canuckxxxx's Single carb manifold build

[mcgovern61]

I tried opening up the throttle quickly a few times while looking down the carb bore. The stumble occurs when the gas from the accelerator pump is spraying in. Seems like a lot of gas spraying in there. I am wondering if there isn't too much gas.

I cannot speak for the single carb setup, but I do know for fact that when my OEM 1100 floats were out of adjustment, I got the same hesitation when I would drop the throttle and I could smell raw gas out the other end. I agree that you may be experiencing the same thing with the accelerator pump putting in too much gas.

 

[joedrum]

since we got rid of dans power valve it has beem all positive dialing his bike in ...I don't have it either just a useless device with no adjustment garbage can is where mines at ...the bike runs so much better without it...I think accelerator pump isn't the cause ...but yes to answer your question webers are so cool you can change accelerator pump jet ... this is a place I havnt been on this carb ... it very possible you might be on something there .... but im still on the air side as being to much and to slow in speed to atomize gas reguardless if its just right rich or lean ... lean acting ...rich is what I finally concluded what was going on.... on my bike

 

[Ansimp]

It does sound like too much fuel from the accelerator pump IMHO, keep up the good work at temperatures below what I keep my beer at ( and I like cold beer) :salute:

 

[dan filipi]

I'd like to hear what it does with accel pump disconnected.
I don't think that's the problem per se, what I do think is happening is poor atomoization exacerbated and fooling us into suspecting too much gas.

What I found is once the gas is being atomized better, the jetting can be leaned, but not acceleration leaning as in disconnecting the accel pump.

 

[dan filipi]

Canuuk, try this....

Run the bike to warm it up real good.
Since it's so cold there, put a blanket on the engine laying over the top of the frame/false tank.
We want to hold the heat in to warm up the plenum and runners.
After 5 minutes, start it up.
How does it run now. I bet better.

 

[canuckxxxx]

dan filipi » Thu Nov 21, 2013 2:37 pm[/url]":100ou6qr]
I'd like to hear what it does with accel pump disconnected.
I don't think that's the problem per se, what I do think is happening is poor atomoization exacerbated and fooling us into suspecting too much gas.

What I found is once the gas is being atomized better, the jetting can be leaned, but not acceleration leaning as in disconnecting the accel pump.

I tried running with accel. Cam removed. It was not better.

I will try closing in the plenum, as you suggested Dan, to get the plenum warm. Besides we have a warming trend going on here now.

The atomizing from the accel. Could be improved also

 

[joedrum]

try shooting that heat gun you have in the top of the carb air intake maybe

 

[Ansimp]

canuckxxxx » Fri Nov 22, 2013 8:41 am[/url]":3pjwpeg4]

dan filipi » Thu Nov 21, 2013 2:37 pm[/url]":3pjwpeg4]
I'd like to hear what it does with accel pump disconnected.
I don't think that's the problem per se, what I do think is happening is poor atomoization exacerbated and fooling us into suspecting too much gas.

What I found is once the gas is being atomized better, the jetting can be leaned, but not acceleration leaning as in disconnecting the accel pump.

I tried running with accel. Cam removed. It was not better.

I will try closing in the plenum, as you suggested Dan, to get the plenum warm. Besides we have a warming trend going on here now.

The atomizing from the accel. Could be improved also

You will need some accelerator pump or it will also stumble ( the reason for an accelerator pump in these carbies) but too much fuel from the accelerator pump will also cause it. If memory serves me correct you reduce the length of the return stroke so that the plunger has less distance to travel and therefore less fuel is pumped.

 

[canuckxxxx]

Ansimp » Thu Nov 21, 2013 4:24 pm[/url]":272d6oj6]

canuckxxxx » Fri Nov 22, 2013 8:41 am[/url]":272d6oj6]

dan filipi » Thu Nov 21, 2013 2:37 pm[/url]":272d6oj6]
I'd like to hear what it does with accel pump disconnected.
I don't think that's the problem per se, what I do think is happening is poor atomoization exacerbated and fooling us into suspecting too much gas.

What I found is once the gas is being atomized better, the jetting can be leaned, but not acceleration leaning as in disconnecting the accel pump.

I tried running with accel. Cam removed. It was not better.

I will try closing in the plenum, as you suggested Dan, to get the plenum warm. Besides we have a warming trend going on here now.

The atomizing from the accel. Could be improved also

You will need some accelerator pump or it will also stumble ( the reason for an accelerator pump in these carbies) but too much fuel from the accelerator pump will also cause it. If memory serves me correct you reduce the length of the return stroke so that the plunger has less distance to travel and therefore less fuel is pumped.

Can you change the stroke length?

 

[Ansimp]

The nut on the spring tension dictates the amount of fuel if I remember right. Make some adjustments and observe the delivery or maybe google some more information.

 

[dan filipi]

Canuuk, try what I said about letting the runners and plenum warm up.
It's important to let the engine warm good so when you shut it off, heat will rise and warm up the plenum.
If it's left running, the plenum will stay cold because it's the evaporation of the fuel which is keeping it cold. Much like a flame torch on high makes the propane bottle get cold, it's the liquid propane vaporizing that's soaking up heat from the bottle and atmosphere.
This evaporation process is important because an engine doesn't run on raw fuel, it runs on the vapors. Raw fuel is what your smelling out the exhaust.

