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Post by grayghost999 on May 5, 2014 18:41:04 GMT -6
Hi all, Sorry for the foolish question and if its in the wrong section. I have been skimming the threads for 2 days now and didnt see any threads that touched on my question. I see alot of posts about the great things you can do with the exhaust mods and i am excited about trying some of them. I mentioned a few of them to my brother in-law and he said that I would have to re-jet my carbs if i change the stock exhaust in any way.... is that true? I really hope not. taking the carbs back out was horrible the 4 times ive done it so far!
thanks and sorry if i missed the thread that has the answer to this.
Dan
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Post by Blaine on May 5, 2014 21:32:31 GMT -6
Hi all, Sorry for the foolish question and if its in the wrong section. I have been skimming the threads for 2 days now and didnt see any threads that touched on my question. I see alot of posts about the great things you can do with the exhaust mods and i am excited about trying some of them. I mentioned a few of them to my brother in-law and he said that I would have to re-jet my carbs if i change the stock exhaust in any way.... is that true? I really hope not. taking the carbs back out was horrible the 4 times ive done it so far! thanks and sorry if i missed the thread that has the answer to this. Dan No. You only need to rejet if you modify the intake.You may need to do a idle mixture adjustment.   |
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Post by grayghost999 on May 6, 2014 5:35:31 GMT -6
Thanks alot man!! Cant wait to chop it up |
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Post by zekkfett on May 6, 2014 8:46:50 GMT -6
he said that I would have to re-jet my carbs if i change the stock exhaust in any way.... is that true? I really hope not. Ah... the age old debate. Everyone's opinion will differ on this, but there is some science behind it all. First, an engine is a big air pump. It pumps air in, and it pumps air out. The factory exhaust is set up to provide backpressure on the exhaust, which is ALWAYS needed on a naturally aspirated engine. Backpressure allows the valves to close FULLY, and in part, helps to "pull" some of the spent exhaust gasses from the combustion chamber. If you do any type of mod to the exhaust that removes any backpressure, or removes the backpressure fully, (open pipes) you are changing the air pump; allowing MORE air to flow through the pump. Remember Newton's laws?? One of them being: "For every action, there is an equal and opposite reaction." You CANNOT change the airflow into or out of the pump without adjusting the fuel that goes with it. Another really funny thing that most people do not realize, (and this applies to ALL internal combustion engines, and has been scientifically proven) is that the stock air filter has MORE THAN ENOUGH capacity to create all the power the engine will ever make, and will filter FAR better than any aftermarket or "high-flow" filter. The reason why K&N's "work": they WILL flow more air at the cost of ****** filtering of the air coming in. Dyno results speak for themselves, most aftermarket "high-flow filters" or "cold air kits" will make you LOSE horsepower, if you don't adjust the fuel delivery along with them. The ONLY reason you should EVER run pods on our 454's is for ease of working on, or removing the carbs. But then again.... If your carbs are right, there should NEVER be any reason to take them on and off, and on and off... If you're going to do something as simple as drill a couple holes in the first baffles, no, no rejet is needed. There are enough other baffles inside the mufflers to still have enough backpressure to operate properly. Any slip-ons or custom exhaust that is mostly open, the answer will ALWAYS be yes, you need to rejet. SOME stock mufflers off other bikes may not need a rejet, but chances are you will, as that muffler was designed to operate on the engine that it came off of. The dyno numbers will tell the truth, and I have done this experiment before. I had a customer come to me one time with new Vance and Hines slip-on's and wanted them installed. I asked where the jet kit was, and he says, "From my research, you don't need a jet kit to do just slip-ons." I proceeded to tell him what I just explained here, and he wasn't having any of it. So I drew up a release of liability and made him sign it. I made a deal with him; I told him I would do the job for free IF I installed the pipes and he MADE horsepower or it stayed the same. He agreed. (Who wouldn't, for a chance at free labor??) 