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#336240 - 10/02/10 2:08 am Triumph Crankshaft Balancing  
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BikeNut Offline
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Please comment on the quality of this work. This was done by a local shop that has been in business for over 50 years. Two of the holes go through the weight. I am not happy and my mechanic refussed to use it. I would like your comments to reenforce my replacement claim.



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#336247 - 10/02/10 2:38 am Re: Triumph Crankshaft Balancing [Re: BikeNut]  
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Bud Provin Offline
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Did they use bobweights to balance it, and a normal balance factor? I can't imagine the crank being in balance with this much weight removed.

#336258 - 10/02/10 3:54 am Re: Triumph Crankshaft Balancing [Re: Bud Provin]  
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phantom309 Offline
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spfld vt
something is really wrong with there math.


Tim Joyce
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#336271 - 10/02/10 10:26 am Re: Triumph Crankshaft Balancing [Re: BikeNut]  
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triton thrasher Online content
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Are replacement flywheels easy/cheap to get?


Amateur Loctite enthusiast.
#336272 - 10/02/10 11:03 am Re: Triumph Crankshaft Balancing [Re: BikeNut]  
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Dick Harris Online content
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What was the balance factor that you were aiming for???? Dick

#336275 - 10/02/10 11:36 am Re: Triumph Crankshaft Balancing [Re: Dick Harris]  
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Beljum Offline
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Holy smokes!! I guess you already figured that is bad from the responses so far.


This is a pic of my preunit crank that has been running very well. A guess would be that yours shouldn’t look too much different.



Here is the real deal back in Meriden. I suspect that there were a lot of smooth ones and a lot of not-so-smooth ones.



Nothings easy.

There is a thread over in the garage sale that you might want to check out per TT’s suggestion..

http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=335127#Post335127



Hi Dick!

I was just typing this response and I saw your post. I was gonna ask the same question. I seem to remember a while back that you had a few cranks balanced using different factors. If indeed that was you, what was the outcome?


If we are lucky maybe this will ignite another balance factor discussion grin .


Go for a ride on a preunit laugh

September 2010 Cuyahoga Valley Ride

'55 "The Mighty 6T", '73 Commando in boxes, '01 DR650, '90 CR250

#336289 - 10/02/10 12:29 pm Re: Triumph Crankshaft Balancing [Re: BikeNut]  
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Dick Harris Online content
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Mon'n Beljum,that was me.I was working on a couple of pre-unit cranks.I did the crank in my '57 TR-6a at 65% and my son wanted his done at 70% on his original '55 T-110. I really can't say that one was better than the other but I know mine is very comfortable at 55-70 at which time it starts buzzing a bit. We rode the two bikes the 300 miles down to the Triumph Come Home rally a couple of years ago at around 65 most of the time and nothing fell off so I guess that's a good thing. JubeePrince (Steve) took a ride on my bike so maybe he could give you an unbiased idea of how if went. Once again, I think that the side to side balance is much more important than the actual balance factor,which calls for dynamic balancing.

#336301 - 10/02/10 2:00 pm Re: Triumph Crankshaft Balancing [Re: Ray in Sunny CA]  
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Originally Posted By: Ray in Sunny CA

Von Dutch used to do stuff like this to people he did not like.

A reasonable person would just refuse to do work for someone he didn't like.


When given the choice between two evils I picked the one I haven't tried before
#336316 - 10/02/10 2:59 pm Re: Triumph Crankshaft Balancing [Re: Dick Harris]  
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Originally Posted By: Dick Harris
JubeePrince (Steve) took a ride on my bike so maybe he could give you an unbiased idea of how if went. Once again, I think that the side to side balance is much more important than the actual balance factor,which calls for dynamic balancing.


Not sure how unbiased it is being as that bike was the ONLY pre-unit I've ever ridden, but it was VERY smooth...at certain RPM's smoother than my factory-balanced T140J!

Dick, I think I told you this already, but I could operate that clutch with two fingers....like butter! At the risk of a thread hi-jack, what's the secret there?

Does the side to side (axial) balancing smooth out the "rocking couple" effect?

I recall reading that T140's require 75% factor....is that correct?

Steve


'77 T140J
"Vintage Bike". What's in your garage?

"The paying customer is always right."

