Topic: DP315 cam: Valve lash 0.25-0.30mm reduced to 0.10/0.15mm - less comp. Cam tests

[PeWe]

I adjusted my DP315 cam today. This profile is an old RC315 with recommended valve lash of 0.3mm. (0.012").
I have had thoughts about the risk the lash will hammer dimples in the lash caps. (5mm valve stems)

I have measured the cam before and noticed how much the overlap change (increase) with the less ("normal") lash of 0.1 mm (0.004") IN, 0.15 mm (0.006") EX.
Checked compression after adjustments.  Now in the 145-160 PSI area, last summer 175-180 PSI (probably 0.25mm lash)
Maybe 0.3mm wich is the recommended on cam card.

No other changes except for about 2000 km since last compression check.
First 600 km this year with Red Line fuel additive to clean chambers and pistons from carbon due to too rich needles last year. (SI-1 COMPLETE FUEL SYSTEM CLEANER)
This should not reduce that much if all carbon left the chambers/pistons.

Butt dyno:
Engine lost torque, is more "screamy", love higher rpms. I noticed less torque since I needed to gear down to 4:th more than usual. It felt weaker around 180 kph on a smaller road in windy weather. Before better response when twisting throttle against the wind on 5:th gear.
Nice sound when letting it rev up to +9000 on 3:rd before 4:th.
Engine idle has now less mechanical rattle with less valve lash.

I have wondered about the DP/RC315 huge valve lash.
1.) Cam found too give too small amount of torque, workaround is more lash that reduce the overlap.
2.) Adjustable cam: Much lash for more torque, less lash for a "racer" cam (higher overlap).
3) Adjustable for high CR pistons. The adjustments of today should like >12.5 CR pistons. (mine around 10.5:1)

I'll increase compression with next cam.
I like less rattle and more torque.
I'll try Megacycle 125-20 first and hopefully get compression back to 180 PSI something.
It had 52.5 degrees overlap at 0 lash, less at 0.1/0.15mm lash

The DP315 had 54.5 degrees overlap at 0.3 mm lash (68 degrees at 0 lash) My measurements when timing the cam.

The "RC295" numbered cam had 47 degrees overlap at 0 lash.
0.1mm IN, 0.15mm EX lash will reduce overlap.

Compression and cams have to be matched.
My bike various bores have had good street manor with 180-195 PSI compression without pinging getting soo hot. Hotter it runs, better oil it has to get

I knew that I have to do some work again 

[MRieck]

 Per....that's the beauty of lash caps....easy to replace. A lot of duration does that with cams....you need gap to get the valves closed long enough to build pressure. I would try .006 intake, .008 exhaust and see what that does.

[754]

PeWe,  I an slightly  confused as too what they were it when you felt more torque?

I am surprised at how well my 836 with a 315 pulled at 4K. Better than my Andrew's A in a stock bore/compression
But I had other stuff done that helped Dow  low on the 836,m like ...
small dia primary pipes..... Webers.. and maybe unported  head, and higher compression.

 The A has nothing under 3K, just a dog.. I expected better midrange, and less up top..  it does pull fairly hard after 6K.

[PeWe]

Frank, the cam work really fine with the recommended lash. Smooth and even power all the way up to +8000 rpm. Good torque from low as well.
I made a test yesterday to reduce the lash to more "normal" values. This reduced the compression due to the increased overlap and engine felt different.

I'll see how the compression will be cranked up by the Megacycle 125-20. I have also RC295 and CX-7 on the shelf and my oldest cam Action Fours SS-1.

- Maybe others have same experience of a modified CB750?
Compression measured by a simple compression tester, around 175 PSI is minimum.
Cam will affect that. More overlap decreasing the compression, need higher CR pistons. I had 185-190 PSI with my 836 and old RC pistons. More than that might cause pinging on std fuel.