98 Honda Shadow Spirit, on the dyno with stock pipes, air filter and jets, made 39 horsepower and had an air/fuel ratio of 16.4 : 1. Lean from the factory. Threw on the slip-on's, no jet kit, ran the bike on the *** dyno, no noticeable lean condition(s) OR power gain: then ran 3 more times on the dyno: max power, 35hp @ a slightly higher RPM and an air fuel ratio of 17.1 : 1. VERY lean! Pulled the carbs right on the dyno, installed a Stage 1 jet kit with the clips on the second needle position, 3 more power pulls on the dyno, made 44 horsepower with an air-fuel ratio of 15.4 : 1. Almost perfect. I made a killing that day, btw. Because the customer had to end up buying a jet kit from the dyno shop, which I then marked up a tiny bit to make a lil profit, and he had to buy three different dyno sessions @ $25 a pop. Also, we pulled the slip-on's back off and made a power run with everything stock and just the stage 1 rejet: 42 hp. Since that first trip many moons ago, I have made many more trips back to the dyno. I WILL NOT install exhausts or intakes anymore with making a trip to the dyno and a signed release of liability. The owner of the shop and I have become close friends, and he lets me have up to 9 runs for the price of 3. Awesome dude. As I said a few moments ago, you cannot change one end of the pump, without changing the other. Not trying to start an argument or anything, but if need be, I will argue this case to the death. lol  IF Japanese bikes weren't already so lean from the factory to pass US emissions standards, I would say throw some different pipes on with no jet kit, and you'd likely make the same power, just would sound a LOT better and prob get a TINY bit better gas mileage. Sadly this is not the case, as they come so lean from the factory, adding any more flow to the pump will only make it leaner, and you stand the chance of burning a hole in your pistons, and on our 25+ year old bikes, it's hard to find new pistons.... ALMOST ALL Japanese bikes can benefit from a Stage 1 jet kit, straight from the factory. They run them lean to pass emissions, the Stage 1 kit just bumps it back to where the fuel delivery should be. Another fun fact: Up to a point, the more power and engine makes, the more efficient it is, and the better the MPG's will actually be. Case in point, our 454's and a 86 Vulcan 750. We make right at 50 hp, the Vulcan, 68 hp. Even though the engine is bigger and makes a lot more power, you'd think the Vulcan gets worse gas mileage, no? In fact, no, the Vulcan gets better mileage. The more power you make, the less throttle it takes to get to the same speed, which means you are actually using less fuel. My point in that little subject is: if you rejet to the appropriate jets, you can have 2 of the exact same bikes, one with a full intake and exhaust, and the other stock; the properly jetted bike will be more efficient than the lean factory bike. (Better MPG's) I know I've done more than a few bikes with exhaust and rejetting, and customers come back to me saying the MPG's have went UP and they think something is wrong because their buddies have had their bikes rejetted and lost power and MPG's and they just think that's normal. And as I said earlier, EVERYONE will have differing opinions on this subject, but you can't argue with science; and in my case from experience, you can't argue with a dyno. Hey Blaine, (hint hint....) --- And an extra special EDIT ---- For those of you guys running pods and your bike gets hotter than it probably should or you've blued your pipes after installing pods, it's a good chance you're VERY lean.... Hotter running engine is one of the signs that your bike is lean. Also, at altitude, this theory goes to the wind, as you will actually need to rejet LEANER because there is less oxygen in the air at altitude. The downfall to this, is that if you jet for riding at altitude, when you come down out of the mountains, you are running DANGEROUSLY lean. Stock sea-level jets should be just lean enough for you fellas at altitude, even with pipes and filters. |
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Post by grayghost999 on May 6, 2014 10:13:13 GMT -6
darn! zekkfett, that was an awesome read! not only does it make me hate how hard it is to remove the carbs lol but it actually made me wanna rejet when I do the new exhaust!
Thanks for the reply!
