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Post by zekkfett on Jan 29, 2012 23:16:04 GMT -6
Has anyone thought about, or attempted to run just a single carb?
Seems like it would be easy in concept. Single 37mm instead of 2 34mm's; with say....140 jets.
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Post by Blaine on Jan 30, 2012 0:24:00 GMT -6
Has anyone thought about, or attempted to run just a single carb? Seems like it would be easy in concept. Single 37mm instead of 2 34mm's; with say....140 jets. The hardest part would be fabricating a intake to go from single carb to duel intake.I would think that it would have a negative effect on the performance.   |
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Post by zekkfett on Jan 30, 2012 9:38:00 GMT -6
It really wouldn't be too hard to fab something much like an exhaust Y pipe. Or mod a U pipe. If you could find something in an appropriate size. I like the idea, and performance of 2 carbs, but it can be a hassle to rebuild, tune, and sync 2 carbs.
From research I've done on cars, it has a slight effect on top end performance, maybe lose 3 or 4 HP. Depending on how long you make an intake, you could make more torque, which could also be beneficial. I'd be willing to lose 3 or 4 HP for simplicity and ease of maintenance.
Has anyone tackled a project like this before?
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mradam
Junior Member
Posts: 214
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Post by mradam on Jan 30, 2012 12:52:14 GMT -6
your biggest issue would be tuning for you're tunnel length. it's just a matter of playing with jets and needles, my one concern would be scavenging. does this engine have enough duration to pull in the required mixture to run well??
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Post by ibuiltmine on Jan 30, 2012 13:16:00 GMT -6
Hey guys! I have built a couple single carb intakes on bikes. kz440, kz750-twin, xs650, and a 450 rebel.
The last one I did was as simple as could be. literally a piece of exhaust tube with a 90* bend stuffed into the left intake. then another piece T-d up to the first piece. I welded around it, then used a die grinder to smooth the hole best I could on the inside.
Then I just used the stock carb, unmodified (already jetted for pods) It fired, ran smooth, and worked like a charm. If I hot rodded it, like full throttle through all 5 gears, it would start to sputter in the top end. I always though I would put a bigger petcock, and raise the float level or something, but never bothered it too much.
Im going to build the 1into2 intake for the one im working on right now.
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mradam
Junior Member
Posts: 214
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Post by mradam on Jan 30, 2012 15:01:09 GMT -6
You know, i would really like to see some info on this. the one thing i see now is that any intake you build will take up more room......
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Post by zekkfett on Jan 30, 2012 19:04:26 GMT -6
Im going to build the 1into2 intake for the one im working on right now. You're going to build one for the 454? |
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Post by zekkfett on Jan 30, 2012 19:06:15 GMT -6
The one thing i see now is that any intake you build will take up more room...... Depending on fabrication skills, it could be quite small. And with the airbox removed, it would STILL be easier to service, only having to remove one carb, and one filter. |
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Post by zekkfett on Jan 30, 2012 19:07:44 GMT -6
If I hot rodded it, like full throttle through all 5 gears, it would start to sputter in the top end. A little bigger main jet would have solved that. But that is one disadvantage to a 2 to 1 conversion. |
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Post by ibuiltmine on Jan 30, 2012 19:34:23 GMT -6
[quote author=ibuiltmine board=has thread=3325 post=24883 time=1327950960}If I hot rodded it, like full throttle through all 5 gears, it would start to sputter in the top end. A little bigger main jet would have solved that. But that is one disadvantage to a 2 to 1 conversion.[/quote] Thats what I was thinking, like 2 sizes, but it ran good otherwise. I love CV carbs. They are so forgiving. and yes, Im building a 2 in1 onto the 454ltd I am working on now. |
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Post by zekkfett on Jan 30, 2012 19:50:13 GMT -6
And yes, Im building a 2 in1 onto the 454ltd I am working on now. DEFINITELY get, and post, some pics; and let us know what works for you. Personally, I don't know if a single stock carb will work, don't know that it would be big enough. Although you never know, 140 or 145 jets may make it run like a champ. Along with the other POD filter setups. Bet it would get plenty of vacuum running on one carb. Wouldn't need restriction in the filter. Come to think of it....If you need to restrict PODS with stock carbs, maybe a stock single carb WOULD work.... Hmm.... I wondered about doing it to a few dirtbikes and quads that I've had over the years. Never had the equipment and time to tackle it though. |
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Post by ibuiltmine on Jan 30, 2012 20:23:09 GMT -6
