| Author | Message | ||
     Strato9r |
With winter coming up, I've got some maintenance and mods planned for my 9r. One of the things I'm thinking of is to pull the cylinder heads for inspection, and perhaps some tweaking while I'm at it. As a guy that does engine machine work for a living, (and also is aware of the effects of high rpm on valvesprings) I'd like to keep well ahead of any potential problems, and massage things a bit, if there is a bit of power to be gained. At the shop that I work at, I do all of the cylinder head work for the local dealership, as well as some of the independant shops. We've had really good results with the cutter profiles that I've developed for our Serdi Valve Seat machining center, specificly for Twin Cam, Evo, and Sportster cylinder heads. These profiles, coupled with some sensible porting, have worked out great, delivering solid, usable power gains across the board, without sacrificing reliability. Here are the mods I'm considering: 1. Install larger valves, allowing me to go with the full radius seat profiles I've got on hand, opening up the area beneath the seats proportionate to the new valve diameters. A bit of bowl work, blend in the short side radius, that's about it. I dont want to enlarge the cross section of the ports to any great degree as I'd like to be able to keep mixture velocities up. Any recommendations on valve sizes? 2. Tighten up the quench area to the .030", .035" range. I'm not planning to do any of that sweet 15 degree stuff as I really dont want to change pistons, unless I spot a problem. (I really dig the fact that those XS650 Yamahas used that angled quench!) Make sure that the chambers are equalized, polished and free of potential hot spots. 3. Valvesprings. I'm using the stock xb9 cams. I'm not sure what the lifespan of a set of stock springs is like, but I do know that the bike sees redline frequently. Any recommendations on a good set of replacements, that will work well with the stock cams, but not increase pressures to the point that the stock rockers and pushrods begin to deflect? Or, are there other valvetrain parts that I should consider upgrading, even if the engine's redline doesn't change? 4. Electronics. I'm using a factory race kit; will it work with the mods I have planned, or are there better ECU's out there? I really am happy with the mileage and the way the bike runs, (other that a bit of a hole in the powerband between 4000 and 5000). I know that the stuff I've got planned has proven to work really well on carbureted bikes; I'd just hate to do all of this and then see little gain because the brain running everything can't figure out what to do with a bit of extra airflow, and the slight gain in compression I might see. It almost seems a shame to even consider opening up this engine since it has only 30,000km on it. But I'm a chronic tweaker, and everyone I've done engine work for asks when I'll be doing mine. And honestly, I started thinking about getting inside of this thing since the day I bought it. Any advice you folks have would be much appreciated!! | ||
| Glitch |
While I can't help with much, I can help (a little) with regards to your ECM. ECMspy will allow you to adjust your ECM, while you have to build the cable to connect to the bike, the software is free. You could also go with Direct Link, for a price. Do a search for ECMspy to get the details. Al at AmericanSportBike, sells and has all the details for the Direct Link. Almost forgot. There's the Remus Fueler, as far as I know it adjusts itself. Matt at Trojan-Horse can help you with that. All are board sponsors. As far as your power band hole. It could be you need to open the exhaust a little. You've got the Race ECM, open airbox, and wrapped headers, with ?stock exhaust? | ||
| Jayvee |
Might be a dumb question, but why keep do all the heads and valves and springs, but keep it a '9' ? Why not start by putting on a 1250 kit? | ||
| Blake |
That would require a new/different (longer stroke) crank, which means splitting the cases and a bunch more work. Maybe you meant "a 1050 kit"? Then you are looking at a larger investment in order to purchase a new set of cylinders, and pistons. (Message edited by blake on October 19, 2007) | ||
| Cjburr |
doesn't the "9" have the same heads as the "12".....if so then you already have the 15 degree squish heads and pistons...correct ?? | ||
| Blake |
Same heads, yes. The "9" pistons are domed where the "12" pistons are not. You can run the XB9 pistons though as you imply, they just increase the compression up to 12:1 or thereabouts (don't quote me on that, I cannot recall for sure). | ||
| Cjburr |
my mistake, after further thought they both have the XB heads which don't come with the 15 degree squish. They have the "bathtub" chambers and a flat squish area. Thanks, my something new learned (or rather remembered) for the day. Chris | ||
| Strato9r |