Dan
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Post by zekkfett on May 6, 2014 10:58:06 GMT -6
dang! zekkfett, that was an awesome read! not only does it make me hate how hard it is to remove the carbs lol but it actually made me wanna rejet when I do the new exhaust! Thanks for the reply! Dan Glad you enjoyed it! I actually thought I was rambling on a bit, but it seemed complete to me, so if it's too long for some to read...sorry! haha I just hate to see mis-information spread. I'm not saying Blaine was wrong, and in fact he is right. SOME bikes won't need a rejet for just pipes. H.D.'s and Victory for example. Most of them were designed here in the US and have the appropriately selected jets for the region the bike is shipped to. But most Jap bikes are SUPER lean from the factory. They are designed in Japan and the jets are appropriately selected for the environment, mountains and all. Mountains and the ***##$%#@ $^$@$#%@!! U.S. E.P.A. are the reasons they are jetted so lean from factory. I know from personal experience, that the dyno doesn't lie; and I've never had a jap bike that didn't need the jet kit for a pipe change. :/ If you simply adjust the idle mix, yes you will make it a bit richer at idle to just above idle and eliminate the decel pops, but what about the entire rest of the rev range? It's still leaner everywhere else. A factory bike that has never had anything done with it, can benefit from a little adjustment to the idle mix, and get better throttle response, but it's still going to be lean everywhere else. Another thing I wanted to add in the original post: Never, ever, EVER go with a straight through pipe setup if you want to make more power for street riding. You will lose about 25% of your usable power and about 35% of the torque of the engine with straight pipes, because there is no longer backpressure or the scavenging effect. You will ALWAYS lose usable power! And sound like @$$, IMO. I HATE straight pipes.... Drag bikes are the only bikes that should have straights on them, because they stay so high in the rev range where straights will actually make power. And that powerband for straights is tiny, usually only about 700-1000 RPM's. And don't forget, most straights are actually DESIGNED for the bike they are going on to make the MAX power. Simply making your own straights will not get you anywhere near the performance of even the OEM exhaust. Most people suffer from the Placebo effect. The exhaust is louder, so they think they're going faster; when they actually aren't.... |
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Post by grayghost999 on May 6, 2014 11:51:18 GMT -6
What id like to do is what I saw posted alot. chop the pipes in front of the H and then run some pipe down to new mufflers, like some old Porky Pig mufflers or something. now I have to go skimming the carb posts for Jetting information lots to learn since this is my first bike but you guys are awesome! so glad I found this forum! -Dan |
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Post by Blaine on May 6, 2014 12:43:53 GMT -6
dang! zekkfett, that was an awesome read! not only does it make me hate how hard it is to remove the carbs lol but it actually made me wanna rejet when I do the new exhaust! Thanks for the reply! Dan Glad you enjoyed it! I actually thought I was rambling on a bit, but it seemed complete to me, so if it's too long for some to read...sorry! haha I just hate to see mis-information spread. I'm not saying Blaine was wrong, and in fact he is right. SOME bikes won't need a rejet for just pipes. H.D.'s and Victory for example. Most of them were designed here in the US and have the appropriately selected jets for the region the bike is shipped to. But most Jap bikes are SUPER lean from the factory. They are designed in Japan and the jets are appropriately selected for the environment, mountains and all. Mountains and the ***##$%#@ $^$@$#%@!! U.S. E.P.A. are the reasons they are jetted so lean from factory. I know from personal experience, that the dyno doesn't lie; and I've never had a jap bike that didn't need the jet kit for a pipe change. :/ If you simply adjust the idle mix, yes you will make it a bit richer at idle to just above idle and eliminate the decel pops, but what about the entire rest of the rev range? It's still leaner everywhere else. A factory bike that has never had anything done with it, can benefit from a little adjustment to the idle mix, and get better throttle response, but it's still going to be lean everywhere else. Another thing I wanted to add in the original post: Never, ever, EVER go with a straight through pipe setup if you want to make more power for street riding. You will lose about 25% of your usable power and about 35% of the torque of the engine with straight pipes, because there is no longer backpressure or the scavenging effect. You will ALWAYS lose usable power! And sound like @$$, IMO. I HATE straight pipes.... Drag bikes are the only bikes that should have straights on them, because they stay so high in the rev range where straights will actually make power. And that powerband for straights is tiny, usually only about 700-1000 RPM's. And don't forget, most straights are actually DESIGNED for the bike they are going on to make the MAX power. Simply making your own straights will not get you anywhere the performance of even the OEM exhaust. Most people suffer from the Placebo effect. The exhaust is louder, so they think they're going faster; when they actually aren't.... Your right.I must mention that the Canadian bikes are jetted richer from the factory than the U.S. models.( I keep forgetting that). Also we get them emissions delete.(No PAIR system). |
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Post by zekkfett on May 6, 2014 22:15:20 GMT -6
