the DR650 thread

[Mongle]

Originally Posted by doug s.

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.

[procycle]

Originally Posted by Mongle

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.

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.

[trailrider383]

This post makes me appreciate my simple DR all the more. http://www.advrider.com/forums/showp...3&postcount=33

Every time a new thumper comes out I get excited and think it might be something to replace the DR. Then I read posts like this. All that just to change the oil.

[Mongle]

Originally Posted by procycle

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.

.

Yes, when we stroke the pin ends up being into the oil rings. No biggie though, you run a shorter pin with a support rail. Like so:




Two diffrent ways of getting the same tamato juice! We often go this route to keep rod length longer for geometry and because custom rods are more expensive then the pistons. Of course, you only need one rod...we need 8

[Albie]

Originally Posted by trailrider383

This post makes me appreciate my simple DR all the more. http://www.advrider.com/forums/showp...3&postcount=33

Every time a new thumper comes out I get excited and think it might be something to replace the DR. Then I read posts like this. All that just to change the oil.

What's the big deal, I use Rotella in my DR.

[RichBeBe]

Originally Posted by Mongle

Two diffrent ways of getting the same tamato juice! We often go this route to keep rod length longer for geometry and because custom rods are more expensive then the pistons. Of course, you only need one rod...we need 8

You could also run the stock length rods and use a cylinder spacer on the DR. Just another tomato juice.
We would do that on some bikes that could run stock rods on stroked cranks (two piece rods with plane bearings made it easier)Though somewhere i have a cylinder spacer for a stroked RZ350 laying around.
Not gonna work on your V-8's though

[YnotJP?]

We got many rods from Spade Carillo in the mid 1960's, for small block Fords and Chevys. Never had a rod problem.
They are a thing of beauty. Needing only one is nice. But, you should buy two, just to have one to hold and look at.

[trailrider383]

Originally Posted by Albie

What's the big deal, I use Rotella in my DR.

Say what?

[procycle]

Originally Posted by RichBeBe

You could also run the stock length rods and use a cylinder spacer on the DR. Just another tomato juice.
We would do that on some bikes that could run stock rods on stroked cranks (two piece rods with plane bearings made it easier)Though somewhere i have a cylinder spacer for a stroked RZ350 laying around.
Not gonna work on your V-8's though

Yeah, but if you're after 10 mm more stroke there are multiple problems to overcome after spacing up the cylinder. Cam chain length, upper motor mounts, fitting carburetor and exhaust pipes, oil lines, etc. It's certainly a lot easier with a 2-stroke.

[canoli]

So the ongoing struggle to get my Safari tank dialed in continues. When I last checked in you guys told me to fill it up and see how far I can get before it craps out. Seemed like the logical thing to do so I filled it with 33 liters (still had some in the tank when I rolled up to the gas station) and rode it for 275 miles. Then 5 miles from town in 108 degree heat, it stopped. It looked like I still had a lot of gas left so the only thing I could do was shake the bike a bit and luckily got some gas into the engine. Once at home I let everything cool down and I sprayed the carb inlet elbow with ALOT of WD40 and proceeded to empty the remaining gas into another container. When the Safari finally ran dry I found that it still had an additional 4 1/4 liters of gas remaining…and I was pissed. So I stripped the tank off grabbed a set of vice grips and cranked the elbow over to the 90 degree position. Was pretty happy that nothing snapped off and after I put the tank back on I re-routed the lines and removed the cheap inline filter I installed.



This is what it looks like now.


Does this look right to you? How bad is that bend in the hose?

Going out for a ride tomorrow and hopefully I can get another 50-60 miles before it goes dry. If not, I might be putting the Safari in the flea market and picking up a Acerbis. I really need the range and don't want to carry external containers if I don't have to.



Stay tuned and thanks again for your help.
Canoli

[Rusty Rocket]

Originally Posted by RichBeBe

You could also run the stock length rods and use a cylinder spacer on the DR. Just another tomato juice.
We would do that on some bikes that could run stock rods on stroked cranks (two piece rods with plane bearings made it easier)Though somewhere i have a cylinder spacer for a stroked RZ350 laying around.
Not gonna work on your V-8's though

Easy on a 2 stroke, but with OHCam, you'd need a longer camchain. That was how I immediately thought it would be accomplished, but the more I thought about it, the more confused I became.

[RichBeBe]

Originally Posted by procycle

Yeah, but if you're after 10 mm more stroke there are multiple problems to overcome after spacing up the cylinder. Cam chain length, upper motor mounts, fitting carburetor and exhaust pipes, oil lines, etc. It's certainly a lot easier with a 2-stroke.

Originally Posted by Rusty Rocket

Easy on a 2 stroke, but with OHCam, you'd need a longer camchain. That was how I immediately thought it would be accomplished, but the more I thought about it, the more confused I became.

