Dual Carbs on 125 rebel (lot's of pic's)

[Are (yes it is my name!)]

For a long time i've been thinking about putting dual carbs on my Rebel. And this spring i bought 2 new carbs, but when i came home they were way to big and hit the petcock, and there was no room for filters. So i the idea was put on the shelf for a while.

but then about a month ago I did some re-search and found out that many 125cc honda cb's were delivered with dual carbs and 17hp from factory (my rebel's only got 11 :lol: ) And the engines are virtually identical from -77 and up.... So I decided to find a set from a cb, but it proved to be harder than i thought, so i decided to fabrikate the intakes myself.

17 hp cb:
http://i9.photobucket.com/albums/a85/are-mnja/cb125.jpg


Here are the universal carbs i bought:
http://i9.photobucket.com/albums/a85/are-mnja/dual1.jpg

Here I'm taking out the hole in the intakes to match the intake-port's perfeckt.
http://i9.photobucket.com/albums/a85/are-mnja/innsugidreibenk.jpg

This is before the final hole was taken, it shows the o-ring seal.
http://i9.photobucket.com/albums/a85/are-mnja/innsug3.jpg

Mounted. I'm going to try and take out the long studs and insert shorter ones, but if that wont work i'll make a spacer.
http://i9.photobucket.com/albums/a85/are-mnja/intake.jpg


The carbs on the bike:
http://i9.photobucket.com/albums/a85/are-mnja/dobble3.jpg
http://i9.photobucket.com/albums/a85/are-mnja/dobble2.jpg
http://i9.photobucket.com/albums/a85/are-mnja/dobble1.jpg



The plan is to make a connectin on to the original airfilter-box because theres almost no room for individual filters on the carbs.
I haven't found out how to do it yet, but i imagine welding togeather some tubing and using rubber connections (radiator hose or something)
But the 2 carbs will probably require more air-flow so i have taken a hole in the box:
http://i9.photobucket.com/albums/a85/are-mnja/luftfilterboks.jpg

There's still some work left to do, like throttlecables and cutting and bending the intakes to make the carbs stand straight. Don't know when I'll get it done, the original plan was to do it by Christmas ,but other things like exams and personal matters get in the way. But Atleast I'm getting close :lol:

Are

[cTc]

Looks like the wrench time is paying off, keep us posted on the progress.

[GearJammer]

Very impressive machine work, Are! As I recall, there were a few doubts mentioned about whether or not it could even be done, but you're doing it!

On the need for more air flow & the lack of clearance with the stock airbox being used, if you lost the airbox, would it solve both problems ? Meaning, wouldn't it allow the desired air flow & offer adequate clearance for some pod filters ? Or is there simply not enough room no matter what ?

[Are (yes it is my name!)]

Very impressive machine work, Are! As I recall, there were a few doubts mentioned about whether or not it could even be done, but you're doing it!

On the need for more air flow & the lack of clearance with the stock airbox being used, if you lost the airbox, would it solve both problems ? Meaning, wouldn't it allow the desired air flow & offer adequate clearance for some pod filters ? Or is there simply not enough room no matter what ?


Hi. Yes there were a few doubters out there......And i'm hoping to prove them wrong. Almost anything can be done with lot's of imagination and a little bit of skillz :wink: I'm lucky enough to be blessed with a wery helping father and accses to almost every tool i need. The fabrication was mainly done at school (mechanic school) and the teachers had just recently done something simmilar, so i got a few good tips on how to do it. But still i did everything on my own, and if i can do it, anyone can.


As for the airflow there is absolutly no room for pod-filters whatsoever. The "downtubes" from the frame make it impossible, i even had the intakes shortend but it didn't help much. Removing the airbox wont do any difference either because it's mounted behind the downtubes. I'm sure i'll find a sollution, just gotta give it some time........

Are

[GearJammer]

That's great that you've got access to the needed tools & have the support of others. It's even cooler that you've been doing this work yourself.

I definitely hear you about the minimum clearance because of the frame.

Couple thoughts:

An oval shaped air filter that might fit between downtube & intakes, using one oval filter to fit two carbs.
Cutting the pod filters down to the needed clearance (I've done this before & it works great on Triumphs with similar clearance issues)
Curved/angled rubber breathers for the intakes that would run to either side of the downtube, allowing the use of pod filters attached to the breathers

[Are (yes it is my name!)]

I just did some searching and found a filter that would fit.
http://i9.photobucket.com/albums/a85/are-mnja/filter.jpg

Cutting a pod filter as you say has crossed my mind, but aren't they cone shaped? Wouldn't cutting it shorter make the endpiece to small to fit back on?

