to everyone with cv carbs trying to run pod filter

650ed wrote:

otakar wrote: You don't want KZ750 carbs because they are Keihin and they are SHIT.

:laugh: :laugh: :laugh: No argument here.

You know what's funny? In the 2 stroke world Mik's are shit and Keihins are the way to go. Ask the Honda guys. lol


ok, back on topic.

Well in either case... Are you comparing 30 year old carbs to todays technologies of what shit is? :S

Keihins (CRs) shit... I think not thank you much.... :laugh:

It's the exception that proves the rule. :laugh:

Marneman wrote:

cavanaughracing wrote:

Polar_Bus wrote:

kzbigrick wrote: Ok age old question. Why can't I get my bike with cb carbs to run right with pos filters? Ok here is the answer and the solution to your problem. I have a kz 900 with some late model cv carbs on it (don't ask got it that way) with pod filters on it. Bike was running like shit when gave anymore than about 1/4 throttle. Started searching the net to only find the same answer "pods on cv carbs don't work". I don't like being told something won't work so I kept asking until I asked a guy that owns a local shop and this is the fix. If u look at carb there is a kinda kidney bean shaped port , well the pod filters block air flow thru this port. Cv carbs use air(suction) to raise slides. When twist throttle it opens butterfly which supplies air to motor and to carb to move slides via those ports. All u have to do is notch the rubber inside the pod that mates with port. U can pop the filter off the boot and put boot on carb so u can see where and how much to notch. I was lucky to get 2500-3000rpm out of my bike before I did this now it is running fine. U will still have to do some jetting as with any performance upgrade. I hope this post answers this age old question and saves a lot of headaches for people.

Ive read this "fix" before. And while I do understand what the idea is, I don't believe this is the "end all" correction for why CV's simply run like garbage with pods. If this above mentioned fix was the true issue than why do the pod mfg's not advise to perform this check and or modifiy the design of the pods to ensure the carb CV vent passageway is unobstructed ? CV carbs were intoduced 21 years ago, and 21 years later most performance tuners are still scratching their heads at how to get pods and CV's to cooperate together....

Only the stupid ones :laugh: They make jet kits for CV carburetors that allow them to work properly. I've installed lots and lots of them. Factory, K&N, DynoJet....

Once you yank the airbox, it changes everything. The easiest route to a properly running bike with CV carbs is to buy the jet kit. Pissing around with larger pilots jets is the first mistake most guys make. That technique is so ancient that carburetors were measured it cubits :woohoo:

Am I dreaming???? Or did Larry C just say that there is a way to make BS34's work properly? I know, I know....burn em and get some smoothies, but for those of us on a limited budget I am curious on your thoughts (Otto, Larry, Roy) on getting the best results with the BS34's. Mine are the US made version with the fixed needles. I am curious if the Dynojet or other kits are worth the $ given that they retrofit the needle issue with adjustable ones. Any thoughts? BTW, were talking stock airbox with a k&n filter here, 4-1 Kerker.

FWIW

First, let's address this needle nonsense. What I have seen every time, in every kit I've ever installed is a DRASTICALLY different needle than the stock needle. It's far more than a stock needle with clip groves cut into it. It's precisely right there, the needle, that corrects the fuel curve for the most part.

You should have seen the original jet kit needles for an 84 900 ninja. They had to revise them because they were so short that it was possible to have them lift out of the needle jet and jam the slide open. Fortunately it's the throttle plate that controls engine speed so no accidents [to my knowledge] ever happened from that situation.

I was wrenching on bikes when the first Kawasaki's and Suzuki 4 cylinder bikes to be fitted with CV carburetors arrived at our dealership new. That was 1981 for the Kawasaki models.

At first, there were no real tuning components available for those carburetors. The norm back then was to shim the needles up with washers. Increase the main jets 4 sizes and install a larger pilot. Did that work? Sort of. It was a half ass arrangement at best. It took a lot more time than traditional mechanical throttle slide carburetors did to dial in and the results were less than stellar for all around performance.

It wasn't long before the jet kits started being produced by Dyno Jet. The kits were not always perfect but they were far better than the previous tuning method for CV carburetors with POD filters. We were very busy through the 80's installing hundreds of those kits.

What was nice about them is they allowed you to easily and fairly price a job for a customer. We established a base line price to install a kit with the base line jetting. If further tuning was required, it would be additional cost. Many kits worked quite well with the base line jetting. If anything, a needle clip position change and or main jet swap were required depending on the exhaust system used.

I've tuned many racks of CV carburetors over the years and YES they are a good carburetor for certain situations. Certainly anyone who is proficient as a mechanic can install a jet kit in CV carburetors and get a bike running reasonably well. It's not difficult.

But let's settle some total bullshit that some members here with vested interests in selling carburetor parts out the back door [so to speak] try to get people to believe.

1 - CV carburetors are NOT superior in mid range performance to a rack of smoothbores. That's such total horse shit.

2 - RS carburetors are NOT significantly superior to all CV carburetors in WFO throttle performance. That also is total horse shit.

3 - Sinking $500 into a rack of ancient CV carburetors when a brand new rack of RS Mikunis can be had for about another $150 is also total horse shit.

