Author Topic: Please help a newbie regarding a weird sound (Read 3074 times)

FLo · « **on:** February 16, 2009, 02:36:22 PM »

I was hoping for some input or advice from anyone kind enough to respond. I'm a newbie rider, bought a 78 cb550k last year to learn how to ride. Took it out of storage (carbs drained, stabilizer in tank) yesterday and this is what happened...

-after a few kicks, got her to start.
-everything sounded good, except I noticed when I was warming her up, the rpms while idling dipped intermittently for a quick second at a time.
-excited from a long winter, I took her for a ride and everything was good. Except it was freezing as hell. Returned home after 10 minutes with no problems.

-today, fired her up for a longer ride. Noticed the same dipping of rpm during warm up period. After about 15 minutes, the engine took on a weird deeper sound. A severe lack of pull was experienced and after a couple minutes she stalled. Managed to start her up again, and rode all the way home with the whimpy bass sound, and huge lack of power. Once in a while I'll get a sudden jolt of power, only to return to very slow acceleration/speed.

I have a feeling that this might be carbs, but being a newbie, I don't really know. I'm planning to take it to a mechanic, but I'd rather take it with more knowledge and insight. Also, I put on a mac 4-1 exhaust last summer and rode it 3 months with no problems.

Thanks in advance for you help

Jonesy · « **Reply #1 on:** February 16, 2009, 02:42:13 PM »

Sounds like one, possibly 2 cylinders are dropping out. I notice the same thing when I'm running low on fuel and have to switch to reserve- you twist the throttle and get more throaty bass instead of power. Once all 4 carbs have fuel again, the power comes back.

Can you check if the carbs are all getting fuel? There could be a blockage in the fuel system somewhere, slowing down the flow. Maybe the gas cap vent could be blocked as well.

Also, are you still running points, or do you have an electronic ignition? One set of cylinders might be intermittently firing and then quitting. On a 4-pipe set up you'd hear loud popping as the fuel vapor that has built up lights off, but on a 4-into-1 system it gets burned off by the other cylinders..

heffay · « **Reply #2 on:** February 16, 2009, 02:43:59 PM »

change the plugs and add a motorcycle amount of fuel additive carb cleaner.
here comes the fun part...

run the crap out of it.

if it only sat over winter... its usually not as bad as it seems.

Gordon · « **Reply #3 on:** February 16, 2009, 02:50:36 PM »

Kind of sounds electrical/ignition related to me. Fouling plugs, leaky plug wires, or a bad connection between the plug wire and plug cap can cause those symptoms, as can a bad condenser or bad points.

FLo · « **Reply #4 on:** February 16, 2009, 02:55:27 PM »

Wow! 3 replies in 5 minutes. This forum is truly a valuable resource!

Thanks guys, I think I'll try changing the plugs and carb cleaner first.
I don't know anything about points, but the previous owner installed Dyna 3-ohm coils.

Gordon · « **Reply #5 on:** February 16, 2009, 03:01:46 PM »

When changing the plugs, unscrew the plug caps from the wires and check the condition of the end of the wire inside the sheath. Over time the wires degrade and sort of shrink back inside the insulation. If that's the case with yours, snip off about 1/4" from each one and reattach.

Do you know if the P.O. installed a Dyna-S ignition plate, too? If you don't know, just remove the points cover on the lower right side of the engine. It's the small-ish, round, chrome dish held on with two large screws.

heffay · « **Reply #6 on:** February 16, 2009, 03:01:50 PM »

2 came from w/in riding distance of each other!!!

mystic_1 · « **Reply #7 on:** February 16, 2009, 03:44:08 PM »

I had the same thought as Jonsey, did you verify that you have gas? Have you tried running it on reserve?

mystic_1

FLo · « **Reply #8 on:** February 16, 2009, 03:57:07 PM »

Quote from: mystic_1 on February 16, 2009, 03:44:08 PM

I had the same thought as Jonsey, did you verify that you have gas? Have you tried running it on reserve?

mystic_1

Yes and yes. Same ugly sound.

mystic_1 · « **Reply #9 on:** February 16, 2009, 04:06:16 PM »

Good, and good. Just checking.

Pulling the plugs and having a look will certain tell you more about what's going on. Post pics of the plugs if you can, remember to mark which one came from which cylinder.

The three necessities for combustion are fuel, compression, and spark. Fuel and spark are the only ones likely to be intermittent like you describe, and the plugs are the quickest to check.

One thing to check is the temperature of the exhaust pipes where they come out of the head. If you have one or more cylinders that are not firing, the pipe will be noticeably cooler than the others. Careful when checking, easy to burn yourself.

cheers
mystic_1

Jonesy · « **Reply #10 on:** February 16, 2009, 05:07:45 PM »

Quote from: Gordon on February 16, 2009, 02:50:36 PM

Kind of sounds electrical/ignition related to me. Fouling plugs, leaky plug wires, or a bad connection between the plug wire and plug cap can cause those symptoms, as can a bad condenser or bad points.

