After 10+ years of ownership and reading many posts warning about staying with the original airbox, I've reached a point where the bike has never run better so why not give pods a try and see for myself.
I found a few posts where a few people were experiencing success with their pod installations and it seemed like the jetting combination that everyone was using is:
slow jet: 38
primary: 80
secondary: 120
There's even a few YouTube videos of guys running with pods on CV carbs. From my research, it seems like you'll need a well running bike with reasonably good/consistent compression across the cylinders to even attempt to run pods.
Over the years, I've come across a number of old timers who have waxed poetic about "laminar flow" being key to the success of the airbox which I interpreted to mean that the flow of air into the carbs needs to follow a long straight (reproducible and higher velocity) path in order to improve the likelihood of the heavy aluminum pistons achieving lift during acceleration. The key difference between the old school carbs that can run pods all day long and the CV carbs are the fact that the old school carbs have their valves connected directly to the throttle where the CV carbs use vacuum to pull the pistons open.
Although my bike has never ran as great as the previous riding season, that's not to say that I didn't experience some trouble. I had a slight hanging idle occasionally, once the bike warmed up and also the #2 exhaust ran much hotter than the other 3 pipes. I think my carbs are not absolutely clean, so I'm going to double check all the circuits and make sure everything is clean and there are no missing parts when I go in to replace the jets.
NOTE: Not all of the carbs are the same for the 79-82 cb750 DOHC bikes. Apparently some years have pressed in slow jets that are not easily replaceable. You'll need to check what you've got before ordering.
I picked up these pods from Amazon for about $59 because they are not the cheap gray ones that everyone else seems to use and they are less costly than the K&N pods which seem spendy. These well built pods appear to be very solid and use foam instead of gauze. I hope it will be OK to just use the K&N oil I have on my shelf and don't need to buy special foam air filter oil.
I also ordered the individual jets from Jets R Us for another $54 including shipping. I ordered the "OEM equivalent" which typically sell for about half of the price of the original parts. There are a few posts about sticking to OEM instead of using generics to avoid unexpected running behavior or difficult to diagnose issues and if I had seen those opinions before I ordered, I might have ordered the more expensive parts instead.
With the jets in hand (approx 4 day delivery!) I found some tiny metric drill bits I bought several years ago and thankfully had a few bits that I could use to measure these jets just to put my fears to rest since JETSRUS does not do refunds. I found 2 bits measuring 1.15mm and .75mm and they seem to confirm the sizing of my 120 and 80 jets so I have a little more comfort that the 38 is likely sized as expected even though I didn't have a bit that small.
Ordering the jets individually is way cheaper and will hopefully be more effective and less trouble than the more expensive dynojet kits which go for more than $100. I could have drilled out my current jets, but my OCD is preventing me from drilling anything. I feel like the next owner (probably my son) might look at these jets marked 68 (or whatever) and not know that I've drilled it out to some other bigger size. I also want to be able to switch everything back and know what to expect with the old parts if I need to diagnose an issue, so it made a lot of sense to keep the old stuff on hand instead of swapping in brand new jets if I experience trouble and inadvertently introduce another variable.
I plan on keeping the airbox and the connectors around as long as I can, just in case. I don't want to be that guy that gets rid of the original parts and then starts having trouble and can't go back to the old setup.
I pulled the carbs and went through them again cleaning and spraying the passages with brake cleaner and compressed air. I have never broken the carb bank so I know that this is probably in my future if I start getting a fuel or an air leak but it should be much easier to remove and reinstall the carbs without the airbox in the future.
When installing pods, you need to make sure the slide lift ports don't get covered by the rubber insulators on the pods because the air that enters those ports help to raise the slides. If they are blocked, you'll get all kinds of running/acceleration issues.
The original insulators have a very smooth flow directly into the ports but my new pods have a lip blocking them. I trimmed as much as I could but the insulator separates from the body if I cut too much off so I had to mend the one that separated with some epoxy.
The mounting flange and clamp is a little too wide for the narrow mounting surface of the cb carbs but they seem to secure just fine.
The bike started on the very first crank after sitting for 8 or 9 months and this is a great improvement in cold starting compared with the old setup with airbox and stock jetting which would require at least 2 or 3 tries to get running. Amazing!.
Blipping the throttle results in really great throttle response and I'm really excited about this jetting change. Unfortunately, I have a leak in carb#2 so it has to come out again before I can ride it. The prospect of pulling the carbs pretty much derailed a whole season 2 years ago because I didn't want to pull everything out when I still had the airbox, but this will be a walk in the park.
I'm not too happy with the resonated exhaust tip, just cruising around the neighborhood I can tell it's obnoxiously loud. My son also told me it was crazy loud from inside the house, so I'll put back the original mac canister and just run quiet.
Riding Impressions
She definitely smells like she's running rich now so I turned the fuel mixtures screws in from 2.5 to 1.5 turns to fix a slightly hanging throttle. This seemed a little weird because leaning out the idle to fix a hanging idle is the opposite of what most people normally suggest.
I found a few posts where a few people were experiencing success with their pod installations and it seemed like the jetting combination that everyone was using is:
slow jet: 38
primary: 80
secondary: 120
tips for adjusting/compensating the base jetting:
- decrease main jet area by 2.8% for every 1000 feet above sea level
- 1/2 turn on the fuel mixture per jet size
- 3 or more turns on the fuel mixture screw go 1 size bigger pilot
- 2 turns or less on the fuel mixture go 1 size smaller pilot
There's even a few YouTube videos of guys running with pods on CV carbs. From my research, it seems like you'll need a well running bike with reasonably good/consistent compression across the cylinders to even attempt to run pods.
