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/cgi-bin/YaBB.pl General Category >> Rubber Side Down! >> Big Bore Build - Part 1 - Cylinder /cgi-bin/YaBB.pl?num=1593567475 Message started by DragBikeMike on 06/30/20 at 18:37:55 |
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Title: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:37:55 This is the first in a series of reports outlining a big bore engine project. The project will incorporate a 97mm bore with a modified cylinder head (my Stage III). I will be building a spare engine so I can simply swap out engines and test. I intend to judge the initial results based on cranking pressure, ease of starting, required fuel, drivability, audible noise, operating temperatures, seat-of-the-pants power, and timed acceleration runs. If the results of the initial evaluation are good, I will continue to run the big engine to see how reliable it is. The foundation for the big bore engine is a used lower-end assembly I purchased on eBay. It is a five-speed unit form a 1997 LS650. Getting that lower end to Hawaii was an interesting project in itself. The cylinder is another eBay treasure. I have no idea how old it is, but it was in very poor condition with a scored bore, bent & broken fins, cobby sealing surfaces, and years of baked on crud. It will be matched to a Wiseco 97mm piston assembly, part number 4597M09700 (originally designed for the DR650). The cylinder head is the take-off from my 2016 LS650. It only had about 3000 miles on it when I replaced it with my Stage II head. It’s in excellent condition and will be a good foundation for the Stage III mods. The Stage III mods will include larger intake valves along with reshaped intake runners, and enlargement of the exhaust port to a full 1.79” to match my Mac header. I will flow test the finished head and post the results. Target compression ratio (CR) will be 10:1. I expect that combustion chamber volume will be reduced slightly by the larger intake valves. The cylinder will be trimmed or shimmed as necessary to achieve a static CR of 10:1. Low-lift flow will be improved with the Stage III head, so I have chosen the Web 402 cam. It has significantly less duration than the Web 340b (cam I am currently running). The 402 should compliment low end torque. The high end characteristics should remain similar to my current setup due to the enhanced cylinder head flow. It will be interesting to see how it shakes out. The 402 cam requires heavier springs with more travel. Valve guides may have to be trimmed. Valve-to-piston clearance must be verified. The 402 is not a bolt in cam. I will use acceleration benchmarks from my tight-quench engine and the 94mm Wiseco engine I am currently running. The tight-quench engine was quite a bit faster than the Wiseco pop-top engine. Comparative 2nd & 3rd gear timed runs on the completed 97mm engine should give us a good feel for how the big motor stacks up. Let’s get started. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:38:46 The Wiseco 97mm piston kit includes the forged piston, a ring set, a light-weight tool-steel wrist pin, and circlips. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:40:37 The 97mm Wiseco piston provides three significant advantages over the stock piston. First, it is forged. The forged material is significantly stronger than the stock cast material. Second, it has a slightly taller compression height (about .025”) combined with a pop-top (.060”). The taller compression height and the pop-top increase the compression ratio. Third, the larger diameter piston increases the engine displacement. An increase in displacement without a corresponding increase in combustion chamber volume will also increase compression. It’s a double whammy, more compression from the pop-top plus more compression from the increased displacement. So, by simply installing the 97mm Wiseco you bump up displacement by 43 cc and you bump up compression by about 1.2 points. You end up with a 695cc engine with a compression ratio of about 9.5:1. It’s all good. Here’s a look at the stock cast piston next to the forged Wiseco. Note the smaller, stronger, and lighter Wiseco wrist pin. Also note the little mini pop-top and the nice valve reliefs. Those valve reliefs permit installation of high lift cams with lots of overlap. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:41:31 Negative aspects of the Wiseco are weight and noise. The 97mm Wiseco assembly is 11 grams lighter than the stock assembly. That will probably affect balance a little. I am currently running the 94mm Wiseco. It is a whopping 52 grams lighter and it shakes a lot. I suspect the 97mm vibration level will be significantly lower than the 94mm, probably close to stock vibration levels. This shows the two pistons from the bottom. Note how the stock cast piston has a full circle skirt while the Wiseco forged piston has a partial skirt. I’m not really sure if the partial skirt has any advantage over the full skirt, but I’m confident the stock cast piston runs a lot quieter than the Wiseco. You can run tighter clearance with the cast piston. The full skirt combined with the tighter clearance results in far less piston slap and the associated noise. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:42:31 You can’t build a 97mm engine without a 97mm cylinder. So, to me, the logical place to start was boring out the cylinder. If I can’t get the cylinder bored, I can’t build the engine. I’ve always wanted to try and bore a cylinder but have also been told that it’s not a job for a lathe. Lot’s of folks have told me that you must use a cylinder boring machine. My used cylinder was a real jalopy. No big loss if I screw it up. Why not give it a try on the lathe? Learn a thing or two. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:43:15 Broken & bent fins. Corrosion. Beat up sealing surfaces. It was nasty. