SINGLE CARB MOD

info on the carb is a little screwey....i cannot find model specific info, everywhere i read says "1983 harley". its a 42mm.

 

the manifold is complete. i just need to finish making the air filter mount, and fix the choke spring on the carb...then starts the jetting "fun". since its only one carb, it shouldn't take too long YAY!

 

fuggin sweet!

 

yessir

 

Sure hope it works after going thru all that trouble to mount it. It looks to me like it may get in the way of your left leg when riding? Just sayin'.

 

The end is near!!! I see the light at the end of the tunnel and its Zookie on his modified XJ

 

painter- ALMOST! this model will not be compatible with forward controls. with MY legs in normal riding position, there is about 2" between my shin and the carb. if this works out well i will probably tear it down and buy some nice header bends to make a much more compact manifold so i can tuck the carb in better. for now, ITS ALL HANGING OUT! i should probably put a marker light on the end of the air filter, to keep DOT happy

waldo- the end is near, and then tomorrow i leave for LI again for the rest of the week. BALLS! i am glad i got it this far though, its still very cold here and i didnt think i would be able to make enough free time to get this much done. once i am done with my lunch, i am going to rush and get boring stuff done asap and hopefully i can go powdercoat this along with some paying customers items.

 

Hi Zookie Great build by thinking outside of the square. With all the problems
you kept on going and never gave up on the idea. Now hopefully the sweetest
part of all when you can fire that beast up. Cant wait for that.

Bob

 

thanks bob, although i must give you some credit for the helpful links and pictures!

powdercoat is cooling. will load pictures this evening when i get home. stay tuned....

 

i need a new camera

its "S&S wrinkle black" powder from www.powderbuythepound.com

 

Zookie,
I sure hope it runs with that carb on it, even if there's a loss of power, it is still a great mod and one for the books.

 

http://www.powderbuythepound.com/S-and- ... INKLE.html

 

Saweeeet!

 

Mean setup... Love that finish

 

i think there will definitely be a loss of power on the top, because of the way the carb runner intersects the rail perpendicularly, however i really dont ride it up there so its not a huge issue. i think low-mid will be nice, maybe even an improvement from the long runners. maybe not. it would be nice if i had a "before" dyno chart to compare to. i dont.

it will be great if i get an improvement in efficiency. i think it will do better on that front because carbs work much better when there is a continuous draw on them rather than a pulse. the fuel droplets will be marbles compared to bowling balls i think.

 

Hi Zookie Just wondering how the single carb mod is going

Bob

 

i got back to CT today, spent a little time on it but not much. manifold and carb are bolted up. it starts and runs on choke only and at 5000 or more rpms. it fouled plugs pretty quick and spewed unburned fuel out of the exhaust. here comes the jetting from scratch process. i am going to try and get an assortment of jets tomorrow. also, i need to adjust the float level and check the valve because the carb is dripping fuel out of the mouth while sitting with the engine off.

even in the terrible state of tune, it was VERY snappy. rev limiter was used a few times by surprise.





here is my average leg placement while riding, with the new carb in place:



and here is the unhappy display of screaming rpms on one cylinder and unburned fuel spewing everywhere from the exhaust:

 

Hi Zookie. Looking good "Its Alive" I have sent u a PM catch u later

Bob

 

Just tell everyone it's a two stroke for now! 8O
:twisted: :twisted: :twisted:

 

I hate to say it but the only thing that makes sense in my mind on a 4 banger is (Fuel injection to each cylinder independently) now boy does that open a can of worms to figure out eh? Be a good topic to sick those guys down at ITT on to create, eh? )))) grunt007, XXJ750R Seca, still trying to erect the old gal but I now have my Harley exhaust pipes to go on her, problem is they are not off of Sportster but off of shovel head probably. They are still going on, I like their look. Only problem is I will have to compensate for going from 1 1/2" pipe to 1 3/4" opening on the muffler! Good side, they are built like a TANK! Also, they weight so much that I shouldn't have any trouble getting traction off the line )))

 

Hey grunt, are you referring to this build?
http://xjbikes.com/Forums/viewtopic/t=29313.html

 

Yeah, already been done, man.

 

EFI would be GREAT. but i got this carb for free, and i dont want to spend large amounts of cash on a bike i only have for the purpose of saving money.

if not for the financial end of things, EFI would be done already. its hands down the BEST.

as for my carb....i hit a MINOR setback today. jets are not the standard keihin style, and people want A LOT of money for them. so........i will need to break out the drills and make my own.

