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Discussion Starter #1
I did a search here and CB350/360 carbs and pod filter topics popped up more frquently than weeds in my lawn, but I'm going to give it another go.

CB360 with a vintage header. Tip of the pipe ends at rear wheel axle. Silencer baffle is packed with fiberglass, so back pressure should be adequate. Uni pod filters. Stock airboxes and intakes are long gone. I live in thin-air Denver. Vast majority of riding will be around town with some canyon carving (higher-yet elevation).

As I recall, one of the members here has the "magic voodoo combination" for jets and needle settings which would allow for a decent compromise. I know a good tuner who can do the final tweaks so having a good starting point from people who play with such issues would be helpful and appreciated.
 

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I believe you can send your carbs to crazypj and he will make them work. It's more than just changing fuel jets.

Best contact him through PM and discuss.
 

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Discussion Starter #3
quote:Originally posted by hillsy

I believe you can send your carbs to crazypj and he will make them work. It's more than just changing fuel jets.

Best contact him through PM and discuss.
Just did it. Thanks.
 

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I replied to e-mail, send another if you want address so I can do mods.
Will still need fine tuning but at least I can get rid of the mid-range richness with pods.
Uni's are a good choice, they are slightly more restrictive than K&N so cause slightly less problems
 

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quote:Originally posted by Acemon

Tip of the pipe ends at rear wheel axle. Silencer baffle is packed with fiberglass, so back pressure should be adequate.
Just out of idle curiosity, how did you conclude that back pressure was adequate? Is it a straight through muffler with zero back pressure or is there an actual baffle in there creating back pressure?
 

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I have no idea why everyone thinks you 'NEED' back pressure, you don't
Correct exhaust length and diameter is what is needed.
Anything over 2psi is wasting a LOT of power
 

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PJ just what do you consider correct length and dia. for a 360 ? Length of pipes and how long on mufflers. I have a CL upswept pipes are staying even if it costs me a little power.
 

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PJ, I agree totally. I wanted to hear the rationalization. People regularly rationalize why this or that idea will or will not work and much of the time it's based on faulty assumptions.

In reality any pipe system will create a pressure profile depending upon its shape, diameters, length etc. As you mentioned, what's important are length and diameter for a particular application. Changes in exhaust back pressure do effect cylinder emptying and also change intake velocity and cylinder filling and therefore jetting.

BTW one study I read suggested that on a mid sized auto engine, 1" Mg of exhaust pressure equals 1 hp lost.
 

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Stock pipes are about the right diameter and length, slightly too small ID but not by much
I did work it out but can't find the numbers.(28.5"?)
I know my 2:1 is about 2" too long on primary pipes, haven't bothered to shorten it yet as it does improve torque
Stock are double skinned so a LOT smaller inside diameter than they look
Stock silencer is pretty restrictive though so something with better flow helps a lot.
Stock outlet is only about 3/4"?
Total length needs to be about the same as stock, don't fit restrictions to pipes, go up slightly on ID and about 1.5" outlet (mainly because it looks right and doesn't affect performance too much)
Running 2:2 you need staggered exhaust with CL pipes because they are a lot different in length
 

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Discussion Starter #10
quote:Originally posted by Teazer

quote:Originally posted by Acemon

Tip of the pipe ends at rear wheel axle. Silencer baffle is packed with fiberglass, so back pressure should be adequate.
Just out of idle curiosity, how did you conclude that back pressure was adequate? Is it a straight through muffler with zero back pressure or is there an actual baffle in there creating back pressure?
It has a removeable baffle (tube with punched holes) similar to the one with my long-gone GT550. In retrospect it's straight-thru but I would imagine the turbulence of exhaust gases through that area would be somewhat "restrictive".

I might be mistaken about the need for back pressure but I seem to recall that being a factor in the design of an engine. I like the sound of straight pipes but I'm too socially considerate to run them on the street.
 

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Discussion Starter #11
quote:Originally posted by Teazer

quote:Originally posted by Acemon

Tip of the pipe ends at rear wheel axle. Silencer baffle is packed with fiberglass, so back pressure should be adequate.
Just out of idle curiosity, how did you conclude that back pressure was adequate? Is it a straight through muffler with zero back pressure or is there an actual baffle in there creating back pressure?
It has a removeable baffle (tube with punched holes) similar to the one with my long-gone GT550. In retrospect it's straight-thru but I would imagine the turbulence of exhaust gases through that area would be somewhat "restrictive".

I might be mistaken about the need for back pressure but I seem to recall that being a factor in the design of an engine. I like the sound of straight pipes but I'm too socially considerate to run them on the street.
 

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Discussion Starter #12
quote:Originally posted by Teazer

BTW one study I read suggested that on a mid sized auto engine, 1" Mg of exhaust pressure equals 1 hp lost.
I'm glad you mentioned that. It's something I think about when turbo fans refer to the exhaust output as being "free" energy. The boost obviously results in an overall gain in HP, but not as much as if an outside source provided the compression.
 

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Discussion Starter #13
quote:Originally posted by Teazer

BTW one study I read suggested that on a mid sized auto engine, 1" Mg of exhaust pressure equals 1 hp lost.
I'm glad you mentioned that. It's something I think about when turbo fans refer to the exhaust output as being "free" energy. The boost obviously results in an overall gain in HP, but not as much as if an outside source provided the compression.
 

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PJ,
Have you tried running the stock rubber velocity stack from the OEM filter with a Uni or K&N on it? Does it make jetting the carbs for a pipe easier?

Ken
 

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PJ,
Have you tried running the stock rubber velocity stack from the OEM filter with a Uni or K&N on it? Does it make jetting the carbs for a pipe easier?

Ken
 

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Hi Ken,
I'm going to try it, got one cheapie pod glued onto a modified airbox to carb rubber but can't remember where I put the second rubber though
I can't ride until next month so haven't worried about it too much (haven't ridden since before surgery on 3rd Jan :()
I don't think I have a set of stock carbs at present, already mofified them for K&N
I'll let you know what happens
 

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Hi Ken,
I'm going to try it, got one cheapie pod glued onto a modified airbox to carb rubber but can't remember where I put the second rubber though
I can't ride until next month so haven't worried about it too much (haven't ridden since before surgery on 3rd Jan :()
I don't think I have a set of stock carbs at present, already mofified them for K&N
I'll let you know what happens
 
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