Anatomy of Mikuni Carb : Pro Tip

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A Mikuni carb can be a great upgrade to your motorcycle. Knowing what the basic parts are and how they affect tuning is key. We walk you through some of the basic parts of a Mikuni HSR42 to show you how it works.
#Mikuni #Carb #HSR42

[@jpcycles]

Get more tech tips on Countersteer : www.jpcycles.com/countersteer?Anatomy_of_Mikuni_Carb_:_Pro_Tip&V-pv4F7h4kw&feature=youtu.be

[@gavinmattingly5969]

Where did you get the adapter at for 40 bucks?

[@kendrickpavey6683]

This is the best Mikuni flatslide video I have found that gets to the point quickly and explains exactly how it works. Thanks!

[@bharatnagarajan5780]

Thats good one, Part 2 would be great showing how to change the rubber gasket to the slide.

[@garycjohnson1070]

I've watched several of the Mikuni rebuild videos and learn a bit more from each. This one was equally informative and I learned the necessity of having the right tools, screwdrivers, etc. The assembly lube used looks suspiciously like Yamaha marine grease but the take-away is lubing the gaskets and seals with a thin film before reassembly. I'll look for the tuning tips as well since there was't any mention of the pop-off pressures, etc. My GP 1200 has triple Mikuni's and has been running ragged, lacking the "hole shot" acceleration it came with so I'm diving into the carbs.

[@arthurleino]

I have Mikuni VM on my Shovelhead. The Throttle cable was used on the Delorto pumper that was on it before.

[@PeterShamray]

Don't need to remove the allen bolt holding the needle clip. Just loosening allows moving the clip to the side, out of the way.

[@Chatterbox-zo9xl]

Nice instructional video can we get to the fuel filter location

[@jpcycles]

thats kind of a get-in-where-you-fit-in situation. Normally I run mine closer to the carb than the tank.

[@kennethk6763]

Thank you so much. Best video I found on this carb.

[@adrianschulz5839]

Awesome vid man, thanks!

[@CarlosGarcia-ls4hn]

You mentioned the clacking sound from the slide when the o ring wears out, is that something that can be easily replaced? On my bike, it does it when it is cold, but not hot, What would cause it to do that?

[@shawng7902]

Getting ready to tear down an older revtec with a 42 on it. So with the adapter it will swap over to a normal HD air cleaner? I have a SE and they want their old one gone.

[@davidpillado6749]

Mikuni has many open ports. I know 1 is for VOES, but what about the others? Do I just block them off or leave open? Thanks

[@gavinmattingly5969]

Where did you get the air filter/cleaner adapter at? Or do you have a link?

[@SD-nj1cy]

Does the gentlemen giving the presentation work for J&P or somewhere else?

[@basmu7067]

How come they don’t have a electricity wire ? Changing out my stock Chinese garbage and just got my Mikuni Vm24 round slide in the mail today. So I’m trying to figure out why the old one has a green and yellow wire slot on the side. I have to drop the whole engine just to get the carb out because the screws are stripped on the intake manifold and the throttle cable where it connects . It’s a headache but it’s whatever

[@royz6872]

What Mikuni would be best from my Screaming Eagle 110 engine please as it is running a CV Carb at the moment.

[@francissalazar6436]

Running drag pipes on 92 FXR with hsr42, carburetor always dumped fuel so took manifold and carb off put new rubber caskets on manifold intakes, new rubber spigot for manifold to carb, put new seat and needle in carb no more fuel dump, have air screw at 2 1/2 turns out but bike smells rich ! Any suggestions?

[@munkyassproductions9178]

great video I wish I knew about that bolt on the bottom before I jetted my carb 20 different times.

[@badsanta518]

If it took you 20 tried to get the main jet right, you needed more help than just that.

[@JohnRodriguez-nr5uz]

I just bought a bike with this carb and it’s been sitting for 6 years so the slide won’t even open. Not sure if it’s rebuildable or not. Any advice on what route to take?

[@Webbrace]

Sounds like the oring on the slide is stuck. The carb is 100% rebuildable. Find a dealer with a Sonic Cleaner and have it cleaned. Put in a rebuild kit, and a new pilot jet, and you should be good to go.

