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DR650 Cam Evaluation (Read 1202 times)
DragBikeMike
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DR650 Cam Evaluation
05/02/18 at 23:01:50
 
I have finished my evaluation of the DR650 camshaft.  I have learned a few things in the process.  For instance, you must use the rocker arms to establish the correct timing events.  The rocker ratio changes as the rocker arm swings through it's arc.  The ratio increases as the cam lobe moves the valve to towards the max open position.  Geometry, should have paid more attention to that class.  

Here is a picture of what does not work:
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DragBikeMike
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Re: DR650 Cam Evaluation
Reply #1 - 05/02/18 at 23:04:09
 
Here is a picture of another setup with a short travel indicator.  The data looked a lot better, but I could tell it still wasn't right.  Gotta have those rocker arms in the mix.
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Re: DR650 Cam Evaluation
Reply #2 - 05/02/18 at 23:08:10
 
So I bit the bullet and pulled off the head cover.  Now I could check the valve timing with the rocker arms included in the mix.  Here is a shot of a good setup.  Note that the dial indicator is now contacting the valve adjuster tip on the rocker arm.  The indicator is angled to the exact angle of the rocker adjuster.  It was easy to setup and the numbers were repeatable and very accurate.
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DragBikeMike
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Re: DR650 Cam Evaluation
Reply #3 - 05/02/18 at 23:21:09
 
Here are the timing numbers on the DR 650 cam.

@ .040"

I/O 14 degrees BTDC
I/C 46 degrees ABDC
Duration 240 degrees
Max lift .365"
TDC lift .090"

E/O 52 degrees BBDC
E/C 8 degrees ATDC
Duration 240 degrees
Max lift .364"
TDC lift .068"

Valve overlap 22 degrees


@ .050

I/O 10 degrees BTDC
I/C 42 degrees ABDC
Duration 232 degrees
Max lift .365"
TDC lift .090"

E/O 48 degrees BBDC
E/C 4 degrees ATDC
Duration 232 degrees
Max lift .364"
TDC lift .068"

Valve overlap 14 degrees
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DragBikeMike
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Re: DR650 Cam Evaluation
Reply #4 - 05/02/18 at 23:51:37
 
I am confident that these timing numbers are within +/- 1 degree and +/- .001".  They are more precise than the numbers I collected on the stock cam (see prior post "cams stage1 vs stage 2 vs stage 3") because I didn't have to fight with the valve springs and alternator auto rotating the engine.

Comparing the DR 650 cam @ .050" lift points to the stock LS650 cam @ .050" lift points  yields the following:

The DR cam opens the intake valve 30 degrees earlier.  This has to promote a much better cylinder fill.  Intake noise and blowback at low speed will probably increase but it should be negligible.

The DR cam closes the intake valve 8 degrees sooner.  This should bump up effective compression ratio and may make the engine a bit more prone to detonation.  This cam is less desirable for increased compression ratios and increased displacement since increasing displacement generally increases compression ratio unless you enlarge the combustion chamber volume.

The DR cam opens the exhaust valve 12 degrees earlier.  This has to promote better blowdown, but the exhaust noise will probably increase a bit.

The DR cam closes the exhaust valve 12 degrees later.  This should improve cylinder evacuation at higher speeds.

The DR cam has 14 degrees of valve overlap (stock has zero).  This will promote better cylinder evacuation and fill due to the inertia of the gases.

The DR cam has .030" - .032" more lift.  I assume this is not a problem with spring coil bind since the DR uses the same springs as the LS and several members of the forum have reported that they are running the DR cam with the stock LS valve springs.  The additional lift should get the gases in & out a little quicker.



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DragBikeMike
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Re: DR650 Cam Evaluation
Reply #5 - 05/03/18 at 00:05:27
 
Observation.  I noted that the stock LS650 cam has oiling holes drilled in each lobe.  Pressurized oil flows through heavy chamfers in the LH cam bearing into a void on the left side of the cam.  That oil then fills the hollow cam body and is forced out through these oiling holes.  I'm pretty sure the intent is to force oil between the rocker pad and the cam lobe.  The DR650 cam does not have these oil holes.  It is most certainly hardened steel and would be difficult to drill.  A #47 drill bit fits perfectly.  That's a very small bit and could break quite easily.