And a oval filter to fit both carbs would also work. When i think about it, it's accutually not that hard to make.

I'm going to send a mail to the company who sells the filters and ask if they could meassure them. It's the same company that i bought the carbs from, but at the time they did not have theese filters for sale.

Are

[GearJammer]

Interesting filter there, Are, I hadn't seen that one before.

On the pod filter cut-down. UniFlow foam pod filters come in various diameters for your intake & have a chrome end-cap on the furthest/outside end. Inside, there's a light spring to keep the foam shaped. You can easily cut the foam with a pair of scissors to the right length. Then you remove the spring & lose it. The chromed end-cap can be easily pryed off the foam & then re-attached to the shortened foam by using super glue, any industrial strength glue or even JB Weld. In other words, you'd be cutting it down from the outside end & not disturbing the rubber throat of the pod filter that actually goes onto the carb intake. Works great!

[cTc]

What if the filter mounts were bent 90 degrees and the filters were outside the frame on each side, kind of like the tornado style intakes. or is ther not enough room around the frame rail to go that route either.

Later

[Are (yes it is my name!)]

http://i9.photobucket.com/albums/a85/are-mnja/bilde.jpg

Like this one? They would hit the side-covers......now i know i could cut out to make some room but the covers are newly painted, so i really dont want to do that......

As for now i'm going to buy those round foam ones pictured above......I'm hoping they will fit.

I'm going to update as i go along....

Are

[cTc]

Sounds good, I'm sure you will get it straightened out. Let us know how it goes.

[Are (yes it is my name!)]

Not much done lately. But christmas came bearing gifts :D

Filter:
http://i9.photobucket.com/albums/a85/are-mnja/filter1.jpg
Its going to work just fine, because they are very soft. They can be squeesed real thin and still flow good.
http://i9.photobucket.com/albums/a85/are-mnja/filter2.jpg


I have cut and bent the intakes 8 degrees (same as stock manifoild) and i'm hoping to get it welded soon.
http://i9.photobucket.com/albums/a85/are-mnja/bydinnsug.jpg

Next on the list is to make the throtle-cable(s). anyone who can think of a bike that's got 2 into 1 throtlecable that can be modified to fit?

[GearJammer]

Good to see that you're continuing to make progress, Are & it's looking great!

I'm not very familiar with Japanese bikes as the 250 Rebel was my first Jap bike & now this 450, but there were a LOT of smaller displacement Jap bikes running dual carbs over the years, so you'll probably be able to find one that would work.

Another thought here: My 450 has a single throttle cable that operates a single linkage which connects both carbs. Would that be an option for your set-up ?

[cTc]

I would say the linkage would be the easiest fix for the throttle cable problem.

HMMMMMM......... 3 carbs on the shelf........... new project bike......... NAAAA..... I better not, I would love to stick 2 carbs on this project rebel, but I'm stretched out as it is, it would be another who knows when it would get done project.

[GearJammer]

LMAO!!! I hear that! My Bro had about 5 project bikes in his back yard. Everytime he'd go outside with goodly intentions on getting something near completion, he'd look over here or over there & get distracted by another project & end up pretty much walking around in circles.......hehehe.....Too many bikes = such a problem, right ? ROTFLMAO!!!

[Are (yes it is my name!)]

Hmm...A linkage would have worked if the carbs were vacum operated. The carbs i have need a wire to lift the carb piston, but on the 450 the pistons are operated by the engines vacum. And therefore they also have the wires(linkage) on the outside of the carb, if you get what i mean :lol:

Are

[screamineagle]

Are,
Are you saying that the carbs need to be pulled but a 1 into 2 cable? Well if that is your only problem try getting cable from a BMX bicycle. One that has a spin collor on the goose neck. Most of those cables are pulled by one fitting at the lever, into a spliter that leads to two cables comming out. It might just work.

[Are (yes it is my name!)]

Hahaha....Thanks..Thats an exelent idea! :D It just might work! :D

[cTc]

I think there is a good chance that will solve the problem.

[GearJammer]

Are, I might be wrong on this & if so, hopefully someone will correct me. But I believe it's the stock petcock on the 450 that's vacuum actuated. When the engine isn't running, no fuel is supposed to flow & it would theoretically prevent fuel from filling the carbs & possibly ending up in the crankcase.

There is an accelerator pump in these Keihins, both for the 250 & 450, but not sure that that would be effected by any throttle cable mods.

The piston (carb slide) would still be pulled by the throttle cable. As mentioned earlier, this 450 has the stock vacuum actuated petcock, stock dual carb set-up with all those vent hoses & only a single throttle cable connected to a single linkage to pull both pistons (slides) simultaneously.