Mike, I liked the smooth sound when I reduced the lash. 
I'll see how the next cam will work. I hope it will have a smooth power curve and not too much power increase around 7000 rpm so I'll loose the grips
It would be fine with more cams to try, 125-60 and /70 

I'll check the compression on one cylinder with different lash before making the surgery.
I have planned to test the Megacycle 125-20, it has hard welded rocker arms in it's box

[livefast_dieold]

I've been banging my head on a wall with the valve lash of the DP315 for a couple of years now.

I'm actually using 0.2 mm of lash (high compression pistons), it seems to be the perfect combination for torque vs high rpm HP. Consider that on the track I never use the bike below 6000 rpm

[PeWe]

Did you hear the difference at idle?
Lash  0.3mm, engine has a harder sounding idle, more hammering. 0.1in/0.15 ex softer sound.
It depends on the  pistons too. 12.5 CR pistons must work different than mine that give around 10 something with my head.

I saw that a package has arrived with parts at my post office, new adjuster screws so I can change cam and rockers that will get new adjusters. Boring weather make me tired and lazy.
More compression values will follow.

[754]

I've been banging my head on a wall with the valve lash of the DP315 for a couple of years now.

I'm actually using 0.2 mm of lash (high compression pistons), it seems to be the perfect combination for torque vs high rpm HP. Consider that on the track I never use the bike below 6000 rpm

This first paragraph I do not understand?
 You buy it from a cam manufacturer, set it to the specs they recommend, it should work..
 I don't have enough experience to second guess them, I left the research to them.
 You can't expect things to stay the same when you start extensive mods, of course many of the mods will short ten engine life and cause noise.. there is no free lunch..

[PeWe]

These experiences are good to have in mind to tune the compression and cam timing. Increase valve lash and compression will increase. But lower lift and duration. Different In vs Ex can change the behaviour too.
So, there are things that can be tuned despite a single cam.

I'll see which cam it will end up in the end. I like the DP315 cam with 0.25-0.3 mm lash. Perfect for street. I did not realize how much the lash affect the compression.

[livefast_dieold]

I've been banging my head on a wall with the valve lash of the DP315 for a couple of years now.

I'm actually using 0.2 mm of lash (high compression pistons), it seems to be the perfect combination for torque vs high rpm HP. Consider that on the track I never use the bike below 6000 rpm

This first paragraph I do not understand?
 You buy it from a cam manufacturer, set it to the specs they recommend, it should work..
 I don't have enough experience to second guess them, I left the research to them.
 You can't expect things to stay the same when you start extensive mods, of course many of the mods will short ten engine life and cause noise.. there is no free lunch..

That's what I know as well! But apparently for the DP315 was "designed" this way back then, basically, you fine-tune duration with valve lash (that's what I have understood with the information gathered so far here and there). This was confirmed also by Buzz @Dynoman.

[754]

 I agree, experimenting can find new things..
 But in the back of my mind, there was a reason for the recommended lash.. they must have tried a few different figures.
I know people that ran cams that recommends .006 and ran less right out of the box..  due to worry.. I worried less about a bit of wear, than it actually working well..
 I suspect the big lash increases lubrication. It's Not as loud as zi expected it to be.  But I dontvreally let it sit and idle either.

[PeWe]

The relatively huge lash of the RC/DP315 has been up before and no absolute reasons found. Except for easier lubrication of cam lobes, longer cooling times in seats.
I started to think that the lash is one way to crank up the compression for CR 10 something pistons. Cam became popular and widely used. Guys with more CR might have installed it with smaller lash and got a good working combo.

livefast_dieold might have more CR and smaller lash work therefore really fine?

I ordered pistons that should give around 10.5:1 in my 24.4cc chambers. Pistons look like the 12.5:1 pistons but machined a little to adapt the compression. 5 g is missing
http://www.dynoman.net/images/engine/piston/dp1000-71r/DP1000-71r.jpg
The 10.5 pistons weigh 185 g, 12.5:1 195 g, mine 190g.

[PeWe]

I have changed cam to Megacycle 125-20
Lash: IN 0.1mm, EX 0.15mm  Compression 185 PSI  (cyl 1,4 - 185 PSI, cyl 2,3 - 180 PSI)
I have not done any road test (boring weather). It sounds fantastic when I started it and let it idle. Really quick throttle response.