Agreed, I was more stating another option. The shorter rod is the way to go since you have the skirt clearance. The engine mount is the only real problem that I see on a DR.
We used to do it on a lot of 4-strokes, some you needed a new cam chain and some you didn't though rarely were the strokes 10mm. Though we did make and sell a few .250" spacers for Suzuki GS1150;s, which would be a for a pretty big stroke

[amk]

Originally Posted by canoli

So the ongoing struggle to get my Safari tank dialed in continues. When I last checked in you guys told me to fill it up and see how far I can get before it craps out. Seemed like the logical thing to do so I filled it with 33 liters (still had some in the tank when I rolled up to the gas station) and rode it for 275 miles. Then 5 miles from town in 108 degree heat, it stopped. It looked like I still had a lot of gas left so the only thing I could do was shake the bike a bit and luckily got some gas into the engine. Once at home I let everything cool down and I sprayed the carb inlet elbow with ALOT of WD40 and proceeded to empty the remaining gas into another container. When the Safari finally ran dry I found that it still had an additional 4 1/4 liters of gas remaining…and I was pissed. So I stripped the tank off grabbed a set of vice grips and cranked the elbow over to the 90 degree position. Was pretty happy that nothing snapped off and after I put the tank back on I re-routed the lines and removed the cheap inline filter I installed.



This is what it looks like now.


Does this look right to you? How bad is that bend in the hose?

Going out for a ride tomorrow and hopefully I can get another 50-60 miles before it goes dry. If not, I might be putting the Safari in the flea market and picking up a Acerbis. I really need the range and don't want to carry external containers if I don't have to.



Stay tuned and thanks again for your help.
Canoli

I cannot pinpoint you to the exact cause of the problem, but the theory of problem solving is simple enough. DR does not have a gas pump, i.e. gas flows free to the carb by its weight and atmospheric pressure.
So the first one is to make sure the carb's inlet is below the petcock. The last usually has a pipe of 5 cm. height inside the tank, so everything under the the pipe is stayed there forever and cannot be used.
Second, make sure the gas inside is under the atmospheric pressure, the breather is not blocked etc. Just take the gas cap off and depress start button again.
Third, remove all barriers between tank and carb's inlet, i.e. filters, here I am not sure, but there probably is a small oem one right in the tank petcock or in the carb. Take the petcock out, open it, disconnect the hose from inlet and blow into petcock, should be no resistance to the air flow.
It is one of three reasons, which one is yours? It actually may be all 3 of them simultaneously.

[Kommando]

Originally Posted by canoli

So the ongoing struggle to get my Safari tank dialed in continues. When I last checked in you guys told me to fill it up and see how far I can get before it craps out. Seemed like the logical thing to do so I filled it with 33 liters (still had some in the tank when I rolled up to the gas station) and rode it for 275 miles. Then 5 miles from town in 108 degree heat, it stopped. It looked like I still had a lot of gas left so the only thing I could do was shake the bike a bit and luckily got some gas into the engine. Once at home I let everything cool down and I sprayed the carb inlet elbow with ALOT of WD40 and proceeded to empty the remaining gas into another container. When the Safari finally ran dry I found that it still had an additional 4 1/4 liters of gas remaining…and I was pissed. So I stripped the tank off grabbed a set of vice grips and cranked the elbow over to the 90 degree position. Was pretty happy that nothing snapped off and after I put the tank back on I re-routed the lines and removed the cheap inline filter I installed.
This is what it looks like now. Does this look right to you? How bad is that bend in the hose?

Not quite right. The DR and other carbed bikes are primarily fed by gravity. There's a bit of suction/siphon going on too, but the primary method of getting gas into the carb from the tank is by gravity feed. As long as there is no kink or blockage in the line, you basically just want the fuel to NOT have to flow uphill to get into the carb. Suction will overcome a little bit, but it can also allow air-bubbles to get into the line and affect fuel flow. The flow from my petcock to my carb is all either down or sideways. There is no uphill flow. As long as my tank is venting ok, I have no flow issues. I can run my tank pretty dry. Route your fuel lines so that there is NO uphill flow. If you can't do that, you may want to install a fuelpump.

[TRAVELGUY]

I had a temporary problem with emptying my safari also. Was getting a vapor lock at the aftermarket filter I had installed. Changed to a different filter and all went well. When the vapor lock happened I could just blow into the tank vent and clear the vapor lock then tank would empty. When I disconnect my fuel lines from the carb to drain my safari the tank totally empties.

Hope this info helps.

TravelGuy

Originally Posted by amk

I cannot pinpoint you to the exact cause of the problem, but the theory of problem solving is simple enough. DR does not have a gas pump, i.e. gas flows free to the carb by its weight and atmospheric pressure.
So the first one is to make sure the carb's inlet is below the petcock. The last usually has a pipe of 5 cm. height inside the tank, so everything under the the pipe is stayed there forever and cannot be used.
Second, make sure the gas inside is under the atmospheric pressure, the breather is not blocked etc. Just take the gas cap off and depress start button again.
Third, remove all barriers between tank and carb's inlet, i.e. filters, here I am not sure, but there probably is a small oem one right in the tank petcock or in the carb. Take the petcock out, open it, disconnect the hose from inlet and blow into petcock, should be no resistance to the air flow.
It is one of three reasons, which one is yours? It actually may be all 3 of them simultaneously.