[@brentrlarson4153]

On my new mikuni i thought it was bad gas but with fresh fuel it coughs and spits thru air cleaner what do i need to adjust

[@yngvardharjo3704]

nice work man

[@getoffmygrass6974]

Great tutorial. Imho, I think keeping the Phillips screws on the bowl is key to not over tightening and cracking the body as they will start stripping if turned too tight. Kind of a safety blanket. Best performance carb for street riding imho but extremely sensitive to certain builds on the pilot circuit. Follow the manual exactly as written and this carb will wake up any bike with satisfying results. Biggest con is it’s inability to make atmospheric changes, so if you live in an area like New England as I do, be prepared to make fine adjustments on your pilot as the cold weather comes in.

[@mikeyikesem3828]

Is there a video that shows how to tune this carb?

[@mikeinvegas1]

Awesome video. I want to clean jets in my mikuni hsr42. What do i use to clean jets . I didn't start my harley enough in-between riding. Can tell i have a plugged jet. Do i need to take jets out?

[@normansmith4064]

Take the bowl off, clean out the gel'd fuel particals and then unscrew the jet, you can then use a pipe cleaner or a small enough drill bit

[@Webbrace]

The main jet should be OK, just clean it. Replace the pilot jet. For a few bucks its easier than trying to clean it.

[@youtubeistrh4666]

How do they perform in the mountains?

[@rockgear2275]

My carb running too high on idle,i unscrewed the idle until loose but the idle is still high,what should i do?

[@hectoraponte8005]

I have this carb on a bambardier ds650 having issues with cold start any tips ?

[@jwrappuhn71]

Is there going to be a part 2? Thanks.

[@jpcycles]

We could make that happen.

[@sammybrown6730]

@@jpcycles if you guys could set the air fuel screw that would be helpful. Manual says that after 2.5 turns out if idle does not drop then pilot is too large and should be lowered. I don't hear anything change in mine after 2.5 turns out no matter how small I go in the pilot. Today I tried a size 15 and I have a hsr 45 on a v111....

[@joshwalters5875]

Great video thanks

[@allincamo]

Hey have a 42mm on a 2007 ,1200 and she has a cough on accelerating. Any ideas ??

[@billtmarchi4320]

Try adjusting the accelerater pump. It's adjustable to let more or less or delay or spontaneous spray of gas when you give it more throttle. He kinda talks about it in this video. What it does is shoot a little spray of gas into the carb when you give it throttle, because you are op3ning up the airway and it needs a shot of gas until the vacuum starts to suck gas into carb on its own.

[@allincamo]

Any advice on what to check or do, low speed coughing, ? 42 mm on a 2007 ,1200 sporty with pipes.

[@christopherologist]

Check for intake leaks first, with the engine warmed up. The mikuni manuals are available online for free. If you follow that word for word, you will have a great running bike.

[@JCcanU]

Running to Richa grey clean plug is ok . a black plug is to rich tan can be ok or just a hair to rich , raise the needle C clip up a Notch . Up is Lean Down is Rich , Evo 1200 like lean burn same with a 1340 .

[@blackmambbb]

Great vid pal x

[@rhinevalleygarage]

Can you lean out or enrich the air fuel with the enrichment screw? I have this same carb and my plugs a pretty black from running rich

[@kendrickpavey6683]

The only adjustment screw is for the pilot jet which really only affects idle and the first 1/8 of throttle approx.

[@hankreardon6998]

The idle adjustment screw is basically an air screw. If you turn the screw out, you will add more air leaning out the mixture. If still rich you may need to change the idle jet to a smaller one.

[@Savage-lx5yj]

Is the little orange cap on the fitting near the top a vent?

[@motorcyclemike8555]

Vacuum

[@dgmenace73]

I really hope you or someone else on here can tell me how to remove the brass jet in bowl? I think I have an issue with the check valve in bowl coming from plunger to the port. Any input will greatly be appreciated. Thanks.

[@normansmith4064]

Turn it with a flat head screwdriver. It unscrews, it should anyway

[@dgmenace73]

@@normansmith4064 ok....will try but it has no slot....hole is tiny

[@normansmith4064]

@@dgmenace73 does it have any hex head on it? Or is it completely smooth?