Fitting round pegs into square holes since 1961...
#336327 - 10/02/10 4:24 pm Re: Triumph Crankshaft Balancing [Re: BikeNut]  
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lit67 Offline
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What Bikenut did not mention in his email was that there were actually 3 cranks taken to the this shop on the same order for balancing. One was mine and the 2 others were his. Two of the cranks came back ruined as you see in Bikenut's post, as well as in the picture below. Mine is a 1959 Bonnie crank that had survived 60 years without any damage from previous owners. Holes were drill all the way through the outer ring and were drilled so close together that the holes meet at the bottom, leaving a paper thin piece of metal between the holes. I had kept the crank for over 5 years for a project that I knew I would be doing eventually. Unfortunately, that has changed now. All of the cranks had new sludge tubes and the journals were skimmed to 10 under. The work performed doesn't meet any balance factor, so that discussion is really irrelevant. The person who supposedly did the work has been at the shop for over 30 years and has done work for me and others in the area for years. My belief is that someone less experienced actually did this work. We will not out the shop (yet) due to the respect we have for the owner, who is a legend in the motorcycle field. We plan on meeting with the owner to discuss the work, hence Bikenut's request for opinions.



Lit67
Normal, Illinois
1960 Triumph T100A
1965 Trophy TR6SR
1967 T120R Bonneville
1969 TR6C Project
1965 BMW R60/2 Project
1976 BMW R90/6
2006 Harley Heritage Classic


#336336 - 10/02/10 5:13 pm Re: Triumph Crankshaft Balancing [Re: BikeNut]  
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I can not give an opinion, Lit, but I leave it to you to compare that drilling frenzy with the job on my BSA A65T crankshaft.



It was balanced left to right also. Don't ask percentages. I forgot.

BUT (the big but): not only the crankshaft was balanced. The machinist insisted I give him the rods and pistons, so he could involve these in the complete balance job.
The rods were equalised top and bottom (reciprocating weight and "horizontally moving" weight).




He told me every crankshaft balance job must involve piston weight, rods, and ofcourse the shaft.
And I have no reason not to believe him.
I have not ridden this shaft yet. It has not even been installed yet, as time is an issue on my side.

Last edited by Ger; 10/02/10 5:16 pm.

Ger B

#336401 - 10/03/10 10:34 am Re: Triumph Crankshaft Balancing [Re: BikeNut]  
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Tasman Online content
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I've put a few hundred miles on this crank with no problems. You can see the small holes go all the way through. The guy who did the balancing was recommended to me and he wanted the pistons and rods to do a proper job. I was more than a little concerned when I got it back and I showed it to a Britbike mechanic but he wasn't overly worried. I put the extra holes down to the fact that I'm using a 6T crank in my pre-unit T100.


"Live the life you love, find a god you trust and don't take it all too seriously"

Pre-units rule!

Mid fifties Triumph T100
#336421 - 10/03/10 12:35 pm Re: Triumph Crankshaft Balancing [Re: BikeNut]  
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The original balance factor on the pre-unit 650 was 50% as far as I know. I have seen cranks simalar to the pictures shown, that on road bikes worked fine for long periods without blowing the flywheel but I certainly wouldn't use that wheel on a bike meant for high RPM. I did notice that the only crank that had metal removed from the crank webs was the BSA crank. It is usual that the drive side is a bit heavier therefore needing more metal removed,but I didn't see that on the other flywheels shown. Anyway,Steve,that clutch is just a standard four spring unit with the correct springs. It is unusual in that it doesn't stick after sitting aroung for long periods,and yet it doesn't slip. Don't know what to tell you. The rocking motion is why it's necessary to get it balanced side to side,therefore,dynamically. If you think about,one web could be an ounce light and the other an ounce heavy and it would balance perfectly on knife edges. Dick

#336424 - 10/03/10 1:06 pm Re: Triumph Crankshaft Balancing [Re: Dick Harris]  
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phantom309 Offline
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spfld vt
Dicks right you can get away with alot of stuff on the street you can on the track.:-)


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#336558 - 10/04/10 7:42 am Re: Triumph Crankshaft Balancing [Re: phantom309]  
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Peter R Online content
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It is hard for me to see why a crankshaft, that apparently has been running ok for 30 years or more suddenly needs the "swiss cheese treatment" as seen in the pictures above.
Unless a completely different set of pistons and conrods are to be used, or for some reason a different balance factor is required, I can not see why such a huge amount of metal needs to be removed to obtain correct balance.


Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
#336727 - 10/05/10 9:36 am Re: Triumph Crankshaft Balancing [Re: BikeNut]  
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Tiger Offline
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Not only you Peter.


1969 TR6R
7.62 x 51 is not a maths puzzle.

Moderated by  John Healy 


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