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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Big Bore Engine - Part 2 - Head /cgi-bin/YaBB.pl?num=1595224521 Message started by DragBikeMike on 07/19/20 at 22:55:21 |
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Title: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 22:55:21 This is the second in a series of reports outlining my big bore engine project. Part 1 covered the cylinder. If you haven’t read Part 1 you can find it here. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1593567475 Part 2 covers the cylinder head. I am currently running my Stage II head on a 94mm bore. It runs very good. For the 97mm big bore, I took the cylinder head to the next level, Stage III. Larger 34mm intake valves were installed, and the exhaust port was enlarged to a full 1.79” to match the Mac header. The valves were setup to accommodate cams up to .420” lift. Let’s get started. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 22:56:54 The core was a stock head removed from my 2016 LS650. It has about 3000 miles on it. This is the box-stock intake port, warts and all. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:00:53 You might look at that cobby intake port and think a little cleanup with a die grinder will provide a huge increase in flow. Well, it doesn’t. Cleaning up all that ugly stuff helps a little (about a 3% increase if combined with back-cut valves), but it doesn’t amp up the flow like you might think. On the Stage II head, I found the big flow increase (about 9%) came from reshaping the floor of the port to make the short-side radius more gradual, then widening the left and right port runners to compensate for the vertical reduction in area. The cleanup combined with the epoxy/widening mods resulted in a 12% increase in flow. The nitty-gritty details on those mods are in the report on the Stage II head. http://suzukisavage.com/cgi-bin/YaBB.pl?num=1565076891 To improve the short-side radius you must build up the floor of the port with epoxy. This is the third time I have done this epoxy mod to a LS650 head. I flow tested each head and got almost identical results on all three. This port modification works. It’s easy to do. The improvement is substantial. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:01:35 First, the port surface must be prepped for the epoxy. I just use a very course carbide burr in a drill extension. Use the extension as a handle and work the burr over the surfaces where the epoxy will be applied. Don’t turn the burr with a drill or die grinder, just scrape away at the surfaces by hand to make it as rough as possible. You want a good anchor for the epoxy. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:02:21 Start by washing the entire head in hot soapy water. Get it super clean. Then work on the port surfaces with the carbide burr. When your done with the carbide burr you should have a surface finish like this. Very rough, deep scratches, lots of burrs raised up. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:03:01 Once the port is roughed up in all the areas where epoxy will be applied, clean it with copious amounts of Brakleen and a small wire brush. It has to be pristine, no oil or grease allowed. After the Brakleen has dried, apply a thick layer of the epoxy (be generous, pile it on). You want plenty of excess to allow shaping the floor of the port. My go-to for this job is JB Weld HighHeat. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:08:40 This should give you an idea where this is headed. You can see the epoxy on the floor of the port. I have started shaping and blending the epoxy with a Dremel tool and a small abrasive roll. Note that the once-round right-hand runner is now starting to look oval. It is bigger left and right than it is top to bottom. That will naturally occur due to the epoxy build-up, but I also widen the port substantially with the Dremel tool. Each runner ends up about .080” (2mm) wider than stock. The widening also narrows the thick bridge in the center of the two runners. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:09:48 Once the epoxy has been blended and shaped to the desired configuration, and the right & left runners widened .080”, I go through the stud hole and drill & tap the epoxy to prevent the cylinder head stud from pushing the epoxy off the port. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:10:37 I get 8mm exhaust manifold studs (Dorman 03411) from O’Reilly auto parts. Then cut the small hex off with a hacksaw and file a nice radius on the end. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:11:22 The stud fits nice and provides a fairly smooth surface for the air to flow over. It also serves as an additional anchor for the epoxy. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:12:25 This is a cross section of the port with dimensions. It’s pretty simple. The epoxy on the floor of the port runs at an incline to the apex directly below the valve guide and then arcs into the throat of the port runner, right at the edge of the throat. It’s a buildup of about .16” (4mm). The runner is widened by about .08” (2mm) to help compensate. You can see how the arc is much more gradual, so the airflow doesn’t have to make such a tight turn. This sketch plus the photos in this report should be more than enough info to allow anyone to replicate the port. As you will see from the flow curves, the configuration works great with the stock intake valves too (Stage II). |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:13:23 It’s easy to measure the runners with a simple inside caliper. The apex of the arc needs to be directly below the edge of each valve guide. The vertical distance should be .95” from the top of the runner (aluminum) to the apex of the arc (epoxy). |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:14:09 Since the runner is now oval, the horizontal distance will be larger. The distance right to left will be 1.17”. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:15:24 The 34mm Kibblewhite valves are intended for an early Honda CB350 (1968-1973). They are Kibblewhite part number 30-30361. The Kibblewhites are only slightly larger (1mm) than the stock intake valves. The stem diameter is reduced in way of the port. That reduction effectively increases the port cross section. It also reduces the weight of the valve. The Kibblewhite stem is .06” (1.5mm) longer than stock so rocker geometry might be a problem. I did a contact check to make sure that the rocker adjustment screw doesn’t get too close to the edges of the valve tip as the rocker swings through a full arc. It was fine, but the longer stem could result in accelerated guide and stem wear due to side loads. I guess we shall see. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:16:28 I experimented with 35mm valves but there just doesn’t seem to be enough valve seat material to allow safe installation of 35mm valves. I don’t have the equipment or skill necessary to install larger seats. A typical 650cc single with a four-valve head uses intake valves around 38mm. The 33mm intakes on the LS are ridiculously small. Looks like 34mm is the best I can do. This shows the Kibblewhite valve (on the left) next to a stock valve (on the right). Both valves have a 30° back-cut which improves flow about 2%. It’s worth doin the back-cut. The undercut stem in way of the port (Kibblewhite) takes up a little less space, so there’s more room for air to flow through. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:17:13 To install the larger valves, the seats must be cut. Neway valve cutters work well. You end up with blisters. It’s all hand work and it takes a lot of effort. I do the port work before I do the seat work. That way, I don’t run the risk of rat bites in a pristine seat. I made some special laps that use abrasive paper. They polish off any little burrs left by the carbide cutter. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:19:45 The finished product had 46°seats, 31° top cuts, 60° bottom cuts and 75° throat cuts. Bluing spots were perfect, and the valves didn’t leak a drop when I tested them. I was satisfied with the finished product. The port may not be pretty, but it flows darned good. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:21:50 Now that the intake port was finished and the larger valves installed, it was time to see how it flows. Prior to starting work on the head, I did baseline flow tests. It matched the data I had previously taken on my other stock head. I knew the flow bench was providing repeatable data. I also had the flow data from the Stage II head. So now, I could test the Stage III and see how things stack up. The trusty flow bench has two full-size shop vacs (5.5 HP & 6.5 HP). Even with that much power, the bench can barely keep up with this Stage III head. It will pull 15” H2O (my standard test pressure) but there ain’t much reserve. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:22:55 At max valve lift, the stage III does not flow quite as much as the stage II, but the average flow is significantly better. I can’t explain why the max lift flow is less. It will be interesting to see how it works. On the surface, everything points to improved performance. The flow is higher at almost every point on the curve….but that might be deceptive. From another perspective, the Stage II curve tracks the stock curve at all the lower lifts (to about .200” lift). Then the flow amps up. That might be better. It might help low rpm power delivery. The flow bench can’t tell me that. Only experience can. The average flow on this Stage III intake is about 12% better than stock (136.5 vs 121.3) and 3% better than the Stage II (136.5 vs 132.4). The green line says it all. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:24:28 Time to move on to the exhaust port. The exhaust port has two grotesque impediments to flow. An item I refer to as the “dipsy-doodle”, and a reduced outlet hole (only 1.3” diameter). I can’t do anything about the dipsy-doodle. It’s in the roof of the port (the critical flow area) and I have no way to fill it in. The super-small outlet is another story. I can fix that. Here you see the stock 1.3” outlet with the dipsy-doodle lurking in the back. The circular scribe line shows where this port is headed. When complete, the outlet will be in the shape of a capital “D” laying on it’s side. The Stage II head also uses a “D” shaped port, but it is only 1.5”. I want to see what will happen when I open the port up all the way to 1.79”, which is the inside diameter of my Mac header pipe. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:25:20 The smallest cross sections in the exhaust port are right at the edges of the valve guide boss. That can be improved a bit by rounding off the edge. Seemed like putting a generous chamfer on the blunt guide should also help. The chamfer didn’t yield any flow improvement but what the heck, gotta try. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:26:07 Another problem is the left-hand exhaust runner. The bridge in the center of the exhaust port forms a straight vertical wall. I felt it would flow better if the runner were actually round. It did flow better. Here’s that flat vertical wall on the left-hand runner. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:26:49 Might as well start by enlarging the outlet. That will provide a little extra room to get at the rest of it. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:27:31 Now the 1.79” flow bench adapter mates nicely with the port. The header pipe will too. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:28:30 Of course, the seats had to be blended into the adjacent aluminum port. I have no idea why the aluminum has these big circumferential undercuts, but there’s no way to get rid of them without enlarging the port more than I want to. Just blend things in best as possible without enlarging the port. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:29:20 Rounding off the guide bosses was a straightforward operation. I didn’t get carried away. I want to leave ample material to maintain the press fit between the cast iron guide and the aluminum boss (don’t want to relax the hoop stress by thinning out the wall of the boss). Just round off the edge to open the cross section a bit; help the hot gas get past the boss. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:30:03 I used my valve guide trimmer to apply a small chamfer on each guide. Maintain a slight blunt tip, you don’t want a knife edge on this thing. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:31:01 Then it was time to address the left-hand runner. I worked on the bridge a bit to establish a round cross section. Rounding the left-hand runner improved flow measurably on my test mule. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:31:35 A 30° back-cut was applied to each valve. It was ready to test. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:32:27 As you can see, this is a vast improvement over the stock head, and a significant improvement over the Stage II head. Question is, will the 97mm engine like this free-flowing exhaust port? Will the port be lazy and kill low end torque? Will it work well with my modified muffler or will the muffler simply negate any flow improvements I derive from the port? The flow bench can’t answer those questions for me. Just have to try it and see what I learn. The average flow on the stage III exhaust port is 31% better than stock (125.7 vs 96.1) and 12% better than the Stage II (125.7 vs 112.0). |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:33:30 The port work is complete, it’s time to set up the valves for a big cam. I will be running the Web 402 on this engine. With the LS650 rocker arms, duration on the 402-grind is about 240°/240° (measured at .050” valve lift), and lift is about .400”/.374”. The stock valve springs can’t handle the lift, they coil bind at .400” lift. Also, they aren’t strong enough to maintain valve control with the cam’s aggressive opening ramps. Web sells a spring kit for the 402-grind. When I tried to order that spring kit Web was out-of-stock. Their supplier (RD Valve Springs) could not provide a delivery date. Things looked bleak. The Web sales rep had no idea when the kit might be available again, or even if the kit would ever be available again. After a lengthy search, I came up with these. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:34:20 At about $15 bucks a copy, these SuperTech springs are a bargain (if they hold up). I load tested all eight springs and they were very close to the SuperTech specs. If you plot the load test data you can see that the ST springs are substantially more robust than the stockers, but just shy of the RD springs that Web provides. The ST springs can also handle the lift. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:35:02 Dimensionally, the SuperTech springs suite the application. The stock retainers fit just fine. Installed height agrees with the LS spec. The finish is good, very smooth, no stress risers evident. Things are looking up. The ST spring is on the left, stock spring on the right. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:36:15 Now that the spring problem is out of the way, time to address valve travel. There must be enough room between the bottom of the spring retainer and the top of the valve guide seal to accommodate the higher lift cam. When the valve is fully open, you want some room between the retainer and seal. Web specifies a minimum of .030” clearance, while Kibblewhite specifies .060”. I have always used .060”. This is the measurement in question. It needs to be about .060” more than the specified valve lift. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:37:30 There are several ways to address the clearance problem. One is to use different valve spring retainers. The other is to trim the valve guide to make it shorter. I opted to use different retainers. Kibblewhite spring retainers 30-30105 with cotters 30-30106 solved the problem. They also reduce the weight of the valve assembly to provide a little more cushion for high rpm operation. It’s also pretty easy to trim the guides. I did that on the Stage II head when I installed the 340b cam. That cam has .420” lift and I was able to achieve sufficient clearance by trimming the guides, and that was with the stock retainers. In the interest of full disclosure, I had some trouble with identical Kibblewhite retainers about a year ago. I was going to try them on the Stage II. I had done some minor machining to prep them for use with the stock valve springs and noticed what I thought was an inclusion. When I examined the retainer at 5x magnification it was evident that the defect was a crack. Further examination revealed that all four retainers were riddled with cracks. I contacted Kibblewhite and they stood by their product. Standup guys all the way. They asked that I send them the retainers and they replaced them with two full sets. Even though I had tampered with their part they still stood behind it. Good company. Gotta hope those cracks were an anomaly. Here you can see why the Kibblewhite retainers will allow more travel before the bottom of the retainer hits the guide seal. But, like all things hotrod, fix one problem create another. See how much higher the top of the retainer is. That could hit the underside of the rocker arm. It will have to be checked. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:38:13 Here you see the Kibblewhite retainer and cotters next to stock components. Note the position of the bead in the cotter. That is a key element in the final position of the retainer on the valve stem. As the bead is positioned lower in the cotter, the retainer assumes a higher position on the stem. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:39:39 With the Kibblewhite retainers and cotters, I now had ample valve travel. I can run the 402-grind cam with no fear of collisons between underside of the retainers and the valve guide seals, and there is enough margin to permit the installation of the higher lift 340b cam. With the retainers sitting higher on the valve stems, the spring installed height will increase. The springs have to be shimmed to restore the installed height to 1.300”. I haven’t found any suitable off-the-shelf valve spring shims. I use 5/16” x 1-1/4” fender washers. These cheap washers (of questionable pedigree) work out pretty good. The manufacturing quality control is sooooooo bad that the thickness of the washers varies wildly. Perfect for coming up with shim stacks of varying height. This bulk package ranged in thickness from .051” to .078”. Fortunately, the tops and bottoms of the washers are parallel within .001”. No Leaning Towers of Pizza. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:40:28 Then all ya gotta do is drill out the 5/16” hole to suite the valve guide. A step drill works great. The 1-1/4” OD fits the cylinder head perfect. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:41:11 When you reassemble the head, you place the appropriate stack of shims under the spring seat. You must end up with a spring height of 1.300”. I use a spacer of predetermined thickness along with dial calipers to verify installed height. Spacer thickness added to caliper reading equals installed height. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:41:58 If your shim pack exceeds about .100”, you need to start worrying about the spring seat interfering with the guide seal. Pay attention to the clearance between the guide seal and spring seat. Here you can see how nice the fender washers fit. There’s two stacked up here. I like to label them with an engraver. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:42:33 Don’t forget to drop that spring seat on before you drive home the guide seal. It’s a terrible waste of a seal. I’m embarrassed to admit I’ve done it a time or two. You should also verify the spring installed height before you drive on the seal. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:43:36 Make sure that the spring seat doesn’t interfere with the seal. There must be some clearance here. You should be able to spin the seat around the guide. If not, you will have to take it apart and trim the spring seat. I use an old used guide seal to check this. That way I know that things are right before I drive on the new guide seal. I hate to waste these seals. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:45:17 Now it’s time to lube up the valve with assembly lubricant. I really like the RedLine stuff. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:46:08 Break out the trusty valve spring compressor. I’ve had this old girl since I was a kid. I think she’s better than 50 years old. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:47:02 Install the springs, retainers & cotters. Repeat until all four valves have been installed with their springs shimmed to the correct installed height of 1.300”. Note that all the springs have a liberal coat of assembly lube. Ready for break-in. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:47:41 I measured the combustion chamber volume after reassembling the head. It is now 55cc. Those new intake valves take up a little extra room. I will need this value to confirm my static compression ratio. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:48:29 Remember that spring retainer clearance issue? I was worried about the retainer hitting the underside of the rocker arm. Now it’s time to check that. Install the camshaft along with the head cover and rocker arms. The cam must be in the TDC compression position. Use a few head cover bolts to make sure the head cover is up hard against the head. You need about .060” clearance between the spring retainer and the underside of the rocker arm. This .050” copper wire passes through with plenty of room to spare. Good to go. If the wire had not passed through, I would have ground the underside of the rocker arm just enough to allow the wire to pass through. Check this at all four spring retainers. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 07/19/20 at 23:49:32 I’m not an advocate for polishing. I prefer to test it with the flow bench and look for significant, measurable improvements in flow. The finished ports are relatively free of imperfections. There are no big chunks of stuff sticking out into the air stream. Good enough. Let’s face it, after a few miles of operation the crud is gonna start accumulating and that pretty mirror finish will be buried. The completed cylinder head flows much better than the Stage II. It can handle a cam with up to .420” lift. It’s ready to install on the big bore engine. I’m chompin at the bit to give it a try. I hope you find this report informative and I welcome your questions and comments. Knowledge is power. Mike |
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Title: Re: Big Bore Engine - Part 2 - Head Post by kamelryttarn on 07/20/20 at 03:53:54 Your level of skill and knowledge is nothing short of amazing! I am very grateful that you share both the information and the pictures with us :) |
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Title: Re: Big Bore Engine - Part 2 - Head Post by Armen on 07/20/20 at 06:18:49 Amazing! Thanks for sharing your hard work. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by FinnHammer on 02/05/24 at 14:36:01 Mike, A short revival of this thread, related to the modification of the exhaust port. This port is the first one I am going to try my hand at, and there is one detail I don't quite understand. It is the flat part, the one that makes the port into a "D" instead of a round hole. What keeps you from rounding the port by grinding into the floor of the port? I am opening up to a 1.65" ID header. Cheers, Finn Hammer |
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Title: Re: Big Bore Engine - Part 2 - Head Post by DragBikeMike on 02/06/24 at 00:06:51 Finn, it is my understanding that the "D" port is intended to mitigate exhaust reversion. The hot gas flows easily over the bottom edge as it exits the port, but any reverse wave (acoustic or pressure) will run into the flat face on the bottom. In effect, it should reduce the reverse flow (it serves as a dam). I have seen articles and books that discuss problems associated with exhaust reversion, and it can get so bad that it actually forces the fresh intake charge back out of the carburetor. Reversion that bad is usually associated with open headers (straight pipes). It can be a real torque killer since a carb doesn't care which way the air is flowing, so each time the charge reverses flow it picks up more fuel. The mixture goes grossly rich. In severe instances, it can change direction several times before the exhaust valve closes. Long duration cams with high TDC lift and lots of overlap aggravate the condition. Another reason to leave the bottom of the port alone is the exhaust gas tends to run along the top of the port, so opening up the bottom only increases port volume, which decreases gas velocity. I suspect that in the case of an exhaust port, the differential across the port is so high that the gasses are going to fill that port regardless of the inertia developed in the column of hot gas. Even though the mass will want to run along the top of the port, the pressure will force the mass to fill the port top to bottom. But as the pressure bleeds off, the smaller port volume will start to yield dividends by maintaining gas velocity and dragging the burnt charge out of the cylinder. I don't have any hard evidence that this "D" port theory works any better than a round port. I just know that a number of reputable head porters use "D" ports, and their heads are generally recognized as good performers. Jerry Branch, HeadQuarters, and Edelbrock all use "D" ports. The "D" port isn't going to result in better numbers on the flow bench, but it shouldn't hurt flow either. If it mitigates reversion, then I think it's a good idea. |
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Title: Re: Big Bore Engine - Part 2 - Head Post by FinnHammer on 02/06/24 at 12:25:17 Mike, Thanks for the explanation which makes some sense. One more reason for asking is I saw this port from a KTM 250, and actually, at the time, I took it to be a round port, but now that you mention it, even this port has a bit of "D" to it. A "D" port it will be, then!. Cheers, Finn Hammer |
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