I'll see if it will be as nice as the DP315 was with its recommended lash. Good torque from low. I hope the clutch will not slip 

DP315 compression in same cylinder had 155-172 PSI depending on the lash. 172 PSI with 0.3 mm which is the recommended.
155 PSI  with 0.1/0.15mm (Other cylinders had 145, 150 PSI. Cam lobes differ some or in combination with lash not equal)

EDIT: Added photos of my compression tests on cyl 4. DP315 and last with higher compression Megacycle 125-20
Cheap one but must work OK when comparing, rel meas. abs might not be exact.
http://images.biltema.com/PAXToImageService.svc/product/large/2000022140

Megacycle 125-20 cam has different data on Internet. (Wrong compared with mine and cam card)
This is the cam card from megacycle that was shipped with the cam.
IN: Total lift:  0,388"  (9,85 mm)   268°  29°/59°   105°      
EX:  Total lift: 0,337" (8,56 mm  283°   73°/30°   111,5°
Overlap: 59

Megacycle 125-20 cam timing:
at 0 lash and 0.04" lift
IN: Total lift:  0,379" (9,63mm)   dur: 265,5°  open/close: 28,5°/57°  LC: 104,25°
EX: Total lift: 0,329" (8,35mm)   dur: 279°       open/close: 75°/24°     LC: 115,5°   
Overlap: 52,5

at running lash 0.1mm/0.15mm and 0.04" lift
IN: Total lift:  0,376" (9,54mm)   dur:  262° open/close: 26,5°/55,5°   LC: 104,5°   
EX: Total lift: 0,320"  (8,13mm)  dur:  276° open/close: 72°/24°          LC: 114°
Overlap: 50,5°

DP315 cam timing:
at 0 lash and 0.04" lift
IN: Total lift: 0.368" (9,35mm)  Dur: 278,5°  open/close:35°/63,5°     LC: 104,25°   
EX: Total lift: 0.368" (9,35mm)  Dur: 282,5°   open/close:67,5°/35°    LC: 106,25°
Overlap: 70°

at running lash 0.30mm/0.30mm and 0.04" lift
IN: Total lift: 0.352" (8,95mm) Dur: 265°   open/close:28,5°/56,5°   LC:104°
EX: Total lift: 0.354" (9,0mm)  Dur: 266°   open/close: 60°/26°        LC: 107°
Overlap: 54,5°

My conclusion is that the overlap with running lash should be around max 55° with CR 10.5-1 (50° better  )
The compression in my engine will probably increase a bit if I use my RC295 that had 47° overlap at 0 lash, less with running lash.
Maybe 190-200 PSI something
170 PSI seems to be minimum.
150 PSI work but engine is dull and boring. Probably OK in countries with low octane gasoline.

DP315 with smaller lash must be OK with CR 12.5 pistons.  12.5 pistons might be the recommendation for that cam in general?

This reminds me about when messaging with Mike  5 years ago that recommended not that much duration but higher lift that fits my 34mm inlet valves. This will keep up the compression.
I have confirmed that now by practical tests with 836, 900 and finally 1000cc. I have learned how my bike will feel the differences too. 

10.5-1 is generally recommended for street use... But some cams need more

Update April 30:
Road test today in boring and a little bit windy weather. My butt told me that the DP315 with 0.30 mm lash has more torque, earlier as well as later... 160-180 kph on a country road, DP315 has better response on 5:th gear. Windy weather add some more resistance.

I had higher expectations about more compression when testing. It might act different when engine works, exhaust opens so much earlier with less lift as well.

I'll see if the DP315 returns direct or if I let CX-7 to visit with a little bit more lash for a few degrees less
Nothing done in vain, the rockers needed to be replaced anyway.

[PeWe]

Changed cam today again. RC295 copy went in. A cam I found used on eBay with RC295 scratched on its side under the washer.

Franks frame kit has worked hard as saloon doors since a few years back. I have lost the count of all frame off-on, off-on changing cams and move engine out and in.

