| Author | Message | ||
     Buellistic |
XB head: Big intake valve BLAST Carb.: Small bore Is this an example of choking a chicken ??? (Message edited by buellistic on August 21, 2006) (Message edited by gearheaderiko on August 21, 2006) | ||
| Gearheaderiko |
No. The Blast uses essentially the same carb as a Sportster or Big Twin, minus an accelerator pump. | ||
| Gearheaderiko |
MyGPT: Why not use a front head? Using 2 front heads or 2 rear heads has been done on twins before. You'll have to work out the cams as everything is now reversed and you cant just swap cams front to rear.Which also means you'll have to get the cam timing right because its no longer a just line up the marks affair. The carb/intake probably wouldnt clear the frame without a lot of work. And while throwing the carb in front to force feed it air, it would be less work to use a filter/ram air system to the stock location. Of course, if you want to just throw on a front XB head, thats easy! | ||
| Buellistic |
Gearheaderiko: In answer to you post Monday, August 21,2006 - 11:13 pm ... Why do you think BMC came out with the 44MM(can be bored larger if necessary)Big Bore Carburetor Kit PN 27934-99 which requires INTAKE MANIFOLD KIT PN 27473-01Y ... Now you really should bore out your BLAST Carb. and flow your intake manifold, what do you think ??? After all that is a BIG INTAKE VALVE in the XB head, PLUS the port is BIGGER and well flowed from the factory ... In BLASTing LaFayette (Message edited by buellistic on August 22, 2006) (Message edited by buellistic on August 22, 2006) | ||
| Ezblast |
What is the max lift of the stock springs? GT - JBOTDS! EZ  | ||
| Gearheaderiko |
First, the 44mm carb is for a modified XL or a Big Twin both being -at least- 1200cc. Lets forget the extra cylinder. Just one cylinder is at least 600cc. The Blast is still only 500cc and just adding an XB9 head is hardly going to make its flow needs that of a 600cc engine. Just adding an XB9 head and cams wont even come close. The intake manifold port is .030 bigger on an XB9 than the Blast. Hardly a significant difference and given the fact that a stock Blast intake manifold probably wont match up to the stock intake port, at least some matching of manifold to head should be done for better performance whether its a stock or XB head. You're still thinking in twin mode. The 40mm carb can flow enough cfm for 500cc or 1340cc. Thats a huge difference. Throwing a big carb on a mostly stock engine will more than likely result in worse bottom end and no gain in the upper rpms. Generally a mistake newbies make in modifying anything. The XB valves are one step bigger than the Blast. Bigger valves are available (Big Twin). The advantage in using the XB head is not huge bolt on horsepower. Its in getting a bigger valve, flowed head, off the shelf and being able to use XB (SE550 or '04 XL-close in specs to the B70's) cams. It's generally cheaper than getting the Blast head done and still being able to rebuild it with off the shelf parts. Why do I think the BMC came out with the Big Bore carb kit? Its for twins!!! Certainly not usable for a Blast in stock form (the carb or the Blast). | ||
| Buellistic |
Gearheaderiko: In PLAIN ENGLISH then: Bore your Road Racer BLAST Carb. out and it will run better !!! In BLASTing LaFayette | ||
| Gearheaderiko |
A better carb on a Blast=good idea. A bigger CV Kehein carb=bad idea. So apparently you didnt understand a word I wrote. A bigger carb on anything but the most modified Blast engine is a waste of time and money. A carb is not a supercharger. The engine must be matched to the carb and be able to utilize its cfm flow. Will putting a CV40 carb make your lawnmower run better? No, its too big, but your logic says it must make it run better. Do you know why hi performance multi cylinder engines use multiple carbs instead of just one big carb? Do you understand why air flows faster through a small venturi rather than a large venturi? Do you understand that air flow makes a carb work? Do you understand the relationship of cfm (cubic feet per minute) and that a 1340cc engine needs a lot more fuel than a 500cc engine? Yet the Blast sized carb can feed both. But you think its needs to be bigger? Again, putting a bigger carb on a Blast will hurt the bottom end, make it harder to tune, and only give any possible results at the high rpms. Do you understand the difference between a street motorcycle and a race prepped motorcycle? There are pictures and details all over Badweb about MY Blast. Maybe you should search them and get a better understanding. EZ and I run comparatively the same engine setup. My motorcycle just happens to be prepped for the racetrack. IN PLAIN ENGLISH: You dont know what your talking about! | ||