Thanks much for the responses! I have the race ECM, K+N air filter, have opened up the airbox, have the headers wrapped, and the factory race muffler. As for displacement, I certainly would not mind splitting the cases at some point and opening them up to accept a set of 3.812" bore cylinders; we've done a fair number of Sportster cases so it's no big deal. I believe that combination works out to 1170 cc, and trust me, I'm tempted. As far as changing the crank assembly, I really like the 12's abundant torque, but I love the 9's personality. Since I have not yet worked on a set of XB heads, I'm depending on the expertise of more experienced members, and yeah, it sure would be slick if they already had the 15 degree quench. I take it that if the 12 and the 9 pistons can actually be interchanged, (with a corresponding change in compression ratio, of course) that the connecting rods on the 9 must be longer. This is not uncommon in automotive and industrial engines; 360 and 390 Fords use pistons with the same bore and compression distance, as do International Harvester MV404 and MV446 engines. This does give the shorter stroke engines a bit longer rod to stroke ratio, which does reduce frictional losses to an extent, but of course the extra torque produced at lower engine speeds by a longer stroke will nearly always overcome a Smokey Yunick approved rod to stroke ratio, until the revs are high enough. I really like the idea of keeping things as close to original design as possible for the time being, though. Obviously, an enormous amount of research went into the original XB9 engine. I'm a firm believer in effective cylinder head work, though, and I'm sure that many of you have seen small block Chevrolet engines that put out impressive numbers, including Brake Specific Fuel Consumption, using conservative camshaft timing and compression ratios, but with a well designed cylinder head. That's my goal with these mods I have planned. To improve, if possible, the QUALITY of incoming induction flow, balanced with an exhaust port that maintains high enough velocity to properly scavenge the combustion chamber within stock RPM limits. Between that, anything that can be done to optimize the combustion process, ie.: tightening up the quench area, is also up for consideration. (Cutting out a bit of the pasta will also help, but that's gonna be a little tougher, living in a house with two other good cooks!) The info that Dave offered up regarding the ECMspy and Direct Link really took a load off as far as any concerns with unwilling or improperly informed electronics. Obviously, there is indeed a wealth of knowledge in this vault!! | ||
| Panic |
"the connecting rods on the 9 must be longer" Yes, the XB9 rods at 7.27" are longer than the XB12 (and all older Evo engines) at 6.926" by .344", 1/2 the stroke length difference. For amusement: the array of possible rod lengths for juggling stroke lengths, compression distances, etc. also includes the older ironhead 7.4375" and the special S&S 7.113". | ||
| Jayvee |
Well, I did not know that, I assumed the relationship of the 9 to the 12 was like the 883 to the 1200, ie bore size. But it's the stroke ! Amazing to me, I did not know that. I haven't followed the XB series very closely, until now, I am also looking at a set of XB heads to install, as opposed to porting the ones on my M2. | ||
| Strato9r |
Wow! I would never have guessed that those old ironheads had a longer rod than the 883/1200 Sportys or either XB! (I guess they needed all the help they could get!) Usually you only find rods that long in some kind of flathead; I wonder if the K models used that rod length as well? | ||
| Panic |
All 1932-85 45, K, KR, and iron Sportsters have the same rod length and stroke length - 3-13/16, same as Evo 883, 1100, 1200 and XB12. 1954-56 KH has the same rod but longer stroke. Exceptions: 1983-84 XR1000, which was the first use of the 6.926" rod, hence, the -83 part number. 1968-69 "low-boy" KR, some of which used a really special 6.4375" rod. | ||
| Jimidan |
Same heads, yes. The "9" pistons are domed where the "12" pistons are not. You can run the XB9 pistons though as you imply, they just increase the compression up to 12:1 or thereabouts (don't quote me on that, I cannot recall for sure). According to my good buddy, this combo runs about 12.3:1. We built an engine for an X1 track day bike using all Buell engine parts using this combo and it runs great...on 93 octane fuel, with no pinging (at 40 thousands squish). It has X1 cams in it, which really makes it a reliable valve train. It has the 44mm carb on it. The heads have been worked to about a stage 2. We are using the Screaming Eagle module on the 3rd setting. I highly recommend it. (Message edited by jimidan on November 08, 2007) | ||
| Blake |
Excellent info! Thanks Jimi. | ||
| Strato9r |
Good to know that a compression ratio as high as 12:1 is possible on pump gas! I just missed on the bidding on a new XB12 crank assembly on Ebay; it was really not that expensive, and I would have used it in a set of Blast cases that I have if not as a future upgrade on my 9, like Diablobrian's setup. | ||
