Intake leak

[neuryder]

Greetings all. I finally scratched a 30yr old itch and now own my first bike, a 97 Magna with 6700 orig miles. Its been stored a very long time and seldome riden. Having spent several hours cleaning and polishing, draining and replenishing fluids, gas, oil, coolant, etc. the bike runs great. My issue is a moderate to severe backfiring and sputtering on Cyl's no. 3&4. I had a local Honda tech give it a listen and he immediately suggested an additive to clean up the fuel system. I am nearly 3/4's way through the bottle and allthough it has made big improvements, Cyl's 1,2 & 3 run/sound great, Cyl no. 4 still sputters and barks most of the time except under positive throttle. Thinking there might be other forces at play, I did a lil inspection and noticed a distinct difference in the looks of the base of the carbs where they mount to the cylinder head. No's 1-3 look like new, No. 4, discolored and contaminated. I'm "assuming" this is a pretty good indication that I have a intake leak and wonder if this is something that can be repaired or do I need to have the replacement parts (boots) before tearing things down to that level? By the way, this site has been a huge help to me in getting to know the bike better and my greatest appreciation to all those involved with it.

[TLRam1]

I am guessing the discoloration could be from fuel from the carbs over flowing. I don't know which cylinder you are calling #4 but if it's one on the left side fuel might be it.

You can continue to run cleaner through the system which may or may not help. Possibly have to pull the carbs for a cleaning. If it were me I would do that anyway.

If you are not up to doing that depending where you are located someone might be willing to help. Where are you located?

[neuryder]

 I only call it no. 4 cuz thats the number labelled on the plug wire, Its the forward cyl. on the right side. The discoloration appears to be limited to the base of the carb. A mechanic at work tried something with a dollar bill. He pressed it to the edge of the exhaust pipe and let it lay across the exhaust port. We watched as the bill was showing signs of being drawn back against the open exhaust port and then puffed away in a pretty rapid succession with the obvious sputters. I'll try uploading a pic of the carbs, sorry, its not a very big place to fit a camara. the "clean" carb is what 3 of the 4 look like.

Mike

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[neuryder]

By the way, I'm located way up north here in good ol "slower, lower" Delaware and I appreciatte the offer.

[roboto65]

Number four is on the left side where the kickstand is if I am thinking right this morning have you looked at the airbox to see if any oil is coming from there and runing down to the carb. If this is the case this is normal just some blow by when riding and it settles on the left side when you put it on the kickstand to that side. If not well the Magna is a little fickle about sitting for any length of time and the slow speed jets will clog and cause this rough running try some Seafoam see if that helps...

[Chad in Michigan]

#4 is the front right, as he stated. (where the vacuum hose comes off that cylendar to the fuel shutoff diaphram)

#1 is rear left (sitting on the bike)

#2 is Front Left

#3 is Rear Right

#4 is Front right

[Chad in Michigan]

Have you tried adjusting the 'd' screw on that side? it looks rusty in your picture. if it is adjusted in too far, it will pop/backfire on decel pretty bad. there is also an o-ring underneath there along with a washer and a spring. maybe the o-ring is torn letting air enter? that 'd' screw is an idle mixture adjust screw.

[hootmon]

IF I rememeber correctly, to properly adjust these, you are supposed to SLOWLY turn these in (one carb at a time) until the idle increases. Then turn out 1/4 turn..
Anyone want to confirm /  tell me I don't know what I'm talking about!!!
It's OK... I can take it...

[neuryder]

Its awesome to get some great advice, thanks all! "d" screw? is that what that rusty thing is?, no, I have tried anything like that yet. Call me dumb but is there a tach and dwell device available for bikes, I used to have one back in my 4 wheel motorhazard days. Anyway, Thanks again! I'll let you know if things improve. BTW, the addittive I've been using is called "Star-Tron", works pretty good.

[hootmon]

is there a tach and dwell device available for bikes,

A dwell meter is used when Points are used in an ignition system. The Magna has an electronic ignition and no points, so a dwell meter would not be useful. There is a method covered in the Magna Service manual to check the timing that is being produced by the electronic Ignition (CDI) with a timing light.

[Greg Cothern]

IF it sat for awhile then the idle jet is partially clogged, you can continue to run fuel additives such as Seafoam and enjoy the ride method of cleaning..
OR pull the carbs and clean the jets.

Chad is correct #1 is left rear as you sit on the bike, with #3 right rear.

[neuryder]

Thanks again for the advice and information! I'll continue with the addittive and put off an attempt at working on the carbs till this winter if things don't improve, I tried that once with a Holley dual pumper four barrel, it wasn't pretty... Have a great weekend!