[stefan11488]

Hi I've very new to motorcycles and engines, however I'm decently mechanically inclined, I can fix thing reading the shop manuel for instance. My motorcycle is a 1979 honda cb650 and my question is what is involved in putting pod filters on my bike. I read everywhere that re jetting is necessary, but no where can I find which jets to change or how to do it or which size I will need. Thanks for all the Help

 

[robertob]

You will not be able to find the right jets on the internet. You might get close, but you will still need to do your own tuning because every motor is different. Usually the low-speed jets will be close to correct but the main jets will be too small and often the needle profile will not work with pods.

I'd start by going up 2 or 3 sizes on the main jet and then testing it. Keep going up on main jet size until full throttle produces sputtering. Go down one size - if it pulls clean with full throttle but sputters in the midrange, it's close to correct. Then lower the needle to fix the midrange, which often leans the off-idle and means you have to go up on pilot jet size...

It's all interconnected.

 

[kenessex]

The CB650 does not have adjustable needles. You can richen it up by using a thin washer under the top of the needle to lift it up. You can not make it leaner. Why do you want to put pods on this bike? With a stock motor and exhaust they will not gain you anything except intake noise and jetting issues. If you ave changed the exhaust then they may(note: or may not) gain you some performance. Until you know what you are doing, stock is good. If you are going to use this as a learning experience, then there are better carbs to learn on.

Ken

 

[stefan11488]

Well this might sound dumb but I was thinking more along the lines of an aesthetic reasoning, I have seen this bike with pod filters and I am currently in the process of building a cafe bike out of it and think it looks much better with the stock air box removed. I am also moving all of my electronics into the tail. I am not really looking for performance gains. Thanks for the replies they are appreciated

here is an example of what I'm looking to do this bike was done by Cafemotowerks (to give credit where its due).

 

[kenessex]

Aesthetics is a good enough reason. I would save that fr last then. Get the bike up and running first and then start making all the cosmetic changes one at a time after you have all the mechanicals sorted. The bike you have posted is nice looking, but I suspect that there are some issues with it for seating. A lower seat, lower bars and stock footpegs usually don't work very well comfort wise. Needs rearsets. I am not a fan of stock rear shocks and the stock wheel sizes for handling.


Ken

 

[HackAsaw]

should read "You can not make it leaner without a bit of effort"

but both the slide and the needle assembly can have their whole attitudes changed after a few minutes in the lathe....

I'm not 100% sure on those exact carbs but many have washers under the needle already which can be removed or thinned

and most have enough meat in the slides to accommodate a deeper counterbore

quote:Originally posted by kenessex

The CB650 does not have adjustable needles. You can richen it up by using a thin washer under the top of the needle to lift it up. You can not make it leaner. Why do you want to put pods on this bike? With a stock motor and exhaust they will not gain you anything except intake noise and jetting issues. If you ave changed the exhaust then they may(note: or may not) gain you some performance. Until you know what you are doing, stock is good. If you are going to use this as a learning experience, then there are better carbs to learn on.

Ken

 

[kenessex]

HackA,
True enough. Most people without any carb experience are reluctant to start boring carb slide needle holes or machining needle retainers. In this particular case, I seem to recall that the top of the needle in these carbs has a fairly thick plastic piece swaged onto it that could have a considerable amount machined off to lean out the mid-range. Not a job for a beginner I think.

Ken

 

[stefan11488]

I just had an idea, so the air filters are all about cleaning the air to mix with the gas in the carburetors, correct? Is there a way to measure airflow? So what if I added a piece of tubing between the pod filters and the carbs and rigged up my own extra filter inside the tube to further restrict airflow. Maybe I wouldn't even need to measure just do a trial and error to get the pods with extensions to have the same airflow as stock. Just an idea so don't laugh

 

[HackAsaw]

heck for all the typing you could have already slipped them on.......

if they are CV carbs........ heck they may just kinda roll with it and help themselves like CV's kinda do

 

[stefan11488]

I want to make sure its smart to buy four air filters first!!!lol

 

[crazypj]

The 79 should have slide carbs soyou have a chance of jetting it close. You need to know if you have 2 jet or 3 jet carbs, accelerator pump and air cut valves. Various diaphragms wear out or dry out with age and may need replacing, depending on what your starting with. I haven't done a 650 for quite a few years now but they are not the easiest to get right. Shimming the needles is a very bad idea.