[@dgmenace73]

@@normansmith4064 completely smooth inside the bowl....I think it may have a spring loaded ball that you can see near bottom of the outside of bowl. My guess would be to push that ball in and somehow pull the brass jet out?

[@normansmith4064]

Is it like the one here? mikunioz.com/vm-round-slide-carbs/vm38-carb-parts/?v=13b249c5dfa9

[@patrickconnolly2997]

Didn’t say anything about the red capped thing on back and black capped thing which is the two things I was wanting to know about.

[@jsta625]

Love the hsr42 got it on my evo ,,the only hard thing to find for them is a nice big velocity stack, but I heard mikunis don't like velocity stacks

[@Scottbianchini]

How do you replace the rubber boot for the accelerator pump? Does anyone know? Mine ripped

[@charleswhite2874]

Isnt there a small washer that goes on the needle, beneath the E- clip?

[@jpcycles]

you can shim the needle up if you want to make slight adjustments

[@Webbrace]

Yes, there should be a small plastic washer under the clip on the needle, cushion. Sometimes it stays on top of the slide when the needle is removed, or it comes out with the needle. But you should run it to keep the needle from bouncing around.

[@mariokoziak7015]

What is that Red screw on engine inlet side

[@dgmenace73]

Question: I have similar carb....TM33-8012, TM28SS for 86-88 Suzuki DR200. I have completely rebuilt carb all but the float. I can't seem to get the accelerator pump to spray fuel out the nozzle. Spring, plunger, the rubber bushing that the rod slides in, o-ring on the AP nozzle and main bowl o-ring, then the rubber boot. I just don't why it won't pump...any suggestions?

[@bobbyd0656]

Did you have any luck? I have the same carb on my 92 DR250.

[@dgmenace73]

@@bobbyd0656 yeah....it took a while to find all the parts but once I got everything I needed it went fine afterwards

[@Scottbianchini]

How do you replace the rubber boot for the accelerator pump?

[@dgmenace73]

@@Scottbianchini on my carb. 42A20, also 42A21, then (I think) a TM28SS is the "new" Mukuni part # for. Carb has flat slide & accelerator pump.....once you get the AP push rod out the boot will just slide on. I found my issue was in the check-valves inside the bowl.....the ball in port at bottom. I soaked it, sprayed airgun in the ports, the AP cylinder and brass jet around the edge of bowl and it started working great!

[@blessedheart3917]

How do they compare to s&s carb?

[@gabrielnader8954]

What is the adapter called

[@arthurleino]

Nice video.

[@hfreakhilz]

Pump nozzle keeps changing spray direction it ends up towards the filter. What’s the fix.

[@Webbrace]

Replace the O-Ring on the pump nozzle. The rubber will shrink over time.

[@YouTubsockor]

Turn the nosles so they face the cylinders - they can be turned around - the O-ring hold them in the direction you leave them in

[@bradgoodale4325]

Not trying to be that guy either but you had a great video. I love it. But however, when you start to say around 815, don’t lose that clip does it go over or under the circle clip on the needle there’s some details here that everybody I think is watching the video for and you’re talking about every other thing but I think whatever everybody wants to know then you don’t have it on there right away, it’s been cut. I get it I get it.

[@robertzacharias499]

How to set the air

[@maxeden6958]

My vent fitting leaks gas anybody know how to fix?

[@chadman4965]

Don't forget the needle jet!

[@dekrev]

Rockin -

[@johnmartin9318]

0 I'm getting a lot of smoke out of my carburetors one after I tuned them in

[@slgarra3985]

Would have been awesome if you just didnt disuss what other carbs have the whole time. (If it was suppose to be about this particular carb versus everything else out there...I had to watch it more than once just to catch the Mikuni info) Less confusing if you would have actually had a side by side of the others you kept talking about instead of all that blah blah while supposedly featuring this carb since those that came here wanted help with this carb yanno?

[@slgarra3985]

More detail on the needle clip positioning would have been helpful if you get time someday.

[@normansmith4064]

All mikuni carbs are not pull-slides, some are CV. Why are you speaking as if there's no such thing as a CV mikuni?

[@Chatterbox-zo9xl]

Nice instructional video can we get to the fuel filter location

[@Chatterbox-zo9xl]

Nice instructional video can we get to the fuel filter location