I was re-adjusting my Idle jets to 2-3/4 turns out based on recommendations from you folks. I have a lot of stumble on the low end and almost always have to choke the bike at start up.
1) I am unable to adjust the right rear carb - Not enough leverage / finger space
(I will be re-jetting sometime soon and will re-adjust then. I know it's best to do them all the same, but I just can't get it until I take the whole carb unit out, and I'm not doing that until I re-jet.
2) I noticed all of my carb boot clamps are loose on the rubber tubes, but they have spacers and are all turned as far down as they will go.. So, have the rubber tubes shrunken or were they always loose, and should I be concerned?? I know loose tube clamps is a problem on my wife's V-Twin Sabre, but I have not heard anyone talk about this on a Gen-3 Magna.. Any concern here??
Thanx
The rubber boots can create vacuum leaks when they get old.
So what made you decide to adjust the idle jets (pilot jets)? Was there symptoms that resulted in your adjustments?
Just curious, and remind me again of your setup? K&N? Exhuast? etc...
Quote from: Greg Cothern on September 29, 2009, 02:41:52 PM
The rubber boots can create vacuum leaks when they get old.
So what made you decide to adjust the idle jets (pilot jets)? Was there symptoms that resulted in your adjustments?
Just curious, and remind me again of your setup? K&N? Exhuast? etc...
K&N - one hole drilled in the back of each exhaust stack
The bike has always needed choke to start/run at start up and has a bad low end stumble. Nothing new, but want to improve it.. Suggestion was 42/105 for jets - The bike is still on the lift waiting to get put back together presently.. I'll let you all know if there is any difference when I get it down and run it.
Where is the low end burble? Is it right off idle? You might, even though you ride it quite a it, need to clean the idle jets.
Now with that said, I would probably not go with the 42 jets, but would go the course on the rest of your plan for your setup.
I think the stock mufflers even with a hole drilled, will not handle fully handle the 42 jets. I would SERIOUSLY like to see the air/fuel #'s from a set of stock pipes at idle with the stock 40 jets. I bet ya a coke that they are going to be VERY close to perfect.
Now if you change to aftermarket mufflers with the K&N then YES I am a strong believer that the 42, 105's, and K&N will fit most applications...
Quote from: Greg Cothern on September 29, 2009, 05:37:42 PM
Where is the low end burble? Is it right off idle? You might, even though you ride it quite a it, need to clean the idle jets.
It's from right off idle through about 4K, on again - off again - on again - off again hesitation, things really light up above 6.4K
I believe that 105's, and extra shim, and adjusting your pilots to 2 7/8's maybe even 3 turns out will be a good place for your setup.
Quote from: Greg Cothern on September 29, 2009, 05:56:28 PM
I believe that 105's, and extra shim, and adjusting your pilots to 2 7/8's maybe even 3 turns out will be a good place for your setup.
I forgot to mention that I already have an extra shim.. This made no difference in the stumble..
Might have some sort of air leak. Fire it up raise your idle adjustment so it idle's steady over say 1200 rpms. Spray at the carb boots etc with ether or carb cleaner etc, something that if you have a leak it will cause the engine to speed up.
IF no changes then you dont have a leak.
I've adjusted the 3 cylinders per your recommendation - the right rear cylinder I turned out about another 1/4 turn, but do not know where it was to start with..
I took the bike for a ride.. The low end stumble is pretty much gone.. I still get a little stumble around 4500 - 5000 (This is not a idle jet thing). Since I already added a shim, would 105's take this out, or should I stay where I'm at at stock mains??
(not related todays changes) The bike runs the same as it ever did, so I do not believe there is a leak, and the boot clamps closest to the carbs are tight, it's the ones near the cylinders that are not tight, but the boots seem to be sufficiently sealed..
Thanx Greg for your help as always..
Yeah the 105's should help, as the midrange is created with the idle jet, needle, and mains working together to meter the midrange.
Next month I plan to dyno tune my bike in my dyno operators class. I currently have stock pipes with two 7/16 holes in the rear plates, a K&N filter, the stock 40 slow jets, 105 main jets, two extra shims on the needles (3 total), and have the A/F screws at 2-3/4 turns out. I'll plan to check/adjust the valve lash, put in new plugs, and sync the carbs before running my base line. I'll keep you informed on what jetting/adjustments I end up with to get optimum performance.
We have a dyno shootout this weekend and I'm trying to get Chad to bring his bike out, but the weather does not look promising. Don't know if they'll let me run mine since the chain guard broke off a couple weeks ago. Last year I got 78.0 HP and 46.3 ft-lbs of torque with this set-up without any modifications to the pipes.
Quote from: BA on September 29, 2009, 10:39:11 PM
Don't know if they'll let me run mine since the chain guard broke off a couple weeks ago.
You mean the plastic "extra heavy duty" one. :-P
Actually I was using Dobies aluminum one and the front tab broke off the swingarm. It looks like it was a cold weld, so it couldn't take the extra mass. I'm going to reweld it back on, just haven't had time to bring it into the maching shop at work.
The one plus to having adjusted my idle jets is the bike idles much better now than before.
The engine used to lope some at idle, but now runs much smoother and more even across the cylinders.