Clunking Vibration in First Gear

[wrecks]

Hey everyone,

I have appreciated this forum for all the information that I've already gleaned from and used. So thank you all for that.

I have not found this though. Recently, my '86 R65 has started to have a clunking vibration when accelerating in 1st gear. The vibration seems to be around 2K RPM and for a brief moment the clunking starts and sounds like it is coming from the instrument cluster or below. This morning while it was cold it did not do it but once I was out and about for a few miles it started doing it again. It may not happen at higher gears simply because I usually keep the RPM higher once I get going.

If you have any ideas what this might be it help me get more comfortable with the bike. It feels like now that something in the steering might fall off although it is all solid when I stop and inspect it.

Thanks
Rex

[Bob_Roller]

My first guess, might be the spring loaded 'cush' drive in the driveshaft starting to slip .

[wrecks]

Hmm I read this thread http://www.bmwr65.org/cgi-bin/yabb2/YaBB.pl?num=1259237697/15 and I'm not sure we are talking about the same noise or maybe mine isn't as far along as his.

A little more on the noise. I said clunking but that may be a little strong. It seems that on accelerating the RPM hits a resonance frequency that makes the noise and kind of shakes the bike (not a real hard shake). Once it is past that RPM it no longer makes the noise and it does not make the noise when decelerating through the same gear and RPM.

[Bob_Roller]

The 'usual' R65 vibration is in the 4000-4500 rpm area, most evident when you are in fifth gear .

Some bikes exhibit it more than others .

This vibration is a 'buzz' type vibration, not a clunking type noise .

[tvrla]

This is a noise near the instruments at around 2-3K.

First off, I hope you're not lugging the engine! It will vibrate and rock the frame and shake the whole bike - don't make it work hard below about 3500 RPM!

Second, how's the speedometer cable. Try disconnecting it and see if the noise goes away.

Perhaps there's a piece of sheet metal vibrating on something - maybe a cable or the speedo cable passing by the headlight mount.

Did one of the fasteners loosen in the headlight mount?

[wrecks]

This sounds more like it. I'll check this as soon as I can. In the meantime can you tell me the proper way to accelerate out of first gear without lugging the engine once in a while. I'm new to riding a motorcycle much less an airhead. Do I just keep the engine rev'ed to 3500 and use clutch slippage? What if I'm going slow in traffic then go to speed up? Engine is already engaged and about 2K RPM and I go to accelerate do I just accelerate slower or engage the clutch?

[Barry]

'm new to riding a motorcycle much less an airhead. Do I just keep the engine rev'ed to 3500 and use clutch slippage? What if I'm going slow in traffic then go to speed up? Engine is already engaged and about 2K RPM and I go to accelerate do I just accelerate slower or engage the clutch?  

I don't think you should have to avoid using lower revs altogether. Personally I think the whole issue of lugging is a little over done. The engine likes to operate in the 30000 - 5000 RPM range but of course you have to pass through the lower revs first and there should be no need to slip the clutch to do it. My bike will easily pull from 2000 rpm up with no vibration or protest I just don't give it full throttle at those revs as that would be lugging.  If the bike did protest on a light throttle at 2000 RPM I'd sell it tomorrow as that's not the sort of bike I want.

[tvrla]

Lugging is hard to describe - I've tried before and it's one of those things like explaining what's so cool about riding motorcycles.

First off, the power band on these bikes starts around 3500 RPM. How do you explain power band? No engine produces power at all RPMs - it has to do with design parameter that focus on the intended use. Sport bikes tend to have a very narrow power band to create peak power, but these bikes have a wide power band because they're intended for touring and general use. Anyway, they don't begin generating real power till about 3500 and starts dropping off (just guessing) about 6500 or 7K.

That doesn't mean you can't use any RPMs but the power band! It just means that if you want the bike to work hard (like gunning it to pass, climbing a steep hill with a load), those are the RPMs to do it in.

Otherwise the motor will shake side to side and you'll really get the feeling it's protesting. That's what lugging is and what's hard on these engines, don't do it! In those situations get the RPMs up by shifting down or just back off the throttle and take it easy. Let it take its time picking up speed.

Using lower RPMs is fine - just don't lug it! Also, lugging happens much easier in the lower RPM range. Keeping the engine revving is easier on these 650s than lugging. They're not Cadillacs with such a powerful engine you don't have to pay attention to it - they're more like old VW Bugs and you're constantly shifting to keep the motor in the power band.

Does that make sense?

[Altritter]

Lugging is hard to describe - I've tried before and it's one of those things like explaining what's so cool about riding motorcycles.
 

A good way of understanding "lugging" is to read Joh Muir's How to Keep Your Volkswagen Alive—A Manual of Step by Step Procedures for the Compleat Idiot [long out of print]. (Remember, our boxer is similar to 1/2 the original Beetle engine, but with more complicated carburetion.) In a section titled "Through the Gears" in the chapter "How to Drive a Volkwagen," Muir writes: "The worst thing, next to not warming up the engine and over-reving, is to lug the [R65]. 'Lug' means to under-rev the engine with a load on it." The same warning came in the driver's manual of my first BMW, a 4-wheeler 2002tii—do not operate at sustained speeds of <3000 rpm. (It would both lug and carbon up—as I learned with German speed limits during the first Arab oil embargo.)

A small-displacement, short-stroke engine (e.g., the Type 248 engine in the R65, as opposed to its longer-stroke Type 247 brethren) protests low rpm by making funny noises and issuing strange vibrations. (By contrast, my first auto, an old (even then!) 1954 Studebaker Commander with 3-speed-manual, 232-cubic-inch V8 (!), would, despite its small displacement for a V8, pull smoothly away from a traffic light at idle rpm because of its eight cylinders and 90-degree firing (with careful clutching, admittedly).

[Barry]

Lugging is what we feel when an engine is loaded at low revs producing vibration and shock loading on the bearings as a direct result of cyclic variations in the crankshaft rotational speed. Every revolution the crankshaft speeds up and slows down in between the power strokes with only the flywheel inertia to even out the power strokes.

This perception of lugging at any particular engine revolutions is therefore directly related to the engine load (it will slow down more between power strokes under heavy load), the number of cylinders (more power strokes per revolution) and the mass of the flywheel. So an engine with a heavy flywheel will not protest as much as one with a lighter flywheel and a 6 or 8 cylinder engine with more power strokes per revolution and particularly if it has a torque converter or dual mass flywheel as an in built shock absorber will hardly be perceived to lugg at all even at low revs.

When we talk about airheads I think we sometimes forget that the earlier bikes with heavier flywheels will be slightly happier at lower revs which may explain some differences in perceptions about lugging.