Mikuni Carb Swap, Looking for Advice.

#1
My motor is currently as follows:

Predator 363 (212cc)
18 LB Springs
ARC Flywheel and Rod
Stock Carb with .36 jet and emulsion tube
CS Grind Clone Core Cam

Next weekend (i'm working crazy hours... 84 a week, so I have ZERO free time this weekend) i'll be installing some minor things.. like a split sprocket adapter, 57 tooth rear sprocket, NGK Plug, RLV extreme chain (#35)... and that will be my basic setup.

I mention all this, because I also ordered my final "big" upgrade. I ordered the Mikuni 22mm kit from GoPowersports, and BEFORE I install it (i've learned from my previous mistakes to seek advice BEFORE the installation), I am wondering if you guys have any advice to give me before I install it. The big things on my mind are:

1) Is the stock jetting on this carb going to be alright with my current setup?

2) Is this carb physically larger than the stock one? Cause i'm working with pretty much no spare room.

3) Is this carb going to function better if I upgrade to even stiffer valve springs? And if so... HOW much better?

4) What kind of performance increase can I realistically expect to see after this installation? In regards to mph as well as acceleration and throttle response?

I decided to install the carb now so I could use in the Detroit Gambler Mini Bike Rally next month... so I could see how my setup REALLY performs with no fears of legal reprocussions.... so I really am not looking to do ANYTHING like upgrade my cam again, or do head work, or any of that stuff. So, while things like valve springs, or changing my gearing, or new jets.... that type of thing is totally fine with me.... I am hoping to NOT dump any further large amounts of cash (read as: More than 20-30 bucks at a time) into this thing. So yeah... any advice or personal experiences would be welcomed and appreciated.
 
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#4
What motor and what size valves?[/QUOTE

212 hemi, stock valves... and YES... i'm guessing by "Chikuni" you mean the chinese knock off of the mikuni.... and that is absolutely what it was/is. I'm not exactly sure why GoPowersports is doing so well... cause their prices aren't the best... on ANYTHING... but, OldMiniBikes does an absolutely AWFUL job at properly labelling their parts as to compatibility or what would pair well with it, or putting together packaged kits.... and their search function is AWFUL. If you search "mikuni 22" it will literally come up with page after page of stuff that has NOTHING to do with that carb. Gopowersports website is streamlined... so, i've been buying my stuff through them. I'm assuming that later down the line i'd be able to buy the real Mikuni, JUST the carb, and the filter and intake manifold would still fit right? Does it make a big enough difference to make that future upgrade worth it?
 
#5
So hemi has larger 27 / 25mm valves and flows more air than a stock carb flows. You would benefit from the chikuni. Most run well with 125 or 130 main. Use the pilot jet it comes with and the idle air adjustment setting will tell you if it needs changing. You will have to learn how to set slide height/idle air adjustment and also how the enrichment device works as it functions differently than a choke. I would install a 125 main leave all else alone and see if you can get it to idle and run ok. The enrichment device riches the mixture and also allows extra air in so it may start and run fast (2.5 to 3k) this could cause clutch to engage and bike to move so be careful. On mine I turn enrichment on then about halfway to off to prevent creeping. You may want to remove chain till you get it setup correctly and get use to enrichment device.
 
#6
So hemi has larger 27 / 25mm valves and flows more air than a stock carb flows. You would benefit from the chikuni. Most run well with 125 or 130 main. Use the pilot jet it comes with and the idle air adjustment setting will tell you if it needs changing. You will have to learn how to set slide height/idle air adjustment and also how the enrichment device works as it functions differently than a choke. I would install a 125 main leave all else alone and see if you can get it to idle and run ok. The enrichment device riches the mixture and also allows extra air in so it may start and run fast (2.5 to 3k) this could cause clutch to engage and bike to move so be careful. On mine I turn enrichment on then about halfway to off to prevent creeping. You may want to remove chain till you get it setup correctly and get use to enrichment device.
Man, thank you so much for all of this! The taking the chain off while tuning is something I probably wouldn't have considered, and although I had read about the enrichment device, I had NO idea it was that much different from a choke... and by that, I mean: "I thought it WAS a choke." haha I'll read up more on adjusting all this stuff. I found a good article about it.... but, in the article they never said what kind of motor they were using, or what mods had already been done.... so, I disregarded pretty much everything I read. It DID mention that it came with a 95 or 100 jet... but, that article also suggested the 130 main (but with a 12.5 pilot). So, if two people recommended the 130 then i'm assuming thats no coincidence so i'll go ahead and order that tomorrow. Thanks so much man! If you have any other advice for me, or think of anything else, please let me know! Man I love this forum! I'd be lost without it!
 
#7
Take a look at this pic then look at your carb. see the hole at 2 oclock? That is the enrichment hole, when the plunger is down the hole is closed and nothing gets thru, when plunger is up you will see hole open. It goes to a air bleed hole in the front of the inlet. There is also a path to the fuel as well so the air traveling from front to back picks up extra fuel as well to enrich the AF mixture. DSC01087.JPG
 
#8
Take a look at this pic then look at your carb. see the hole at 2 oclock? That is the enrichment hole, when the plunger is down the hole is closed and nothing gets thru, when plunger is up you will see hole open. It goes to a air bleed hole in the front of the inlet. There is also a path to the fuel as well so the air traveling from front to back picks up extra fuel as well to enrich the AF mixture. View attachment 107210
Cool man when I get my carb i'll check it out. It said it shipped today from GOPower but i'm in Michigan so.... not sure how long that took last time I ordered from them
 
#9
Hey, so.... everything i've read has said to go with the 130 jet on the Chikuni.... well... my carb arrived today, and although I ordered the chinese knockoff kit.... GoPowersports actually sent me the real deal Mikuni carb. Clearly labeled "Mikuni" and has the Japan stamp on the side instead of "Made in China". So... i'm wondering... is the 130 jet still the way I should go, or should I rig it up and see how it runs stock.... maybe with the C-clip on the needle in the last setting down? Is there any real difference in performance between this one and the chikuni I THOUGHT I was getting?
 
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#10
Does the carb look like the pictures I posted above? Does it have the oval slide opening? If so it is a Chikuni. The say made in japan and mikuni.
 
#11
Does the carb look like the pictures I posted above? Does it have the oval slide opening? If so it is a Chikuni. The say made in japan and mikuni.
CRAP! I thought the Chinese ones said they were chinese! Those Commies fooled me AGAIN! haha... yeah it looks likes the one in the pictures. It said "Made in Japan" and "Mikuni" so I just figured it was the real deal one. I KNEW it was too good to be true!
 
#12
hello i have been reading alot and i am also in need of assistence if one of you guys could head to my page and check out my thread and give me some insite and or details on how i can fix my problems i would greatly appreciate it!

thanks!
 

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