BSA Owners' Club Forum

The BSA Workshop => Singles => Topic started by: MICKREEVES on 13 October, 2017, 10:24:38

Title: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 13 October, 2017, 10:24:38
My B44 vibrates badly on a light throttle opening, opening to accelerate stops the vibration,
closing throttle to overrun stops it as well. This is most noticeable at high RPM.
So bad, bits are dropping off or breaking.

I thought it must be bigend play, or possibly smallend or mains.
I have stripped the top end this morning.
No play to be found at all. I  cant mend something if it aint broke!

I wonder about balance factor?  The piston is 71/798, 1/2 mm oversize. It looks quite normal.
I see bsa part numbers. 41/794 standard, 41/795 + 10 thou, 41/797  + 20 thou (1/2mm)

The engine is not loose in the frame. I cant think what it can be.
I will order a new rocker gasket, and rebuild when it comes.
Any suggestions? Do they ALL have this fault??
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 13 October, 2017, 10:41:02
answering my own question!
I checked again.
Gripping the piston with both hands, push up and down, moving around and sideways.
Finally found a point where a very small amount of play was felt. Enough to hear a small click.
Im guessing that that is the answer?? ANY play is not acceptable??

Suggestions for a good supplier for replacement bearing please.
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: JulianS on 13 October, 2017, 11:53:15
Just read a contemporary road test of the 1970 441 Shooting Star. The tester reported lots of vibration.

On piston part numbers - the numbers in the BSA parts lists are for a complete piston - including pin and rings - the number you see on the piston is the number for the bare piston.

You could try Alpha Bearings for a bigend .
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: ANDY HIGHAM on 13 October, 2017, 16:27:11
There is no reason why a B44 should vibrate badly.
Don't assume BSA correctly balanced the crank, they probably balanced the prototype then made all the production ones "similar"
My B31 (400cc) crank/rod/piston assembly was balanced by Phil Pearson and the bike is smooth as silk all the way to 80 + MPH
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 17 October, 2017, 10:27:23
answering my own question!
I checked again.
Gripping the piston with both hands, push up and down, moving around and sideways.
Finally found a point where a very small amount of play was felt. Enough to hear a small click.
Im guessing that that is the answer?? ANY play is not acceptable??

Suggestions for a good supplier for replacement bearing please.
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 17 October, 2017, 10:34:19
I have stripped the engine.
I dont think a new bigend was really needed. There is JUST perceptable movement.
Now I have it stripped, I will fit a new alpha bearing.
I suppose the whole job was a waste of time and money, but I still want to get rid of the vibration.
I might try making a weight, 58% of the rod and piston (is this correct? ) Then drilling the flywheels as needed.
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: ANDY HIGHAM on 17 October, 2017, 18:16:12
Not quite. The piston assembly and the top part of the rod is reciprocating mass, the lower part of the rod is rotating mass. Also, is 58% correct or just what was thought to be correct 50 years ago?
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: JulianS on 17 October, 2017, 18:24:47
You need to make sure, when fitting new big end assembly, that the crankshaft/flywheel assembly is as near to perfectly aligned as possible.

If not so then expect vibration even if balance is correct- aim to get it within 0.001 inch. Bad alignment can also mean loss of power.

I would suggest you consult a specialist and get it dynamically balanced rather than static.

Basset Down Balancing did a B25 for me some years back and the improvement was very noticable.
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 18 October, 2017, 10:16:35
I have shipped my crank to Alpha for replacement and balance.
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: DEREKANDERSON8 on 18 October, 2017, 19:24:50
I have shipped my crank to Alpha for replacement and balance.
Mick

I take my hat off to you mick! you certainly don't mess around when you have a problem to deal with, from having a bad vibration to the crank being sent to SRM for repair 4 days have passed!

Excellent I hope you keep us posted  :D

regards

derek
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 27 October, 2017, 18:36:16
Still waiting for the crank back from Alpha.
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 28 November, 2017, 14:48:19
Engine reinstalled, new fuel tank, Now not charging, no winkers at the rear.
Not back on the road, but the engine runs and is no better for vibration than before
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: DEREKANDERSON8 on 28 November, 2017, 17:00:26
Engine reinstalled, new fuel tank, Now not charging, no winkers at the rear.
Not back on the road, but the engine runs and is no better for vibration than before
Mick

oh dear that's not good, is the vibration just as bad then?
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 09 December, 2017, 12:24:06
Quick test run this morning.
Vibration just as bad.

Crankshaft alignment.
I replaced my C15 bigend myself. When it came to realigning the shaft, the best I could get was -
drive side, 1 thou out. Timing side, 7 thou out.
repeated tries just moved the error back and forth.
The engine runs fine, no excessive vibration.

My B44 big and small ends were replaced by ALPHA, who also realigned the shafts and checked the balance factor.
I can live with the vibration, but the bike tends to shed bits on the road!
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 21 December, 2017, 14:46:33
I managed to get a satnav to work long enough on the bike to get a speedo check.
The speedo reads 10 MPH high, so my top speed of 85 MPH (as the book says) is only 75 MPH.
Comments please from other B44 riders!
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: Editor on 21 December, 2017, 16:27:26
I had a B44 back in 1997 and it suffered from serious vibration. I asked around and was told they all do that sir, mainly due to the high compression. So I sold it and got my self a Norton Commando - Big Mistake!
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: ducati2242 on 22 December, 2017, 19:30:01
just finished a 1967 b44 and it runs vibration free , ish , only done 40 miles so far but no problems , apart from the useless front brake which i have now rebuilt with an 8 inch drum.


Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 23 December, 2017, 08:37:55
Why was the Norton a mistake?

B44, low vibration? I wonder why? Or how?

I wonder if the b44 crank has insufficient counterbalance for the larger piston?
Mine was checked by Alpha Bearings.
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 23 December, 2017, 08:49:27
My B44 has twin leading shoes brake. works well.
My C15 has the normal brake, smaller size. Works even better! I dare not put full pressure on it , for fear of locking the wheel.
I have made a twin leading shoe conversion for the c15, which I intended to summit for the club magazine, but I never got around to trying it.
Mick
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: Editor on 23 December, 2017, 13:59:28
My B44 was tooth loosening and finger numbing at around 60-65MPH which was very uncomfortable at the time.
The Norton Commando's problems were Front Disc Brake (original lockheed) was useless, the oil tank bottom mounting cracked and all the oil flooded the garage floor, the head gasket leaked oil all over my left leg, the RH Exhaust ring came out, not surprised it was held in with araldite, (both issues fixed properly). It was the Interstate and the seat width meant I struggled to reach the floor, fell over when stationary twice, plus, as I wear specs, revs below 2500 meant the specs shook and my vision was blurd, isolastics were shot so it wallowed alarmingly when taking a bend at speed, I could go on. All these things could have been improved and some eliminated but that would have cost 1500+ and at the time, the bike was just not worth it!
Chris
Title: Re: B44, Bigend, Piston. Bad vibration.
Post by: MICKREEVES on 23 December, 2017, 17:14:32
That Norton must have been a bad'en! Perhaps mistreated.

I think Ill stick with the B44 for now. The vibration can be tolerated, and it does respond heartily as i open the throttle.
Mick