High Idle and Jetting Questions at Altitude

[JAXMagna]

Hi, I'm new to the forum and live in the Denver area.  But I wanted to post here because it seems like there's a lot of knowledge about the Magna on this board.

I have two main questions:

1) My Magna seems to idle too high (1800 - 2000) and wanted to know if there were certain things I should look for when trying to resolve this?

2) I was curious if anyone could "guess" at what the jetting should be for 6,000 ft, stock airbox, currently stock jets, and Jardine drag pipes?

Ok, so now some info - This is a 94 Magna I recently bought from a friend in the DFW area.  The engine seems to be completely stock, including #40 slow jet and #102 main jet, except for the Jardine drag pipes.  It had been sitting up for about a year and a half when I picked it up recently and brought it back to CO (I live just under 6k ft above sea level).  It was not running at the time.

I pulled the carbs and gave them a thorough cleaning and the bike seems to run well.  Although I'm thinking it's running a little lean from the looks of the plugs and the popping on decel.  But, hey it's running now   Even if I back the throttle stop screw completely out the engine still idles at close to 2k rpm (once the engine is good and warm).  The throttle cabes do not seem to be tight enough to cause this either... although I will double check next time I'm working on it.  I have the pilot/fuel screws turned out exactly 2 turns (I did this because of the altitude).  Should I maybe turn them out to 3+ turns?  Is there anything else that might cause it to idle so high?? Oh, and I have not yet synched the carbs up... but I plan to shortly.  It's 1.8 degrees F out right now so I'll probably wait for a warmer day     

The other thing I'm curious about is the jetting at this altitude with the Jardine pipes.  Is the popping on decel a true indication of it running lean?  The bike has #102 main jets and I'm assuming the rest of the carbs are bone stock too.  I have a set of #105 jets and a set of needle shims as well.  But I had thought those might be too rich for 6K+ feet even with the Jardines.  Was I wrong?  Any thoughts on that??

Any thoughts, comments, or suggestions would be appreciated.  Thanks in advance!!

J

[Greg Cothern]

Welcome to the forum...

I will take a stab at a guess for your altitude adjustments.
I would install a shim on the carb needle and set the pilot at 2 1/4 turns out and go from there.  A little decel pop is actually correct, but just a hint of decel pop.  Not a pop pop pop pop etc.

Obviously you are in a different situation with less air so smaller adjustments are needed to get your correct.  You could I guess go with the 105's and a shim and if its too rich add a K&N...  But I am going to guess and say the 105's are not going to be needed.  A shim is about a half a jet size, and with pilot jet adjustments I think we can get you to the right settings. 

Try the shims and bump up the pilots and go from there, if it still has moderate decel pop open the pilots to 3 turns out and see what the results are from there.

[roboto65]

On the Idle there is a little knob on the left side of the bike under the choke knob turn it one way or the other and that should do ya should be a 1000 rpm + -100!!!  Welcome to the club!!

[JAXMagna]

Thanks guys... I'll play around with that when I can work without freezing my hands off

[MarylandMagnav45]

Thanks guys... I'll play around with that when I can work without freezing my hands off

As Roboto65 said, get on the left side of your bike.  Lean down and look under/behind where the carbs rest, you should see your idle screw. 

Whoever owned the bike before you either wanted his bike to be louder or thought that turning up the idle will keep the bike running if it had trouble starting (in the cold, etc..)

[JAXMagna]

No disrespect to MarylandMagnav45 or roboto56 but the "knob" or "idle screw" on the left side of the bike you guys are talking about is just a device to adjust the throttle stop screw which in turn typically "adjusts" the idle.  The issue I'm having is if that screw (or knob) is back out completely, or even removed, the bike will still idle at close to 2K rpm.  It would be nice if it were as simple as adjusting the idle speed knob thing-a-ma-jiggy.

I'm hoping, that once it warms up, I can play with the fuel/pilot screws to help resolve this.  Currently they are backed out only 2 turns (for high altitude) but it my be running lean which can cause a higher idle (sometimes  ).  I'll try Greg's suggestions and let you know how it turns out though 

Thanks again for the comments!

[Slydynbye]

Sounds like the Carbs might be wildly out of synch with one carb holding the others open.

[roboto65]

None taken Ok did you take the carbs apart or did you leave them as a set most likely when you cleaned them you got something out of whack also . Where you are altitude and with the pipes you have you sure need to be putting more air in the system..
When I did shims and stuff on mine the idle raised up on me but could be adjusted down with the screw. Now if you took them apart well the balance screws are out for sure had that happen also had to pull the carbs and bench sync them and that we be close enough !!!

[TLRam1]

I concur this is not your pilot screw adjustments.

Is your throttle returning all the way down/back? Hard to think all your carbs are running lean for this condition to occur.

Your setup will not cause an issue at idle. I was up there last Aug. in altitudes from 5-12,000K with no issues regarding high idle, stayed in Buena Vista, CO. IIRC I had V&H pipes, everything else stock.

I think you will find it's something else. You may have to reclean your carbs, if you do blow carb cleaner through all the holes and orifices along with compressed air. First I would check all my linkages for binding (you have a push pull system) , insure the air filter is properly seated air tight, no leaks.

Carbs should not be out of sync enough unless they were removed from the mount frame or someone messed around in an attempt to sync.

[MarylandMagnav45]

Another possibility.... (two of them)

Is your throttle cable too tight?

Are your carbs loose?  If they are not fitted tight and snug, they'll suck in air and raise your IDLE. 

[JAXMagna]

Hmmm... the plot thickens...

Wow, great thoughts all!  I really appreciate the suggestions.  I hate the thought of pulling the carbs off again and going through them    I took them off once, took them apart, cleaned them with carb cleaner, blew them out with compressed air, and it was quite a chore pulling them off and putting them back in 

I will make sure I check:

• carb sync
• air leaks around the air box/filter and carb clamps
• throttle cables for tightness or bindings
• turning out the pilot screws

If none of that helps at all I'll just pull those puppies back off and go through them again.  Then recheck everthying... again :p

Oh, and Terry, is your jetting and carbs all stock as well??  Buena Vista, CO is about the altitude that I'm hoping to tune for. 

Thanks again all!

[TLRam1]

Oh, and Terry, is your jetting and carbs all stock as well??  Buena Vista, CO is about the altitude that I'm hoping to tune for. 

Thanks again all!

IIRC they were all stock. I tried to locate the post when my carbs were jetted but couldn't. When I did jet my pilot screws were out apprx. 1 3/4 turns took them to 2 3/4. As you made mention of higher altitude will cause a normal motor to run rich.

If I had rejetted, I would have been at 105 mains, 2 total shims, 2 3/4 turns out on the pilots, K&N filter, V & Hines pipes. And I could have rejetted before the trip.

With pipes added, stock jetting I think you would have no issues with idle according to Allen's crystal ball. I was hampered with a slow bike while trying to pass someone.   

[L J VFR]

I have a question to ask... What is the stock setting of the 3rd gen pilot screws?  Is it 1-3/4 out from a light seat like you said Terry?  I don't remember.

[JAXMagna]

Quick update...  GOOD NEWS!   

The problem seemed to be the carbs were WAY (I mean like crazy WAY) out of sync for some reason.  No air leaks, no throttle cable tension or binding, but I did turn the pilots out just a tad more (2 1/2 total).

Purrs like a kitten and runs like a beast now... and idles perfectly.  Thanks all!!  Gotta go clean up now :p

[TLRam1]

Always nice to hear what the ailment was and you have it running well, did you bench sync or do you have a sync gauge?