CV Carburetor VS Mikuni flat slide explained - ep34 - Roma Custom Bike
ฝัง
- เผยแพร่เมื่อ 11 ก.ค. 2024
- In this episode of Roma Custom we will examine the difference between a Keihin CV carburettor and a flat valve carburetor, in my case a Mikuni HSR 42.
After making a couple of videos on the original Harley Davidson Keihin CV carburetor, I thought I would compare it to a MIKUNI HSR42, often used in transformations on these bikes.
The main difference is that while the former uses a throttle valve and the engine vacuum, the second has the accelerator cable directly connected to a flat valve. So the slide moves in direct relationship with the throttle handle.
During the video, in addition to showing with the help of an animation, the inner workings of both carburetors, we will examine the pros and cons of both the Keihin CV and the Mikuni HSR42.
CHAPTERS:
00:00 - Intro CV carburetor vs Mikuni HSR 42
00:50 - How does the CV carburetor works explained
01:11 - Graph of throttle response of a CV carburetor
01:38 - Why is it called CV (constant velocity)
01:50 - How does a flat slide carburetor works explained
02:44 - Graph of throttle response of a flat slide carburetor
02:52 - Graph comparing the throttle response of the CV carb to the flat slide carb
03:09 - Adjustment screw differences
03:30 - Pros and Cons of both carburetors
04:51 - Suggested settings for Harley Davidson 1340 engine
05:34 - The flat slide is noisy
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Related videos:
How does the CV carburetor works:
• How does CV carburetor...
How to restore and adjust a CV carburetor:
• How to tune your CV ca...
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Made in Rome, Italy we take a look at an European approach to modifying and customizing an Harley Davidson with Custom Cez, an amateur customizer in his home shop.
An RMPnet.com production, music by FAS.
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Exactly right! I never did like the disconnect with cv carbs in many of my bikes. My 88 superglide back in 2000 was upgraded with the mik 42 along with pipes air filter and hot coil. Instant throttle response loved it.
You can almost feel every power pulse of the engine.
A friend has the bike now and his brother with a newer fuel injected Harley tried it out not expecting much with the old technology bike. He was speechless afterwards.
This is probably the best discription I've ever seen in my life good stuff man keep it up
Thx Luciano ;) grazie!
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Thank you for this clear explanation, of both, operation, and benefits of both!
Your videos are very well thought out and informative, keep up the good work
Epic video. Thanks brother. This will help a lot of my buddies understand way better
This is a very very well done video! I think everybody should see it.
Really high quality content, love it!
Great video explaining differences!
Just found this. I appreciate the hell out of you posting videos in both languages. 👍🏼👍🏼 Subscribed
Thanks for the info. Great production 👌
Great video, Thanks for putting that together. Very clear and easy to understand. :)
Glad it was helpful!
Nice explanation and great graphics.
Thank you, this was just the video I was looking for. I am putting an HSR 42 on my '03 Sportster Sport, and this was very informative about what to expect vs. the CV carb.
How is the mikuni performing? Is it very noticable? I am planning swapping my cv also. ( 2000 sportster 883/1200)
Have a trx300 with a CV carb on it, just upgraded to a Flat side Tm32-1 and instant response instead of a laggy CV.
Awesome video thanks so much for making it.
Great animations. Thanks.
Thanx a lot for your help! Great video indeed!
Nice concise and to the point.
A great help to me. Now I am clear that in some carburetor you can control the idle speed by controlling the fuel by turning the screw where as in some carburetor you are allowed to control amount of air to the carburetor for controlling the idle speed.
Yes, usually keihin and clones have a fuel screw and Mikuni uses air scew
great explanation. thank you!
Excellent dude!!
Larry
It’s all about itemization , the flat slide does it better . We had big performance gains through the off idle to mid range on 2 valve Ducati motorcycles . Not only did it increase the mid range significantly but gas mileage was increased dramatically .
Excelente explicacion bro, muchas gracias hno
Awesome video!
Very nice vid.
Even Harley owners will be able to understand this.
Nice, found this when wondering if I could replace the CV style carb on my 70cc moped with a slide style carb meant for a small ATV. I had always wondered why 50cc mopeds had such weird carbs. In mopeds, the extra moving parts and smaller jets means it can get gummed up with bad fuel pretty easy if you don't run them on a regular basis. I will be switching to a slide carb on mine just to see how if feels.
