PlanetMinis Forums banner
Cancel
Create thread New Forums

Yoshimura carburetor sizing for takegawa 4v

Jump to Latest
1 - 20 of 42 Posts

radcorynw

· Registered
Joined
·
64 Posts
Discussion starter · #1 ·
Ive got a 88cc sohc 4v coming from takegawa and I have been looking at yoshi carbs to go with it.. Yoshimura just got some stuff in stock YD MJN24 is in stock and I was about to order it but I am wondering if I should wait for the 28mm version to come in stock instead. I know this tak head will have loads more flow going through than my 88ccTB head I'm on now. Would I see any benefit with the larger version of the carb? Or is the 28mm too open for the 88cc?

I mostly run mid to high range rpm on road. but am still trying to build the motor with a balanced power band not just for top end.. this is why I decided to just ask others what they think would be the best choice carb to go with the new setup and why..
thanks
 
Discussion starter · #3 ·
At first thats what i thought until I read more about the Multi jet nozzle thing yoshimura does and it got me thinking their carbs were larger bore because of that or something. I only have a 22mm on my current setup so the 24mm already seems like a step up.
Anyways I just ordered the 24mm :D
Still down to hear opinions though
 
#4 ·
the 28mm would give you more top end but your wanting more of a balanced engine/power so i would go with the smaller carb to help with the balance of power.
 
#5 ·
Hi
I put my nickel in {20 cents in OZ}
I am running a 26mm Yosi on my XR75 Honda with a 120cc capacity 115 octane fuel and big SR35 takei cam
when I first fired it up, carby run great the fuel atomization due to the modified Yosi needle is great
but first test ride running to lean and had to go up a couple of jet sizes and play with the needle until I got the right A/F ratio on my 5 gas machine
but the others guys are right depends on what balance you want 24mm will be better for thru the range power
bigger carb,if you have big duration cam,high comp piston,port work ect, and want to keep it at high RPM most the time
 
#7 ·
Having run both versions at 26 and 24 on different motor combos ranging from 146cc to 124cc, I'm going to say that a 24mm version is going to be pushing the too big limit on an 88. I don't really get why people think adding a huge carb increases power...it does...but only at like 8k+ so if you are running your motor ragged over 8k 90% of the time, then sure, a bigger carb is going to be great.

Here's a direct compare that I did at one point:
Motor was a Chinese Lifan midblock, bored and stroked to 157cc. had cam and portwork too...75mph+ motor.

I didn't write all this down, but i tried the following carbs on it. TM28 flatslide, VM26, TM24 flatslide, TM26 Yoshi, knockoff VM26, and a VM22. When they were all properly jetted, the TM28 gave the highest top speed...by like 1-2mph, but hands down the most drivable was the VM22. Off throttle torque and midrange was better than all other carbs. It produced the lowest top speed (about 4mph less) but seeing that the majority of my riding was in the 50mph range, it frankly didn't matter. Tunability was more important.

So, when choosing a new MJN carb for a 127cc Nice 4v+r, which is currently in shipment from webike, you know what I chose? the 22mm version.
 
#8 ·
From the tm-mjn 24 there are actually three versions. One for 88cc, one for the 88yosh kit and one for more than 88cc.

(Hopefully coming summer I have a driver with the 88yosh setup. So far gathered an ab27e, tak oil pump and 3-plate clutch, the full yosh 88 kit and the tmjn24 for that specific setup. Now I need time and temperature to build the engine... (and get the gorilla motor plated))
 
Discussion starter · #9 · (Edited)
I actually ordered the YD model and don't think I've seen the YD MJN in 22mm... 22mm is what I am on now with 88cc. Im all for better response at first I was thinking 24 would be big. It was their multi nozzle thing that made me think response issues wouldn't be noticeable if not improved.

^then fatcaaat says he's putting a 22mm on 127cc?... maybe i should have looked through webike a bit more for a 22mm model. I kind of wanted to order within the states though.

my gearing now is about all the motor can pull so its not easy to stay in the super high rpm range all the time with its current 22mm mikuni and TB 88cc

good info guys :beerchug:
 
#10 ·
So they make a vm22 or you mean the flange mount mikuni 22 carb that comes on most bikes or with most engine kits?
Reason I ask is that this carb below works very good on my 125 engine.
From cold start, sto n go, steady cruise and wide open, it's a great all around carb.
I do have a free flowing exhaust also though.
I may try it on my 150 engine also.

Mikuni 22mm Carb - WHS-0957 - CARBS and JETS - Pit Bike Engine Parts - TBolt USA, LLC
 
Save
Reply Quote Like Like
Discussion starter · #11 ·
^that carb is kind of like the one i am running now.

I just found some things out. I got the yd24 for standard Grom so if I want more response with 88cc i can get the multi jet nozzle set which has a nozzle designed for yosh 88cc head.. I'm sure it works for any 88cc. But I'm gonna run it how it comes on my TB head and go from there.
 
