Topic: DP295 from Dynoman vs RC295 and a few other thoughts. (longish)

[y2kc0wb0y]

836cc 10.25:1 J&E pistons
Head ported with upgraded valves, hardware and short steel guides.

Goals - Street bike stop light to stop light drag racing

Thanks for all the advise on that rusty NOS RC295 from way back in the day. Looking at the available DP295 from Dynoman. When comparing against that rusty bump stick it looks different than the DP cam like the lobes were/are reversed. Long exhaust (rusty) vs. shorter exhaust (DP). That assuming the lifts are the same on the two cams. I don't think they are the same or that other cam is not a RC295.

On Dynoman's cam page, the advertised specs are different than the cam card for the DP295.

Website
Specs:
Total Duration: 306° in   296° EX
Lobe Centers: 105°
Lift: .390" IN   .360" EX
Lash: .004" IN    .006" EX

Cam card
Duration .272 In .  263 Ext
Lift@Cam 382 Int 357 Ext
Lobe Center 105 & 105
Lash .004 & .006

The cam card says "check" at .050" . Is that what we're looking at - measurements at .050" ?

Other thoughts

Are we still following the church that anything over .260 duration is going to be slow on the street until later in the rpms? If so, this cam is going to favor mid to top end. Can 836cc with 10:25:1 compression help over come this with port work or is that too mild CR to help? Seems like I should go for as much lift as possible under .260 duration?

[754]

Most people that get a ported head and  bore kit, spend very little time at lower Rpms. Remember you will have a higher rpm ceiling  as well ,  you will be riding at higher rpms than before.,

[Sam Green Racing]

y2, re your Goals - Street bike stop light to stop light drag racing.

I was a drag racer not the engine builder so can't help with any technical details, just the RIDER input.

In 2010, I had a CB750 Automatic built and tuned By Mike Rieck but I'll just stick with the cam and pistons for now.

I can't remember the make of camshaft but I think it was numbered 125 - 75 and was with 10.25 JE pistons. (edit, it was a Megacycle cam)

Over the first few years, it went fractionally quicker on every run as the all new motor settled in.

I was told the DP295 cam would make the bike much quicker so one was ordered and fitted and straight away it ran half a second quicker, a new PB.

Come 2013, the bike was run in and was constantly running consistent times until the end of the year.

I flew over from England at the end of 13 and at the first event, the bike left the line like a scalded cat and ran a full half second quicker, again another new PB but I felt something was not as it should be.

I asked what they had done and was told it had been bored to 915cc. I then told them that the power delivery didn't feel the same and was told the high end 125 - 75 cam was back in the motor.

I asked them to put the DP295 cam back in, they did this and it picked up another full half second with another PB time.

The DP295 in my opinion is the dogs balls for stop light to stop light racing.

Sam.

[PeWe]

"836cc 10.25:1 J&E pistons
Head ported with upgraded valves, hardware and short steel guides. "

You will be very happy with the DP295, thats for sure! 100%
- Head has race springs too, right?

Cam numbers can differ a lot depending on how measured.
Total open/close when valve start to open to fully close will give very high numbers.

Usually numbers are measured at either 0.04" (1mm) or 0.05" (1.25mm) lift. This to better compare cams.

Read crank degrees when valve has opened the specific lift, rotate crank and see at which degree when valve is back to the decided lift before closed.

The small lift in the beginning will not add much.
Cam sprocket must be adjustable do you can it right.
If you let cam open a little earlier (advanced), it will close earlier too, ex valves will follow.
This cam work fine rather "balanced".

I timed my cam @0.04" lift
In 25/55 degrees
Ex 55.5/22

I could have let it open  2-3 degrees earlier or later. The other numbers will follow.
Like retarding it 2 degrees to delay the power in the rpm
In 23/57
Ex 53.5/24

 But I was happy with my first setting since I know how tricky to only change 1 or 2 degrees when not really needed.

The running lash will balance it, retarding Ex a little compared with In when Ex lash is more. So that was probably the "best" setting.

I'm sure you will like the power earlier on a street bike.

Numbers will also differ a  degree  or 2 depending on play in the rocker arm/ shaft.
I reset the dial indicator when I have tightened the valve adj screw so it start to lift valve a little. (No problem if it is reset after 0.02mm movement)
This will overcome the lash.

This is to verify cam numbers.

To set it good for correct real life timing. Set valve lash to the running value. Like 0.004" In, 0.005" ex.

I set mine 0.004"/0.006" (0.1/0.15mm)
This is the feeler gauge I have.
More lash on ex will help valve to cool in seat a litle bit more, dynanic compression will increase with less duration too.
Not much difference....