| Buellistic |
"OUCH !!!" | ||
| Ezblast |
LOL - what is happening here is two different racing philosophies clashing - I know for a fact that HD overcarbed all its flattrackers for more power in a certain band - the down side is that the bikes didn't idle, would die instantly if not constantly reved, and didn't help torque values at all (their racers had 35 ft/lbs - the privateers where hitting 40 and over), just top end HP, however, it did work - they had hp numbers from 60 to 80 hp - depending on other variables - a lot higher than anyone else has ever produced from 505cc/515cc Blast engine - that was/is Old school - used by the 750cc dirt tracker and transfered over to the single. No new tech here, however, it does work - to a point. New school - looks for a working combination of parts that will not only produce usable hp, but torque and everyday usability on the track(street)durability as well - thus the kits produced have lower HP figures, higher torque numbers, but are much more usable with a broader power band and I have seen several privateers get a good 50hp+ and 40+ torque numbers - something HD could not do using their tech. and the bike would idle at the line - lol. HD was running a CV53 carb as a matter of fact on their singles - lol GT - JBOTDS! EZ | ||
| Swampy |
Beullistic, That is correct, too large of a carb will do nothing for you, an engine will only flow a given CFM and putting a carb that flows more than what that ability is will not do anythng for the motor and can actually hurt its performance. With a CV carb the slide is operated with engine vacuum. When you open the throttle, it is the vacuum that opens the slide, if the vacuum drops the slide closes. When you put too large of a carb on the bike the slide will not open all the way even if you have the throttle opened all the way. | ||
| Blake |
Once you reach 45 RWHP or so on a Blast, the stock carb becomes a limiting factor. | ||
| Gearheaderiko |
Thank You Blake, EZ and Swampy. | ||
| Buellistic |
Blake: Does that mean that ERIK's Road Racing BLAST only makes 35 HP ??? Maybe a little biger bore carb. would get it up to 40 HP ??? Ezblast: The Factory BLAST Dirt Trackers have the XB9 STROKE ... If they had the XB12 STROKE they would do much better as Dirt Trackers ... In BLASTing LaFayette | ||
| Ezblast |
"Folks not having complete knowledge of what they r talkin about,lol.the andrews b50 only has .305522 lift.when u combine that with 1.75 rockers u get .53375 total at the valve "- a very cagey racer/designer told me this - so some good springs are needed for the lifters - puts your lift in the B70 area for power delivery, however with a much gentler/smoother ramp/profile - this has always been the cam Erik should have tossed in since the bikes inception - smooth as silk with a really nice take off and midrange - and now with the power range of the B70 - sweet would be my thought! A combo like this would be a definate benifit to a budget racer because of the gentleness of the overall cam compared to the drag racer type ramping of the B70 - which is nice, however, maybe this would be more towards overall longevity. Will see! GT - JBOTDS! EZ | ||
| Blake |
LaFayette, Are you being cantankerous again?  My 100 RWHP Cyclone uses the stock CV carb. It would likely make some more power if I would swap in a bigger carb. | ||
| Ezblast |
Food for thought from a letter written: I've seen a lot of their bikes with Mikuni 42 and 44 flatsides as well, the CV53 is just what he told me on one of my interviews - HD is famous for lieing - lol - However - other topic, the 1.75 lifters would probably be a good thing on the B50 amplifying a really good cam, they would suck on the stock, because of the slow ramping of the low end would be amplified - causing even further bogging - what Aaron was talking about long ago - now the rockers may be the way to go to add more power to your setup, the SE550/XB cam is very simular to the B50 in that it is gentle yet aggressive and with that extra lift you would have even more power and since your head is already set up for the extra lift - it would be a straight bolt in - something to think about. I wouldn't do it to the B70 because it would amplify the low end lag (and then I'd have to play with needle shimming seriously and even more dyno time) - simular to stock - and I'm happy where the bike is at right now with the B70 - and really don't want to mess with the engine anymore on it till rebuild time, just looking for a way to bring the Red a little closer, and with the 1.75 rockers and some heavy-duty springs in combination with the B50 cam I already have in her I may have found it and keep long term dailly driving reliablity - lol - the real problem with the 1.75 rockers has always been that they will amplify any problems with the cam - lol - So ideas unfold! GT - JBOTDS! EZ | ||
