Topic: Backfiring, vibrating and rattling in engine (video)

[IAmCitizenMe]

Ok, I've searched and I can't really find a solution to my problem.

A few days ago, I took my 78 550 on the interstate. It was a particularly windy day and I noticed my bike was bogging down like it was running out of gas. I checked my mileage and I had only put 50 or so miles on it. I flipped it to reserve and the problem persisted. I thought it might have been because it was so windy, but I was sure that wind had nothing to do with it. I was going 70mph. Now, today as I was leaving for class I noticed a low/deep, muffled pop as I was accelerating in 1st, 2nd and/or 3rd gear. Uh oh.

On my way home, the problem seemed to get worse. It almost died accelerating out of 1st gear. It kind of chug-a-lugged for a bit before I was going fast enough to switch to 2nd.

I just got home and I took a video of my bike running in hopes that I would hear something peculiar. It sounds like something loose is vibrating or rattling in the engine. Like a screw that has worked itself loose. At around 1:00 in the video, toward the end, I think the sound is pretty audible.

Keep in mind, I have practically NO idea what I am doing. I've only had this bike for a few months and it is my only prior motorcycle experience.

Help?

(You can hear the sound scattered throughout the video, but I've marked where it get's really loud. The engine sounds more noisy in the video than it really is.)

[Johnny5]

Sounds like the cam chain is too loose.

[Johnie]

Does it make that same noise when you pull in the clutch handle?Honda does experience something called "clutch rattle" and there is a bunch of info on this site about it. Have you adjusted the cam chain? Could be that and info on the easy adjustment is in your owners manual or service manual.  

[IAmCitizenMe]

Would that cause the symptoms I described? I'm worried because it is my only mode of transportation and if I have some time and money to put into this, I need to figure out a way to get to school and work.

What would Johnny5 do in a situation likes this?

[IAmCitizenMe]

Does it make that same noise when you pull in the clutch handle?Honda does experience something called "clutch rattle" and there is a bunch of info on this site about it. Have you adjusted the cam chain? Could be that and info on the easy adjustment is in your owners manual or service manual.  

The noise persists when I pull the clutch. But I think you're right. It sounds like it's coming from the cam chain. But would that cause the problems I was having?

It would always have a hard time picking up out of first gear when accelerating from a stop. It would kind of bog down then kick in after a bit. Like the engine is trying to keep up with itself. It's hard to describe.

[Johnny5]

It might if the timing is off.

[Johnny5]

I use a broom handle and put one end to my ear, and the other touching various places on the engine. You can really hear where noises are coming from this way. Try it in the middle of the engine, in front of the carbs.

[TwoTired]

When's the last tune up that it had?
What about carb sync?

Check the cam tensioner stud lock nut. My 78 550 had stripped threads there, meaning the tension shoe couldn't be locked in place.  Only the internal spring tensioned the shoe which then changed with the RPM.  I had to put a second nut on there to cinch it tight.

Are all the head pipes the same temp?
Could you have gotten crud in the fuel?

It sounds like the cylinder power pulses are uneven.  This makes the internal rotating parts in the trans rattle and whips the primary chain.  ...noise happens.

[tomsweb1]

Sounds alot like my 750, when 1 or more cylinders have stopped running.
Are you sure they are all going all of the time...?

[IAmCitizenMe]

Sounds alot like my 750, when 1 or more cylinders have stopped running.
Are you sure they are all going all of the time...?

Well the headers are all hot after a ride so I figured it was safe to assume that they were all firing correctly. Spark plugs seem fine.

[jsaab2748]

Chris, check your P.M.s

[Johnny5]

By the way, nice bike. Looks like it's in great condition.

[IAmCitizenMe]

Thanks, Johnny5. It is in great condition. I knew I liked the older style Hondas but I had no idea what I was getting myself into when I bought it (obsession). I cleaned it up a lot and everything else I have done to it has been with the guidance from members of this forum. My eternal gratitude.

I adjusted the cam chain. The strange engine noise went away, which felt good. But I still hear the lower noise when I accelerate, though it's now a smoother ride. I would like to open up the engine this winter (keep posted for a rebuild thread) and find that I have avoided a huge disaster by solving this problem. Of course, in my ignorance, I am always paranoid that my bike is slowly deteriorating beyond my knowledge. I set the valve timing, adjusted the cam chain and checked the spark plugs. The only thing I haven't done is sync the carbs because (be prepared) I don't know how. I've tried to look up instructions on how to sync carbs in different ways but the results always wield one-step instructions (step 9: sync carbs). Are there any elementary, color-coded pop-up books on how to sync carbs out there?