There is a reservoir directly below the cam lobes.  That reservoir is supplied oil from the RH cam bearing via a heavy chamfer.  The cam lobes dip into the reservoir so they have a sort of splash lube system.  Obviously, the DR cam survives without pressurized oil lubricating the lobes and rocker pads.  Question is, will the LS engine function OK like that.  I messaged a forum member who runs the DR cam.  He was aware of the absence of the oiling holes and said his runs just fine on the splash lube system.  He has logged approximately 5000 km with no adverse effects on cam or rockers.  7/13/23 This is bogus.
Drill the holes.  They provide lubrication for the main bearings. DBM


Here is a pic of the stock LS cam oil hole.
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« Last Edit: 07/14/23 at 01:07:17 by DragBikeMike »  

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Re: DR650 Cam Evaluation
Reply #6 - 05/03/18 at 00:06:14
 
Here is a pic of the DR cam without oil holes.
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Re: DR650 Cam Evaluation
Reply #7 - 05/03/18 at 00:16:48
 
The DR cam looks like a good cam for a mildly modified engine.  It does not suit the engine that I ultimately intend to build, but for now, I will probably throw it in just to see how it runs.  I have the cam and I'm half done with the preps so what the heck, might as well try it.

I don't think it will work well in a street application with major increases in compression and displacement.  The intake valve closes too early.  The engine would be harder to start, prone to detonation, and possibly be sensitive to heavy traffic and hot weather.  This is bogus.
The cam works great with lots more compression and doesn't pose any problem whatsoever in a street application.  I was dead wrong.
DBM 7/12/23
 The stock DR has 9.5:1 compression so I'm sure it would work good up to that point.  If you have exceptional gas in your neck of the woods (I've heard that 100 octane is available in some regions), I would say no worries.

I hope this data sheds a little light on the DR cam.  It's affordable and certainly an improvement over the stock LS cam.  If I stick the stick in my scooter, I'll let you all know how it works.
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« Last Edit: 07/14/23 at 01:11:00 by DragBikeMike »  

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Re: DR650 Cam Evaluation
Reply #8 - 05/03/18 at 11:52:07
 
BTW, regarding the indicator setups that don't work.  I was taking readings directly off the cam lobes, and then multiplying those values by 1.38 to get values equivalent to movement at the valve.  Since the rocker ratios are a moving target (constantly changing as the cam lifts the rocker) it just won't work.  Also, max lifts calculated using cam BC vs lobe height do not agree with the numbers gathered with a dial indicator.  Obviously, the indicator measures what is actually going on, so if you want actual lift at the lobe, use a dial indicator.  Maybe Stephen Hawkings could have figured it out but it was way past my limited grasp of mathematics.  Direct readings off the valve or rocker arm are the only way to go.
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Re: DR650 Cam Evaluation
Reply #9 - 05/03/18 at 11:55:05
 
Good work Mike.
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Re: DR650 Cam Evaluation
Reply #10 - 05/03/18 at 14:01:31
 
That was an excellent  report Mike.

I'm sure I can speak for most of us. Many thanks. Smiley
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Re: DR650 Cam Evaluation
Reply #11 - 05/03/18 at 15:33:51
 
Excellent work and great report! Thanks!
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Re: DR650 Cam Evaluation
Reply #12 - 05/03/18 at 22:56:54
 
DBM , Another  job well done ! but I don't think the valve lift has as much to do with the increase in hp and torque ,as the fact that the DR cam has overlap and the stock cam doesn't, and their duration is longer. You stated that because of the increased lift the flow in and out is faster , that maybe true as the valves first open ,and the compression is higher,  but the velocity may also fall off faster as the valves open farther and the passages in the Savage head are still of poor design.
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DragBikeMike
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Re: DR650 Cam Evaluation
Reply #13 - 05/05/18 at 12:55:58
 
I guess my comment about getting the gasses in & out quicker was poorly worded.  I don't mean that the additional lift will increase velocity.  What I am getting at is that the cam is going to ramp the valve open a bit faster, which in turn will most likely fill the cylinder & combustion chamber faster.  Of course, that's purely a guess.  I'm basing that guess on the intended application.  The cam was designed for an enduro bike.  It's intended to provide a broad power band with good low end.  Whether or not the additional lift helps or hurts the LS engine will always be a mystery to us.  We don't have the resources to properly test and evaluate the additional lift.  Let's face it, at a certain point, opening the valve any more won't result in additional flow.  The port will be the controlling factor.  But leading up to that point where the port controlls the flow, the DR cam will have positioned the valve at higher lifts than the stock cam would have provided.  Also, if the ports can actually benefit from the higher lift (i.e. the port becomes the controlling factor at a lift point higher than .365"), then for sure the higher lift is beneficial.

I agree that the overlap and additional duration are probably the most beneficial features of the DR cam over the LS.  
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Re: DR650 Cam Evaluation
Reply #14 - 05/08/18 at 05:47:29
 
I had a first ride with the DR cam combined with a well tuned VM36 w. UFO yesterday. A complete blast to ride, lots and lots of torque. Then I noticed some oil bursting out from between my legs, the intake valve inspection cover had came loose and both bolts were just barely on their threads. Friend brought me some oil with his Triumph Scrambler and off we go. On our ride back I noticed that both bikes have quite similar performance on a straight line, but the Savage feels like it is trying to tear my arms off  Grin
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