Knocking noise

[katmando]

:-( I have a little story about a real nice stock 78 gs1000 I bought.I bought this from a gentlemen,in the suburb of pittsford outside of rochester,NY.He had it in his garage for years.Started it periodically,also let it sit.For how long I don't know.He let it sit on the kickstand.As you can guees the left side carbs became gummed up.All this time for years he started it,ran it,on 2 cylinders.The right side.I cleaned the carbs and got it running on all 4's.Now it knocks.When it idles.It didn't knock when it was running on right side only.Any ideas LMK,Thanks,Steve.

[Poot]

these engines are generally noisy, but I'm making my bet that the clearances are off on the valves.

Do you know if/when the valve clearances were last checked?


If the clearances are past the specs, then you will hear what sounds like a soft knocking at idle . It may get worse sounding over time once they continue to loosen. You can try to locate the sound, by using a hollow object (tube of pvc, metal, anything) like a stethoscope to try and see if the valves might be the problem.



A common problem is the rattling sound in the cam chain, but its much different than knocking.

good luck



poot

[flyingace]

You can't make a judgement about knocking or any other noises until you get the bike running properly. Noises can be generated by cylinders not firing or way out of synch carbs.

[chiphead]

Flyingace is right. I recently started my 1100 up after a carb clean and intake boot replacement. When warm it had a very noticeable rhythmic knock from the upper end. Check carb sync and 1&2 were leading 3&4 by a lot. Synced the carbs and the noise is gone. I have seen this on a whole lot of other in line fours as well. Get everything set properly before you worry about engine noise. Improperly synced carbs will also make the clutch basket chatter like hell.

[bwringer]

Yup, synchronize those carbies. If they're out of whack, any engine will sound like a bag of hammers.

[Guy]

[QUOTE=Poot;525501


If the clearances are past the specs, then you will hear what sounds like a soft knocking at idle . It may get worse sounding over time once they continue to loosen.[/QUOTE]

Nah, he's talking through his arse. Bucket and shim set ups will tighten over time, not loosen. That's why regular valve clearance checks are so important. These engines do make plenty of noise though. Could be cam end float. Common enough on these bikes and nothing to worry about.

[katmando]

Ok sounds like I have my work.I will check the carbs.Another question I had is after running this bike for so long on 2 cyl's.Would ther be damage from the left not firing?Thanks all.SteveinNY.

[49er]

Guy's right about bucket shimmed motors. As the valves work deeper into the seats the clearances are reduced.
The knock is probably excessive cam endfloat.
My 79 850 has a similar knock from idle up to 1400rpm when the motor is at normal running temperature. From a distance it sounds like the bottom end was ready to let go.
On pulling the cams, I found wear on one side of the cam chain idler sprocket. It appears to have been caused by wear on the sprocket shaft and a poorly aligned housing assy.
Both cams have excessive endfloat clearance. Without the chain fitted and the valves removed, I could reproduce the sound by sliding the cams back and forward against the thrust rings. With the the cam covers fitted the hammering sound is magnified.
The only cure for this is some creative machining.
If my mods work out, I will post the results.
Out of sycnh carbs will cause odd engine noises, but they need to be way out of wach. They may contribute to excessive endfloat movement too.

Ian G

[katmando]

Ok,just concerned if it was a piston.Sounds almost like a rod.I am hoping it is nothing serious.By the way this bike only has 12,000 miles on it.Seems to me the cam wouldn't be affected.With no lubrication that probably messed it up.I will have to take to Arkport Suzuki.Cross my fingers.Thanks for the help.SteveinNY.

[flyingace]

You can check the rod bearings with a wooden dowel. Remove the plugs and turn the crank until one of the pistons is just past TDC. Then put the dowel thru the plug hole and push down on the piston crown. Any detectable movement indicates a bad rod bearing. This procedure is detailed in the OLD FAQs I believe.

[katmando]

I will try that and look it up in the faq's.Thanks,SteveinNY.