BritBike Forum logo
BritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorBritBike Sponsor SteadfastCyclesBritBike SponsorBritBike SponsorBritBike SponsorBritBike SponsorHepolite PistonsBritBike Sponsor
Upgrade to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Member Spotlight
marinatlas
marinatlas
FRANCE- DINARD -BRITTANY
Posts: 167
Joined: September 2006
ShoutChat Box
Comment Guidelines: Do post respectful and insightful comments. Don't flame, hate, spam.
Search eBay for motorcycle parts in following countries
Australia, Canada, France, Holland, Italy, United Kingdom, USA
Random Gallery photo
a word from..
Manuals on DVD (Shipping included)
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 1 of 2 1 2
Cali. crank balancing companies?
#795807 01/16/20 11:23 pm
Joined: Feb 2005
Posts: 730
Likes: 2
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2005
Posts: 730
Likes: 2
In a prior thread, DennisJ said he found 2 engine crank shops in California, Marine Crankshaft in SoCal and Kenmonth Machine in Sacramento that were able to do Triumph cranks. I'm in the SF bay area so I called Brian at Kenmonth and asked him if he could balance an offset crank for a vintage Triumph, he said to bring out all the necessary parts and he'd show me how it's done. Brian was friendly and enthusiastic so I'm inclined to give them a shot but was hoping someone on here had used them and could make a recommendation? Thanks, Mark

Support Your #1 BritBike Forum!

Check out British motorcycles for sale: British Motorcycles on e-Bay UK, British motorcycles on e-Bay North America
Re: Cali. crank balancing companies?
MarksterTT #795943 01/18/20 5:53 pm
Joined: Jul 2015
Posts: 37
Britbike forum member
Offline
Britbike forum member
Joined: Jul 2015
Posts: 37
Crank grinders in So Cal are vanishing, could be the high cost of operation and the low profit of the work. Anyway I have been to Marine Crankshaft and it is a beautiful shop equipped with everything necessary to make billet cranks, repair cranks, regrind, etc. I have had a lot of Triumph cranks ground by them and the job was outstanding. I have never used them for balancing however.
My "go to" balancing guy passed away suddenly years ago, he primarily dealt with automotive but was equipped to balance Triumph cranks. He once told me that he could balance 3 Chevy cranks in the time it took to do a Triumph twin. Balancing can be time consuming, and time=money for a shop.
That being said I think that it is harder to find someone to care about the job than someone who just wants the money from the job. If someone at Kenmonth Machine expressed interest in helping you I would say that is a big step in the right direction.
Balancing is a subject of great discussion and opinion like engine oil or pineapple on pizza, the most important thing is what percentage it will be balanced to, THEN who will balance it.

Re: Cali. crank balancing companies?
dandruff #795970 01/18/20 11:37 pm
Joined: Feb 2005
Posts: 730
Likes: 2
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2005
Posts: 730
Likes: 2
Thanks dandruff, that was my thought also and the fact that I can hand deliver and talk to them face to face makes a big difference to me. Factor's been determined at 50% for an offset crank so that's what I'll go with. I checked out Marine crankshafts website and I have heard of them but I won't being driving that far so I hope Kenmonth becomes a go to shop for me as I have other cranks I'd like to have balanced also. Mark

Re: Cali. crank balancing companies?
MarksterTT #795993 01/19/20 8:33 am
Joined: Jan 2017
Posts: 1,311
Likes: 22
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2017
Posts: 1,311
Likes: 22
Hi, Thanks for heads up on Kenmonth Machine. I think I'll pay them a visit in person. I want before/after so I know how much it was out & what actual factor it was.

I had personal experience with Revco Precision Long Beach CA. Rabers sent their balancing work there. Dynamic balancing. Very good shop.

On '69 Bonnie with light flywheel. (Triumph used heavy later in year) decided on 68% per Rabers recommendation. Dynamic balance. Is dead smooth 3800rpm,. A place where you run a lot. 65-70 mph vibration returns, but is way better than before. Did very careful before & after road tests to evaluate vibration. Huge improvement!

