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open pipes and pod filters

bigcity81

CB750 Enthusiast
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boston ma
Hey guys its me again, so i sit and stare at the bike and try and visualize where i want it to end up as far as my perfect cafe racer its a 75 750f with an 836 kit in it allegedly it has pod filters and a mac 4-1 exhaust I've been thinking about taking the muffler off and letting the exhaust dump right at the collector. If i do end up doing that where would a good starting point be for jets? I want to make it run good obviously ust seeing if anyone else has a baseline or experience with this thanks again
 
In all honesty you may loose some power by dumping it off right after the collector. You really need to have a little length after the collector to take advantage of the exhaust scavenging, especially on a street motor. If you were racing this would be different because you normally only run in a certain rpm range when you are racing as opposed to the street where you need from idle on up. I ran 4 short straight pipes on my 836 for a while till I could build a good 4 to 1. It lost the good usable power and hurt the torque with the straight pipes and I had to put 130 main jets in and raise the needle 2 notches. It didn;t make anymore power with the 4 individuals and needed the extra fuel for the inefficiency of the exhaust.With my 4 into 1 I am running 125, I play around alot with carb settings trying to get it to pull smoother. What do you have for jets in it right now? I think if it was mine I would start with 120's and go from there.
 
I'd have to check I'll look next opportunity I have. I guess I'll just core out the muffler, now should I be bumping up the size anyways with the after market exhaust and air filter pods?
 
Yeah you will need bigger jetting with the pods and exhaust. I think stock your 75 motor had 105 main jets. But who knows what is in there now after all of these years. I think you will be in the 115 to 120 range depending on what the motor actually is. You will also have to play around with the needle position. Pod filters can be a pain in the but to get jetted right because the air flow is so much different than the stock airbox.
 
Well, I tried to get pods to work on my '74 K-4 and it was a mess. If you look closely at the rubber couplings between the carbs and the air box you will see that they are mini velocity stacks. I put the stock air box back on with new OEM rubber couplings between the carbs and the air box, installed stock jets and everything works great now. So, basically, the stock carbs will not work without the stock air box.
 
You can get them to work well it just takes a little messing around with the jetting. I have pods on my dads 74 750, my 750 hardtail and my 72 cb500. It just takes some messing around.
 
My 79 cb750k is all stock except for the exhaust pipes. It now has 2 into 1. All the baffles were removed before I got the bike and it runs great with the throttle on sounds like a sharp bark. It tends to pop and ping when you let the throttle off fast but it sounds great. A riding buddy now wants to change the exhaust on his brand new harley so people will hear him over my bike!!
Rip those baffles out and let your bike bark!!
Mycrew
 
My very first bike was a 79 gs550 a real shit box it had pods open 4-1 started it with a screwdriver ripped seat side plastics didn't match the tank color a real furious POS but man o man did I love that thing i loooooved the sound of the open pipes nice and loud throaty and a awesome crackle when ya let of the throttle
 
My first bikes were all Brit bikes. No Jap bikes around in the late 50s. Those Triumph twins with stock pipes and reverse cone megs with of course, no baffles sounded very sweet.
At low speed a deep mellow rumble full of portent. Up the revs and things got loud. Not the sharp crack of straights but a whole brass band of beautiful motorcycle melody.
For my little Triumph dirt bike, I made a straight pipe that stuck out to the back end of the tire, then cut off a couple inches at a time till it gargled just right on decel. End just about at the axle. The power was increased substantially. Highly competitive little scoot till those Bultaco 2 strokes showed up. Poor little 4 stroke just had to go to the back of the shop. Still was a lot of fun to play with though.
"Spose this doesn't help with your problem but was fun to remember, Jim.
 
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