[754]

I think he meant to print  clearance at .004 " and .006 "

[PeWe]

I think he meant to print  clearance at .004 " and .006 "

Yes,  I thought I missed a 0 but did not use the calculator

[y2kc0wb0y]

PeWe, 754, Sam.
Thank you for the RD295 information. I purchased a frame kit over a decade ago so I got off the couch and started that. I guess it will help making a cam decision easier knowing I can change my mind for $300 and some labor. FYI: duration numbers butt dyno are very helpful for my decision.

Definitely reworking a performance head I got at a swap meet for race guides, springs, retainer and keepers. The head has an issue with the oil jets housing (someone enlarged them?) but appears to have some nice porting work. I need to sort it but should be interesting once corrected. Will more than like run new 32/28 size valves unless the valve seats are too deep/smoked than probably up size the intake. So the cam would compliment all this effort.

All of which comes because my cam chain tensioner wheel came apart. queue the Violin.

[dragracer]

Personally,  I'd spend most of my money on the head work. That would include going to oversized valves and complimentary port and bowl work. Even a smaller bore with great head work will run better than a large bore with minimal head mods. Engines are just a pump, if you don't allow them to breathe and seal properly, they won't be efficient.

[754]

I would make a sleeve for the oil jet hole , and get them back to stock..

[PeWe]

The guides are cut? Look way too short.
Ports have too much material left. The area close to valve, important to be ported right  Not only a widened port a little bit in from carbs and no more.

I think it is better to start with a fresh head and port it.

Forum member MRieck does that kind of things and everything else making our engines to run better, stock to maximum!

There might be people with ported heads on the shelf. Old heads usually in need of new guides, seat cut and valves.

Below photos from my last refurbished head you can compare with.
Old K2 head to be used in a build.
It has 34mm in valves (F2), ports adapted for that too.  Stock size 28mm ex valves. Race springs, spring force measured when assembled. Ex needed shims.
This head should love to get a DP295!

Head sitting on my K6 (avatar bike) is carved a little bit more.

[scottly]

Regarding low end torque, even a stock cam will only produce maximum torque above 6000 RPM; it's just the nature of these motors.

[PeWe]

Different cams for a CB750 is a very interesting subject.

There are still many different cams available for these old engines.

Interested in testing cams? Frame kit is a good thing.

[NitroHunter]

836cc 10.25:1 J&E pistons
Head ported with upgraded valves, hardware and short steel guides.

Goals - Street bike stop light to stop light drag racing

On Dynoman's cam page, the advertised specs are different than the cam card for the DP295.
Specs:
Total Duration: 306° in   296° EX
Lobe Centers: 105°
Lift: .390" IN   .360" EX
Lash: .004" IN    .006" EX

Cam card
Duration .272 In .  263 Ext
Lift@Cam 382 Int 357 Ext
Lobe Center 105 & 105
Lash .004 & .006

The cam card says "check" at .050" . Is that what we're looking at - measurements at .050" ?

Can 836cc with 10:25:1 compression help over come this with port work or is that too mild CR to help?

Same cam being shown at zero lash (Advertised numbers) and checked at .050". Normal deal.
A big issue you face is getting a 650lb-ish bike and rider accelerating from a dead stop and run 2 maybe 3 gears. I found lots of torque makes these kinds of rides a blast, getting the front end light was fun.
Cylinder pressure made the magic happen for me. You can find online calculators that show you the effects of cam timing and 'advertised' piston CR on the calculated cranking pressure. Bigger cams drop cranking pressure a lot.
I've put together a big bore with too much cam with too little CR and it doesn't make a good stoplight racer, but my pal liked it out on the highway.
I also built an 836 that had 240psi cranking pressure, it ran on ERC 110 gas from the local sprint car shop, from a stop light it was untouchable into 3rd gear with a clean launch. Of course there are many machining variables in these two comparisons, but just some things to consider.
Milled for zero deck, proper squish, and safe valve pocket clearance and your 836 with those flat top pistons and 295 cam will run just fine.

[PeWe]

240PSI with a compression tester used when running engine on starter  and full throttle?
A cheap one from auto part stores.
I guess it is.

My bike has around 195PSI with RC295 and work fine and not prone to ping as it can with a little bit too adv ignition or lean jetting.

I could have chosen thinner gaskets.
RCS  0.010" instead of 0.020"
MLS 0.030" instead of used 0.040".

When I used 836, 185-190 PSI.

Gaskets do not leak today, if they did I should go for the thinner.
I had pinging and hot running engine worries in my mind when going for the thicker gaskets.