| Jprovo |
My 2 cents. I ride Erik's "racebike" on the track... Erik's race motor is a mildly tuned street motor that was built for engine longevity, and not outright power. It has good midrange to top end pull, and runs very well. It is however, not to be thought of as a "race motor" just because it is in a "racebike". An oversized carb is not likely to help this motor out, at least not enough to make it's cost justifiable. Most of the Blasts that I am racing with have stockish motors with stock cams, and a $200 cam change or boring out the carb, or any other engine change other than an air filter, exhaust system, and an ignition module is considered big bucks... We're just in it for the fun right now. It's not like I'm a 15 year old up and coming kid, or Valentino Rossi or anything... | ||
| Buellistic |
Blake: Only when "i" post something, it is there when "i" check it as posted and gone later ??? In BUELLing/BLASTing LaFayette | ||
| Gearheaderiko |
Post moved as it was deemed inflammatory and insulting in nature. Post will be returned to thread if approved by governing parties. Be assured that Blake has your response. Post returned! (Message edited by gearheaderiko on August 24, 2006) | ||
| Buellistic |
Blake: Not at all, just trying to get you'll to rethink the tank ... You do not have to think as everyone else does ... You do not have to build an engine as eveyone else says build it ... You build an engine for what you want to do with it ... In BUELLing LaFayette INFLAMEATORY MY ARSE !!! (Message edited by buellistic on August 24, 2006) | ||
| Ezblast |
 | ||
| Jprovo |
You build an engine for what you want to do with it ... I think that is the point of the whole conversation... I think Erik did. | ||
| Cobalt60 |
A little controversy is always good. Innovation doesn't come from thinking the same way everyone else does. Pop a big bore carb on there and post the before and after results from the same dyno. | ||
| Ezblast |
Its running rich as is and they have a reversion issue to work out first - though leaner jetting may help solve that and add some power. GT - JBOTDS! EZ | ||
| Gearheaderiko |
Plenty of space on the bike for a sponsor. Email me privately and we'll work out a deal! Them big bore carbs dont come cheap! | ||
| Blake |
Buellistic old friend, if you weren't cantankerous, we'd worry about you.  Carry on. Take it easy on Eriko though please. He's dong his best. He just don't know you like some of us do. | ||
| Blake |
Did I just say "dong"? I meant "doing"! Geesh! | ||
| Sportymark |
Ok Thumpers... scored a 04 Sportster head (essentually the same as an XB head but drileld for a breather that will be blocked off) Going on Laura's LSR/Street Blast what is the combustion chamber size on the factory blast head? we can taylor the chamber on the sporty head while we are porting it. Any other weird issues we might think about? (motormount or something fun like that?) we are gonna go through put in nice aftermarket valves, seals and guides, and springs to get the valvetrain nice and light. What is the stock rocker ratio? thinking of some roler rockers to help out the friction in the valvetrain.... Sound like a plan? that and the XB cams we have for it and the SE ignition module shoudl be a good combo for 7500RPM right? And for those of you that frequent the yahoo board don't post anything on there about this yet, it's still a suprise. | ||
| Buelldyno_guy |
My $.02 worth. The Bonneville Blast at 650-cc has RP Stg 3 high flow heads heads, huge Red Shift roller cams, tuned length high flow open exhaust, a seven inch long intake manifold and uses a 45-mm Mikiuni. Somewhere between the pilot jet, the upper end of the needle and way before it gets to the main or Thunder Jet it gets so rich it takes 200 yards to get the throttle open. But before it is suggested; we will be going to the leanest needle next year when we go back as a 750-cc. My point is that you can not just bolt on a bigger carb. It all has to work together and if this thing ever becomes a track bike where you need to open and close the throttle at each turn. Smaller cams, a 41 Mikiuni and exhaust with back pressure would be needed. ... Terry. ... Owner Builder and Rider of the "Worlds Fastest Buell Blast" |