And yes, I'm building a 2 in1 onto the 454ltd I am working on now. DEFINITELY get, and post, some pics; and let us know what works for you. Personally, I don't know if a single stock carb will work, don't know that it would be big enough. Although you never know, 140 or 145 jets may make it run like a champ. Along with the other POD filter setups. Bet it would get plenty of vacuum running on one carb. Wouldn't need restriction in the filter. Come to think of it....If you need to restrict PODS with stock carbs, maybe a stock single carb WOULD work.... Hmm.... I wondered about doing it to a few dirt bikes and quads that I've had over the years. Never had the equipment and time to tackle it though. Just take a second and think about it............. your motor will turn what? 10,000 rpm. How often do you actually red line it? Now, think.... does your bike intake both cylinders at the same time, or do they take turns? Does the volume that the piston is drawing in change just from going from two to one carb, or one to two, or one to 10? no. It all is the same. the carb doesn't car if the motor is turning 1000rpm at idle, or turning 2000 rpm at idle (as in twice as man intake events happening then at 1000rpm) But one thing that is true is the carbs are capable of feeding the motor up to and beyond red line. just because you have one carb on there doest all of a sudden make the carb incapable of running your motor at 6000 rm cruise instead of 3000 rpm cruise. only problem I have ever had with just taking the stock carbs and cutting it in half is the very top end. Otherwise they have worked absolutely flawless. You go putting a larger mouth carb on it, and you will have the same problems as if you put two big throat carbs on. Maybe its been dumb luck, but I have done it a few times and its always worked. Shoot, I only have a 40mm CV on my 95 inch twin cam, and it runs perfect...... |
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qwerser
Junior Member
chop till you drop
Posts: 169
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Post by qwerser on Feb 13, 2012 11:47:48 GMT -6
I had a friend fab me a few different manifolds since Iv'e had the bike. My dad was trying to give me his Weber. The problem we keep running into is that all of the manifolds hes made make one of the cylinders choke due to the distance of the carb from that one side. Since the carb was so big it needed to be outside the bike. It ran alright, but running's not the problem. It doesn't take a rocket scientist to get a bike to run and idle. It was the actual riding part. The rpms were all over the place, and would flood the bike with the slightest twitch of the throttle. So if you want to get a single carb conversion, you'd have to do a lot of work and calculations.
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mradam
Junior Member
Posts: 214
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Post by mradam on Feb 13, 2012 12:58:51 GMT -6
that is what i thought would happen, there really is no way to fab a manifold, with the same tunnel length on this bike, the back bone is in the way. now you suppose you could fab something up the moves the carb further back into the battery area, but then you have used up more room. you could do some fancy bends and maintain the same length but i think your radius' would be too tight and it would look terrible.
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qwerser
Junior Member
chop till you drop
Posts: 169
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Post by qwerser on Feb 13, 2012 13:02:18 GMT -6
The more of a distance from the carb to the engine, the more unstable and inaccurate it is.
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Post by zekkfett on Feb 13, 2012 13:57:28 GMT -6
Qwerser, I think part of your problem was trying to use a huge carb not made for a bike. Jets and needles not made for a bike.
A bike carb of stock size, with the airbox removed, and possibly the battery shifted a little, should fit nicely. Think of an an "E" pipe with the middle leg of the "E" reversed, on the other side of the pipe. DIRECTLY in the center of the pipe. All legs of the "E" should all be as short as possible to get the boots on. Not exactly sure on the carb outlet size....I'd say about 1 inch. 1 inch pipe, if bent on a mandrel bender can make crazy smooth and tight turns. If bent correctly the carb should only be...about 1 inch farther back than stock. From the middle of the "E" there would only be about an inch of pipe to get to the bends and into the head. In actuality, it's much like adding a 1 1/2 - 2" carb spacer; a little more torque would be gained. IF you can get the carb DIRECTLY in the center; (the EXACT same amount of pipe needs to be run from the carb to EACH cylinder) it will run perfectly once tuned. Center is CRITICAL! Centerline of the carb, to the exact centerline of the intake pipe. Also centered on the midline of the engine. Otherwise, one cylinder or the other will always get more fuel. You could fab up a "Y", and insert into the carb end to try to help split the air/fuelflow evenly to each cylinder. "Y" welded into the exact centerline of the pipe. Exact same curve to both parts of the top of the "Y".
Just like race intakes and headers; all pipes in those are the exact same length. If you ever look at a NICE exhaust header, and wonder why the rear pipe has so many twist and turns, and the front pipe comes straight back; this is why. Factory V-8's with center-of-the-manifold carbs, will always give the center 2 cylinders more fuel/air than the front and rear cylinders.
Obviously there would need to be tuning, but with the space the airbox would leave, there should be plenty of room......