Again, if I'm incorrect, someone please chime in with the right info :?

[GearJammer]

O.K., just checked the carb schematics at Bike Bandit. I see what you're saying about the "piston". What I know as a "carb slide" is a "vacuum piston" in these Keihins, just as you've said.

But the throttle assembly must somehow activate movement on the inside by way of the linkage on the outside of the carb body or in the case of duals, the single linkage for both carbs. If you could fab a single linkage to perform the same function from the outside, you'd be good to go. Sorry, but I don't have any spare Keihins to study how they operate more closely. If I can find anything in manuals, will try to offer more info. Unfortunately, Bike Bandit's schematic is too exploded to get a clear picture & many of the carb parts have been discontinued so those parts aren't even identified in their parts listings.

No worries, Are, "where there's a will, there's a way" & you'll get it figured out. We'll try to help as best we can.

[GearJammer]

LOL! Just went thru this thread again. Your carbs have slides, pulled by throttle cables. We're back to the 2 into 1 cable, which should be easier to figure out. Hang in there, you'll get there! :wink:

One thought is to measure the needed distance from throttle at the handlebars to carbs & see if anyone has a stock 2 into 1 cable for another model that would fit, using that measurement. There's also some guys that could custom make throttle cables for you. They'd need to know what type of cable ends are needed for inside your carbs as well as for the throttle, along with the needed cable length, but I'm sure someone could make them for you.

[Are (yes it is my name!)]

hehe..I have no problem making the throttle cables, its just the 2into1 system that bother me. I able to make that to, but i would save alot of work if i could find something that fit's.

I asked a friend @ school today if he had any of thise 2into1 "thingies" lying arround, and he said he's got plenty of them :D So the cable problem is solved. (sort of :lol: ) Still have to make the cables tough.

[GearJammer]

I'm sure you'll get it figured out, Are. If you can do the dual carb mod, the cables will be easy in comparison. Still banging my head against the wall here...should have been paying closer attention to the thread, LMAO!!! :lol:

[Are (yes it is my name!)]

update:

The intake is welded again , and ive used "chemical-metal" (glue or bondow of some sort, that can stand the heat) On the weld to avoid it from suckin in air there (is it called fake-air :shock: ? That's a direct translation from Norwegian :lol: )

Also a wire splitter fell into my hands. hehe......it turns out that modern moped's have theese on them...on wires regulates the trhottle, and the other the oil-pump...

So wire's will be made (can't use the one's who's already on there) as soon as i get time (or as soon as i bother :lol: )

http://i9.photobucket.com/albums/a85/are-mnja/wire.jpg

[GearJammer]

Excellent! You're getting real close to finishing. (And they said it couldn't be done, LMAO!)

Whatever you used on the manifold looks like what we call JB Weld here. Mix the liquid metal & the hardener together, right ? That stuff is very strong & I've seen one motor that had JB Weld repairs all over it. Didn't look too pretty on the motor, but it worked, LOL!

[Snorebaby]

I was reading through this thread and noticed that GJ had made mention of Bike Bandit-- "Unfortunately, Bike Bandit's schematic is too exploded to get a clear picture & many of the carb parts have been discontinued so those parts aren't even identified in their parts listings."

I have found another site www.crotchrocket.com has all the parts listed and they are updated with replacement parts for the "discontinued" parts.

The mod is incredible. It really takes some ingenious thinking to come up with something like this.

Just a thought I would like to share. :)

[Are (yes it is my name!)]

Nothing new really, just some fiddling with those wire's :lol:


I'm not going to kill the original trhotle cable (the bike needs to be original when i'm going to get it registerd at the DNV, so i need to be able to put the single carb back on)

Therefore i'm strugling to make the adjustment piece that's screw'd into the handlebar-controlls....I'm using some old bicycle parts and bolts i had lying around to try and copy it...
http://i9.photobucket.com/albums/a85/are-mnja/wire1.jpg
http://i9.photobucket.com/albums/a85/are-mnja/wire2.jpg


The space is tight, so it's hard to get anything done without moving around everything in the whole garage :? Cant wait til summer, so i can wrench outside :o
http://i9.photobucket.com/albums/a85/are-mnja/hondarod.jpg

[GearJammer]

Looks like you're getting the temporary mod done fairly well, Are.

If the bike has to be stock when getting registered, what are the rules there for choppers ? Do people get the bike registered in the stock form & then chop them later without any problems ?

