Carburetor swap - Page 2

Smithers · #16 07-20-2012, 08:08 AM

I handed off a couple of Benly carbs to a friend of mine who owns a manufacturing company. He was going to have the slide replated on one of them and I gave him a good one that was the example. Well almost 2 years later I called him for them back and he thinks he gave them back to me. Uhhhh seriously!? That is not something I would forget about!!!

Anyhow I think I might be in the market for a carb upgrade! And the blue bike isn't exactly a show piece so it will be fun to try out an aftermarket carb. Will be a good fall project.

Jetblackchemist · #17 07-21-2012, 06:59 AM

Done.

TristanWB · #18 08-07-2012, 01:59 PM

Quote:

Originally Posted by kartgreen

I have a Mikuni VM22 carb mounted on my blue custom and so far it's working out very well .A machinist friend made an adapter plate from 1/2" stock . It took 3 attempts and we had to remove the carb isolator but we still have the breather passages from the head milled into the adapter with the vent hose coming out the bottom right side .
I was concerned about removing the carb isolator because it also acts as a heat sink or heat barrier from the head to the carb but so far the carb has stayed cool but I've only run the engine for about 10 mins. at a time .
I'll post a photo of the bike when we return home in a couple of weeks.

Im thinking about doing this carb swap with the VM22, could you post some photos of the adapter plate that you made? Or some some photos of it on the bike?

kartgreen · #19 08-12-2012, 03:53 AM

Tristan ,sorry just saw this ,while we were at Mid-Ohio a couple of weeks ago ,I found the blue bike wouldn't accelerate beyond a couple thousand RPM .It would just bog and almost shut off . Once we returned home I pulled the carb back off and found my adapter had cracked allowing air in to lean out the fuel mixture . My friend the machinist stopped by and he's going to machine a new adapter from 1/2" alum stock verses the 3/8" we started with . So hopefully this week or next I'lll have a new adapter to try .
We think we have a better design for the adapter as it cracked between the new carb mounting flange and the original carb mounting studs . Spacing is too narrow between the mounting flange studs ,so we're going widen the new carb flange holes slightly .
I did install the original carb and the bike runs just fine . Got a couple of shows to go to in the next several weeks so the bike needs to be running .

kartgreen · #20 08-20-2012, 05:30 AM

We may have given up on the Mikuni 22mm carb ! The throat of the 22mm Mikuni is almost double the size the the stock carb and the sealing surface , O-ring slightly overlaps the bolt hole spacing of the original carb flange . I hoped a gasket between the Mikuni and the spacer would seal the mating surfaces but no such luck . There was also an issue with the flange bolt spacing of the Mikuni 22mm carb that is difficult to over come . We looked at moving the carb up and down on the spacer (adapter) but I'm not convinced we can solve the sealing problems .
So , now what ? We're going to try a different approach . I picked up a Mikuni 18 mm carb ( spigot mount ) and we're going to make an adapter with a spigot . I think that may be a better approach , but getting the jetting , needle settings correct will take some tinkering .
I have a spare running 150 motor so I'm thinking of making an engine stand to help tune the carb . If I can get it to run right on the engine stand ,it should be very close when mounted on the bike .

92merc · #21 08-20-2012, 11:59 AM

On the Honda Ruckus, some guys swap out to a PC20 carb. Now the Ruck is only 49cc's. But this carb is a 20mm. Wouldn't this work?

http://www.bowlsla.com/store/pc/view...idproduct=4882

Jetblackchemist · #22 08-21-2012, 03:10 PM

Done.

ByTheLake · #23 08-21-2012, 05:01 PM

Quote:

Originally Posted by Jetblackchemist

If you're looking for one close to stock, that looks like an option however it is way over priced; and you don't need the extra intake stuff shown in that ad.

If you type 20mm carburetor over at ebay, you'll see pretty much the same carb for under 30 bucks.

The main issue is going to be the center to center measurement on the flange to mount to the intake. Anther member here measured and said it was 38mm center to center, whether that's what it is I can't say for certain because I haven't measured it. The ebay ones that look like stock say they are 48mm center to center.

If ours is indeed 38mm from center to center opening up the holes or slotting the flange on both sides should make it fit just fine.

This thread was started as a discussion meant to serve as a better option over stock, such as CVs, flat slides, and racing carbs etc.

But if anyone wants an option that looks close to stock then something like this http://www.ebay.com/itm/20MM-CARBURE...#ht_4258wt_813 should serve that purpose; bearing in mind the flange may need some slight modification.

Wow, that's quite a close match, visually anyway. I had no idea you could buy a carb that inexpensively. Has anybody used these on a CA95?

Jetblackchemist · #24 08-21-2012, 05:38 PM

Done.

kartgreen · #25 08-22-2012, 10:11 AM

I looked at these carbs at a Chinese motorcycle shop in Akron , Ohio and wasn't impressed . Not much in the way of parts support , jets ,needles , eve
n gaskets , floats and inlet needles and seats weren't available .
But ,I do have to say the Mikuni carbs I've bought recently are manufactured in China also . Just seems there's better parts support available for the Mikuni carbs .

Jetblackchemist · #26 08-22-2012, 04:30 PM

Done.

comp_wiz101 · #27 08-27-2012, 11:34 PM

Quote:

Originally Posted by Jetblackchemist

A lot of Chinese manufacturers have been doing blatant name rip offs, for years in designer clothes etc. they've been moving into do the same thing under many markets, since the 90's Gucci fiasco that made the news. If it is stamped Mikuni, Dellorto or what ever and from China it is a fake; they have been getting away with it and skirting the law saying it is a replica.

So yes when it comes to all things Chinese you get what you pay for.

I wonder if Dellorto makes an affordable 20mm carb. I've got one of their little 14mm SHA's, and they're decently finished.

kartgreen · #28 08-28-2012, 04:56 AM

I looked at a website "Monster Scooter Parts " that lists carbs for the Lifan (Chinese ) motors but I think they are the same carbs that I looked at previously at the shop in Akron .
Jetblack , your points well taken about the quality of the parts coming from China . Looking at the no-name Chinese carbs and the Mikuni ( made in China ) carbs , there is quite a difference in the look and finish . Unfortunatly ,Mikuni as well as many manufacturers in any industry have decided that China is the place of choice to make their products . We just get to purchase them .
Earlier this spring I bought my wife a new AGV helmet ( Italian company ) and of course it was made in China . The quality , fit and finish are what you'd expect from AGV ,it's just disappointing that companies worldwide feel the need to use cheap labor from a country with little to no reguard for worker safety and no enviromental controls . And these same companies also put their own countrymen out of work .
My sister's last day at Diebold ( they manufacture ATM machines , Voting machines ,etc ) in the accounting division is Thurdsday . 300 jobs being sent to India . My sister was expected to train these people to take her job ! I just don't get it !

Jetblackchemist · #29 08-28-2012, 05:03 AM

Done.

comp_wiz101 · #30 08-28-2012, 08:27 AM

Quote:

Originally Posted by Jetblackchemist

...I do suggest going with the 19MM over the 21MM though simply because, the flow from smaller intake into a larger port is easier to manage and adapt than the reverse.

Yes, that sounds familiar... isn't a common problem of "big carb, little intake" issues like bogging down under throttle, because the intake can't draw enough volume compared to the carb?