My first 836 in the 80's had higher compression and I have memories of sudden wheelies on throttle only on first and 2nd gears. Sliding out of the roundabouts too!
Pinging if using wrong gasoline company. Ran rather hot too.

[MRieck]

PeWe, 754, Sam.
Thank you for the RD295 information. I purchased a frame kit over a decade ago so I got off the couch and started that. I guess it will help making a cam decision easier knowing I can change my mind for $300 and some labor. FYI: duration numbers butt dyno are very helpful for my decision.

Definitely reworking a performance head I got at a swap meet for race guides, springs, retainer and keepers. The head has an issue with the oil jets housing (someone enlarged them?) but appears to have some nice porting work. I need to sort it but should be interesting once corrected. Will more than like run new 32/28 size valves unless the valve seats are too deep/smoked than probably up size the intake. So the cam would compliment all this effort.

All of which comes because my cam chain tensioner wheel came apart. queue the Violin.

Those guides are too short. Given the valve angle, weight of the valve and higher lift cam that is a bad combination. I use the Kibblewhite high lift iron guides (so no keeper groove dipping below the seal) and taper the guides on the lathe. You want as much length as you can get on the guide.
 I have used the 125-75 for years with good results getting into the mid 90 HP range (@915cc) with torque in the mid 60's. If anybody wants to "throw away " a 125-70/75 I"ll take it and pay you.

[bear]

Those guides are too short. Given the valve angle, weight of the valve and higher lift cam that is a bad combination. I use the Kibblewhite high lift iron guides (so no keeper groove dipping below the seal) and taper the guides on the lathe. You want as much length as you can get on the guide.
 I have used the 125-75 for years with good results getting into the mid 90 HP range (@915cc) with torque in the mid 60's. If anybody wants to "throw away " a 125-70/75 I"ll take it and pay you.
[/quote]

Your using iron guides these day's?

[MRieck]

Those guides are too short. Given the valve angle, weight of the valve and higher lift cam that is a bad combination. I use the Kibblewhite high lift iron guides (so no keeper groove dipping below the seal) and taper the guides on the lathe. You want as much length as you can get on the guide.
 I have used the 125-75 for years with good results getting into the mid 90 HP range (@915cc) with torque in the mid 60's. If anybody wants to "throw away " a 125-70/75 I"ll take it and pay you.

Your using iron guides these day's?
[/quote] Yes

[Sam Green Racing]

PeWe, 754, Sam.
Thank you for the RD295 information. I purchased a frame kit over a decade ago so I got off the couch and started that. I guess it will help making a cam decision easier knowing I can change my mind for $300 and some labor. FYI: duration numbers butt dyno are very helpful for my decision.

Definitely reworking a performance head I got at a swap meet for race guides, springs, retainer and keepers. The head has an issue with the oil jets housing (someone enlarged them?) but appears to have some nice porting work. I need to sort it but should be interesting once corrected. Will more than like run new 32/28 size valves unless the valve seats are too deep/smoked than probably up size the intake. So the cam would compliment all this effort.

All of which comes because my cam chain tensioner wheel came apart. queue the Violin.

Those guides are too short. Given the valve angle, weight of the valve and higher lift cam that is a bad combination. I use the Kibblewhite high lift iron guides (so no keeper groove dipping below the seal) and taper the guides on the lathe. You want as much length as you can get on the guide.
 I have used the 125-75 for years with good results getting into the mid 90 HP range (@915cc) with torque in the mid 60's. If anybody wants to "throw away " a 125-70/75 I"ll take it and pay you.

Hi Mike, just a little correction to your last sentence. You were reaching the mid 90 bhp range with 836cc not 915cc with the 125 75 camshaft but this thread is about the 295 cam.
Do you remember the motor you built for Art (Sparty), it made 94bhp with 836cc and the 125 75 camshaft.
Here's a copy and paste from Art's page when he took the bike to the drag strip.

So the time slip read:
1/4 Mile ET:     11.903
1/4 Mile MPH:    118.876
1/8 Mile ET:    7.751
1/8 Mile MPH:    91.720
60 Foot ET:    1.805

My times and speeds were much the same but it was all down to the DP295 cam.
I was running high 12s with 836cc and the 125 75 camshaft and ran mid 12s with the DP295.
The motor then went to 915 but the 125 75 was put back in.
It was a little quicker off the line but then went to sleep until the cam kicked back in around 7000 revs. and the time didn't improve much.
We swapped back to the DP295 and on my very last 2 runs, I would have broke into the 11s had I not shut off early knowing I couldn't be beaten.

I hope you and your family are all staying safe in these difficult times.

Sam.