[Johnie]

Keep in mind these older bikes do make some noise. Don't expect it to be a super quite motor as you do have a bunch of moving parts there. Granted, the video was noisey and it sounds like you took care of that with the cam chain adjustment. A motor idling to slow will give a noisy chug too. You have to cut these vintage bikes a little slack.
Regarding the sync...go to the FAQ area of this board under the carb section. There is some nice instruction there.  The first thing you would need to do of course is get a reliable sync tool. A lot of guys use the Morgan Carbtune which is under $100 I believe. I have had mine since 1999 and it is fool proof and one of the most reliable systems out there.  We can run you through the steps.
Last, I did not see it...or I missed it...be sides doing the timing did you adjust the valves yet? Must be done before the sync.

[Laminar]

I set the valve timing

Valve timing is controlled by the camshaft. Did you mean to say that you set the spark timing or the valve clearances?

I'd pull off the eight rocker covers on the valve cover and make sure all of your valve clearances are correct and that you don't have one that's loose.

[IAmCitizenMe]

Keep in mind these older bikes do make some noise. A motor idling to slow will give a noisy chug too.
Last, I did not see it...or I missed it...besides doing the timing did you adjust the valves yet? Must be done before the sync.

Oh, I know they make noises. It's one of the things I love about it. But yes, I took care of the cam chain noise. Where is a good place to buy a Morgan Carbtune?

I made a mistake when I said I set the valve timing, Laminar. I set the spark plug timing. I got rid of the noise but the pop is still there. I am going to go set the valve clearances (for my first time, hoorah) right now.

[IAmCitizenMe]

Oh, Clymer. What the hell are you talking about?



Where do I put it? The Clymer says between the tip of the adjusting screw and the valve stem. But the image in the book contradicts what I see on my bike. I have the 1-4 at TDC. The picture is the intake valve of cylinder 4.

[Laminar]

Undo that locknut with a 10mm wrench and back the screw off with a flat blade screwdriver. At this point you should be able to wiggle the rocker arm around and tell that there's a gap between the bottom of the screw and the top of the valve.

Slip the feeler gauge in between the bottom of the screw and the top of the valve.
Tighten the screw until there's a little resistance to pulling the feeler gauge out.
With the screwdriver in the screw keeping it stationary, tighten the locknut.

Done.

I found that bending the last ~8mm of my feeler gauge about 90 degrees made it easier to get down into the valve cover and in between the bottom of the adjusting screw and top of the valve.

ALSO some people here recommend setting the exhaust valve gap to 0.10mm instead of the recommended 0.08mm. This may make it a tiny bit noisier, but this allows the exhaust valve to stay in contact with the head for just a little bit longer, which lets it dissipate heat better and the engine will run a bit cooler.

[IAmCitizenMe]

Okay, I did what you said, Lam. But now it is WAY noisier. I don't know if I'm just not used to it and it's fine or that the tappets are hitting the covers. If anyone could give me some advice in the next ten minutes, that would be awesome. I have class in half an hour!

Thanks to all ya.

[Laminar]

If the tappets are hitting the covers, you should be able to see marks on the bottom of the tappet covers. I accidentally left one loose the first time I did it and I knew right away.

You followed the manual as far as doing the appropriate valves at the appropriate crank rotation, correct?



Also, it's highly recommended to let the bike sit for ~24 hours without running before adjusting clearances. Even starting the bike up for a few seconds changes temperatures and throws things off.

[IAmCitizenMe]

Well, damn. Clymer does it again. The Clymer manual made no mention of the "X" and "O" chart. In the T 1-4 position I adjusted cylinders 1 and 4 and in the T 2-3 position I adjusted 2 and 3. Is that chart for a 550? Because it doesn't mention the T 2-3 position.

[Laminar]

That is for a 550. There's your problem.

You don't have to use the 2-3 position for anything. Adjust to the 1-4 T position and make sure both of #1's valves are up. If not, go 360 degrees and they will be. After adjusting the four marked valves, rotate it 360 degrees back to the 1-4 T position and both of #4's valves should be up. Then adjust the other four valves.

Ditch the Clymer's

http://depositfiles.com/files/uffzbj1fu

[the technological J]

i am coming into this post a little late but i did a home job on my carbs right after i got the bike and ended up it wasnt letting enough fuel in when winding it up a little and one of the the cylinders wasnt getting enough fuel. i reset the the float height( after rediculous amounts of research[which lead me to this site]) it rides fine

[IAmCitizenMe]

Of course...



I reset everything according to what you showed me and as I was tightening the last tappet... SNAP! I guess I'll have to overnight a new tappet cover and seal before I find out if I fixed my initial problem.

What you told me, Laminar, worked. Some of the valves were very loose. Now they all have the proper clearances.

[IAmCitizenMe]

i am coming into this post a little late but i did a home job on my carbs right after i got the bike and ended up it wasnt letting enough fuel in when winding it up a little and one of the the cylinders wasnt getting enough fuel. i reset the the float height( after rediculous amounts of research[which lead me to this site]) it rides fine

Yea that's next on my list of things to learn. I'm pretty sure (from what I've read) that I have a sticky float somewhere. But we'll see.

I'm getting really good at starting threads that will hopefully someday help out someone as green as me.