Topic: 750 knocking under load?

[Skonnie Boy]

Hey, long story short, I'm about 400 miles from home, having a curious knocking noise coming from my bike.  There's a not-worrisome chatter at idle at city speeds, but the chatter becomes a noticeable knocking noise when I'm in 4th and 5th gear.  I checked and tweaked valve adjustments before I left (though I probably didn't need to), and in so doing stripped 3 of the 8 tappet covers.  Problem is, I adjusted them once and left things on the loose side.  I rethought this, and readjusted them to err on the side of tight.  This is when the tappets got stripped, so I was unable to reach the #3 intake.  What, if anything might this knocking sound be, and is there anything I could potentially do about it on the road?

 

[mrblasty]

Sounds like an adjuster nut has spun off and the tappet and the tappet is clacking against the valve. 

[chaz76vette]

@ mrblasty - my '75 CB550K does the same thing, and I think it's a tappet hitting like you guys are saying. It's so awkward getting the feeler in there, is it something we really need to fix or risk doing serious damage?

[Skonnie Boy]

Um, that seems like something that really needs to be fixed, if that's what it is.  If only I could get new tappets, much less get the old ones off.  I would say file them down to 15mm as a first thought? 

[Spanner 1]

This may sound crazy but did you check your chain..?  A 400 mile ride can stretch an old(er) chain and it will lash off the mainstand....happened to me and I was sure the noise was coming from the front wheel at first !! It was a devil to pin-point the noise and the chain was the last thing I thought it could be ..........maybe ?

[754]

If you dont have a 6 point 17mm, get one.. you need it..
Sat nite, I assume the dealers had no covers, try a salvage place if nothing turns up in the next day..

[Skonnie Boy]

Tightened the chain some 200 miles ago, so its not that.  Got a line on a salvage yard close by, might get new covers there. 

Yeah, just can't get the socket over the #2 and #3 intake covers.  Maybe a friend has a 6 pt. wrench, though.  The covers might be too far gone for that.

[Don R]

What direction from chicago are you?

[Skonnie Boy]

Well, that's the problem.  I'm up in the Twin Cities on a road trip.  I think I've got a line on a file and a wrench, tho.

[andy750]

Vice grips also work great on those rounded off tappet covers. Use that and change them out - or not as the case may be.

good luck
Andy

[mrblasty]

Half of my tappet covers were so stuck the only to get them off was with vice grips.  It sucked having to bite into them like that but the alternative was to let my valve train beat itself to death.

[754]

Yeah, I meant the 6pt to remove the used ones at a salvage yard, to not ruin them, dont much matter if you use vise grips on yours.. IF you have a replacement. (remember 350, 175 & others use this cover)

 BTW I use a flex handle on my socket, not a ratchet, gets in tighter spots. Also you may be able to use visegrips on a 6 point, in a pinch.
 Should take this time to say, many times these covers are overtightened, it really only takes light pressure to seal them , and when done right, you could probably get em off with a crescent wrench, without harming them.

 Off to design an aluminum toolbag size wrench you can carry along, 6pt of course..

[Skonnie Boy]

Long story short, the vice grips are one of the reasons the tappet covers are stripped.  Might be able to get 'em off with a second try.  A toolbag 6 pt. wrench would be just the thing....

Another long story short, thanks to the advice and kind ear of forum member srust58 here in the twin cities, we came to the conclusion that the knocking sound is still within the normal range of "that sewing machine sound" that characterizes 750's.  The running issues I've had is likely due to the near constant rain I had to ride through over two days and the open pods I run.  Many thanks to srust58, who helped me out sourcing a junkyard and and talking me off the ledge, as far as my "problem".  I've said it once, I'll say it again - I've never claimed to be much of a mechanic, but nobody confronts their stupidity better than I. 

Thanks for the advice, all.

[BeSeeingYou]

Skonnie came over to my place and I did not hear anything out of the ordinary so I pulled my bike out of the garage and fired it up to compare and there was not much difference in the sound between the two.  The head sounded pretty uniform all around.  There was no mechanical knocking noise and as long as it does not show up under load you may be okay.  Just too bad the weather has been lousy the last several days and for the next few it looks.  But all is not lost, Skonnie is a Packers fan and Farve and the Vikings are playing the visiting Packers on Monday night. 

[andy750]

Excellent news! Looking forward to more updates!