getting ready to go into the DR900 DR-zilla motor.


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Old 12-26-2012, 10:36 PM   #72182
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So when is production gonna start on it? With that in there would be no stopping a well ridden DR 650/900 on the tracks and trails( I mean jeez all it would have to do is fire once and the earth would spin under you ). I am fairly certain there would be interest in this kit along with the billet 3rd gear and carb. right next to the new shock /forks and seat. well I guess a new larger tank would be a wise move too. With a decent can I imagine it sounds awesome, MASSIVE displacement and single cylinder you could hear that thing fire as it lugs up a hill then crack gets on the powerband PLEASE post a video of that!!!

I agree that a smaller engine doing the same work will be pushing harder to make the same effect as a larger displacement engine. A friend has a DR 200 and he has to have it singing to get to the top of the same hills I do, and he is a lot lighter then I am . I am in the process of trying to get my DR ready for a RTW trip while it would be nice to have it here in North America It would prove to be problematic if I had issues with it in some backwater country.
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PPCLI-Jim screwed with this post 12-26-2012 at 10:49 PM Reason: just a refined thought scheme
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Old 12-26-2012, 10:41 PM   #72183
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Missed Chance

Quote:
Originally Posted by procycle View Post
Maybe this will liven up the party a bit.

That my friends is a 10mm over stroker DR650 crankshaft with custom made Carillo rod getting ready to go into the DR900 DR-zilla motor.
Smilin Jack almost rode down to PC for a visit and a speedo cable today... and missed the chance to see DR-zilla.

Instead a friend stopped by in his cage for my parts run. Better luck next time.

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Old 12-27-2012, 01:32 AM   #72184
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cush rubbers

Hey everyone hope you all had a good crimbo!

Quick question about cush drives.... I've got a new rear wheel and will be transferring the bits from the old wheels, I've got new cush rubbers and my question is should these be lubricated at all? I'm thinking they go in dry as any grease will just attract dirt but the only time I've had it apart before for a tire change they seemed to have some sort of graphite grease on them.

Looking forward to having a proper catch up on the thread.
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Old 12-27-2012, 01:41 AM   #72185
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Quote:
Originally Posted by Chill View Post
Hey everyone hope you all had a good crimbo!

Quick question about cush drives.... I've got a new rear wheel and will be transferring the bits from the old wheels, I've got new cush rubbers and my question is should these be lubricated at all? I'm thinking they go in dry as any grease will just attract dirt but the only time I've had it apart before for a tire change they seemed to have some sort of graphite grease on them.

Looking forward to having a proper catch up on the thread.
I give them a squirt of silicone lube spray to make it easier to get it all together. Silicone is benign, and maybe conditions the rubbers a bit, maybe, whatever that means.
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Old 12-27-2012, 09:24 AM   #72186
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Originally Posted by procycle View Post
I'm confident the stock trans will be up to it (with a billet 3rd gear set).
There's no reason to think it will need any more cooling than the current 790. It will gain a lot of internal cylinder area to shed heat. But really, a bigger motor doesn't just automatically make more heat. It depends on how hard you run it. With the longer stroke and more torque it should have an easy time of of it. In equal conditions a smaller lower powered motor has to be run harder to give the same performance as a larger more powerful motor.
You better put a couple rimlocks in the rear of that one!

Love the welded crank-pin. Hope the clutch can handle it.

What do you have to do to allow for the extra stroke, so it doesn't hit the head?
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Old 12-27-2012, 09:44 AM   #72187
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Originally Posted by Rusty Rocket View Post

What do you have to do to allow for the extra stroke, so it doesn't hit the head?
when at top-dead-center, the top of the piston is in the same location as stock, it's yust that the crank journal is closer to the top of the piston, and the rod is shorter; so when the piston is at bottom dead center, it is further away from the top of the cylinder, thus increasing displacement...

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Old 12-27-2012, 09:54 AM   #72188
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Quote:
Originally Posted by doug s. View Post
when at top-dead-center, the top of the piston is in the same location as stock, it's yust that the crank journal is closer to the top of the piston, and the rod is shorter; so when the piston is at bottom dead center, it is further away from the top of the cylinder, thus increasing displacement...

doug s.
Makes sense.
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Old 12-27-2012, 11:06 AM   #72189
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Question

Quote:
Originally Posted by doug s. View Post
when at top-dead-center, the top of the piston is in the same location as stock, it's yust that the crank journal is closer to the top of the piston, and the rod is shorter; so when the piston is at bottom dead center, it is further away from the top of the cylinder, thus increasing displacement...

doug s.
Does stroking the engine increase the amount of compression? It seems to me that it will. If so, would it still run on normal gasoline?

Would the stroker kit be available as a standalone kit without the big bore? It seems to me that wouldn't be a problem. It might have a tougher time at idle?

Is there an advantage of doing one vs the other assuming very similar final displacement?