And what's that hot rod in the pic ? LOL! Looks VERY cool whatever it is :wink:

[Are (yes it is my name!)]

Tnx...

The bike has to be stock because there is a maximum limit of 125cc and 15hp for 16'yearolds to ride the bike...also, the bike was bought in germany, and that makes it a first-time registration here in norway. If they see any modifications done (to increase preformance) they will demand documentation that it has been done by a certificed workshop, and that it does not exceed 15hp...if it should exceed the 15hp limit, I would have to pay a certain amount of tax pr. 1hp gain in preformance, and the bike would now be considerd a "mid-heavy" bike (max 600cc and 15-34hp) To ride a "mid-heavy" motorcycle you need to be 18 or older, when you get 21 you can drive a "heavy" motorcycle (no cc limit or hp limit)

Norway aint the country to go if you want to build choppers....the first thing that makes it difficult is that the chopper need's to be based on a bike that is in production (or has been) So you can't buy a chopper frame (from for exaple JP cycles) and get it registrated..other demands for a customized bike is that the lights are DOT aproved and so on......same thing with bigger bike's if you increase preformance you need to pay for each 1hp gain(it does not apply to bikes that are 30 years old, or older)....so most wait with the engine mod's til after the registration.....

Hehe, that's my dad's 32 ford roadster, he's been building it for 25 years now, LOL. It's been buildt atleast 2 times with a different style.....pic:
http://www.hondarebelforum.com/phpBB2/album_pic.php?pic_id=39

[GearJammer]

Interesting, Are, and thanx for the explaination. I'm following what you're saying & can see the different hoops that they make you guys jump thru.

The "Swedish Long Bike Choppers" have an excellent reputation over here among many chopper builders. Keeping in mind the guidelines that Norway has, is the "Long Bike" style popular there as well ?

32 Ford roadster. Very, very cool! The '32 Ford is one of the most popular hot rod choices over here, too! I'm strictly into choppers, but know a few guys who prefer the hot rodding scene.

Thanx again...

Edit: Whoa! Just checked out the pic. SWEET!!!

[Are (yes it is my name!)]

There aren't to many "long-choppers" over here, the main style is drag/ground-pounder, but also the classic old-school style is coming back...this probably does have something to do with the laws here in norway....in sweden the bike can be buildt as a "amature build" ,this alowes for use of frame with no earlier title, and more ,eh, should i say severe customization :lol: .....

[GearJammer]

"should i say severe customization ....." ROTFLMAO!!!!

No doubt. Some of those Long Choppers are pretty radical, which is great! Hopefully, they've got plenty of flat roads in Sweden for those long front-ends :D

Classic Old School styling coming back in Norway ? Excellent! At least they allow you Brothers to still have some fun, eh ? LMAO!

[Are (yes it is my name!)]

I really cant belive this, but i started her up today :D It actually worked :shock: To my surprise it fired after one turn of the engine, and it ran normally :D But I adjusted the idle-speed a bit just because it's so freakin loud :lol: Still aditional adjustments needs to be done, it's actually running a bit lean(or i think so, no spark reading yet) because it tends to backfire a bit when I twisted the throttle suddenly....

As for now I wont start adjusting anything, because the intakes needs to be painted....So that will have to be done first.

The feeling when she fired up was just so amacing, I just couldn't belive it worked. Still a bit surprised :lol: And WERY happy :D

[GearJammer]

"I really cant belive this"....I can believe it. Have never doubted your abilities, Are. You set out to do something that many didn't think could be done & you've succeeded! :D

That's EXCELLENT, Are & MUCH respect to you!

Your accomplishments at this age show that the future may hold some amazing possibilities for you & that's great.

Once again, CONGRATS & please keep us posted on your progress...

[cTc]

I'll second that, it really kicks A$$ that it fired right up. Keep us posted, and supply me with pics as you get them to add to your webpage

<> Peace <>

[Snorebaby]

That's Great ARE!!!! I know the feeling of firing it up!!! I knew you could do it. You have the exuberance of youth and a spirited determination to get the job done. Congrats!!

[Are (yes it is my name!)]

Just a short update....

The bikes runs way too rich. The current jet size is 70 (the ones i used at first were 110 :shock: ) I tried alomst all the numbers from 110 down to 70, so i need to save up some money to buy smaller ones :lol: I'll post a pic of the sparkplugs soon :wink:

It dies out when i twist the throtle suddenly. But this only happens on low rpms. Above approx 5000 it works just fine. The top speed is 70 mph(with a 35t rear sprocket and stock 14t front sprocet).