I have little personal experience with balancing though. I've spoken with guys that had motors balanced & ridden a few. Balance factors were all over the place. All but one reported a decided improvement. The one that did not, felt motor was smooth before, '64 Bonnie. All these are dynamic.

That leads me to the conclusion that really dynamic is the butt burning vibration that we all hate. The balance factor more determines the smooth zone of rpm. So I'm not stressing over the factor.

On the '69 Bonnie 65-70mph 4000-4600 rpm was just horrible before. Much worse than other 650s with light flywheel. Revco had to take a great deal of metal off right pork chop to get balance. I have rod, piston scale. I decided to weight used pistons & rods at Rabers. Was shocking the difference in parts. As much as 6 grams or more left to right. Rods were all over the place to on weight. So if you got really unlucky you could have a motor that was up to 10 grams+ out of balance. Again the factor is one thing, but that much out on dynamic will burn your rear end real good, besides put your feet & hands to sleep.

I'm kind of thinking going with the factory 85% on my Tiger 750. I had '70 TR6C that was smoothest motor I ever felt. Don't know why. Still miss that bike.

I'm with you don't want to drive to southern California. Shipping crank from Rabers was easy, they had special shipping crates, but I don't have that. Shipping damage or loss is a huge concern for me. However Sacramento is less than 100 miles so that's very doable. I'd wait ever if takes all day.

Some balancers add grams for oil in sludge trap. Triumph shop manual balance factor is for dry sludge trap. So if they add for oil they are effectively altering the balance factor. Which is fine so long as they have good results.

MarksterTT, what part of SF bay area are you in? I'm in Pleasant Hill.

Please tell us about your offset crank. What are doing for cams? What motor/bike to you have? Is it street tracker?

The offset crank had a small following back in the day. The vibration improvement was known back in the early days, but to run best needs twin carbs.

I guess most Brit manufactures felt two carbs were too costly. The offset in pistons on Harley V twin certainly modified the mixture richer on rear cyl. That was good as it got less air flow.

Some new Triumphs have offset crank & no balance shafts. I've not ridden one. The parallel twins with balance shafts feel really good though.
I find the entire subject of engine balancing most interesting.
Don


1973 Tiger 750
Re: Cali. crank balancing companies?
MarksterTT #795997 01/19/20 10:22 am
Joined: Sep 2008
Posts: 1,509
Likes: 5
Britbike forum member
Offline
Britbike forum member
Joined: Sep 2008
Posts: 1,509
Likes: 5
What does it take to build a crank balancing machine?

SR

Re: Cali. crank balancing companies?
MarksterTT #795998 01/19/20 10:34 am
Joined: Dec 2004
Posts: 10,786
Likes: 47
Britbike forum member
Offline
Britbike forum member
Joined: Dec 2004
Posts: 10,786
Likes: 47
What sort of balancing ?

Static can be done on a wheel truing set up. The weights for your chosen balance factor will cost more.

Dynamic means spending £1000's and then hours of working out how it works.

Re: Cali. crank balancing companies?
kommando #796001 01/19/20 1:20 pm
Joined: Sep 2008
Posts: 1,509
Likes: 5
Britbike forum member
Offline
Britbike forum member
Joined: Sep 2008
Posts: 1,509
Likes: 5
Originally Posted by kommando
What sort of balancing ?

Static can be done on a wheel truing set up. The weights for your chosen balance factor will cost more.

Dynamic means spending £1000's and then hours of working out how it works.

My question was meant for dynamic balancing. I've searched on YouTube many times looking for a cheap and easy solution, because I'm cheap and easy, but no luck.
Pete R (yes I quote him a lot) had a suggestion on how to get around this by attaching weights to the crankshaft drive side (on the sprocket or rotor), but for once I'm not sure if he was serious.
The method he described seemed a bit hit and miss to be honest, and possibly something he'd never tried.

SR

Re: Cali. crank balancing companies?
MarksterTT #796004 01/19/20 2:13 pm
Joined: Oct 2012
Posts: 5,265
Likes: 37
Britbike forum member
Offline
Britbike forum member
Joined: Oct 2012
Posts: 5,265
Likes: 37
I have had several auto crankshafts and several Triumph cranks balanced on machines like this....If you choose the correct balance factor ,all is better..