Hence my question about the bike still having points. I can't recall, but wouldn't the 3 Ohm coils wear out the points faster due to the drop in resistance? (stock coils were 5 Ohms)

Gordon · « **Reply #11 on:** February 16, 2009, 05:11:33 PM »

Quote from: Jonesy on February 16, 2009, 05:07:45 PM

Hence my question about the bike still having points. I can't recall, but wouldn't the 3 Ohm coils wear out the points faster due to the drop in resistance? (stock coils were 5 Ohms)

Yeah, that's why I wanted him to see if the p.o. had installed a dyna-s.

fmctm1sw · « **Reply #12 on:** February 16, 2009, 06:33:59 PM »

Quote from: Jonesy on February 16, 2009, 02:42:13 PM

Sounds like one, possibly 2 cylinders are dropping out.

+1. Mine did this to me when I got caught in the rain one day. I had a problem with my 2/3 points...

FLo · « **Reply #13 on:** February 16, 2009, 08:39:17 PM »

Quote from: Gordon on February 16, 2009, 05:11:33 PM

Quote from: Jonesy on February 16, 2009, 05:07:45 PM
Hence my question about the bike still having points. I can't recall, but wouldn't the 3 Ohm coils wear out the points faster due to the drop in resistance? (stock coils were 5 Ohms)

Yeah, that's why I wanted him to see if the p.o. had installed a dyna-s.

Hey Gordon,

I emailed the PO re dyna-s. I'm too newbie to check. Wouldn't even know where to look. I'll photo the plugs tomorrow, though no sign of fouling. Thanks to all for your replies.

Gordon · « **Reply #14 on:** February 17, 2009, 06:40:57 AM »

Quote from: FLo on February 16, 2009, 08:39:17 PM

Hey Gordon,

I emailed the PO re dyna-s. I'm too newbie to check. Wouldn't even know where to look.

But I explained exactly where to look. $:-\$

Please don't take this in a negative way, because we really do want to help, but if you're not willing to try even the simplest procedure like removing two easily accessible screws to look at your ignition plate, then you're never going to enjoy owning a bike that's going to need continuous care and maintenance.

Dive right in, dude! It's really not all that difficult or confusing once you get in there and see how everything works.

Duke McDukiedook · « **Reply #15 on:** February 17, 2009, 06:49:14 AM »

Yeah, he describes where to look in post #6 in this thread to check to see if you have points. I know all this new jargon being thrown at you can be a little much but you'll get the hang of it prettty fast, you might surprise yourself how knowledgable you can become if you hang in there. Prepare for some technical reading (manual, this board). You have a wealth of knowledge at your fingertips here, don't be afraid to ask questions and get those hands a little dirty- It will pay off.

goon 1492 · « **Reply #16 on:** February 17, 2009, 09:34:12 AM »

+1 on using this board, and don't take it to a mechanic most of those folks will rip you a new one, unless you can find a good ol' boy mechanic.
Believe me brother with us and your hands we can become masters.

FLo · « **Reply #17 on:** February 17, 2009, 11:56:08 AM »

Quote from: Gordon on February 17, 2009, 06:40:57 AM

Quote from: FLo on February 16, 2009, 08:39:17 PM
Hey Gordon,

I emailed the PO re dyna-s. I'm too newbie to check. Wouldn't even know where to look.

But I explained exactly where to look. $:-\$

Please don't take this in a negative way, because we really do want to help, but if you're not willing to try even the simplest procedure like removing two easily accessible screws to look at your ignition plate, then you're never going to enjoy owning a bike that's going to need continuous care and maintenance.

Dive right in, dude! It's really not all that difficult or confusing once you get in there and see how everything works.

Hey Gordon,

I'll take a look at the ignition plate and get back to you. I do appreciate your help, I just didn't know where the ignition plate was. After a quick look at the manual, I think I know where to look. Things at work are a little busy, so I'll get back to you as soon as I can. I'll photo the plate, and plugs and post it here. Give me a day or so...

Thanks Guys!

heffay · « **Reply #18 on:** February 19, 2009, 08:06:52 AM »

i'll try to help a little...

the cover is the round cover on the bottom/front/right side... just behind the headers in this picture

it should look like this... w/out the extra 4 exhaust flanges

this is a dyna s

this is a set of points

the members here are asking if you see a set of points behind the curtain, a dyna s, or the wizard...

Gordon · « **Reply #19 on:** February 19, 2009, 08:11:42 AM »

Well look at you! Mr. fancy visual aids!

heffay · « **Reply #20 on:** February 19, 2009, 08:24:21 AM »

i knew i could count on you for some recognition, gordo.

Gordon · « **Reply #21 on:** February 19, 2009, 08:37:44 AM »

Can I get that second one printed and framed, please? It looks all artsy and stuff...

mystic_1 · « **Reply #22 on:** February 19, 2009, 08:38:00 AM »

So easy, even a caveman could do it

mystic_1

FLo · « **Reply #23 on:** February 19, 2009, 04:41:52 PM »

I'll post a pic soon. Busy I'm work.

Thanks for all the support

Spanner 1 · « **Reply #24 on:** February 19, 2009, 05:42:55 PM »

Go Gordan !, A little miffed that the Poster didn't want to look at his points right then..... I agree, it's always nice when they comply !!!
My pet hate is when loads of folks post answers/suggestions and the Poster goes away, fixes their bike, and NEVER comes back to A. say thanks, and B. to say WHO solved the problem for them...so we can all learn something, o.k., rant over !!

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Author Topic: Please help a newbie regarding a weird sound (Read 3074 times)