 

well i dont have any pictures today, but i did get it to start and idle for about a full minute before a plug fouled. i went through about 20 pilot jet sizes today.

its still too lean (i think). it will only start with choke or a shot of ether, and once the choke is off it will die out, or if the choke is on it will run and smoke and foul plugs.

the main jet is very very lean as well, once the throttle is cracked more than 5% it dies (no smoke).

i am closer but still very far away.

it is VERY responsive though (with choke on...)

 

Bah, youll have it done in no time

 

Which plugged fouled Zookie

 

Zookie I think you would have better results if you shortened the runners to the ports and placed the carb on the backside of the collector between carbs 2 and 3 (facing towards the seat). I'm thinking that the fuel mix may be destabilizing due to the long length of travel and the upward bend to the collector. Just a hunch, but something to try if nothing else works. :wink:

 

Hi orange-n-black I think that you may be going in the right direction.
zookie says that it runs lean and needs lots of choke to get it going.
Then after a while it blows unburnt fuel out of the exhaust and fouls
the plugs up. I am thinking that some of the atomized fuel is
condensing on the intake pipes. This raw fuel then pools in the bottom
of the long pipe that has the 4 intake pipes coming out of it. This fuel
builds up until it is high enough to get sucked into the cylinders fouling
the plugs and stopping the motor.. This is just a theory. As the fuel droplets come out of the fuel air vapor mix the bike seems to be running lean and need more choke but this may only make things worse with more fuel being sucked into the tubes. The raw fuel pools
and the motor sucks in all this raw fuel and makes it look like it is
then running rich. Putting the carb at the back with shorter and more
direct pipes may be the answer.

It may be that the carb is not working properly. It will be interesting
if an answer is found to the problem.

 

all of them

i will be working on it a little more today 8)

 

Ride around the hood and kill the mosquitos :twisted:

 

Is that a puddle of gas where the kick stand is resting?
Watch out!!! lol

 

You say it is running lean? What color are the plugs when you check them?
Its kinda hard for me to believe that the bike is running lean AND fouling the plugs.
I know this is 3rd grade stuff to most but, Black plugs indicate a RICH settings where as powder gray indicates a LEAN setting.

 

maybe not 3rd grade.....

without the choke, it is lean and will not start/run. no smoke, no wetness, no fouling. maybe a pop here or there, but nothing real promising.

it will fire right up with a shot of ether, but after the ether runs out of the manifold it wont run long maybe 1-3 seconds as it stumbles down and dies. no smoke, wetness, or fouling. also, i can keep it going a little longer by pumping the accellerator pump a little (keeping butterfly closed though) so that tells me it wants more fuel.

it will start with the choke on, and run responsively with the choke on, but its short lived because the plugs foul and are black/wet when i take them out. with choke on it ran for 1 minute at the longest before it started dropping cylinders.

this is why i think its too lean without choke, but obviously overly rich with the choke on.

also for what its worth, i am "preheating" the engine with a kerosene heater, because i want the cold engine factor out of the equation.

after todays tinkerings, i think i may need a different carb. i am thinking this harley specific carb is not designed for a constant vacuum application. i think its emulsion tubes and circuits are designed for a "big rush" rather than a constant slow draw.

i think that, because i have taken the pilot jet from 50-100 (keihin sizes) with no noteworthy change. 100 is not even a real pilot jet size, its just not plausible that 100 would still be too lean, and unable to start the bike without a shot of supplemental fuel via choke, acc. pump, or ether.

also, i think i may go back to the drawing board and rethink the manifold. after a "long" run time the engine will stall out and i get a rush of about 10cc's of fuel running out of the manifold. i think as others have suggested, the overall length of intake charge is too big, and fuel may be falling out of suspension/condensing in the manifold before it gets to the cylinders.

so...............

i have discovered one way to NOT make a single carb conversion. its not game over yet.

 

Bobe, exactly what I was thinking. Zookie, I just put 2 VM34s on mine and it works, I think yours will work too. You'll just have to find the right intake design, good luck.

 

Sometimes the simplest route is best.

 

Hi Orange-N-Black. The VM34 carbs that you fitted what can you tell me
about them. Did you have to rejet or whatever and what air filter have u
put on them. I think that they are on your 700 Max. How does the bike
go with these on.

Bob

 

I hope i a m wrong but do you think on top of the runner length the intake pulses between the 1-2 and 3-4 could be fighting each other just a thought

 

put one BS38 from an XS650 on there or a roundslide from a XR250R or something. I have a XR200 replica carb (read Chinese Mikuni) I'll sell ya cheap.

 

26-30mm roundslide never installed

 

Zookie try using ONE of the original carbs with your manifold before you start making a bunch of changes.

 

Hi Orange-N-Black received your PM thanks for the carb info.