[Linked Image from cwtindustries.com]


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
“But I don't want to go among mad people,” Alice remarked. “Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.
Re: Cali. crank balancing companies?
MarksterTT #796005 01/19/20 2:30 pm
Joined: Dec 2004
Posts: 10,786
Likes: 47
Britbike forum member
Offline
Britbike forum member
Joined: Dec 2004
Posts: 10,786
Likes: 47
I too am cheap and dynamic balancing is one of those ones best left to those who have invested in the machinery. The dynamic bit means the crank has to be spinning and sensors pick up the side to side unbalances indexed to the angular positions, no cheap way to do that yet.

Re: Cali. crank balancing companies?
kommando #796013 01/19/20 5:00 pm
Joined: Sep 2008
Posts: 1,509
Likes: 5
Britbike forum member
Offline
Britbike forum member
Joined: Sep 2008
Posts: 1,509
Likes: 5
Originally Posted by kommando
I too am cheap and dynamic balancing is one of those ones best left to those who have invested in the machinery. The dynamic bit means the crank has to be spinning and sensors pick up the side to side unbalances indexed to the angular positions, no cheap way to do that yet.

I'm sure you're right. I do what I can with what I have, some vibrate fiercely, some just right, most somewhere in between. I don't build them as Temples to the Gods of Brit Bikes, I simply try to make them reliable and fun to own. Better stick with that. I have ridden bikes with dynamically balanced cranks, even built one, a Norton 650SS, but that in particular didn't impress all that much.
One of the best I ever rode was my own 71 Bonnie, which must be why I rode it so much for so long. I built it when I was 22. Much later I discovered that I had used two different rods, one slimmer and lighter. I changed it for the later type and balanced the weights of rods and pistons, after which it vibrated more.
Sometimes it's about the luck of the draw.

SR

Re: Cali. crank balancing companies?
MarksterTT #796015 01/19/20 5:08 pm
Joined: Aug 2001
Posts: 5,417
Likes: 61
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 5,417
Likes: 61
I have been involved as a bit player in dynamically balancing large hydro machines. These run at a fixed speed . typically an x and y accelerometer are fixed temporarily 90 degrees apart, then a test balance weight is fitted at a known angular position on the rotor. The machine is run up to speed and the white mans magic in the box works out accelerations in each plane , calculating the optimum balance weight and angular position. While this works very well for a fixed speed machine I have no experience with variable speeds, and i know one thing for sure it does not compensate for bearing miss alignment or shaft errors. As for a home brew set up, accelerometers are cheaper than they used to be , the white mans magic bit is where it would get very spendy or very techy.That stuff was very specialist 10- 20 years ago, we brought in specialists at huge cost, and sometimes no resulting improvement.

SRM dynamically balanced my A65 crank , it hasnt blown a bulb since, so it does work for bikes, it still vibrates , but the smooth zone is bigger, and buzzy vibes are less in the rough ends out of the smooth zone.

Last edited by gavin eisler; 01/19/20 5:13 pm.

71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Cali. crank balancing companies?
gavin eisler #796016 01/19/20 5:33 pm
Joined: Sep 2008
Posts: 1,509
Likes: 5
Britbike forum member
Offline
Britbike forum member
Joined: Sep 2008
Posts: 1,509
Likes: 5
Originally Posted by gavin eisler

....specialists at huge cost, and sometimes no resulting improvement.

A reminder of not to throw too much money at something you have no control over?
I've seen cranks with more holes than a Swiss cheese after a round at a "specialist". It didn't look right to me, the factory can't have gotten it that wrong.
Which is why I haven't used their services, and why I was interested in possibly setting up my own rig.

Better leave well (enough) alone I think.

SR

Re: Cali. crank balancing companies?
MarksterTT #796018 01/19/20 6:00 pm
Joined: Dec 2004
Posts: 10,786
Likes: 47
Britbike forum member
Offline
Britbike forum member
Joined: Dec 2004
Posts: 10,786
Likes: 47
Basset Down were once the go to place for dynamic balancing in the UK but their expert left and they when downhill for a bit, not sure if they are fully back up to speed but the link is.

https://bassetdownbalancing.com/balancing/

Billy Banger was using someone in the Netherlands or northern Europe and got good results.