Just a pic of the carbs with painted intakes and braided fuel lines.

http://i9.photobucket.com/albums/a85/are-mnja/HPIM0485.jpg

Are :wink:

[cTc]

Looks like progress to me. Keep the info coming as you get more done.

[Snorebaby]

Now I know why it's been a while since you have been on here!! Busy as a bee and as productive as one....keep the updates coming!!!

[Are (yes it is my name!)]

Okay, it's not exactly an update, but here are some pics of the sparkplugs:

http://i9.photobucket.com/albums/a85/are-mnja/right.jpg
http://i9.photobucket.com/albums/a85/are-mnja/left.jpg

As you can see, the right sylinder is running slight richer than the left. But then again, they are both running rich :? . I'm going to check if the carb-pistons lift the same, but its very hard to see because of the lack of space. They probably should have been checked with one of them vacum-meters or what it's called. to get the lift time perfect.

I'm buying some smaller jets soon. (by soon i mean maybe before christmas :lol: )

later.....

Are :wink:

[GearJammer]

I can understand the need to lean her out a bit. With the bike originally set with a single carb feeding twin cylinders & then feeding each cylinder with it's own carb, the rich condition would somewhat be expected.

For the sake of example, a 650cc Triumph with single carb might use a 230 main jet. The same motor running duals might use 190's.......230 minus 190 = 40

Your left plug doesn't look too far off, you're definitely getting close. Earlier in the thread you mentioned that you started off with 110's & are now at 70's. 110 minus 70 = 40

I'm sure that the re-jetting process is always a matter of trial & error until you find that sweet spot. It's impossible to compare the mentioned engine sizes & makes, but it's interesting how the math is kinda close :wink:

You're almost there, Are & that's GREAT!

Ride Safe.....

[Are (yes it is my name!)]

Hi Guy's. I'm still struggeling with my jetting.

since the last update i have gone down to #60 jets. The bike now ran even crappier ( :roll: ) no matter what rpm's, I'm getting so F%#@ sick of it, that i'm thinking of going back to the original setup.

But as a last resort, i was thinking maybe smaller venturi's would do the trick. These carbs don't have removable venturis, so I've decided to fabricate them. I was thinking 18mm would be small enough (they are 21mm now)

hopefully I'll get them done by tomorrow. The only problem is that i cant test the bike before all the snow goes away :lol:

http://i9.photobucket.com/albums/a85/are-mnja/HPIM1236.jpg
The plan was just to make a 18mm I.D sleeve to fit infront of the slide-piston. I've seen a guy do the same thing, and he said it worked perfect, untill it came loose :lol:

Are :wink:

[uneasyrider]

Are, A smaller sleeve just may do it, please keep us updated.

Howard

[Duke Bushido]

I'm two years behind the times here, and haven't heard from Are on my board either--

but I was curious how far he'd gotten, so I've been searching about and what do ya know; I find it all right here :lol:

I know there are laws that govern such things, but I figure at this point you've likely gotten the initial registration, etc---

So I'll toss this out:

Is it possible that you might reduce your rich condition by opening up your exhaust so it might more effectively handle the increased fuel load? I'd hate to see you lose the potential power gain of the dual-carb set-up by jetting all the additional mix out....

[Duke Bushido]

Oh--

or maybe re-work the cam so that there is a slightly longer open duration on the exhaust lobe?

[b4v4]

Yo, Are! I never saw this thread before, but you really have a knack for fabrication! You say you have "some skills"? Dude, I wish I had 1/2 of them. I never realized that the ol' CB250 had the same (so it appears) motor as the Rebel. The only thing I could see that could still possibly keep you from attaining those H.P. numbers is if that cam was different. Honda has always been famous for putting motors from one machine into another, but changing the internals slightly. But after seeing what you've done already, I'm sure procuring a cam will be nothing for you. I can't wait to see the outcome.

[Are (yes it is my name!)]

Hi Guy's.

Well, I'll have to admitt that nothing has been done to the bike since the last time I was here. Exept for a jet change. I didnt bother with the "sleeves".

Jets are now #70, and the needles have been raised as high as possible. It runs "okay", but still stumbles a bit. With a top speed of 71mph, I'm satisfied. Besides , I'm selling the bike this fall, due to buing a car.

Duke: The exhaust is opened up. The stock mufflers are cut away, and slip-ons are added.

As for the cam profile, i wont bother messing with that. It's way beond my skills. And wouldn't adding duration to the cam push the torqe curve even higher in the rpm scale?


I've had a lot of fun with my rebel, and I'll probably regrett selling it...But for now my main priority is getting a working car, and fixing the "non working" car :P

See ya'

Are ;)