R50/2 rebuild

[312Icarus]

So after the strange noises in my engine, chronicled here last fall, I had my engine torn down to find a spun main and mashed rod bearing. So after having the crank redone with big bucks, the engine was put back together with new rod bushings , same pistons and bores, by a pro. I got the bike back today, (the guy who built the engine couldn’t do much of a run up as there was a bunch of other issues (carbs mostly) that I didn’t want to pay him to sort, I got it back, get the carbs sorted and it purrs. But...and here is the big but, there is a significant squeak when you take up the throttle quickly, fairly high pitched. Now I’m worried that something may not be right. There is no unusual noise at idle or at fairly high revs (I haven’t ridden it yet as I need to retorque the heads). I’ve just been running in the shop with a couple of box fans.

So the question is...does anybody have any idea if I need to worry and if so, where to look? It sounds like it is coming from the front of the engine. Taking the timing cover off has no effect.

Thanks for any input, before I borrow a trailer and drive 200 miles back to have the pro look at it again, something he will do, but really doesn’t want to!

Icarus

[miller6997]

Many /2s have a squeal after startup that is sometimes caused by the rear main seal. That may be what you are hearing. There was a discussion of this here fairly recently. That seal was replaced on my bike twenty thousand miles ago and it still makes a reduced version of that noise from time to time. However, the noise clearly comes from the rear of the engine and it goes away (at least in my case) after the engine warms up.

[312Icarus]

That would be good news. It sounds like it comes from the front, but I will listen with a stethoscope and see if I can track it a bit better. It seems to come as the crank is “loaded” so to speak,,, adding power/torque to the crank. Does that sound like the above mentioned seal?

Icarus

[Beemer54]

Head Gasket blowing?

[malmac]

1. If the front breather plate is not adequately lubricated prior to reassembly that could cause a high pitched squeal. Check engine oil for aluminium particles - I had it happen to me. I drained the oil to find out I had a major problem.

2. Generator brushes - remove brushes, bike will run and will rule out that as a possible cause.

3. Front or rear oil seal on crankshaft installed dry.

4. Clutch - is the sound affected by pulling in the clutch?

That is all I can think of at the moment.


Mal

[312Icarus]

Not the clutch or the generator brushes. How does one check the front breather plate?

Icarus

[312Icarus]

Re torqued the heads and reset the valves. No change. It only happens once the engine is warm, on quick throttle take up, and maybe as it “unloads”. I’m wonder if somehow the engine torque is thrusting the crank or cam somehow?

I’m loathe to ride it, risking damaging the new crank without a better idea of what i’m Up against. It does seem to be in the front. What is the risk if it is the breather plate? The breather seems to be functioning normally, puffing out regularly.

I can’t really listen with a stethoscope without someone else to trip the throttle. Suggestions?

Icarus

[johnpst]

Aloha,

I'll assume the "squeak" is constant and not intermittent. A cylinder leaking pulses with the piston moving up and down.

The warmed up engine may be a clue. Sorry, my news is not going to be simple. Ask your mechanic if he used a press to install the bearings. If he did, he wasn't familiar with these engines and may have done a couple of things.

1. Pressing the bearings in can score the bearing bores resulting in a loose fit or tight fit. A loose fit would result in the bearing spinning in the bore. A tight fit on the rear might hold it too tight pulling on the front bearing causing it to squeal.
2. You din't say who assembled it so, it's also possible crankshaft shims are incorrectly installed.

Either way, after looking at the outside, the only thing that can be done is to disassemble it, inspect it, and measure everything out, and reassemble it.

Other options are the cam drive gears but they would be a whirring sound. Also, the oil pump shafts could cause a noise but, I'm thinking should rub out pretty quickly.

Sorry, not better news. Good luck. There's a lot of people root'n for ya.

John

[312Icarus]

It is a squeak as you I bring on a quick throttle rev, very short duration. Scotty Sharp did the crank and a local Seattle area wrench who has done hundreds of /2 motors so I assume he knows how to assemble the bearings.

Icarus

[Daves79x]

It sounds like it's the rear main seal 'squeak'. Should diminish as the engine warms and the miles accumulate.

Dave