#12 ·
Here it is....
YOSHIMURA : Mikuni TM-MJN22 Carburetor Kit [770-404-2000]

And it arrived on my doorstep today. I simply do not agree with takegawa or yoshi on carb sizing. I used to think that bigger was better...until i started my own experment. And why Takegawa provides a VM26 with their 88 +r kits is beyond my comprehension. I had a vm26 on top of a well built 108 at one point...and it was a 65mph bike but ran like crap off throttle and had poor response. After installing a mikuni VM20 on it instead, it cleared everything up and I lost no top speed at all.

At some point we lost all sense around what carbs should be on these pitbikes. People are installing 32mm pumper carbs on sub 200cc bikes. My Norton Commando uses a mikuni VM34 at 750cc. My Vintage enfield at 500 cc uses a 28mm. I understand that the factory makes an attempt to balance drivability and emissions with their setups, but everything needs to work in harmony here.

Let's use a ratio just to explain the absurdity for a second:
Stock 70 = 16mm carb
Race prepped 88 = 24mm

Keeping with singles then...

What would a race prepped crf150 need?38mm?
What about a race prepped CBR250? 46mm?
 
#14 ·
Why not keep the 22 carb on it?
Its a good all around carb
 
Save
Reply Quote Like Like
Discussion starter · #15 ·
my mikuni carb is fine and it will be staying with my TB head whatever other bike that ends up on. reason I'm upgrading carb is for responsiveness mostly I just thought with a 4v from takegawa a larger carb MIGHT have an advantage. but 24mm already IS large as confirmed by most opinions in here :)

Im wondering now if my new engine would perform better with the TM MJN 22 over the YD MJN 24.. Part of the reason I chose YD was downdraft and short manifold. It just doesn't come smaller than 24mm. either way I'm stoked it will be here thursday.
 
#16 ·
Cool let us know how it works out
 
Save
Reply Quote Like Like
#17 ·
fatcaaat said:
Here it is....
YOSHIMURA : Mikuni TM-MJN22 Carburetor Kit [770-404-2000]

And it arrived on my doorstep today. I simply do not agree with takegawa or yoshi on carb sizing. I used to think that bigger was better...until i started my own experment. And why Takegawa provides a VM26 with their 88 +r kits is beyond my comprehension. I had a vm26 on top of a well built 108 at one point...and it was a 65mph bike but ran like crap off throttle and had poor response. After installing a mikuni VM20 on it instead, it cleared everything up and I lost no top speed at all.

At some point we lost all sense around what carbs should be on these pitbikes. People are installing 32mm pumper carbs on sub 200cc bikes. My Norton Commando uses a mikuni VM34 at 750cc. My Vintage enfield at 500 cc uses a 28mm. I understand that the factory makes an attempt to balance drivability and emissions with their setups, but everything needs to work in harmony here.

Let's use a ratio just to explain the absurdity for a second:
Stock 70 = 16mm carb
Race prepped 88 = 24mm

Keeping with singles then...

What would a race prepped crf150 need?38mm?
What about a race prepped CBR250? 46mm?
Click to expand...
the thing you are not addressing in all this is how great the volume of air each engine is consuming. An 88 cc engine may not be overly large in displacement, but if it's speed (rpm ) and volumetric efficiency is greater than that of the 500 cc Enfield then it will need a larger carburettor to be able to supply enough air and fuel to have it run at its highest potential. So given that the volumetric efficiency is the same in both engines, which it won't because the 88 has later and better design, the 88 @ 13,000 rpm will consume just over a third of the air of a 500 cc Enfield @ 6,000rpm, but it has less than half the time to do it, so you will need to have a bigger inlet to do so, so the carburettor for the 88 will seem disproportionately bigger than the one on the 500 cc .
From the engines you have described that you have tuned yourself I would guess that not many are running at 13,000 to 14,000 rpm in top gear - which is what a Takegawa 88 or 106 with a Super head + R will do
 
Discussion starter · #18 · (Edited)
Has anybody ran the YD24mjn carb on an 88cc? or even a TM24? I think I'm going to be doing some jetting changes and or a nozzle change on mine and was wondering what other people have done with these carbs on 88cc's.
mine is the GROM carb kit version tuned for 125cc. tuned to my ability she runs, just not right.

Also, does anyone know if the jets and nozzles from YD series and TM series (24mm and 28mm) are interchangeable?
 
#20 ·
radcorynw said:
Does anyone know if the multi jet nozzles from the TM line of carbs will fit the YD line just the same?

Also are they interchangeable between bore? like 22 to 24mm etc..
Click to expand...
TM and YD metering nozzles are different - the YD has no adjustment to raise or lower like the TM does, this in my experience makes the YD less user friendly and hard to tune in some cases.
 
1 - 20 of 42 Posts
About this Discussion
41 Replies
12 Participants
Last post:
fatcaaat
PlanetMinis Forums
posts
2.1M
members
63K
Since
2003
PlanetMinis forum is the internet's largest mini bike community. View thousands of photos, event coverage, tips, tricks and performance mods.
Full Forum Listing
Explore Our Forums
CRF50 KLX110, DRZ110, TTR90 Chinese/Import Minis - General Discussion Z50, CT70 and JDM Monkeybikes Complete Bikes For Sale - All makes and models