Magna Owners Of Texas
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Author Topic: Vacuum leak?  (Read 3161 times)
Greg Cothern
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« Reply #15 on: May 31, 2008, 05:01:43 PM »

Well if ya got wet plugs and with the symptoms you describe I say its too rich.  One way to tell if you have an air/vacuum leak is to fire it up then spray carb cleaner or such around the intake boots etc.  If engine speeds up when you spray it has a leak.
Oh you dont have to pull the carbs to do the shims, the rears can be reached fairly easy and the front if you unbolt the radiator and have a shorty #2 phillips screwdriver can reach them while gently pushing the radiator out of the way.
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Greg Cothern
00 Valkyrie Interstate
96 Magna 
Previously owned:
87 Super
96 Magna project bike
95 Magna
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Magnatic
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More kids = less toys (for me).


« Reply #16 on: May 31, 2008, 05:14:51 PM »

I did spray around the carb boots as well as the airbox looking for leaks, but found
none. Thanks for the tip on changing out shims without carb removal. I will try it.
It seems I have lots of experimenting left to do, but I'll get it right one of these tries.

It just occured to me why the rear two cylinders had very wet plugs, because of the small amount of gas spilled when taking off the gas tank Confused. The front two smelled
of gas and were only slightly damp. I still think I'm running rich. I'm going to go back to the original one shim and start there.
« Last Edit: May 31, 2008, 06:58:49 PM by Magnatic » Logged

1996 Magna (finally one that runs)
1991 Vmax (wicked)
1981 CM400t (doesn't run)
1973 CB750  (doesn't run)
1979 Husqvarna 390 automatic (doesn't run)
Chad in Michigan
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« Reply #17 on: May 31, 2008, 07:16:11 PM »

Dave told me the same thing when I had those issues. I have a '95 running k&n air filter, vance & hines, Dyna 3k Ignition module. I installed the 105 jets and one extra shim and ran with the stock filter for awhile. it was pretty good, definately better than origional setup. i added the k&n and then the trouble started. the k&n/vance &hines allows it to flow better, thus leaner. as soon as i put the old filter in, the midrange stumble got better.
i played around with various setups, and finially found a combo that works great for me. i have tried 105,108,110 and finally 112 jets. i upped the pilot two sizes from stock 40 to 42, then to 45. and i am using 3 shims on each needle, and the d screws are at 3 turns out, but it's just a tad rich at idle, i need to back them down to 2.5 or 2.75 turns out.  if you need part numbers (acutal kehin/honda parts) letme know and i'll shoot them back to ya. One thing to check before you get crazy into this is to make sure you took out the two rubber o-rings on either side of the air filter box. if these are still in while putting the k&n back, there will be an air leak as the lid would not seal properly to the bottom half. hope this helps. -chad



I'm still trying to get my 96 magna sorted out, and I'm stuck again. I installed Dave Dodge's jet/shim kit along with Vance&Hines pipes and K&N filter. Before
this, the bike ran OK except for the usual stumble around 4k that most stock bikes seem to have. Now, under throttle, the bike goes great, but at light throttle it runs rough and pops both decel and accel. I called Dave Dodge and he said it's a vacuum leak somewhere. I removed and reinstalled carbs making sure everything was tight, and still have the same issue.
 
Could a small air leak in the airbox cause this much rough running?  Also, there
is one hose near the hose that connects to the back of the airbox that is not
connected to anything. It comes off one of the tubes that runs between the carbs. I can't find anywhere that it could go. Maybe just some kind of breather hose?

Any ideas of probable vacuum leak areas would be appreciated. Thanks.
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Chad Schloss

Perry, Michigan
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« Reply #18 on: May 31, 2008, 07:44:58 PM »

Ok so I learned something new Orings you say Hmmmmmmmmm and thought the pilot jets could go up so thats a good thing. Thanks Chad Post the part numbers here or on the other carb post  Very Happy Very Happy
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Allen Rugg 
76 Jeep CJ

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Chad in Michigan
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« Reply #19 on: May 31, 2008, 08:04:55 PM »

JETS:
 
112 Main:
Mfg Product Number: 99101-GHB-1120
Description: JET (#112)           for  Honda
Order Quantity: 4
Unit Price: $4.83
Total Cost: $19.32
 
110 Main:
99101-GHB-1110
 
45 Slow Jet:
PRODUCT INFORMATION:
Part Number: 99103-MT2-0450
Description: JET (#45)            for  Honda
Order Quantity: 4
Shipped Quantity: 4
Unit Price: $7.53
Total Cost: $30.12
 
42 Slow Jet: 99103-MT2-0420
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Chad Schloss

Perry, Michigan
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More kids = less toys (for me).


« Reply #20 on: June 01, 2008, 07:27:51 AM »

Thanks for that Chad, great information. It doesn't seem that I could possibly be
running rich going from your experience. I did remove the airbox o-rings, as a matter
of fact I duct taped the seam to be sure! What is your gas mileage with that set-up?
Thanks//Matt
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1996 Magna (finally one that runs)
1991 Vmax (wicked)
1981 CM400t (doesn't run)
1973 CB750  (doesn't run)
1979 Husqvarna 390 automatic (doesn't run)
Chad in Michigan
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3rd Gear Contributor
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Posts: 520



« Reply #21 on: June 01, 2008, 07:30:48 AM »


Check out this thread, it details what I did step-by-step.
I still get between 34-42 MPG depending how I ride. I tend to be on the heavy side Smile the plugs looks just as they should. (finally) they were too white for my taste.

http://forums.delphiforums.com/MagnaRider/messages?msg=14706.1

Thanks for that Chad, great information. It doesn't seem that I could possibly be
running rich going from your experience. I did remove the airbox o-rings, as a matter
of fact I duct taped the seam to be sure! What is your gas mileage with that set-up?
Thanks//Matt
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Chad Schloss

Perry, Michigan
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