A Royal Enfield forum for the people

[Ace.cafe]

At your elevation and air intake type, we have found that 127.5 pilot usually does well.

Your 142 psi is just fine for compression now.

[Street_Kleaver]

At your elevation and air intake type, we have found that 127.5 pilot usually does well.

Your 142 psi is just fine for compression now.

The weather has turned sour with winter rains and jetting is at a bit of a stand still. The couple of short rides I have had I can report the transition into the "fat" powerband is a lot linear now. Likes it's shifted it 250rpm sooner with the 3dg cam advance. Off the bottom it feels like a stock bullet, then she takes off like a slapped race horse! I love it. Haha

For a tuning aid, I've ordered a Koso AFR gauge kit. I'm going to fabricate up a little temporary mid pipe section between the header and silencer for the wide band 02 sensor. I'm a little time poor and the closest Dyno Tuner who will touch my bike is a 4hr drive away. It's why I've taken the avenue of creating my own 02 sensor and AFR gauge setup to make jetting a little easier.

Along with this a Daytona Velona 80mm Digital Speedo. Since I've had nothing but problems with speedos. This at least has speed and tacho which will help me take metrics along with the AFR gauge.

I'm still battling to get a healthy pilot circuit. I called my local Mikuni dealer/expert who has been in the game for 35 years. Stated my case with the big duration cams. He said in their experience with BSA and Triumph big singles with large overlap cams the pilot circuit always has to go a lot richer with Mikuni carbs and not be surprised to go from a 25 to a 40 Pilot.

I've found from experimenting a 30 pilot it was better. At present a 40 I can dial the idle hang out, which is still a little too rich I think 35 will be the sweet spot of a compromise. It's a process of walking each idle screw lower and mixture screw richer until the throttle response is nice along with the idle hang relatively gone. With leaner jets, I couldn't dial the idle hang out at all. Which actually reminds me of the Clubman variant of the BSA DBD34. They didn't idle at all. Always blipping the throttle. I've had 2 stroke race bikes like that in the past with thirsty porting jobs. You learn to live with it.

Main Jet is good at 220. Plug color is good.

Also going to try Mikuni Oz's recommended Needle they have on database for British 500 singles which is a 6DH4. It has a shorter straight section of the needle compared to the 5FP17. When riding it I'm getting a little pining at holding at constant 1/4 throttle with the 5FP17, which is bang on the straight section. Going a larger Needle Jet didn't help. Just makes the issue smaller but makes 1/2 throttle too rich. Which tells me the needle taper needs looking at.

5FP17 has the longest straight section, taper starts latest and is richest.

6DH2 is richer on the straight section, but leaner on the taper. (Used this on the VM32)

6DH4 is the same diameter as the 5FP16 but the shortest straight section and the taper starts sooner and is richer than the 6DH2.

So hopefully when this AFR arrives I can take some metrics and get it dialed in.

Needles.jpg (44.35 KiB) Viewed 2400 times

Ignition timing I haven't touched yet, I understand long duration cams like a little more advance at idle. Ace if you feel like sharing how you perform your ping timing incase what I do differs. I'm always open to learn new techniques. I basically have a nice steady incline hill. Hit it in 4th gear roll on with the engine under load, keep advancing 2dgs at time till I hear pinging and then back it off.

[Ace.cafe]

Regarding jetting, maybe with the long overlap it will want richer. We always used the shorter overlap cams, so there might be a difference.
For the needle, we used 6DP17 but that might not be best if it wants richer. A Fireball would bog down from being too rich with the jetting that works for you, so just go with what works best.

Regarding the ping timing, I did similarly to what you do, but I do it at an rpm lower than torque peak, like about 2800 rpm in top gear, or around that. That is where the danger zone is. It always wants plenty of advance above tq peak, but not below tq peak.
So, I ping time it there around 2800 and make sure the ping is tuned out from the danger zone, but still has as much advance as possible for the higher rpms. That usually will save the piston from seizing during the typical leisurely Sunday ride up a long hill in top gear at low rpm. However, if you always use the gears and keep the revs above 3500 rpm, you don't have to worry about the danger zone and you can ping time it around tq peak(3500 rpm?)for best power. It all depends on what your actual tq peak rpm is, how you want to ride

[Street_Kleaver]

Regarding jetting, maybe with the long overlap it will want richer. We always used the shorter overlap cams, so there might be a difference.
For the needle, we used 6DP17 but that might not be best if it wants richer. A Fireball would bog down from being too rich with the jetting that works for you, so just go with what works best.

Once this AFR arrives, I'll test a few different needle tapers. I'll check the 6DP17. I was going off some older posts on the other forum of Bullets with the TM32 . When I spoke to Mikuni, they actually said the 5FP17 is more of a 2 stroke taper and they used it in vintage Bultaco 2 stroke motocross bikes. The taper is evident of the old 2 stroke power delivery, nothing then everything! Haha.