Nice video, thank you for the good explanation. Would also be interested to learn about pumper carburetors.
Great explanation, thanks
Excellent vid!
Great information! I have hsr42 and been thinking how good it really iş compared to CV. This video gave me the answer. The extra noise of hsr iş something I don't like and also noticed the tender əs of throtle control, especially on low speed (in town). But as told in video it really reacts quickly when needed. One thing that wasnt mentioned in video iş the benefit of idle control on HSR. İt really helps the cold start as you don't have to use throtle for it.
The bike at the end had the coolest air cleaner. I have a hsr48 on my 1275cc drag sportster and that thing is insane. The ability to tune a performance Harley is hands down incomparable. Great video!
I have dreams about that air cleaner now. May I ask the brand or any info I can use to locate one or similar?
Yeah, where can we get these!
Great video!
Thanks!
Wei used to run the keihin FCR flat slide on the R6 back when they were carbureted. It gave you about 3 horsepower but required different jetting from 80-100 70-80 and below 70 degrees outside temp. If you got the needle position and slide cutout right they ran great. They don’t make the bike jerky or anything down low, if you crack it open at low rpm it just bogs the engine. If you like screwing with jets all the time have at it.
Man, this is the best comparison carburators ive seen in youtube. So detailed
THX!!!!
great video 2 thumbs up!!!
Dude, this video was awesome. You have made it so clear about the difference between the two, Thank You bro.
Crazy glasses man, no I don’t want a pair. Great video buddy, thanks 4 the tips, Cheers Teddy
I had a lot of issues with my Mikuni42 and I ended up pulling it off and putting a CV back on the bike. The Mikuni was a noticeable difference but my bike never seemed to like it and the float jet constantly moved out of position and would overflow the carb. Put the CV back on and the bike sounds and feels much better (it's like those engineers knew what they are doing).
A harley davidson with a flat slide is a beast, you should've got it properly tuned. Believe me.
yup any aftermarket slide will be worse than oem one if can't play with carb
Mikuni and the other flatside carbs are infinitely adjustable. That said, it’s also the reason a lot of people can’t get them to run right. There is a LOT of adjustment on a Mik carb. The manual has an excellent walk through to adjust them, but most don’t follow it. They slap it on, tinker a bit with the idle cuirtcuit and maybe the jets, usually in the wrong order or both at once, then give up and go to something else that is easier to get to run “ good enough”.
Once correctly set up, a Mic will seem almost like fuel injection. ALL my HD run Mics, the reliability and performance is unmatched for carbs.
However, if one mostly enjoys just cruising around with an occasional whack through the gears, the CV is a true gentleman. It’s reliable as a stone, gets great mileage and is smooth as butter in the midranges, where most people ride. The myriad kits they built to hot rod the CV are unneeded and , many times, cause issues.
It’s been proven CVs can support engines up to around 90-100 hp. They just perform a bit differently, a bit less responsive it seems.
Bottom line, MIC style carbs are phenomenal performers IF you have the patience to follow the procedures and tune them properly, or know someone that does.
The CV will serve most people quite well as a daily driver and occasional romp, easy starts, great mileage and smooth.
Also note it all has to come together as a package, intake, cams, comp ratio, exhaust all have to work together to make any engine run its best. Running big, open drag pipes and blaming the carb is pretty common when performance suffers.
Running a huge overlap cam in a relatively mild engine, same deal, it just won’t work across the board.
There’s a ton of info today on setting up an engine properly and tuning carbs, all available at your finger tips.
Utilize it, or don’t , but don’t blame a piece of equipment for tuning failures, ie: if you have a stone stock motor, that cam won’t allow in the increased air from a bigger carb and the pipes won’t let it out, there’s no free lunch, do the work as a system, or leave it alone and ride it. A Shetland pony won’t run with a thoroughbred, no matter how nice a saddle you put on it…
@@megastick9324 Great reply. The HD with the Mikuni was sold a while back now. That particular bike was just a rolling gremlin. Someone else tried to hotrod the bike, and I got tired of fixing Daryll, Daryll, and Daryll's Performance Mods. Once I stripped it back to mostly stock, it ran well, but I was just sick of the thing, so I sold it off.