[livefast_dieold]

Just wanted to quickly chip in on this.
As many of you know I've always used a DP315 cam. I did not manage to make it start pulling before 6500 rpm/7000 rpm, which is not ideal in the short and curvy tracks we compete here in Italy. Also, I personally don't like to rev the engine super high, so I never manage to comfortably ride the bike in its power band, as from 7000 rpm it gets to 11000 rpm very quickly and not in a very manageable way.
For this year I decided to re-hauling intensively the engine and change a lot of parts. One of the modification is to "downgrade" the cam to a DP295, hoping to wider the powerband in the low range. It would be terrific to have the engine start pulling at 5000 rpm!

Here's the list of things I'm doing to my engine this year:
> finally bought myself a stage 3 head by Mike Rieck. I always wanted one of his creations, and since my previous head gave up entirely I finally decided it was time to get one. Can't wait to finally assembly the engine and feel the differences with my previous head (which I ported myself 11 years ago!)
> K7 low mileage cranck cases
> abuso racing valves (34 mm in, 29.5 mm ex)
> Kawasaki kz650 pistons
> CR31

Will keep you posted as soon as I can put the bike on the dyno!

[Sam Green Racing]

Ric, you'll notice a big improvement on the shorter twisty circuits with the DP295 cam.

[MRieck]

Just wanted to quickly chip in on this.
As many of you know I've always used a DP315 cam. I did not manage to make it start pulling before 6500 rpm/7000 rpm, which is not ideal in the short and curvy tracks we compete here in Italy. Also, I personally don't like to rev the engine super high, so I never manage to comfortably ride the bike in its power band, as from 7000 rpm it gets to 11000 rpm very quickly and not in a very manageable way.
For this year I decided to re-hauling intensively the engine and change a lot of parts. One of the modification is to "downgrade" the cam to a DP295, hoping to wider the powerband in the low range. It would be terrific to have the engine start pulling at 5000 rpm!

Here's the list of things I'm doing to my engine this year:
> finally bought myself a stage 3 head by Mike Rieck. I always wanted one of his creations, and since my previous head gave up entirely I finally decided it was time to get one. Can't wait to finally assembly the engine and feel the differences with my previous head (which I ported myself 11 years ago!)
> K7 low mileage cranck cases
> abuso racing valves (34 mm in, 29.5 mm ex)
> Kawasaki kz650 pistons
> CR31

Will keep you posted as soon as I can put the bike on the dyno!

Riccardo...good thing that head happened just before all hell broke out! I can't get anything into or out of Europe the past month.

[Tintop]

Riccardo...good thing that head happened just before all hell broke out! I can't get anything into or out of Europe the past month.

Interesting Mike, I just rec'd a pkg by USPS without any issues.  That said, I am waiting for a package from Poland that's taken 5 days to go 300 miles, & last tracking update (Apr 22) said it was cleared for International shipment.  No update since......?  Hope it isn't stuck over there.  If it does come through I might have a back door for you Mike.

[bear]

Those guides are too short. Given the valve angle, weight of the valve and higher lift cam that is a bad combination. I use the Kibblewhite high lift iron guides (so no keeper groove dipping below the seal) and taper the guides on the lathe. You want as much length as you can get on the guide.
 I have used the 125-75 for years with good results getting into the mid 90 HP range (@915cc) with torque in the mid 60's. If anybody wants to "throw away " a 125-70/75 I"ll take it and pay you.

Your using iron guides these day's?

Yes
[/quote]

Great minds think alike.

[PeWe]

So shipping to/from USA is stopped now?
A friend has a package waiting in Florida since over 2 weeks.

I found an interesting cam on eBay USA yesterday, not sold as a tuning cam. Just a cam taken from a 1974.
Typical "Made in USA" billet with K134 stamped.
I wonder when that will arrive so I can identify it. Lobes looks wide  
Hopefully not too much overlap

I could not miss it for $90 USD

This is same way I found my RC295 that was sold as an unknown tuning cam.

[y2kc0wb0y]

Typical "Made in USA" billet with K134 stamped.

PeWe - Happen to know that Cam as it was one I was hunting for awhile. It is Kenny Harmon D grind. Its identified in the following post.
http://forums.sohc4.net/index.php/topic,82842.msg2076487.html#msg2076487
Moved away from that cam because of the duration above .260.

Read everyones concerns about the guides. I don't know much but I figured those were causality to the port work. 100% planning to replace with steel guides.  In fact, everything will be new and upgraded high lift spec top to bottom once I source the valve seats.
Got J&E 10:25-1 pistons and match cylinders in the mail. Thanks Bill Benton.