Mikuni 30MM carb upgrade and setup

[Nicraage]

Will this combo work?
I’ve tried to absorb as much info as I can reading some great threads on this site.
Thanks to the great support on this site I know the following:
I have a 200cc Honda clone engine with a xr200 keihin clone carb.
(I know this from thread with pics): http://chinariders.net/modules.php?n...ht=mikuni+30mm

Here are the upgrades I plan to do ASAP (probably all at once):
1. Rear sprocket change to low-mid 40’s (currently have mid 50’s). Mechanic said he can get one here in Honduras.

2. Muffler replacement (no noise or emission laws, but I don’t want it overly loud and annoying). This seems to be the biggest cost, and I would love some recommendations. I wouldn’t mind spending up to $200 on this, but around $100 would be preffered. (do I need to raise the budget on this?)
here is a used muffler (will it work) http://www.ebay.com/itm/2004-CR250-p...aa7832&vxp=mtr

3. Air filter replacement. I’m thinking of removing the box and using something such as the following. If I had to mod to fit, I could have something made: http://www.amazon.com/UNIVERSAL-CLAM...2mm+air+filter

4. Mikuni 30mm carb, which is where my main line of inquiry will be.
I believe most of the Mikuni’s I’ve found on ebay or amazon are clones. In fact, one reviewer from amazon states the following is, but has mikuni jets (the ones on ebay for $30-40 USD look identical): http://www.amazon.com/gp/product/B00...A24FJG9QJIEUE2 these have no jet specs.

However, I am leaning towards this model on ebay, will this fit or do I need the above "cloned" style? http://www.ebay.ca/itm/370678021479?...84.m1438.l2649
• Specs for the above:
• New Genuine 30mm Mikuni Round Slide Carburetor Mfg# VM30-83.
• 30mm bore,
• 40mm spigot mount,
• 250 main jet,
• 40 pilot jet,
• P-5 needle jet,
• 2.5 throttle valve,
• 6F5 jet needle
• 2.0 air jet.
• Brand new 1st quality in box and ready for your motorcycle, dirt bike or ATV at prices far below retail.
• We are an authorized Mikuni dealer.

Will this carb work well with what I am doing? My altitude is approximately 2000 feet, and I don’t think I would ride it in an area over 3300 feet.

As always, thanks for any input

[katoranger]

The clone Mikuni carbs are fine. I would suggest a UNI foam pod filter over the K&N style that you link. If you only ride street then the one you had would be okay.

The sprocket is a good choice. I had a CFR150r silence on my lifan. It was loud, but it did improve performance.

[culcune]

I agree with a mid-40's rear sprocket. If my bike lasts long enough, I will get one made with 44 teeth vs. The 40 I had made and currently commute with. 5th gear seems to lose speed, but at least it seems to keep up with traffic in 4th, and is not screaming for mercy, either; the stock 56 sprocket held up traffic, and screamed bloody murder doing it! In fact, I would throw a sprocket on now, if I were you. Your exhaust might just need to have a look at; the TMEC bikes in the US came with a very restrictive baffle running the length of the exhaust. Removing it improved the sound and performance without being obnoxiously noisy.

[Weldangrind]

This is my favourite pod-style filter: http://www.ebay.ca/itm/42mm-Air-Filt...93940d&vxp=mtr

[Nicraage]

Thank you all. I just ordered one of the Mikuni's 30mm (probably a clone).

**Should I change the jets in it before I install it? I can buy a few combinations if needed. Any recommendations? (2k-3k feet altitude)

Thanks for the filter advice, I'll be ordering a Uni filter and oil like the one pictured, and I'll modify the air filter box to get more air.

I'm told I can get a better performance muffler for about $75 here. It makes sense, as there are tons of these chinese bikes here.

[Weldangrind]

At that elevation, I'd stick with the 20 slow jet and 100 main that it comes with.

[Nicraage]

Sorry for the Novel below, but some of this info is for the next guy who gets this bike.

I had someone clean my carb this morning and do an oil change. It's a new bike, but I thought maybe it had sat for a month or two after its first start ups, which could be causing my bogging problem.

I pulled my seat to check the air filter. It has a paper box type filter (i'll post pics soon for the next person that has this bike). The intake for the box had 3 holes about the size of a dime each. I added about 16 more holes of the same size to the box. It would be very difficult for water to find it's way there. Note: I will be eventually modding this with the UNI filter when my new Mikinu comes.

It already had a 17T front sprocket. I had a 42 tooth sprocket installed on the rear(bought locally) and chain adjusted. The original sprocket was a 50T. The sprocket is a 4 Bolt pattern, and according to my Honduran bought, Chinese made tape measure, it is 78mm (about 3 1/16") diagonal from center of bolt to bolt, and 59mm (about 2 5/16") center diameter hole.