@@peted2770 yeah, as a bike mech I can tell you, on the older used HDs, and to a lesser extent, the old Jap bikes, the biggest issue is unfu#&ing what all the Daryl’s , and their brother in laws, have done to get back to a starting point.
Excellent 👍
Nice video.. I wanna tell you that its amazing!!
Thanks a lot!
Outstanding!
Thx John 😊
Awesome Video. All your videos are well explained, learned a lot of them. Does the Mikuni HSR42 need a new manifold and air intake, or adaptors? Or can I use my stock CV manifold and air intake? (HD Softail Heritage 1986)
Could you post a link to the air intake that has on it. That looks pretty sick
That accelerator pump on the carb is out of tune as the fuel shouldn't hit the slide when opening the throttle. Other than that, great video explaining the differences between a CV and a FCR carb. I think FCR's sound great because of their sound :P and everybody should know about em'.
Well thought out and delivered impeccably. Well done Cez. I'm in, although not a harley man.
Thank you 😊
Thanks for your video. I think you may be referring more to these on big street bikes. I have a 1987 Suzuki DR200 dirtbike that has a Mikuni 42A21 pumper or Mikuni TM28-1 (the part #'s I have found but not 100% sure)....it's definitely a Mikuni flat slide w/accelerator pump. I bought the bike used with carb apart in a bag. I had no idea it would be so difficult to find parts for....lol. I have found CV carbs online that say they will fit/work but was unsure if I should even try? I will be just trail riding and to me it almost sounds like the CV would be better for my situation. What do you think? I know the flat slide is missing the pilot jet and extremely dirty. I just want to get it running and have no idea about engine , clutch, etc. I can "usually" tune a carb fairly well but never worked on these flat slides with the pumper. Thanks in advance for any help.
Sir how did you make this video on which software ?
Excellent. I'm familiar with mikunis and I love the adjustability. I find these videos cause I got an old Honda with a muddy off idle/ acceleration until I hit about 5000rpm. Then it cleans up and the power disembark is very noticeable. Makes me thing pilot jet or ckt is clogged. Or possible my slide and diaphragm are trash
Well see. If a cleaning and adj don't fix it I'll just get a mikuni kit .
New subscriber KaMotoFriends and Thanks for sharing 😉
Great video man. I'm about to run dual Mikuni 38mm flatslides on an Intruder.
Have fun!
@@CustomCez it rips
Nice good one
Ciao, che filtro carburatore monta quel gioiello?
огромное спасибо!!!
a Slide Carb on a Bike that originally had CV Carb will feel much more snappy or responsive
that is if it is properly tuned.
Hey man. You seem to know this stuff better than anyone else.
I"ve got some old Mikuni BS32SS carbs off an 86 Katana 750 that I'm fighting with, and I'm not at all understanding the pilot screw. It's on the engine side, but as far as I can tell, the pilot screw is metering the total air/fuel mixture being allowed into the engine at idle, not actually affecting the AFM. The only air passage to get past the butterfly, first passes the pilot jet before going all the way to the top of the carb and then back down just behind the butterfly.
Then, there are also 3 other small pilot ports just behind the butterfly, which cannot be metered in any way, which seems crazy?
My problem of course is that while I seem to be able to tune the idle system just fine, I have no control over what those three pilots just behind the butterfly are doing. So as soon as I crack the throttle, I end up super rich and boggy at low RPM, low throttle. Presumably this is because either those 3 pilots are too rich for small throttle openings or for the air being drawn into the system at low RPM. Or perhaps my needlejet is coming into play very early?
I love your animations as they make this shit super clear, but none of them show what I've got with my pilot. Yours all show that the pilot screw is clearly metering either the air or the fuel individually.
Excellent Video!
Thank You!
Christ Bless!
Great video Cez! Well explained. All the dislikers must have EFI
Bro I have a problem with my Mikuni 28 mm flat slide carb with a 17.5 pilot and 260 main jet . It’s on a tillotson 212 cc non hemi with a 32 mm intake valve and a 27 exhaust valve . I have a 310 cam and it’s a stroker crank . I stay in Orange County for altitude. When I get it to start it won’t stay on for long and it runs high ! I did notice when I ingage the choke , it turns on right away . Please help ty
Good vid. But you didn't mention the vacuum drop when you 'dump the throttle'. How does the flat slide maintain fuel flow when intake vacuum drops when the throttle is popped open?