| Strato9r |
OK, it finally sank in, but the special S+S 7.113" rod must be for a 3.5" stroke crank. Was that something that was used in race XBs before the XBRR came out? | ||
| Buellrcr |
the stroke on the race bikes before the xbrr was 3.625 x 3.8125= 1340 cc for the ama race bikes | ||
| Alessio66xb12r |
to Buellrcr have you more details about that motor ??? ...please. bye Alessio | ||
| Buellrcr |
will you have to have special cases made, deck height of the cases is .200 taller than stock cases.i dont know all the measurements. | ||
| Alessio66xb12r |
thank's this is my point : for a race(track) bike 3.8 stroke seems to be a little "long" and when you need some rpms more it FAILs , the 3.1 stroke of 986 xb on the other side give you more rpms but with my 90 kilos weight is not the best choice for me. what i want to know is about the crank assembly . will the 3.6 stroke crank fit on xb12 timken bearings 2004 cases ??? bye Alessio | ||
| Buellrcr |
it will if you put a .200 shim under the cylinders | ||
| Alessio66xb12r |
this is interesting ...i'm on the first oil change on my 88 engine and everything seems going fine .... if in the future i'll need a new engine i will consider this option. now i want to complete this bike (new front end ohlins/2x brembo ) and test it . i was just curious , never heard here about that 3.6 motor . thank you James bye Alessio | ||
| Panic |
"the special S+S 7.113" rod" This was developed to make the longest possible stroke Sportster that will still fit in the chassis (i.e., stock cylinder height): 4-5/16". Using the full length iron Sportster rod made it too tall or the oiston too short, using the original Evo rod shortened the rod ratio too much (1.606:1). For longer strokes (or any modified chassis) they recommend the 7-7/16" (longest) rod. | ||
| Buellrcr |
also need special pistons too,i have a old set of rods laying around some where if i find them i measure them. all so heard if you used xb9 rods and a 12 wheel it will make a 3.6 stroke but not sure dont quote me on that. | ||
| Alessio66xb12r |
i think it is incorrect 12 wheel is 3.81 stroke (96,75mm) using different rods ( xb9 rods , longer than xb12) does'nt change the stroke . stroke is generated by the "pin" position in the wheels. 9 rods and 12 wheel is a pain to assemble maybe impossible using on xb frame..... anyway 3.813 stroke bye Alessio | ||
| Alessio66xb12r |
longer is the distance between pin and the center of the wheels = longer is the stroke | ||
| Strato9r |
Thanks for the ongoing info on rod lengths, Panic, I really appreciate it! Just bored a set of pin bushings for a customer's Panhead project, and he was using a pair of super low mileage '71 Shovel rods that he'd been hoarding for years. They set up at exactly 7.480" on our Berco rod boring machine. He told me that they shortened up big twin rods later in Shovelhead production to 7.44". All of this is coming in kind of handy right now, with the recent aquisition of a set of '04 Blast cases. I'd like to build a stump puller of a single for a Street Tracker project, and since the frame will be built around the engine, stock cylinder lengths and mounting points are of no importance. Therefore, using an early Ironhead or the XB9 rod on a long stroke set of flywheels totally makes sense, as does using the longer big twin Evo cylinder, as they share the same mounting pattern. (which is the same as Knuckle/Pan/Shovel. hmmm, a one lung Shovel......) | ||
| Viper9885 |
ok i've read through this like three times and have been going over things in my head but can't seem to get where i want to be. I have an xb12r and i want to raise my compression....in the same breath i would also like to shorten the stroke to improve rideability and reliability. Is there a way to put a shorter stroke crank along with longer rods, higher domed pistons and an overbore kit that in the end would maintain my exact same displacement, but change the overall engine geometry allowing higher quicker revving (i would also look into valvetrain mods to accompany the higher revs) | ||
| Viper9885 |
also if this cannot be done is it really true that all i have to do is drop in a set of xb9r pistons and my compression will raise to 12.3:1 (i run nothing less then 93 anyways and i live in wisconsin so it doesn't get that hot out) Will any other stock cams fit in that are slightly more aggressive or would i have to go aftermarket? | ||
| Viper9885 |
can you make a custom length rod, I don't mean anyone specifically I am just wondering if one could get one made. I was just brainstorming and personally I think the ideal engine would be a 3.8" stroke 12 crank with the S&S 7.1" rod with oversized 12 pistons in bored out 9 cylinders????? would that work? (are the 9 and 12 cylinders the same height and the ONLY thing that effects displacement is stroke?) |