Bob

 

k gentlemen, here is the next attempt at a manifold!
first i cut the 1" runners, taped them to the carbs for alignmen, and welded them to the plenumt:






then i cut the holes into the main plenum:


cut a wedge out of each side and welded the plenum ends to a taper, and capped it:





cut the carb side hole into the plenum:



and before i had to call it a day, i cut this notch which will take away a significant amount of overall intake volume, and it will help keep the intake charge velocities higher from carb to ports. i will be bending a piece of metal to fit in there nicely, but i ran out of time:



i do not think i will be using the harley carb, i havent found one bit of good info or parts availability for it. all the harley guys are throwing them out for S&S or newer stock carb. not even keihin recognizes that they built the darn thing. so i am waiting to hear back from a friend if he has a carb off one of his dirtbikes BUT...... DWCOPPLE send me a PM with a price shipped to 06437

any thoughts on this design?

 

Personally I still think your first design is workable (not optimum) and would like to see you put another carb on it (a known working unit though).

I don't think the first design totally failed, I think the carb did.

 

hI, first I've been running a single carb on different bikes (in-lines and twins) for many years. But I work on efficiency issues related to fuel delivery methods, heterogeneous and stratified charge systems. Now I build my own injector drive modules and incorporate many other values obtained in the system for the computers input. But that's beside your concerns.

Because fuel is heavy and heavier coming out of a jet from a carb, the fuel has difficulty staying in any kind of a suspension state or disassociated state or atomized if you prefer. Thus why I run a turbo. Your idea will work but will need refinement to allow the fuel to sustain suspension or in gaining disassociation throughout the transfer process from the carb through your intake to the intake port. Maintaining a turbulent transfer is critical to better disassociation. Also the Heat will help you immensely. Don't worry about getting the intake to hot, the fuel is along way from auto detonation in your case. The design you have now is decent other than it should be round. Also without compressed air capabilities you'll benefit from a vortex generator you can weld on the input side of your intake. Directionals from the individual ports help. Before, without the turbo and EFI, I used a Mikuni off my Seca 900 to run the Seca 550 quite well, (I eventually made my own carb for my own needs) cold weather was tough till it warmed up. Also I would use heat deflection and capture to the plenum in order to better disassociate the now Homogeneous substance which you then start running richer. Keep a stock jetting. Once you start getting into a heterogeneous state you utilize more internal energy of the fuel and thus running richer. My blog related to my research is vague about a lot of this but it might help some www.energyextraction.blogspot.com Keep working on it. It will work and you'll like the outcome. One more thing. Make sure you have the right diameter for the total volume of air you'll need so that you don't loose top end power due to volumetric restriction.

 

^^^ That is some serious science!

 

you also just made 80% of a bread box filter

 

Hi Zookie. That is an interesting new desighn. The wedge shapes at the ends should keep the mix travelling faster in the area of the 1&4
cylinders. The carb mounted at the back if you have enough room
should also make a big difference. Looking at it all I think that the
half round deflecter infront of the carb intake may be a bit deep. I can
see the idea there and it is a good thought. With a better carb I think
that the whole thing will work better. Work like this is all trial and error
until it is working properly. Having a good properly working carb would
make things go easier. That Harley carb was a very primative type of
carb.

 

Looks promising, will keep watching with interest.

 

compress - i understand what you are saying. i can guarantee a loss in top end power. i have been riding the bike with a slipping clutch since the day i bought it, and it doesnt pose a problem to me because i really never ride the bike "hard". i ride it for the fuel economy. i will never know if it has a loss of power, because i never use all of the power to begin with.

along with the loss of power, there was a concern with how deep i cut the "notch". i agree that it may hinder performance, but i think it will help the bottom-mid or at least not hinder performance through that powerband.

as it was said before, trial and error! i am ok with a loss of power. i want efficiency! if i wanted power, i would have the head ported, efi installed, a real custom header, hi comp pistons, and.........not and XJ. i know some of you guys absolutely love these bikes, and they are great for their day...but this bike isnt my "love" so if i was going to worry about performance i would start by selling it. not trying to hurt anyones feelings, to each their own! ultimately i want to sell this bike and buy a suzuki DRZ 400 set up for the street. i have no need for a 750cc inline rocket.

i just welded the notch closed today. i can't finish it until i have a carb in hand to mate it to. i tried (with my terrible cell phone camera) to get some good pics of the flow path with the notch.





and just for fun i checked my valves today. they are all great.

 

Hi Zookie The set up looks good mounted up on the intakes. I can see
from your newer pics that the notch as seen from the carb side is not as big as it looked in the earlier pics. It looks like it is in the right place
and that it is the right size to do what you want it to do.

Its looking good and I cant wait until you test this new intake mod. There looks to be plenty of room to mount the carb as well.

Bob