For the road I'd stick with the CV40. But thanks for the vid. sub/Likie
Great point! It's all a chain of delays... not much but enough to smooth out the closing of the slide ;)
My bike came with a round slide carb and the bike stalls if I give it too much throttle off idle any advice
Is there a advantage to a cv carb over a standard round slide carb
How about the round slide carburetor?
What is that air cleaner and where can I get one?
I’m trying to find out too. Did you find one?
@@akilla4reala669 no
@@hotboy197988 I found out that he custom made it. I asked him if he would be interested in making another one, but I haven’t heard back yet. Thanks for the reply! ✌️
@@akilla4reala669 Probably not going to hear back if you haven't already. I would love to get my hands on one. I'll just have to make one myself if I want one.
great info .. but in my byke i used a super E .. i like't ..but i thinking about Mikuni .. cheers
Puoi spiegare nel prossimo video le problematiche di un carburatore di una moto da restaurare?
Please do one of these with the FCR carbs!
I'll look into it :) thanks for the suggestion
Wow my Harley chop I have owned for 3 years came with HSR fitted and it pulls away like no other bike I have had. It jolts away at every set of lights, not smooth. Thought it was a problem and now you have eased my mind in that its the characteristics of the carb. Do you have any tips on tuning it as mine runs really RICH.
Depending on what other mods you have made ( airfilter/pipes or engine), the pilot jet may need changing (richer) and the needle lowering to weaken things off. Lowering the needle will make the bike run weak at 'closed off' throttle positions so the pilot may need enlarging - don't forget to adjust the air screw. The main jet rarely needs to be much bigger than the standard one for the size of carb. The notches on the needle will raise or lower the needle about 1mm each notch - this is a very big adjustment, you can also get thin washers to put under the needle clip so as to raise the needle just partway between notches.
The pilot jet supplied with the carb is good for standard engine/air filter and pipes but may need to be richened. The extra fuel it gives the engine is always there throughout the opening of the carb and so the needle may need to be lowered to weaken things back down again, so do not be tempted to make the main jet bigger.
The needle being too high can mask the need for a richer pilot jet - this can be seen by the bike's engine overheating if you ride with the throttle closed a lot in traffic etc. You may then lower the needle a notch but find it needs to be raised a little from the lower setting with a thin washer or two so as to effectively only lower the needle a half a notch or so depending on the thickness or the washer(s) used.
Highly tuned (altered) engines need a bigger pilot jet to allow the engine more fuel at low revs (throttle openings) as the suction is lower ( - the engine is 'off cam') and finds it hard to suck enough fuel through a small jet making it a weak mixture. As the throttle is opened and more air is sucked through the carb (more air than a standard engine/ airfilter and pipes would allow), it starts to suck too much fuel through the needle and needle jet combination and that makes it a rich mixture, so you lower the needle to weaken it a little. Pilot jets to go to may be 27.5, 30, 32.5 or maybe even 35.
The strong pull you mention as the carb is currently set indicates a needle that is too high as the mixture is rich and gives excess torque - my sportster with Hammer cylinders and cams along with a flowed heads and open pipes has an HSR 45 fitted with a 32.5 pilot, needle is lowered one notch but raised a quarter notch with a thin washer, and it has the 175 main jet that the carb came with..... That is just an example not a recommendation...... hope you get it sorted !
Awesome explanation! Where did u get that air cleaner?
Thank you Billy 😊 i designed and built the air filter, took about a year of prototyping but in the end it come out pretty cool 😎 about 200 moving parts
@@CustomCez That is awesome! It shocked me when I saw it move the first time.
@@CustomCez do you have any to sell, that is a badass filter! i need that lol !
I want that air cleaner so bad
Hook us up with the air filter @Custom Cez Fai Da Te
Ty!!!!!!
Avesome video
top merci
I just swapped my cv for a this carb on my 97 evo. Better starting and better throttle response.
Unfortunately I didn’t feel any power increase.
Disappointing considering here in Australia it was nearly $500 !
I would appreciate any advise.