I don't know how many times I've said "Its the combination of parts that makes a setup good or bad" but that get's lost somehow. It's been all through history that one generation dislikes advice from the previous generation, preferring to find out on their own how to duplicate mistakes rather than learn from the previous generation. We did it too

I could site you examples where stock 34mm Kehin CVK carburetors performed within .010 SECONDS to a rack of RS34 carburetors at the drag strip. So add that up for yourself...A $100 jet kit vs what was about $500 at that point in time. But, out on the street where throttle response is king, that situation get's reversed. While the CVK's were pretty darn good, they couldn't match the midrange pull and crispness the throttle had with the RS carbs.

The problem with BS34's IMO is that guys don't understand them, don't have any money to buy a jet kit & listen to people who don't know how to properly tune them, or don't follow instructions. That last part is a major issue on forums. HENCE...endless threads of drivel with bad results most of the time.

Some of the OEM Keihin CV carbs, those prior to the CVK series were not good CV carburetors to work with when it came to pods. They were just adequate with the air box in place. They had actual air chokes rather than enrichment circuits like the Mikuni BS carbs had. That hurt their air flow characteristics. But keep in mined those carburetors were not used on Performance Models.

I can make pretty much anything work reasonably well. I'm old enough and experienced enough to be able to tell you right from the beginning if the effort is even worth considering...because I've been there..done that.

I come down hard on BS34's because IMO, guys dump way too much money into them. They're not worth it. I see posts from NADS about the cosmic orgasms he's getting from his BS34s... All I can say about that is wear a condom :laugh:

i am sooo with you.. All these ppl talk about on here is take the pods off, etc.. How bout take the time to learn, theres plenty of ppl that do it..

The only reason I have BS34's is that I didn't know the difference. That and I have a set of good looking, newer(1995 police) carbs, with under $200 into them. Lets see how the tuning goes in October. I tell you one thing, Larry told me to get CR's or RS's, and that's what I'll be doing as soon as funds permit it.

thanks for taking the time to help dispell some of the smoke and mirror bullsh!t larry.

so many people seem to act like it is some big secret how they get there cv's to work properly.
it is a freakin mechanical carburetor,no voodoo in there.

lets see if i got this right.
if you want all out performance buy a performance carb.

if you want to use some cv's to "get by" until you can get some performance carbs.
you will need to replace the needles and jets and spend a little time making sure the jets are right and getting the needle adjusted.

is this correct?

i know an airbox is preffered,but can we tune to get "good enough" performance with pods?

do we need to make distinctions between using keihin or mikuni carbs when talking about tuning?

or can the same tuning apply to either?


leon

For the most part, I'm a big advocate of the air box. Clearly there are reasons Pro & Con. Any / all can make sense. Just depends on the situation.

The whole point behind the original jet kits was to discard the air box. But, as things progressed, the kits got even better and allowed you to keep or remove it. Jets were included for both.

I've seen people Bad Mouth Dyno Jet. Well, back when they were getting rolling in the business, they a very good company to deal with. I personally had excellent results from them. They would go out of their way to assist if the needles weren't quite right. They knew and practiced good customer service.

okay larry,in your opinion(i understand how that goes,everyone has em)

i have perfectly fine running 28mm mikuni's w/ accelerator pumps,on my stock pistoned,cammed 1980 z1r.

i have some mikuni bs's off a katana 600.

is there anything for me to gain from switching carbs and dialing in the bs's?

tia,
leon

531blackbanshee wrote: okay larry,in your opinion(i understand how that goes,everyone has em)

i have perfectly fine running 28mm mikuni's w/ accelerator pumps,on my stock pistoned,cammed 1980 z1r.

i have some mikuni bs's off a katana 600.

is there anything for me to gain from switching carbs and dialing in the bs's?

tia,
leon

Some improvement, yes , if you wanted to do it correctly. Everything should be viewed from Return On Investment.

Lets look at this from the R.O.A. approach.

You need Jet Kit, Manifolds, Filters = $xxx.xx and the labor effort / time factor.

You have a KZ head with small port runners flowing about 8CFM less than a J Head. You're going to have a pretty poor port match at the port entrance and it's going to be the worst type. Big over small rather than small onto big [boot vs port entrance]. IE... a ledge will be formed directly against the air stream.

I've had guys say that's better..it breaks up the fuel when it hits the ledge.... don't know about that being correct but it dam certain mucks up laminar air flow

Now if you took the same money value needed for the carb swap and instead found some nice drop in cams, you would probably like that R.O.A. better. You could bolt them right in on stock sprockets, adjust the valves and hit the road.

In about 15 minutes time you'd have enough feel for what the bike is running like to sort your jetting out with the 28's you already have. Those later 28's with the pumps were a dam good carburetor IMO. Much nicer than those early 28's that were fitted to the Z1 series. They were jetted way too rich and the synch adjusters blow. I haven't seen a good rack of them in decades. Most are just plain worn out.

Thanks Larry for the detailed answers. Myself,I try and limit my answers to less than 100 words as I can't type worth a hoot.

Carbs are like anything else on a bike,you just got to learn. I would rather do carbs any day than adjust shims. I hate shims but it is the first thing that needs to be right before you do anything.

I learn hard. Roy