I've studied and worked with refrigeration quite a lot in my life.
Boiling points of different liquids can be lowered by reducing the air pressure.
We reduce air pressure below the throttle plate when it's closed.
Closed, the boiling point of the raw fuel is lowered.
Once the throttle is opened, air pressure increases which means the boiling point should also increase.

In the case here, I think what's happening (and what I've observed on my bike) is since the air pressure is high with little heat to help evaporation, the fuel is in a raw state so without speeding the air flow with a restrictor in the runners to reduce air pressure on the valve side, (lowering it's boiling point) heat must be added to the assembly (plenum) so once the raw fuel/air mix hits it, it vaporizes. Or as much as possible.

 

[canuckxxxx]

joedrum » Thu Nov 21, 2013 4:12 pm[/url]":1elq66rw]
try shooting that heat gun you have in the top of the carb air intake maybe

I've watched too many road runner cartoons to try that, LOL

 

[dan filipi]

Started the bike this morning.

Best I can describe how the heat affects it is like when starting it and during warm up with the stock rack.
Mine wouldn't idle without choke and at a fast idle.
Acceleration would be real sluggish and bogging even with choke until it warmed up a bit.

This is the same way mine runs on the single.
Once the plenum isn't ice cold, it will idle good but acceleration is still a bit sluggish and bogging.
As soon as engine temp get's to beginning of the thick line and my heat pipes are hot, acceleration is real good with no bogging.

 

[backlander]

They make fuel preheaters for diesels like on my dodge, do any of the diesels like VW's use a preheater ? Just throwing this out as a thought.

 

[canuckxxxx]

Well I put the accel. cam back on today and started the bike up and let it warm up completely. I went through the tuning procedure shown here
https://www.carburetion.com/Weber/adjust.htm
I found that the idle mixture screw had to be backed out about 2 1/2 turns for smooth idle. According to them this would mean that I need larger low speed jets. It should only take about 1 to 1 1/2 turns out to get good idle if the jetting is right. But I think I will wait until I have the plenum heated and then test again before I start changing jets.

I also notice, after doing that, that there was less stumble when blipping the throttle than what I had before. This could be because of the idle adjustment I made but could also be due to me taking the accel. cam off and putting it back on again. Spray doesn't seem as much as before but hard to say for sure. I can only go so far with tuning on the driveway. I really need to do some road testing now but weather will not permit that for a while.

The next logical step would be to work on getting heat to the plenum. So I will turn my attention to that now.

This is probably a topic for another thread.
My ultimate plan is to build the manifold using 1 1/4" grab rail which puts the plenum right on top of the coolant lines on the top of the engine. In fact I need 1/4" thick spacers under the runner flanges in order to raise the plenum up enough to clear the plumbing. I am thinking that I might be able to make a mold of a shape that would fit closely over the coolant lines and the underside of the plenum and then cast it out of aluminum. Maybe I can put a big blob of modeling clay on top of the engine and then squash the manifold/plenum down to get the shape. So that heat can be conducted right to the plenum bottom.

Do any of you guys have experience with casting aluminum?

Brian

 

[dan filipi]

No experience casting but that's an excellent idea to get heat. Lots of heat right there.

 

[joedrum]

well I see tour making some good moves brian im pretty caonfident now you will make it ...its not what I say or anyone else its what you will do for yourself ..your learning the carb ...great work

 

[canuckxxxx]

We have an unexpected break in the weather here yesterday and today. Temperature right now is 7C and the roads are clear enough of snow and ice that I took the old beast for about 10 km spin.

Overall I am very pleased with the way it ran. Still a little hesitation but I could almost live with it the way it is right now. The big bog/stumble occurs only when I am taking off from a stop. If I give it a bit too much throttle or let out the clutch to fast it will fall on it's face (not stall but just kind of sit there and gurgle) in which case I pull in the clutch and ease the throttle on and ease the clutch out. Any other time when I am rolling along I might get a bit of hesitation when speeding up and then a nice surge of power. It seems to have a bit more low end torque when cruising along in 5th gear at only about 3k RPMs; it will power away quite nicely when I try to speed up.

When I got home I checked the temp of the plenum with my calibrated hand: it didn't seem quite as ice cold as the other times. The other thing I was impressed with is how hot the top of the engine and the coolant plumbing is when the bike if thoroughly warmed up. You could burn yourself on the coolant lines and you cannot keep you hand on the top of the engine block. Lots of heat here and only about 2" away from the bottom of the plenum. A properly shaped lump of aluminum to bridge that gap might keep that plenum nice and warm. I was going to save that move for the grab bar build but now I am thinking I will do it with this setup and if it makes the bike run flawlessly then I don't need the grab bar build.

Anyways, I have been doing all this testing with no air cleaner so will work on that plus buy some modeling clay and try and form a shape for top of engine-to-bottom-of-plenum to eventually cast in aluminum.

I am very encouraged and more committed now. Keep you all posted

Brian

 

[dan filipi]

Good progress!
Sure is nice when it all starts coming together.

I really like your idea of blocking in to get heat from the engine.
Helps avoid all the extra plumbing and chances for coolant leaks.

 

[joedrum]

just great brian