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Post by ibuiltmine on Feb 13, 2012 22:21:26 GMT -6
Qwerser, I think part of your problem was trying to use a huge carb not made for a bike. Jets and needles not made for a bike. A bike carb of stock size, with the airbox removed, and possibly the battery shifted a little, should fit nicely. Think of an an "E" pipe with the middle leg of the "E" reversed, on the other side of the pipe. DIRECTLY in the center of the pipe. All legs of the "E" should all be as short as possible to get the boots on. Not exactly sure on the carb outlet size....I'd say about 1 inch. 1 inch pipe, if bent on a mandrel bender can make crazy smooth and tight turns. If bent correctly the carb should only be...about 1 inch farther back than stock. From the middle of the "E" there would only be about an inch of pipe to get to the bends and into the head. In actuality, it's much like adding a 1 1/2 - 2" carb spacer; a little more torque would be gained. IF you can get the carb DIRECTLY in the center; (the EXACT same amount of pipe needs to be run from the carb to EACH cylinder) it will run perfectly once tuned. Center is CRITICAL! Centerline of the carb, to the exact centerline of the intake pipe. Also centered on the midline of the engine. Otherwise, one cylinder or the other will always get more fuel. You could fab up a "Y", and insert into the carb end to try to help split the air/fuelflow evenly to each cylinder. "Y" welded into the exact centerline of the pipe. Exact same curve to both parts of the top of the "Y". Just like race intakes and headers; all pipes in those are the exact same length. If you ever look at a NICE exhaust header, and wonder why the rear pipe has so many twist and turns, and the front pipe comes straight back; this is why. Factory V-8's with center-of-the-manifold carbs, will always give the center 2 cylinders more fuel/air than the front and rear cylinders. Obviously there would need to be tuning, but with the space the airbox would leave, there should be plenty of room...... word! get it running with the stock carbs without pods, (like 12 jet sizes bigger on the main to start) then make your single intake out of one of those carbs. two carbs to one should work fine, just will not have the absolute top speed that two carbs has. (think triumph bonneville vs tr6 heads. exact same motor, just diferent head to run one carb or two.) |
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Post by ibuiltmine on Feb 13, 2012 22:24:13 GMT -6
You know, i would really like to see some info on this. the one thing i see now is that any intake you build will take up more room...... I was geared up to do it on the one i am bulding now, but do not ahve the room... bummer.... |
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qwerser
Junior Member
chop till you drop
Posts: 169
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Post by qwerser on Feb 14, 2012 23:18:05 GMT -6
Yea but I like speed. That's why I just ordered an ex500 engine.
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Post by chopperfreak2k1 on Feb 20, 2012 20:13:16 GMT -6
available space aside, i think too much emphasis is being put on the runners being the exact same length. look at the cb 750 and so on 2 into 1 intakes. they are not the exact same length, due to the frame being in the way but they seem to run good, why?
each cylinder draws X amount of fuel charge. the carb doesn't know which cylinder wants the charge. so saying this cylinder or that cylinder gets more fuel is incorrect i believe. this only matters on initial start up, when there is no charge in the runners.
once the runners are charged up each cylinder draws the exact same amount of charge wether the runner is 1" or 1' long. i have seen inline 4's run well with the carb mounted at #1 cylinder and feeding the rest through a very simple intake and #2, #3, and #4 all having straight cut 90 degree turns.
now when we're talking about race applications then yes, every last 1/10th of a HP is critical and runner size, length, shape becomes paramount. in our application just seal it up and fit it proper.
another point, our single carb is capable of feeding both cylinders. the carb is only feeding one cylinder at a time and can do this well except when high rpm and duration start to fight each other. it is then that you need a bit more fuel as IBM has pointed out.
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Post by vincebighair on Apr 1, 2019 8:18:57 GMT -6
I've done 2 into 1 using vm 36 and 38 mikuni carbs. The 38 is best with full review range and pulls amazingly . Tried vm34 the other day and struggled to pick up in 1st gear and bogged on full rev. The manifold bends off to the right with pancake filter. Looks great
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Post by bikeman on Apr 2, 2019 4:19:43 GMT -6
I don't know why people think they can improve on the design. development. and execution better than Kawasaki. it's doomed from the start. if a single carb was the best way to go they would have done it already and cut costs.
now a single carb can work reasonably on 360 degree engines provided the inlet tract is the same length because fuel is supplied first to one cylinder then the other. so the balance stays the same. but the kawi twin has a 180 degree crank. think about it all the fuel is supplied to the engine within 90 degrees of rotation then none or very little for the next 270 degrees. in order to run a twin on one carb it would have to be bigger with large jets to get enough fuel in over this period.
but the draw on the carbs is not equal it all goes to the first cylinder to fire so this one runs rich. before the intakes close the other cylinder starts to require fuel but it's still being supplied to the first one so the this one runs weaker. result uneven running. you may not be able to detect or rectify the in-balance so long term engine reliability could be suspect. and yes it has been tried before no one has yet come back to say the bike is better has more power or uses less fuel than it did as stock.
I wonder why.
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Post by eaglerider on Apr 7, 2019 4:49:37 GMT -6
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