"RC295"
at 0 lash and 0.04" lift
IN: Total lift:  0,391" (9,93mm)   dur: 259°  open/close: 25°/54°   LC: 104,5°
EX: Total lift: 0,361" (9,18mm)   dur: 257°   open/close: 56°/21°  LC: 107,5°   
Overlap: 46°

at running lash 0,1/0,15mm (.004"/.006") and 0.04" lift
IN: Total lift:  0.382" (9,70mm)   dur: 254.5°  open/close: 22.5°/52°   LC: 104.75°
EX: Total lift: 0.354" (9,00mm)   dur: 251°   open/close: 53°/18°  LC: 107.5°   
Overlap: 40.5°
Compression measured is between 185 -195 PSI.

This cam has harder idle than DP315.
No road test yet. Let's see if it has same really good low rpm torque as the DP315 has with its recommended lash of 0.3mm.
DP 315 is a really good street and touring cam with calm idle in my engine.

I'll not test CX-7 since I have seen other dynos with that cam and remember how it was with 836.

Not as early torque as my dyno runs with DP 315  and Lotus Root 4-4 pipes. Diffusors in gave earlier torque bumb between 3000-4000. No diffusors in, even more torque came later at 4000-6000 rpm
No numbers 4-4 pipes without diffusors gave more top hp but less torque.

Maybe the DP315 cam will be the best cam for my setup and street use and need of early torque.
Difficult to be without when I have got the taste for it.

If my butt like the "RC295" combo, I'll take it to the dyno to measure.

[PeWe]

Road test of the RC295 today. Cam is approved by the butt method!
Nice raw power with less need of gearing down when passing cars. Thought that 3:rd was in when twisting the throttle but tacho revealed that 4:th was in.
Again need to watch out when twisting and release in time since 180 kph happen really quick.

DP 315 is also a good cam but must have lash around 0.25-0.3mm to get the power.
Why not a RC315 with 0.15mm shaved off the lobes? Same cam with half lash than original with 0.3mm lash, right?

Both these cams work fine with 4-4 pipes. The overpriced early CB750 design, Yamiya Lotus Root with less restrictive junk inside work fine with both RC cam profiles.  I have drilled diffusers in the pipes, not that loud and the old CB750 look.
HM300 replica pipes No numbers work too but no diffusers is a must.

I'll check a day for a dyno to get the power printed.
Photos of the cams, DP 315 and cam with RC295 lightly engraved on the washer side. Maybe an old one?

I'm sure most of you have seen them many times. Same with nude women...seen many but always very interesting...still..

[TurboD]

Pewe it is great to see someone experimenting and thinking out side the box, too many simply bolt a part in as per manufacturer specs. I learned that playing with valve lash can be huge during my time building racing 4 stroke go cart engines.

Your results to this point are spot on as to what I would expect with the cams tested. I have said it before and will say it again. I don't care for many of the old RC DP cam grinds, the 315 is one on them. I never liked all the lash required to make it perform (usable), I have always said the 295 was the best most usable choice between the 2.  For the record opening up valve lash is most always harder on everything not easier.

Look forward to your findings.

[754]

My 836 went  about 24 years if on and off use with a 315 in it set at.012.
 Because I ran the turbopipe, I suspect it eventually caused a guide or two to stick.. stock guides.
 That then hammered a few lobes on the cam.
 I should dig out the cam and measure it, see  the other lobes or journals are worn..

[TurboD]

I am sure that a 315 will last forever at the suggested lash... My comment was in general, a wider lash can tend to "hammer" or "shock" the entire valve train (cam included) causing extra wear. When I see a cam with a suggested lash setting that is greater or out of the norm (bike car gocart), I always think something is being Bandaided.

[MRieck]

I am sure that a 315 will last forever at the suggested lash... My comment was in general, a wider lash can tend to "hammer" or "shock" the entire valve train (cam included) causing extra wear. When I see a cam with a suggested lash setting that is greater or out of the norm (bike car gocart), I always think something is being Bandaided.