Maybe you can PM him for details or search his posts for details.

Re: Cali. crank balancing companies?
MarksterTT #796028 01/19/20 7:17 pm
Joined: Jun 2007
Posts: 6,923
Likes: 16
Britbike forum member
Offline
Britbike forum member
Joined: Jun 2007
Posts: 6,923
Likes: 16
I was lucky when I was building a lot of bikes to know a world renown crank balancer who had a soft spot for old Triumphs. He didn't really give me a discount and most balance jobs cost 3-500$ but it was money well spent since he would throw other work in as well. He inspected and addressed the rods, specifically and checked every one for twist, stretch and oval and if he found one out of spec he would call me and tell me to get another one. He did a lot of racing 500 cranks in prior years and had a good sense for which balance factor worked for each application. He also balanced Formula 1 and Nascar cranks and made a lot of money doing it.
He moved on, but the bikes remain. Several of them had no vibratory period at all and were as smooth as a Commando at 70mph. His machine was a hugely expensive and large "Hydraulic" type with a built in crank grinder. Grinding wheels were something like three feet in diameter.
I have no idea if there is anyone out there comparable these days. Subsequent work I have had done is not quite up to this standard, but still worthwhile doing in my estimation, particularly if you like to ride at highway speeds for any time.
Dynamic balancing address the secondary imbalances which are in the horizontal plane perpendicular to the wheels, whereas primary balance is in the vertical plane in line with the wheels. Secondary imbalance translates to vibrations felt in the footpegs and grips, where vibrations are most problematic. In other words, you can get the balance factor right on the money and still have a bone shaker. However, you can get the balance factor wrong but with a dynamic balance job still have a bike that is rideable. But get them both right and you are on the way to having a really smooth bike that is a pleasure to ride all day.
But you still need to get some things perfect like ignition timing, especially getting them exact left to right, and perfect carb balance if a twin carb bike.
Oddly, even after doing all these these, I had several bikes that still vibrated somewhat, leaving me to wonder where I had gone wrong. Turns out that port biasing can make all your hard work for nothing. Something I learned only much later. And this explains why I have had the best results with twin carb bikes.
And certainly the primary drive is worthy of attention as the factory found out. The chainwheels of later bikes were balanced.
I recently addressed some annoying vibration in my current bike by replacing the chainwheel with an alloy type. My bike become much more enjoyable to ride after that.
Lastly, a stretched chain or unbalanced wheels contribute greatly to vibrations. Just putting on a new chain can transform your ride.
Cheers,
Bill

Last edited by HawaiianTiger; 01/19/20 7:51 pm.

Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Black Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Re: Cali. crank balancing companies?
Stein Roger #796029 01/19/20 7:18 pm
Joined: Aug 2001
Posts: 5,417
Likes: 61
Britbike forum member
Offline
Britbike forum member
Joined: Aug 2001
Posts: 5,417
Likes: 61
Originally Posted by Stein Roger
Originally Posted by gavin eisler

....specialists at huge cost, and sometimes no resulting improvement.

A reminder of not to throw too much money at something you have no control over?
I've seen cranks with more holes than a Swiss cheese after a round at a "specialist". It didn't look right to me, the factory can't have gotten it that wrong.
Which is why I haven't used their services, and why I was interested in possibly setting up my own rig.

Better leave well (enough) alone I think.

SR


More of hint, balancing isnt a magic cure all, it wont fix a bent shaft and it wont fix miss aligned bearings.
When SRM did my crank it came back with one fresh hole, they seem to know what they are doing.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
Re: Cali. crank balancing companies?
MarksterTT #796030 01/19/20 7:56 pm
Joined: Jun 2007
Posts: 6,923
Likes: 16
Britbike forum member
Offline
Britbike forum member
Joined: Jun 2007
Posts: 6,923
Likes: 16
Here's a couple of tips. If you find a crank with holes drilled into the porkchops, the crank has already been dynamically balanced. Save your money and balance your piston and rod assemblies yourself.
If you find a crank that a paperclip will stick to, get another crank as this one has been magnafluxed and cracks found. No need to de-magnetize a broken crank.
Cheers,
Bill


Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Black Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Re: Cali. crank balancing companies?
MarksterTT #796034 01/19/20 8:51 pm
Joined: Oct 2012
Posts: 5,265
Likes: 37
Britbike forum member
Offline
Britbike forum member
Joined: Oct 2012
Posts: 5,265
Likes: 37
The holes in the cheeks as Bill mentioned above seen here in ....I was skimming about .015" off the flywheel for cam lobe clearance....I was told it wouldn't affect the balance job....But, what did affect the balance was my bad choice of balance factor for a 750 kit on a 650 in a 70 frame....I told the shop the balance factor for the 750 OIF. ........The handle bars and foot pegs were ok but the vibration felt though the seat blurred my vision and set my butt on fire at 55-60 MPH.... Above and below this speed was ok...I regeared the bike but it always had the rough zone.... Lesson learned...

[Linked Image from i.imgur.com]


79 T140D, 96 900M Ducati ,61 A10 .On a bike you can out run the demons..
“But I don't want to go among mad people,” Alice remarked. “Oh, you can't help that,” said the Cat: “we're all mad here. I'm mad. You're mad.
Re: Cali. crank balancing companies?
MarksterTT #796037 01/19/20 10:11 pm
Joined: Nov 2012
Posts: 1,681
Likes: 20
Britbike forum member
Offline
Britbike forum member
Joined: Nov 2012
Posts: 1,681
Likes: 20
I had the old fellow (Phillip) at Bassett Down Balancing do my pre-unit 650 3-piece crank in 1998.
He had his own preferred way of going about it. Rather than drilling holes, he sculpted the cheek, top and sides of the top, for the dynamic part of the exercise.

Then (after after doing the rods and pistons) he set the factor to 71%, again by scalloping symmetrically the sides of the flywheel in a long smooth fashion.

He was thinking about stress risers. I don't know if that is real, or just an fastidious old fellow? It certainly looked very tidy, and must have been more effort than drilling. All for £70 at the time.
It has resulted in a very sweet engine.

Re: Cali. crank balancing companies?
MarksterTT #796040 01/19/20 10:36 pm
Joined: Jun 2007
Posts: 6,923
Likes: 16
Britbike forum member
Offline
Britbike forum member
Joined: Jun 2007
Posts: 6,923
Likes: 16
When I dropped a Routt 750 kit on top of my '67 Bonnie, that bastard shook like a wet dog. However, that usually didn't bother me much since most of the time I was hanging on for dear life and didn't notice.
It's really all about perceptions.
Now that I'm older, my posterior seems a bit more delicate and I'm not riding nearly as fast, so my perceptions are more noticeable.
Cheers,
Bill

Last edited by HawaiianTiger; 01/20/20 7:20 pm.

Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Black Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Re: Cali. crank balancing companies?
kommando #796041 01/19/20 10:43 pm
Joined: Jan 2014
Posts: 927
Likes: 34
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2014
Posts: 927
Likes: 34
Originally Posted by kommando
What sort of balancing ?

Static can be done on a wheel truing set up. The weights for your chosen balance factor will cost more.

Dynamic means spending £1000's and then hours of working out how it works.



I've done the electronics on a few different balancing machines, mostly prop-shaft ones but one or two
crank balancers. The mechanical side is the expensive part, drive and load cell coupling. The construction needs
to be very rigid so large bed plates etc.
These days a high speed plc type controller will do the job but it does need load cell front ends. If you want very
high resolution and flash screens, of course that will also add up. For these old crates, ten point res would probably
be ok so measuring deflection in 36 deg radians. Using a 360 inc encoder means the speeds wouldn't be too high
so not too hard to do.