Regarding the ping timing, I did similarly to what you do, but I do it at an rpm lower than torque peak, like about 2800 rpm in top gear, or around that. That is where the danger zone is. It always wants plenty of advance above tq peak, but not below tq peak.
So, I ping time it there around 2800 and make sure the ping is tuned out from the danger zone, but still has as much advance as possible for the higher rpms. That usually will save the piston from seizing during the typical leisurely Sunday ride up a long hill in top gear at low rpm. However, if you always use the gears and keep the revs above 3500 rpm, you don't have to worry about the danger zone and you can ping time it around tq peak(3500 rpm?)for best power. It all depends on what your actual tq peak rpm is, how you want to ride

I know the typical ping area you speak of. I had to do the same with the stock and R cams. But actually they were a smidge retarded to baseline ignition timing. Same area, under 3000rpm and a lazy uphill grade hitting the "tractor" zone and you'd get the old "clickle, clackle".. Down shift and spin the motor up.

With the Hitchcock cams, not even a hint of that down low in that same circumstance. It will lug but no detonation what so ever. To describe it, the motor in that rpm range and tractor zone feels softer in its engine rpm cycling for lack of a better term. Where as the Stock/R cams felt like a bomb with each rpm cycle. Which was a fine tune with the ignition timing not to retard it too much to get backfiring.
Now its at 1/4 throttle it feels flat with a bit of lean hesitation coming off the pilot/cutaway to the straight section of the needle. That little twist more once it starts feeding from the needle taper it livens up again.

Tick over wise comparing the Hithcocks cams Vs Stock & R cams. The idle can be set extremely low and the throttle response is actually very good. Where as the Stock and R cams if the tick over was that slow it would cough and bog, which likes a higher idle speed.

The compromise I'm finding with these long duration cams is the larger /leaner cutaway (4.0 supplied) is needed along with a richer pilot circuit to enrichen the slow speed circuit. So the slide position can be set as low as possible with the larger/leaner cutaway for more airflow at tick over balancing it out with a richer pilot. Where as the issue was opposite with the shorter duration cams where it actually liked a richer cutaway on the the VM32 which was a 2.5. To richen the transition from pilot circuit to 1/4 throttle and beyond. That's where the straight section of the needle is coming into play being leaner at 1/4 throttle. Mikuni world wide has a supply/shortage for TM slides. So a 4.0 is it unfortunately. The base can be taken down to make a richer cutaway. But that will also lower/leaner the needle position along with it.

Hitchcocks can't give me any jetting specs because they have jetted these cams to AMAL's. No Mikuni's. AMAL is not common for parts for Australia but I've been using Mikuni's since I was taught to jet them by old timers. So its a double edged sword for me at present.

I'm keen to get this AFR and see actually what is going on. I don't think I'll get accurate readings at slow speed which is common for big overlaps not burning fuel well, but 1500rpm+ should get good data.

Its frustrating but I'm make positive steps!

[Guaire]

"Main Jet is good at 220. Plug color is good."
220 is a big main jet!
ACE - What's the difference between StreetKleaver's cams and the the ACE Performance cams?

[Ace.cafe]

Much longer overlap and higher lift on the H cams.

My designer's opinion goes like this.
For the Bullet redline, the massive overlap is not necessary. It is more suited to a high rpm racing machine which needs extended open valve time during overlap because the breathing time is shortened at those very high rpms. At normal Bullet rpms, efficiency is lost because the target rpm range for those cams is at rpms that a normal Bullet cannot reach.

For the lift, generally higher lift is useful at most rpms, and therefore would be considered a good thing, especially in the midrange torque. We use very high lift with the roller rocker system, so it should be apparent that we like high lift.
However, these kinds if mods are not "a la carte" options, and it is important to consider how all the rest of the breathing tracts interact with a mod such as this.
We have large amount of flow bench data on Bullet ports of stock and modified types. I am quite sure that we have the most varied and extensive file of Bullet head flow data in the world.
Our flow data concludes that stock Bullet ports and most modified Bullet ports show flow curves which flatten-off by .350" lift, and flow will not effectively improve at valve lifts higher than .350". This is why we use .350" lift cams. What you will get from the higher lift cams is a longer duration of maximum port flow, not increased port flow. So, it essentially behaves as a duration increase of the nose of the cam grind, and not as the expected higher port flow increase one would hope to see from higher lift. Certainly this is not bad from a breathing point of view, since some breathing duration increase should occur, but it comes at the expense of unnecessary higher stress on a weak Bullet valve train. Also, all the lift increase must come from the cam lobe on a 1:1 valvetrain which requires reducing the cam base circles to fit in the cam chest next to the crankshaft seal boss which is already in very close proximity to the lobe sweep.