...or the application is pretty unique.

[PeWe]

Good to get response about similar findings
I had to write about it here since it can help others using same or similar cams or getting a result as I have seen.  And it's fun to open a discussion about cams with the pro's that have decades of experiences.

The exhaust system must be an important factor and how the bike is ridden too. I start to understand why there are so many cam profiles for the CB750.

The funny thing is that DP315 feels like a softer cam than the 295 profile. Probably less abuse on the valve train too. The idle when the lash was small was very soft and smooth. 1000 rpm no problem. 295 runs harder and the torque is really good.

The Megacycle 125-20 worked better with rather open 4-1.

I'm sure there are no bad cams out there, it must be matched with the other parts and how it will be used.
I did no test CX-7 since I'm sure it must have a good 4-1 or 4-2-1. I remember when I used it with my 836 and how loud my bike was. Really screaming with my old 4-1. When I replaced the cam with my old action fours SS-1 cam I got the old well known sound from the 80's back.
I hope I can get time for dyno in May. This will show the difference compared with DP315 that I still like. It had good smooth and a little bit softer power compared with the 295.  Graphs will be published here when available.

I might get ideas to build another engine with higher compression to see how the DP315 will like that. Complete old K1 lower part is under my bench, 849 and 900 setups are also on the shelf together with an old ported head, VM29 carbs. Plus CB900 rods to crank up the compression. Hindle 4-2-1 also in my garage. I had plans to use it on this bike but it work so nice now with the 4-4.

Question is if it will be tested in my K2 build that has a restored and completed stock engine. It has also a Frank frame kit for easy cam swaps.

Edit: Just got answer from my local tuning shop that they have moved to another building, dyno not yet ready. Have to wait until summer.

[TurboD]

I would be curious as to back to back dyno numbers on both cams. I have more than once removed a 315 and replaced it with a "smaller" other brand cam to end up with a better performing bike. I just sold a like new 315 on feebay last week, no more for me.

I have also used cam simulator programs to help pick and design cams for nearly 20 years, With the proper knowledge and experience they can be very accurate. Even on a simulator the old 315 does not fair well, in fact the 295 (though not great) shows making more power from idle all the way up to any reasonable redline. Pewe your 315 feels softer than the 295 simply because it is.

[livefast_dieold]

I would be curious as to back to back dyno numbers on both cams. I have more than once removed a 315 and replaced it with a "smaller" other brand cam to end up with a better performing bike. I just sold a like new 315 on feebay last week, no more for me.

I have also used cam simulator programs to help pick and design cams for nearly 20 years, With the proper knowledge and experience they can be very accurate. Even on a simulator the old 315 does not fair well, in fact the 295 (though not great) shows making more power from idle all the way up to any reasonable redline. Pewe your 315 feels softer than the 295 simply because it is.

Interesting, can you name the software you are using?

[PeWe]

It's a pity that I cannot see the power on dyno for a while. The bike feels strong and I worry about clutch slip.
It would be nice to see an array of cams with the torque curves. I like early strong torque, not tame screaming revs up to after 5500-6000 rpm where the torque suddenly wake up with a fun area around 6000-9000 and demands really open exhaust. I think that this is OK in race bikes and probably referred.

[PeWe]

TurboD, did you try higher CR with the 315 cam? Like 12.5:1

[TurboD]

I have tried a number of versions over the years, I use the old desktop dyno and dyno2000 the most. I still have not found one that I like or feel good about when it comes to power adders. *Note* any and all of these are no different than any other tool used for testing, they are only as good as the operator and take some learning.

Pewe When testing with the sim software I have tried every combo I could come up with. Yes on the baseline engine setup I use, the 315 at 12.5 shows a 7hp gain at peak power over 10.5. Again, at 10.5 or 12.5 the 295 still shows an advantage over the 315. Interesting enough, the 315 at 12.5 only shows 4hp more at peak power over the 295 at 10.5.

[gschuld]

Interesting.  What are the HP peak rpm numbers between the 295 and 315?

I’m assuming the 295 peaks a bit lower.

George