the PVC manifold didn't go so well so now I'm making one from copper plumbing parts

[dan filipi]

Question, is the mikuni flange a solid block of rubber or something else?

 

[chuck c]

The only things worrying me now are I don;t like how much the Mikuni parts are stretched to go over the elbows. I am afraid of them popping out. I wish they were a closer fit but I don't have the means to improve them. A straight coupler is easier to turn down a bit so I might go back to using them. The carb flange doesn't give me anywhere to attach the cable so I'm considering ditching it and making one that does from pvc. That would cost me the sweet ability to take the carb on and off with just a hose clamp and not fight to get the nuts on and off the carb studs in the tight space. The solution is a custom pvc mount that is attached to the manifold with a hose clamp. Gonna have to noodle on that one.

 

[canuckxxxx]

dan filipi » Tue Nov 04, 2014 7:41 am[/url]":1f2d50pm]
Question, is the mikuni flange a solid block of rubber or something else?

Mikuni flange is rubber with an imbedded steel plate for flange.

 

[chuck c]

dan filipi » Tue Nov 04, 2014 10:41 am[/url]":l9tg9qyn]
Question, is the mikuni flange a solid block of rubber or something else?

They seem to be typical of all motorcycle carb mount/intake boots. Rubber molded around a metal flange. The junkyard one I have is aluminum inside but some are might be steel. The flange is rigid and the boot is flexible.

The darned Solex method of mounting works great on a VW but it's less than ideal on a Goldwing!

 

[chuck c]

I'm already toying with the next design. I was thinking about the lack of a plenum and no reserve of mix ready to go on a quick demand. So if I used a large diameter tube in the center and branched straight 1" runners from it, it would hold that reserve. That design has been done but I can't imagine it having smooth, equal flow. How could I solve that? Like this:

The runners and tube from the carb are tangent to the ID of the 3" tube. This will should might cause the mix to spin in that plenum, helping it mix and it's still able to make a smooth direction change into the runners. In that cross section the mix will be spinning clockwise. The smaller tube in the middle is to keep the mix against the wall and discourage it from taking a shorter path. What do you think? They have clear PVC in some sizes. I could get some and hook up a shop vac to a runner to see if it will do what I think.

I ran some numbers. Each cylinder is 275cc and these runners have a volume just about half that. The 3" plenum will hold about 500-600cc.

It also hit me that leaves a lot of unburned but very ready to ignite mix in the manifold when the engine is turned off. Not sure I like that. But the Solex is perfect because the anti-diesling fuel shut off can be tied to the ignition and shut of when it does. The engine would purge itself of remaining mix as it coasted to a stop.

 

[canuckxxxx]

Chuck, I don't think you want to go too big with the plenum. The air/fuel will slow and gasoline will fall out of suspension. :nea:

I came across these rules of thumb for designing an intake system that came from a VW site. This was talked about on this site early on and some people will remember it. :read:

Brian

rules of thumb for runner size etc

• canuckxxxx
• Nov 5, 2014

 

[slabghost]

Capacity of the plenum should be about equal to the motor size. 1000 - 1200cc. Depending on the design plenum can be part of other sections like the 2-1 adapter.

 

[chuck c]

Given those guidelines I'm right in the ballpark. Rerunning the numbers the 1.25" runners are about 211cc and the 3" ID plenum with 1.45" OD tube down the center is 1170cc. Now, that big pressure drop from the carb into the plenum has a real danger of causing fuel to condense out but the swirling should fight that. I think I would add a small clear blister on the bottom so I could see liquid gas collect if that was happening and how much. If it did and I couldn't eliminate it I would consider the design a failure.

If you're bored do a search on YouTube of guys using nothing more than a gas can or bucket instead of a carburetor just by having the air flow over a good size surface area of liquid gas. If it's warm enough gas vaporizes enough on its own. There are small engines and large pickups running this way. It's not very practical but I bet it could be a great way to run a generator that runs a fairly constant RPM. It's a bit dangerous because it's ready to burn all the way from the can/bucket/whatever to the engine's intake and most guys do this experiment using plastic flex hose with sketchy connectors. One spark and you're gonna have a really bad day.

My point is a little liquid gas in the plenum is no big deal as long as it stays there and doesn't go to the cylinders. It will vaporize again with good airflow.

 

[canuckxxxx]

According to the guide the plenum should be about 1.5 to 2 time one cylinder volume. So for GL1100 one cylinder is 275cc so plenum of 400cc to 550cc is suggested.

Also, volume of runner should be 1 cylinder volume or 275cc.

Brian

 

[joedrum]

hmmm ...in this math ..witch i dont put much value to ..things look bleak for manifolds setups ...there is so much more in the equation ..thats totally left out ... the speed of flow and rpm capability of motor in question and cam differences in operation....so i wouldnt put to much into this ...its flat out outcome that is the most crucial thing ... not math except for a some what guild line....

 

[canuckxxxx]

I agree Joe. We can see from the wide range of designs that work well that it is, at best, a very rough guide. And at worse it's misleading. I just posted it because it came up in a previous single carb build.

Brian

 

[joedrum]

well brian you like me and others have taken this to point ...where things like this make since to us now ... we have outcomes that go well past math ... but it is all good ...info good and bad ...is well look at here .... kudos to all

 

[dan filipi]

The only math I did building mine was the valve head is very close to 1" diameter......good enough for me.....build it :smilie_happy:

 

[Ansimp]

dan filipi » Fri Nov 07, 2014 1:58 am[/url]":3t9318o4]
The only math I did building mine was the valve head is very close to 1" diameter......good enough for me.....build it :smilie_happy:

I like your logic Dan and it works! :good:

 

[slabghost]

1200cc = 73.228 cubic inches. 3"x4"x6" = 72 cubic inches. Seems the type 4 plenum is very close to this.

 

[joedrum]

yah what he said.... :thank_you:

 

[chuck c]

slabghost » Thu Nov 06, 2014 6:04 pm[/url]":ew38elao]
1200cc = 73.228 cubic inches. 3"x4"x6" = 72 cubic inches. Seems the type 4 plenum is very close to this.

That's probably why everyone that's tried it is happy with it.

 

[chuck c]

Designing machines and stuff is what I do and I like tinkering with ideas. I'm enjoying the challenge of making the easiest possible DIY manifold. The next one will be for performance.

 

[joedrum]

yes ...well that just isnt the case chuck c......for yrs and yrs i whatch other rip apart manifolds put on heat and did all kinds of things ... and there singles never perform good and a bunch were type4 setups ...and the claim that singles could never run as good as stock was just excepted .....

truth is stock running is at a very low level in my opinion and easy to beat....no one for what ever reason got there carb right ...the carb all along for years was the problem ...the one guru who talk big words constantly and turned manifold building into brain surgery ...could not dial in a carb ...and lashed out at anyone who tried in big words ...what a joke....just like on a stock set up ..if the carb are not right they aint going to work even at a low level of exceptance....

ITS THE CARB THAT HAS TO BE GIVIN THE MOST CONCERN ...IF IT DONT WORK CARB IS NUMBER SUSPECT ...ok im done :hihihi:

 

[chuck c]

Once I actually have tubes connecting the carb with the engine I will be able to work on the carb. That will be the next logical step. I would appreciate any info anyone has on setting the Solex for the Wing. Someone must have done it. I think it will need smaller jetting as the carb for a 1600cc engine probably feeds too much fuel for an 1100.