So ultimately in my opinion, it would be better to raise the inlet port roof profile to give better flow angle and increase actual port flow numbers at higher lifts before committing to high valve lifts. Then you get more out of the modification. And then, to make the most out of the big duration and overlap, use a larger carb, manifold, port, and valve, to enable unchoked port flow into the higher rpm range where those cams are targeted to work best, and yield the hp increase from those rpms. And the rotating and reciprocating parts in the crank system had better be built strong enough to handle it.

So in the end, it's a symphony, not a solo. Make it all work together.

[Street_Kleaver]

After battling with jetting for these cams for nearly a month trying different things and configurations.
I'm giving in to defeat.

I can manage to jet it so if feels nice through the midrange and amazing up top. But it just won't behave around idle. Which is needed with a street bike. So I feel these are only for the track. I'm at my wits end. I don't think using a afr will help me either. The problem won't go away. Which is most likely the overlap.

No matter what I do. I adjust it to idle, the rpms hang after blipping the throttle. If I adjust it to not hang. It won't idle. Regards what jetting changes I make Richer Needle jet, Leaner Pilot and vice versa, trying to get the slide into a low position. Nothing fixes my issue. Even a carburetor swap from a VM32 to a TM32. Same problem, the idle issue got a little better. But didn't solve it.

So I dug out the R cams again had a better inspection. So the issue with the bush was a burr/deformation on the very outer edge of the bush on the engine side where it had been pressed in in the inlet cam. I gave it a hit my my countersink bit and fixed!

To use these cams again I'm going to have to re-do a lot of work. Pull the head off and another base gasket in. Since with the base gasket the R cams sat at 165psi. Which was very hard to manage with our premium fuel.

ACE
A question for you? If I put the 3-way gear on the 3dg retarded setting would it be more suited for what I'm chasing? As in a smidge more power up top? For all the 100km/h/62mph work for my area.
I'm thinking with the standard base gasket the compression from 165psi with a 3dg pinion retard down to 150psi and gaining a little more top end. While making it a little safer for our 95 Premium (91 US).

The positive, The R cams previously didn't have my fancy velocity stack airbox or TM32.

While everything is apart again. I might look at getting my standard rocker box blocks machined down to accept Samrat rocker arms. I don't like the cast alloy Samrat rocker blocks. Their tolerances don't feel right compared to standard rocker boxes, The samrat cast alloy rocker boxes have some diagonal play. I read somewhere on the forum this is a common practice.

[Ace.cafe]

Yes, you could retard the R Cams with the adjustable pinion. It's not ideal becaust it already has 112° lobe center, and 115° is a bit late, but I think it would work to help your situation if you don't want to pull the cylinder again. Inlet opens at 32°BTDC with the R Cams, so dialing it back to 29°BTDC shouldn't hurt anything. If you don't get enough vacuum on a 115° lobe center, then something is wrong.
You will need to ride it to evaluate how you like the power curve with the changes.

[Street_Kleaver]

Ah. I'll run the standard timing. Pull the cylinder and install 2 base gaskets. I have one thats 0.55m and another thats 0.70mm. Also 2 that are the earlier Bullet paper gaskets that are 0.2mm.

I figure I gained 8 to 10psi by removing a 0.55mm. 2 base gaskets should get me just under 150psi. Then I will have less detonation issues with our Premium fuel.

Previously I had to have the ignition 10dgs retarded and still had to be very mindful with the compression at 165psi.

[Street_Kleaver]

Update.

2 base gaskets installed. Compression is 145-150psi now instead of previously 165-170. Bit safer for our fuel.
Price "R" Cams back in and everything set back in it's standard positions.

Installed the Dayton Velona 80mm Speedo. What a trick bit of gear this is. Since the "mode" and "select" buttons are under the unit where you can't get to them once its mounted in the Nacelle. I folded up a neat little staino panel for the remote "mode" and "set" waterproof buttons underneath the right hand side. Its got some good features.
Km/h & Mp/h. Tacho, Max Speed, Max RPM, Trip 1 & 2, ODO, Redline/Shift Light. Speedo drive is a direct bolt into the existing speedo drive. Tacho pulses wires straight into the Pazon Electronic igntion. Was a fiddly job but well worth it.

Next one the list was whipping up a little temporary mid pipe section to mount the 02 sensor for the AFR gauge.
It's a KOSO Mini 4 AFR gauge. Has a range of 12 to 17. Which is more than enough for tuning a carburetor. What brought this on is because my local Dyno guy won't touch my bike since its Carbureted and its kick start. Next closest Dyno is 4 hours away. So I'll just do it myself. With the Digital speedo and the AFR. Jetting should be a lot easier with some data to record as I go.

I didn't get to test it all out. It was getting late and I didn't want to upset the neighbors.