Over the years, I've come across a number of old timers who have waxed poetic about "laminar flow" being key to the success of the airbox which I interpreted to mean that the flow of air into the carbs needs to follow a long straight (reproducible and higher velocity) path in order to improve the likelihood of the heavy aluminum pistons achieving lift during acceleration. The key difference between the old school carbs that can run pods all day long and the CV carbs are the fact that the old school carbs have their valves connected directly to the throttle where the CV carbs use vacuum to pull the pistons open.
Although my bike has never ran as great as the previous riding season, that's not to say that I didn't experience some trouble. I had a slight hanging idle occasionally, once the bike warmed up and also the #2 exhaust ran much hotter than the other 3 pipes. I think my carbs are not absolutely clean, so I'm going to double check all the circuits and make sure everything is clean and there are no missing parts when I go in to replace the jets.
NOTE: Not all of the carbs are the same for the 79-82 cb750 DOHC bikes. Apparently some years have pressed in slow jets that are not easily replaceable. You'll need to check what you've got before ordering.
I picked up these pods from Amazon for about $59 because they are not the cheap gray ones that everyone else seems to use and they are less costly than the K&N pods which seem spendy. These well built pods appear to be very solid and use foam instead of gauze. I hope it will be OK to just use the K&N oil I have on my shelf and don't need to buy special foam air filter oil.
With the jets in hand (approx 4 day delivery!) I found some tiny metric drill bits I bought several years ago and thankfully had a few bits that I could use to measure these jets just to put my fears to rest since JETSRUS does not do refunds. I found 2 bits measuring 1.15mm and .75mm and they seem to confirm the sizing of my 120 and 80 jets so I have a little more comfort that the 38 is likely sized as expected even though I didn't have a bit that small.
Ordering the jets individually is way cheaper and will hopefully be more effective and less trouble than the more expensive dynojet kits which go for more than $100. I could have drilled out my current jets, but my OCD is preventing me from drilling anything. I feel like the next owner (probably my son) might look at these jets marked 68 (or whatever) and not know that I've drilled it out to some other bigger size. I also want to be able to switch everything back and know what to expect with the old parts if I need to diagnose an issue, so it made a lot of sense to keep the old stuff on hand instead of swapping in brand new jets if I experience trouble and inadvertently introduce another variable.
I plan on keeping the airbox and the connectors around as long as I can, just in case. I don't want to be that guy that gets rid of the original parts and then starts having trouble and can't go back to the old setup.
I pulled the carbs and went through them again cleaning and spraying the passages with brake cleaner and compressed air. I have never broken the carb bank so I know that this is probably in my future if I start getting a fuel or an air leak but it should be much easier to remove and reinstall the carbs without the airbox in the future.
When installing pods, you need to make sure the slide lift ports don't get covered by the rubber insulators on the pods because the air that enters those ports help to raise the slides. If they are blocked, you'll get all kinds of running/acceleration issues.
 |
| Airflow through the slide lift port in the bellmouth will lift the slide, don't block them |
 |
| Smooth uninterupted air is desireable |
 |
| Lip area could be a potential disruption to airflow into the port |
The mounting flange and clamp is a little too wide for the narrow mounting surface of the cb carbs but they seem to secure just fine.
The bike started on the very first crank after sitting for 8 or 9 months and this is a great improvement in cold starting compared with the old setup with airbox and stock jetting which would require at least 2 or 3 tries to get running. Amazing!.
Blipping the throttle results in really great throttle response and I'm really excited about this jetting change. Unfortunately, I have a leak in carb#2 so it has to come out again before I can ride it. The prospect of pulling the carbs pretty much derailed a whole season 2 years ago because I didn't want to pull everything out when I still had the airbox, but this will be a walk in the park.
I'm not too happy with the resonated exhaust tip, just cruising around the neighborhood I can tell it's obnoxiously loud. My son also told me it was crazy loud from inside the house, so I'll put back the original mac canister and just run quiet.
Riding Impressions
She definitely smells like she's running rich now so I turned the fuel mixtures screws in from 2.5 to 1.5 turns to fix a slightly hanging throttle. This seemed a little weird because leaning out the idle to fix a hanging idle is the opposite of what most people normally suggest.
Seat of the pants butt dyno tells me the bike feels faster now. This can be attributed to slightly improved gearing, weight reduction from the swing arm swap (ride has definitely improved) and of course the richer jetting and more air from running these pods.
I took a ride on a cooler day (roughly 65 degrees) and kept my revs about 4k rpm or higher and was rewarded with *significantly* better acceleration compared to running with the stock airbox, cams, coils and exhaust where I would have to wind the engine past 7k rpm to get an acceptable seat of the pants acceleration so I am extremely impressed with this setup.
Not sure what all the fuss is about, pods appear to be a non issue as long as the jetting is correctly set. I'm loving the setup so far. So glad I didn't have to change the jetting a step at a time because it would have taken a really long time.
Not sure what all the fuss is about, pods appear to be a non issue as long as the jetting is correctly set. I'm loving the setup so far. So glad I didn't have to change the jetting a step at a time because it would have taken a really long time.
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