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:44:10 A rigid setup would be needed to maintain a straight bore. That would require a heavy-duty boring bar. Some 1.5” aluminum hex stock did the trick. This thing was solid. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:44:54 A 1.5” torque plate was modified to attach the cylinder to the face plate on the lathe. It worked well. It was easy to get the cylinder running true and it was solid. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:45:40 A workpiece this size must be turned at a low speed. The speed was set to 200 rpm. Feed was set at .15 mm per revolution. That speed and feed produced a decent finish. It took 5 minutes to make one pass. The depth of cut was about .004” per pass. For the final pass, the feed was reduced to .075 mm per revolution to achieve a better finish. If you ponder that feed and speed stuff and the length of time for each pass and the depth of cut, you will probably figure out that I was standing in front of that lathe for a very long time. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:47:34 These short videos of the hobby lathe in action will give you a feel for how the thing performs. It’s a pretty old lathe and it’s pretty beat up, but it got the job done. https://www.youtube.com/watch?v=bvnpV2cQ36A&feature=youtu.be https://www.youtube.com/watch?v=X1I3fn-3aY8&feature=youtu.be |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:48:19 Since the cylinder was in the lathe, might as-well clean-up the cobby base gasket surface. Just a quick kiss with the tool bit and it was in good shape, perpendicular to the bore too. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:49:42 You want to stop boring about .005” under the finished size. The Wiseco 97mm piston skirt is 3.8175” and I was shooting for .0025” clearance (a bit more than Wiseco recommends), so my finished size goal was 3.8200”. I stopped boring the cylinder when I reached 3.8140”. Plenty of wiggle room. Now it was time to hone the cylinder to achieve the proper finish and size. You need a way to hold the cylinder without clamping it radially. If you clamp the cylinder radially it will distort the bore and you will ruin the cylinder when you hone it. The cylinder also must be clamped between torque plates to simulate the stresses imparted on the cylinder by the normal clamping force of the cylinder studs. On this job, I found that to be particularly important. The solution was a cradle that attached to the torque plates. Now the cylinder could be clamped in the torque plates and suspended in the cradle. A drip pan was set up under the cradle to catch all the slop. This is not a job for a spring hone. You must use a rigid hone with a micrometer feed, and you must continuously monitor the size as you hone. Use coarse stones to get within about .0015” of the finished size, and then switch to fine stones to bring it home. Lots of honing oil is in order. A mixture of nine-parts kerosene to one-part motor oil does a nice job. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:52:37 Periodic measurements with an inside micrometer and dial bore gage assure you stay on track. If you start seeing a taper develop you can favor the small area of the cylinder with the hone. Turn the cylinder over periodically and switch honing direction (top to bottom, bottom to top). Go slow and continually take measurements. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:53:26 Back up those measurements with a feeler gage check to make sure it’s right. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:54:10 The drip pan is a must. Wet honing is messy. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:54:58 The finished product was gratifying. It was round and straight within a few ten-thousandths of an inch. Not pro-stock quality but easily good enough for sweet-street performance and a decent life expectancy. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:55:40 I must discuss my observations on cylinder rigidity. This thing gets real thin when you poke it out to 97mm. I could tell right away that it was flimsy. The bore diameter would change dramatically when I released the torque plates. The skirt of the cylinder would expand by about .0007”, the center got smaller by .0010”, and the top went oval by .0011”. Reinstall the torque plates and everything went round & straight again. If you compare the stock cylinder to the 97mm you get a good feel for the reduction in liner thickness. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:56:35 The 97mm cylinder weighs 1 lb. 3 oz. (538.641 grams for Armen) less than the stocker. That’s a lot of iron. The skirt is thin. As I previously mentioned, the skirt expands outward when you release the torque plates. This thing is nowhere near as rigid as the stock cylinder. I think if there is any sort of reliability issue it will center around this thin cylinder wall. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:57:14 Bumping up the bore size will require a special head gasket. The stock multi-layer steel (MLS) gasket is too small. Head gaskets that overhang into the bore can cause hot spots with associated pre-ignition and detonation. You want to use a true 97mm gasket. This picture shows the stock gasket overhang. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:57:53 Copper Gaskets Unlimited (CGU) in Phoenix, AZ offers a true 97mm copper head gasket for the LS650. They also offer cylinder base gaskets. Their gaskets are available in a variety of thicknesses which will allow slight adjustment of deck height and combustion chamber volume. I’ll be using their .026” thick copper head gasket. As you can see, it fits perfectly. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 18:58:31 After I was confident that the cylinder bore was good-to-go, I dressed up some of the broken stuff and cleaned it up a bit. I’m debating whether or not to paint it. Hey, it’s only gonna get dirty. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 06/30/20 at 19:01:05 So, was boring out my cylinder worth all that trouble? For me, yes. It was interesting and I improved my skill set. It took a long time and required a lot of effort, but the finished product was very gratifying. It’s amazing what you can accomplish with a little tenacity and patience. Would I recommend a project like this for any of you hobbyists? Absolutely. Get a junk cylinder and give it a whirl. It’s a terrific learning experience. Did I do a better job than a bonafide machine shop? Probably not. I imagine I may have done a better job than you could get at some sketchy machine shop or a motorcycle shop with a cheap boring machine, but I doubt that my finished product is as good as what’s expected from a top quality engine rebuilder. In Part 2 of this report, we will go through the cylinder head, install the bigger valves, modify the ports, flow test, and set it up for a big cam. Part 3 will inspect and setup the bottom end. Part 4 will cover engine assembly. Part 5 will install and test the engine. As usual, I hope you find this report informative and I look forward to any comments or questions. Knowledge is power. Stay safe out there. Respect the Vid19. Mike |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by kamelryttarn on 06/30/20 at 23:33:21 As always I am in awe of your great work. You have done an amazing job there. Thank you so much for sharing it with us! |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by Armen on 07/01/20 at 04:33:29 Awesome! Great work, well documented (as always!). Can't wait to see the performance testing! thanks for sharing |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by srinath on 07/01/20 at 04:34:48 When the skirt is so thin don't it run the risk of breaking at the bottom of the stroke - as in - in the old days the 89 GSXR750 connecting rods were used in a lot of hopped up GSXR motors regardless of what the build was. Those had longer rods - they were super short stroke but had the longest rods of all GSXR air oil cooled. The thought was there is less stress side ways at the bottom of the stroke - and we're only talking a 2mm longer rod. Some thing some thing angularity something they used to say. Cool. Srinath. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by LANCER on 07/01/20 at 11:19:08 I don't recall anyone posting about a break in the wall at the bottom of the cylinder. I've not had that issue to date. Thanks for the data DBM. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by srinath on 07/01/20 at 12:35:17 7C717E7375622227100 wrote:
Yea savage probably has longer rods than the GSXR or any year, and spins slower than any GSXR … besides, those likely already had thin sleeves being 4 cyls. Bore em and thin becomes wafer thin. Cool. Srinath. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by Dave on 07/01/20 at 13:04:40 Great job DBM.....anxious to read about your results. I have been running a 95mm Wiseco for the last 10,000+ miles and I am well pleased with it. A larger 97mm might be even more fun! When the piston is down in the bore below the aluminum......the rod is not at much of an angle and there likely aren't large sideways forces like there is in the mid bore when the rod angle is high. I have never heard/read of a Savage cylinder of any bore size breaking. Most cylinder failures are related to running the bike out of oil. I have read of 2 piston/cylinder failures from improper boring (1 too tight and 1 too loose). |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by Jdvt600 on 07/01/20 at 16:19:36 This is going to be exciting! The forum members here are phenomenal! |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by DragBikeMike on 07/01/20 at 23:34:27 I am not worried about the cast iron liner breaking. My concern is over circularity & rigidity. The entire cylinder, top-to-bottom, is very flimsy now. I have never seen a cylinder that distorts this much when you release the torque plates. It's probably not a big deal. I'm just saying that if it's gonna misbehave it will probably be related to the flimsy cylinder. Stuff like elusive ring sealing, seizures, rattle & resonance, stuff like that. No one is reporting those problems so I suspect it's gonna work just fine. Srinath, long rod engines make more power. You want to run the longest rod that you can reasonably fit into the engine. Probably not an option for us since there isn't exactly a cornucopia of speed parts available for the LS650. I believe the desired rod ratio is 1.75 or better. For instance, an engine with a 6" rod and a 3" bore has a rod ratio of 2. The LS has a 3.7" bore and the rod is about 6.6" so our rod ratio is around 1.78. Good but not best. The longer rod geometry increases dwell at TDC so combustion pressure has more time to build, improves the angle of the rod in relation to the piston which reduces piston thrust, and improves the angle between the crank journal and the wrist pin which results in better mechanical advantage. All good stuff if your looking for more horsepower and torque. Dave, encouraging to hear you've logged over 10K on the Wiseco. I'm not sure how many miles I have on the Wiseco 94mm. Will have to check. I am satisfied with it so far. It's a very easy way to grab a few more ponies. |
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Title: Re: Big Bore Build - Part 1 - Cylinder Post by LANCER on 07/02/20 at 04:06:58 I installed the 97 about 12 or 13 years ago and only had one issue with it about 7 years ago, but that was due to sitting for an extended period and upon startup a rusted piston ring caused the piston to be yanked free and a small part of the piston to be left on the cylinder wall. Photos were posted of it back then. Was able to reuse cylinder after cleanup and a good hone. I talked with Bill at Bore Tech about a little divot in the wall down low in the cylinder and he said it was not an issue, it was usable, but the digit was not caused by the piston being yanked, it was in a different spot. |
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