Your right.I must mention that the Canadian bikes are jetted richer from the factory than the U.S. models.( I keep forgetting that). Also we get them emissions delete.(No PAIR system). Yeah, the Canadian and European models were whole different monsters as well. I will say this: Canada got the best of the bikes in the 70's and 80's. Far less of governmental intrusion on the import and guidelines for emissions for bikes back then. The Europeans got screwed as well by their licensing system the CC limits on bikes. But that was the 80's... The Canadian govt. now has about the same stranglehold on the manufacturers as ours does; which is why I said "Hint hint" to you earlier Blaine. Even the newer Canadian models are pretty lean from factory... In the earlier post, I just assumed the OP was an American, I didn't even think to look. haha  Which is why I left the response I did. Speaking of the Europeans getting the raw end of the deal... I kinda like the way they have their licensing system. I think if it were implemented in more places, there would be FAR less accidents in general; but more so the single bike accident rate would drop DRASTICALLY. But I'm also the kind of person that thinks that if you are going to get a driver's license, you should also HAVE to get motorcycle endorsement as well; barring any medical issue that would prevent you from operating the bike. If everyone were forced to get one, and go through a mandated MSF/ABATE course, more people would be aware of the bikes around them. Just my opinion on the subject(s). Curious to know what other people think.... |
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Post by Blaine on May 7, 2014 5:25:03 GMT -6
Your right.I must mention that the Canadian bikes are jetted richer from the factory than the U.S. models.( I keep forgetting that). Also we get them emissions delete.(No PAIR system). Yeah, the Canadian and European models were whole different monsters as well. I will say this: Canada got the best of the bikes in the 70's and 80's. Far less of governmental intrusion on the import and guidelines for emissions for bikes back then. The Europeans got screwed as well by their licensing system the CC limits on bikes. But that was the 80's... The Canadian govt. now has about the same stranglehold on the manufacturers as ours does; which is why I said "Hint hint" to you earlier Blaine. Even the newer Canadian models are pretty lean from factory... In the earlier post, I just assumed the OP was an American, I didn't even think to look. haha Which is why I left the response I did. Speaking of the Europeans getting the raw end of the deal... I kinda like the way they have their licensing system. I think if it were implemented in more places, there would be FAR less accidents in general; but more so the single bike accident rate would drop DRASTICALLY. But I'm also the kind of person that thinks that if you are going to get a driver's license, you should also HAVE to get motorcycle endorsement as well; barring any medical issue that would prevent you from operating the bike. If everyone were forced to get one, and go through a mandated MSF/ABATE course, more people would be aware of the bikes around them. Just my opinion on the subject(s). Curious to know what other people think.... I totally agree Zekk. |
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Post by treasurestate on Jan 24, 2021 22:38:24 GMT -6
dang! zekkfett, that was an awesome read! not only does it make me hate how hard it is to remove the carbs lol but it actually made me wanna rejet when I do the new exhaust! Thanks for the reply! Dan Glad you enjoyed it! I actually thought I was rambling on a bit, but it seemed complete to me, so if it's too long for some to read...sorry! haha I just hate to see mis-information spread. I'm not saying Blaine was wrong, and in fact he is right. SOME bikes won't need a rejet for just pipes. H.D.'s and Victory for example. Most of them were designed here in the US and have the appropriately selected jets for the region the bike is shipped to. But most Jap bikes are SUPER lean from the factory. They are designed in Japan and the jets are appropriately selected for the environment, mountains and all. Mountains and the ***##$%#@ $^$@$#%@!! U.S. E.P.A. are the reasons they are jetted so lean from factory. I know from personal experience, that the dyno doesn't lie; and I've never had a jap bike that didn't need the jet kit for a pipe change. :/ If you simply adjust the idle mix, yes you will make it a bit richer at idle to just above idle and eliminate the decel pops, but what about the entire rest of the rev range? It's still leaner everywhere else. A factory bike that has never had anything done with it, can benefit from a little adjustment to the idle mix, and get better throttle response, but it's still going to be lean everywhere else. Another thing I wanted to add in the original post: Never, ever, EVER go with a straight through pipe setup if you want to make more power for street riding. You will lose about 25% of your usable power and about 35% of the torque of the engine with straight pipes, because there is no longer backpressure or the scavenging effect. You will ALWAYS lose usable power! And sound like @$$, IMO. I HATE straight pipes.... Drag bikes are the only bikes that should have straights on them, because they stay so high in the rev range where straights will actually make power. And that powerband for straights is tiny, usually only about 700-1000 RPM's. And don't forget, most straights are actually DESIGNED for the bike they are going on to make the MAX power. Simply making your own straights will not get you anywhere near the performance of even the OEM exhaust. Most people suffer from the Placebo effect. The exhaust is louder, so they think they're going faster; when they actually aren't.... Replying to an old thread here (I know), but I wish that we had a bike guy like you around here to tune carbs. Not sure if I even know of a dyno in Helena or not. |
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IF Japanese bikes weren't already so lean from the factory to pass US emissions standards, I would say throw some different pipes on with no jet kit, and you'd likely make the same power, just would sound a LOT better and prob get a TINY bit better gas mileage. Sadly this is not the case, as they come so lean from the factory, adding any more flow to the pump will only make it leaner, and you stand the chance of burning a hole in your pistons, and on our 25+ year old bikes, it's hard to find new pistons.... 
Which is why I left the response I did.