I had the rivets drilled on the chrome muffler end piece, and pulled it off. My original idea was to pull out the baffle and try to shorten it. Once the end piece was off, I discovered the muffler was sealed by weld. Rather than cut the welds, I opted instead to drill 4 1/4" holes around the end of the exhaust, and had the chrome end piece riveted back on.

Oh, and I had a car horn installed in place of the barbie car horn I Highly advise this!!!!!!

Grand total parts and labor $100

Results: WOW!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I had the bike I expected when I bought it!. Throttle response increased dramatically! Acceleration increased dramatically! No more bog at full throttle!!!!! Top speed increased; I'm not sure how much, I will find out Monday on the way to work, but I was doing about 80-90km in 3rd gear, and previously topped out at 110km. Sound is what I wanted. Not too loud (unless I full throttle), but traffic can hear me next to them.

Now here is the kicker: I rode around for about an hour on paved and dirt roads. Had a smile from ear to ear. I decide to grab some food at the center square in Comayagua. I sit in the center park restaurant for about an hour, eating. Starts to get dark, so I go home. Bike wouldn't start!!!

I reach down to choke it, and the gas had been switched off. I got it started, and idle felt weird, so I messed with it for a few mins. I ride home, and now I have the throttle bog again at full throttle!!!

I'm so ticked :evil: I'm assuming some little punk messed with the bike, hoping I would leave it, so he could steal something off it (theft is terrible here). I can't imagine what he could have done to make the throttle bog come back, it was too dark to see much, so I will mess with it in the A.M.

[Lucien]

It could be a dirty gas tank, maybe you will need to reclean your carb and before riding again, add an inline fuel filter :wink:

[zingshoen]

loosened the spark plug cap? put pizza in the tank? not kidding, know someone to whom that happened. or do you have a lockable cap?

and hey, nothing wrong with novels

[Nicraage]

Originally Posted by zingshoen

loosened the spark plug cap? put pizza in the tank? not kidding, know someone to whom that happened. or do you have a lockable cap?

and hey, nothing wrong with novels

wow, that's terrible . I'll check the plug before I head out. No pizza, thankfully a locking tank.

Everything here gets stolen. I've been burglarized twice. I had a contour camera on my dash, which also is a helmet cam. I had some great footage of driving around here, but that all got stolen when my computer and hard drives were all taken. I'll probably get another camera, now that I have the bike.

[SpudRider]

I hate thieves. :evil: Where do you live?

I hope you get the problems sorted out. At least a vandal couldn't put any pizza in your fuel tank! 8O

Spud

[Nicraage]

I live in Honduras. A lot of nice people here. Most are poor, but still good. But there are so many thieves. Very dangerous country, I'm surprised I haven't been shot yet. I've only had a few direct robbery attempts. A guy with a machette, two guys with a knife, and four guys who thought their numbers would be suffice.

But the burglaries and theft of "opportunity" are terrible. Can't set your phone down in public, and I come home every day to see if someone broke in again.

Other than that, I love this country. I had some great driving footage from my helmet/dash cam, but that got stolen, along with my hard drives. Not many road rules here.

[Nicraage]

Now for a question. I just received my mikuni (probably the clone)

http://www.ebay.com/itm/30MM-MIKUNI-...b0ed4d&vxp=mtr

It came with the clip on the bottom, so I moved it to the middle. It starts only when I choke it. It will seem to idle nice for 15-20 seconds after adjusting the main screw., but then it pops once and turns off. I can't find another adjustment. Aren't there supposed to two adjustment screws? The link has pics if someone can point it out.

It seems like I need to increase the gas flow, because when I turn the throttle a little bit it is fine, and there is no more bogging at full throttle.

One more thing, when I let it idle, I can turn the throttle no problem. But when I do a quick jerk of the throttle from idle, it immediately dies.

Any thoughts?

[FastDoc]

It seems like I need to increase the gas flow, because when I turn the throttle a little bit it is fine, and there is no more bogging at full throttle.

One more thing, when I let it idle, I can turn the throttle no problem. But when I do a quick jerk of the throttle from idle, it immediately dies.

This may be normal ofr a non CV carb :wink: .

Rapid opening of the throttle raises the maniford pressure rapidly and drops the suction needed to draw atomized fuel into the venturi causing a sudden leaning of the mixtuure past the point where it will ignite and the motor will stall.

[Nicraage]

Originally Posted by FastDoc

It seems like I need to increase the gas flow, because when I turn the throttle a little bit it is fine, and there is no more bogging at full throttle.

One more thing, when I let it idle, I can turn the throttle no problem. But when I do a quick jerk of the throttle from idle, it immediately dies.

This may be normal ofr a non CV carb :wink: .

Rapid opening of the throttle raises the maniford pressure rapidly and drops the suction needed to draw atomized fuel into the venturi causing a sudden leaning of the mixtuure past the point where it will ignite and the motor will stall.

ahh, thanks. Do you know if there is there only one adjustment screw on this carb?