3500 RPM Rattle

[XS1100_OEM4ME]

OK, "EVERYTHING" on this bike has been gone through with the exception of a motor overhaul (17,000 orginial miles on the bike) It starts, runs, idles and preforms perfectly BUT, I still have a noise (best discript would be a rattling sound) at 3,500 RPM. If going along at 3500 and I give it just a slight amount of gas, it "rattles" till 4000 Any gear, any time. Goes away at 4000+ and can't hear anything at idle Any idea's

[bikerphil]

That is not uncommon on a 79SF, mine does the same. It sounds a bit like piston slap but it is not harmful to the engine. There was a Yamaha tech bulletin about it somewhere. I use mid grade fuel to lessen it.

[XS1100_OEM4ME]

Man

Man, Phil, you are once again a life saver I was getting ready to face the fact that I needed a rebuild. That is exactly what it sounds like, "piston slap". EVERYTHING else on this bike works perfectly (after many $ and much work) I am hoping you are right on the botton with this "rattle". Effect's nothing except my brain

That is not uncommon on a 79SF, mine does the same. It sounds a bit like piston slap but it is not harmful to the engine. There was a Yamaha tech bulletin about it somewhere. I use mid grade fuel to lessen it.

[cywelchjr]

I thought that TSB was supposed to be for the 80/81 bikes. I know mine has that, and actually sounds more like a knock, which is what the TSB describes the sound as, and if I disconnect the vacuum advance it's gone. It's also not there under HARD acceleration either, just light to medium. According to the TSB, it's actually a form of preignition/ping, and is supposed to be FAR more noticable with a fairing (such as I have). I have 30,000 miles or a bit more on this engine now and the sound has not changed any, other than it's worse if I advance the timing some, and less if I retard it some, but other than that, it's one of the constants of my bike.

And I agree about the mid grade fuel, it does help, and I figure premium would help more if Brutus didn't hate premium so much.

[XS1100_OEM4ME]

Prem Fuel

I use Prem Fuel. A knock would be an accurate discription, just didn't want to invite all the "you spun a rod" answers I am thinking if I had, I would "know" by now

I thought that TSB was supposed to be for the 80/81 bikes. I know mine has that, and actually sounds more like a knock, which is what the TSB describes the sound as, and if I disconnect the vacuum advance it's gone. It's also not there under HARD acceleration either, just light to medium. According to the TSB, it's actually a form of preignition/ping, and is supposed to be FAR more noticable with a fairing (such as I have). I have 30,000 miles or a bit more on this engine now and the sound has not changed any, other than it's worse if I advance the timing some, and less if I retard it some, but other than that, it's one of the constants of my bike.

And I agree about the mid grade fuel, it does help, and I figure premium would help more if Brutus didn't hate premium so much.

[bikerphil]

Mine's been knocking for 30K and is weeping a bit from the left crank seal, might be a sloppy crank bearing too. I run advanced timing a couple degree, that might contribute. Mine doesn't do it until the engine nice and hot. Lean mixture can contribute also. I might have the wrong vacuum advance on mine too, they differ in opening time IIRC.

[XS1100_OEM4ME]

Thanks

Thanks Phil, no worries mate, 30K knocking and still cranking. I will just "RIDE" and take my cel phone

Mine's been knocking for 30K and is weeping a bit from the left crank seal, might be a sloppy crank bearing too. I run advanced timing a couple degree, that might contribute. Mine doesn't do it until the engine nice and hot. Lean mixture can contribute also.

[crazy steve]

Cy hit it on the head; it's preignition caused by too much timing at the transition between throttle openings. It can move around at bit rpm-wise depending on the bike, but 3500 rpm is pretty typical. It's not particularly good for the motor, but you can minimize it with riding technique; simply give it more throttle quicker, dropping the vacuum and retarding the timing. A gentle roll-on only prolongs it. My '78 did this from new (although never badly; it was usually just a few knocks and it was done), and fuel grade never seemed to effect it much. It was always worse in hot weather...

[bikerphil]

One heat range plug colder BP7ES may help too. I can't remember but I think when I first got my SF it had those but only 13K on the clock. It didn't knock then.

[cywelchjr]

Yamaha CLAIMS in the TSB that it's not harmful and that it's just an annoyance, and some have replaced the vacuum advance with the one recommended in the TSB and not had it fix the problem. I for one tend to just get on it more to avoid it, and understand that because my fairing acts as a megaphone so that I hear every little noise from my engine, including the gurgling of the oil going back down to the pan. I can literally tell the difference in the sound between my Windjammer III and my Windjammer IV, the III is far less of a megaphone. I'm really thinking about putting some egg crate foam on the inside surface of the fairing to deaden the sound just to make me feel better.

[XS1100_OEM4ME]

Putting an END to this!

Thanks, just hearing so many of you guys have the same "KNOCK" helps me put an "END"to this. I am going to ride, and ride her hard. And when she rattles, I am just going to "jump on it" and pump her harder Ill make sure she is well lubricated and ignore the noise she makes from now on

[XS1100_OEM4ME]

OOP's

OOP's Sorry wrong picture I was talking about my bike, not my Well you know

[old_chopper]

Oh no, that was the correct picture!

[foreda]

Gas

I started using Fina gas in all of my bikes. Fina gas has no ethanol in it and I have noticed a marked improvement since using it. Thought I'd share this with you guys!
Dale

[cywelchjr]

I started using Fina gas in all of my bikes. Fina gas has no ethanol in it and I have noticed a marked improvement since using it. Thought I'd share this with you guys!
Dale

Well, not all of us are lucky enough to be able to get that, we are lucky to get gas that works at all around here.