The potential is there ( as it can support more power ) if you wish to go with hotter cams ect.
Personally I would only go to stage 1 for longevity. Harley engines have long strokes and piston speed comes into play here with hot upgrades. You can only rev them so high. Great engines for cruising and midrange torque
Great video, but mikuni hsr 42 (what most harley owners use) comes with 25 pilot (which is good for most evo and TC bikes) and an often overlooked fact is that the polished hsr42 (for some unknown reason) often comes with a 26 pilot jet installed from factory
I thought this video was going to be chat, but it turned out really good! Thumbs up
Do you sell that air cleaner????? I want !!
I’d like one too. Did you find one elsewhere?
Sir plz tell me which carburetor is good for long route and top speed and engine life increased cv or mikuni ? For 125 cc
CV
What are cleaner is that
are you ok cez i miss you’re videos
You not making videos anymore?
I changed to a Mikuni on my 95 fxstsb. I noticed a little quicker throttle response but not really a huge difference.
On an HD you can really feel the difference
What about a d slide carb?
OMG where did you get that air cleaner
I want to know too! Did you ever find out from anywhere else?
crf450R supermoto. i cant decide what carb. eventually gonna have the atheno 510cc kit
pros of cv. zero. pros of a real flat slide{mikuni} literally everything apparently
Thank you.
You bet 😉
👍👏👏👏👏
Thank you 😊
How About Its compared To other Carburetors Like The PE Series Or Keihin PWK Series TBH I have The Similar Carb Like The stock harley But its Come from Mikuni And Lot smaller Venturi
the old nidle jet - this guy really seems to know what he is talking about lol
6:12 what air cleaner is that?
I am also interested in that air cleaner. Smooth part!
Me too. Has anyone found out what kind it is?
what filter case is at 6:18 ?
I made it 😊
@@CustomCez that’s AMAZING! Would you consider making one for me? I’ll be glad to pay you for it of course. Really nice! 👌
When you say where you're money went does that mean the mikuni gas mileage sux ???
Hahahha, you are not wrong 🤣🤣🤣
So if I want better gas millage go with a CV ??What I have now a older FLHTCU with compliance fittings and the older style carb.
@@samstinkeringaround8961 basically from what I got from this is cv is more fuel efficient, flat slide gives better performance. If you are wanting more horsepower you might be disappointed with a flat slide carb. If it was me I would buy a big bore kit before a carb. That way you have more power and the acceleration is smoother. If you buy the big bore kit and still need more power, get a performance carb and make sure your pipes arent smaller than the diameter of your exhaust port. The more air you can push in and out the faster you can go in simple terms
If you get better mog with the CV, its because your FCR is jetted too rich, or you keep stabbing the throttle a pumping fuel into the manifold when you should just be cruising.
Ciao come si fa x contatare
FCR carbs give precise and strong throttle response. They are also more reliable than CV carbs.
Would do a Hrs42 on my blast but hard to set up a Tps
Would have to switch over to a voes
I don’t have voes on my ultima with a mikuni.
@@akilla4reala669 switched to voes with my sportster carb
You have a blast as well?
@@thatbuelldude189 no I don’t. I’m very fortunate to have several bikes, but not a blast. The bike I was referring to is a custom ground up build . Stay safe on them streets! 😁✌️
@@akilla4reala669 same
Have a 01 M2 Cyclone as well
Hopefully getting a hardtail sporty with a built Cyclone motor soon
That motor should put 120 horses to the ground
Going to be a good lil upgrade on my m2
@@thatbuelldude189 sounds awesome. Definitely try to update me.
mi vendo ..... ecco cosa vuol dire mettere i like a sti venditori di patate!
Bitchin' evo, baby!
What about a SU carb🤔😎
I don't want to hear any harley boys complain about a $300 flatslide carb upgrade. The flatslides for the VMAX is literally 10x more expensive. Really. $3K for vmax flatslides...
They are 4 and the harley only uses 1
I don't want to hear any VMAX boys complain about 3k for flatsides. You could have bought a Harley.
Translation "Come to us and pay too much for some over rated shit."
For what the MIKUNI flat slide cost me it damn well better make a big difference .😠
Cez, ma che minchia di fine hai fatto?!
A gay moment at 5:38