I should probably be asking Jeff, but anyone with engine knowledge should be able to help I think.
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Old 12-27-2012, 11:19 AM   #72190
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Originally Posted by procycle View Post
I'm confident the stock trans will be up to it (with a billet 3rd gear set).
There's no reason to think it will need any more cooling than the current 790. It will gain a lot of internal cylinder area to shed heat. But really, a bigger motor doesn't just automatically make more heat. It depends on how hard you run it. With the longer stroke and more torque it should have an easy time of of it. In equal conditions a smaller lower powered motor has to be run harder to give the same performance as a larger more powerful motor.
According to physics, more power has a direct correlation to more heat , but as you said, the larger area should help offset that. I know given my propensity to pin the throttle on pretty much everything I ride, I'd be running it hard.
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Old 12-27-2012, 11:32 AM   #72191
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Originally Posted by Feelers View Post
Does stroking the engine increase the amount of compression? It seems to me that it will. If so, would it still run on normal gasoline?

Would the stroker kit be available as a standalone kit without the big bore? It seems to me that wouldn't be a problem. It might have a tougher time at idle?

Is there an advantage of doing one vs the other assuming very similar final displacement?

I should probably be asking Jeff, but anyone with engine knowledge should be able to help I think.
All things being equal, yes, a longer stroke will increase compression. I will modify the dish in the top of the piston to compensate.

This will never be a kit. In any case it would not work with the stock piston because the stocker is too long below the wrist pin. With the stock piston you could only increase the stroke a couple of millimeters before the bottom of the piston hits the crankshaft. The 790 piston is a much more modern design and has the necessary clearance under the piston.

As far as what is an advantage - It totally depends on what the goals are for the end result. Longer stroke makes more torque at the expense of rpms and vibration and depending on the motor can be more difficult or expensive than just a bigger bore.
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DR900 Big Bore Stroker buildup
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Old 12-27-2012, 12:58 PM   #72192
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Originally Posted by PPCLI-Jim View Post
So when is production gonna start on it?.... I am fairly certain there would be interest in this kit....
Sure, plenty of interest until we start talking about the cost. A bare minimal 900 kit - custom built crank & rod, modified 790 kit, gaskets, etc would run at least $3000. Add a cam, 3rd gear and whatever will be necessary to keep the clutch hooked up and it would easily go $4k-$5k or more.

Nope. Never going to be a kit but if someone else besides me is crazy enough to want to do this I'll be happy to help point them in the right direction.
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www.procycle.us - Everything for your DR650 and lots of other great stuff!
DR900 Big Bore Stroker buildup
TurboDiesel Corvette - go to the end to start at the beginning
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Old 12-27-2012, 01:57 PM   #72193
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Originally Posted by procycle View Post
whatever will be necessary to keep the clutch hooked up

Nope. Never going to be a kit but if someone else besides me is crazy enough to want to do this I'll be happy to help point them in the right direction.
Reminds me of the 750cc 2 stroke Maico single that Rick Sieman and DirtBike magazine built back in the last century
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Old 12-27-2012, 03:37 PM   #72194
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Quote:
Originally Posted by doug s. View Post
when at top-dead-center, the top of the piston is in the same location as stock, it's yust that the crank journal is closer to the top of the piston, and the rod is shorter; so when the piston is at bottom dead center, it is further away from the top of the cylinder, thus increasing displacement...

doug s.
Your thinking is a little confusing. Using the same rod and piston would make the piston HIGHER in the bore.

Most stroked engines use a shorter compression height on the piston (distance from piston pin centerline to top of piston) to make up the diffrence so the piston doessn't hit the head. A 10mm stroker would have 5 mm more at TDC and 5 mm more at BDC. So- all things being equal you would make the compression height 5 mm shorter so the piston top ends up in the same location. By doing this you increase the stroke but the piston TDC height from crank centerline ends up being the same.

You can use shorter rods but that often leads to piston to crank counterweight clearance problems.

And yes, increasing the stroke increases the compression. More "swept volume" with the same compression volume = higher compression ratio. Compression ratio = Swept Volume + Compression Volume / Compression Volume.
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Old 12-27-2012, 04:15 PM   #72195
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Most stroked engines use a shorter compression height on the piston (distance from piston pin centerline to top of piston) to make up the diffrence so the piston doessn't hit the head.
You can't do it that way with most modern motorcycle engines because the wrist pin is already as high in the piston as is practical. There just enough room between the wrist pin and the cylinder head to fit rings with no extra distance available to make a shorter compression height.

Quote:
You can use shorter rods but that often leads to piston to crank counterweight clearance problems.
Which is how this one is done with a 5mm shorter custom made Carillo rod. The thing that made it possible is the 790 piston which has a lot of counterweight clearance with the stock crank.
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DR900 Big Bore Stroker buildup
TurboDiesel Corvette - go to the end to start at the beginning
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