Re: Cali. crank balancing companies?
MarksterTT #796054 01/20/20 2:34 am
Joined: Feb 2005
Posts: 730
Likes: 2
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2005
Posts: 730
Likes: 2
TR7RVMan, if you make it out to Kenmonth, l'd like to hear about it. I'm in San Carlos and the bike is sort of a streettracker standard idea based on a modified C&J monoshocker (offcenter left 3") oil in frame and a TR7RV bottom end with long rod top end using MAP nikasil big bore kit and T140D head that was originally going to be modified to a single carb but I'm not sure now since I've decided to use MAPs offset crank. When I heard Falicon had gone out of business, I called MAP to see what was up with future offset cranks. Rick said they were searching for a new supplier but in the meantime had 4 std 82mm stroke cranks left in stock,...then he made me an offer I couldn't refuse and I ended up with a crank and more. Holy crap, best late Christmas ever! I have no idea how that happened but I had given up on having my own offset crank made so it was this or nothing. Although, if I like how this engine turns out, I still may pursue my own crank for another project, depends on cost for a one off and how much time I have left for this kind of stuff.

Thanks guys for the input, Hawaiian Tiger, my Routts 800 kit shook also but my 750 pistons weren't bad, the bare 800 piston alone was like 364 grams I believe (about 100 grams heavier than MAPS 825 kit) and it appeared that he had one big slug forged and whittled down the outside for the smaller bores so the big one had really thick skirts etc.

Hillbilly, I checked my notes and ED V. said they balanced a T140 at 85% in a race frame and it shook real bad so they went back to 70* and it was "smooth at rpm" so just the opposite of you but similar results.

Ed G.'s offset cranks are balanced at 50% after trying 60% and 45%, with 60% being smoother from idle to 5000 rpm and 45% smoother at high rpm but not so much at lower r's.

Re: Cali. crank balancing companies?
MarksterTT #796100 01/20/20 7:32 pm
Joined: Jun 2007
Posts: 6,923
Likes: 16
Britbike forum member
Offline
Britbike forum member
Joined: Jun 2007
Posts: 6,923
Likes: 16
It takes some real dedication to tear apart a Triumph motor just to experiment with balance factors. I think a lot of us would like to see a database of balance factors vs all the variables, but I suspect that is a bit too much to ask. This is where seat of the pants experience wins out.

For what it's worth, my balancer recommended 58-62% balance factor on Triumph motors, whether they were 500 or 650cc. I found the same results as you. That made for a motor that was smooth at at all rpms. Admittedly, I never revved these motors beyond 5k or maybe occasionally higher as they were top notch restos worth a lot of money. I geared them up a bit to make sure that at LA Freeway speeds one could keep up with traffic in comfort without the feeling that the motor was going to come apart. Nothing from the factory even comes close.

He recommended 85% balance factor for motors routinely run above 6k rpm. I believe they do smooth out at higher rpms with the higher balance factors.

Don't know what the factory was thinking with 70% BF for Triumphs in BSA frames (OIF, 71-on) Only the 650's are smooth enough in my estimation. 750's suck and I hate riding them.

Off topic a bit, but 120 degree triples are inherently smooth, inline sixes are basically dead smooth (Jaguar xj6) and v12's have to be experienced to be believed. (flywheel ring gears routinely munched by folks trying to start a running motor)

Cheers,
Bill

Last edited by HawaiianTiger; 01/20/20 7:55 pm.

Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Black Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Re: Cali. crank balancing companies?
MarksterTT #796137 01/20/20 10:51 pm
Joined: Jan 2017
Posts: 1,311
Likes: 22
Britbike forum member
Offline
Britbike forum member
Joined: Jan 2017
Posts: 1,311
Likes: 22
Hi Bill, What would you do for factor on T140 motor? Factory calls for 85%. I tend to agree T140 type motors shake worse overall. Some much worse.
I have no idea what it will cost, but I'd like to have before measured. I want to know how much is taken off where on crank to get dynamic corrected.

Vibration is a whole subject which of course includes chassis & all bolt on parts as well as motor. I've got to get this right best I can.

Going only to .080 thick head gasket from standard .050" thick made a very noticeable improvement. Even my wife noticed riding pillion.

Replacing stock mufflers with Emgo repro stock type mufflers which were about 2# lighter each made a noticeable difference.

Reversing the lower spacer under P clamp rubber for bars made a gigantic improvement in bar vibration. Basically removed most of rubber mounting. The play in rubber from factory even from new was really a lot. I just started experimenting. I was going to experiment with rigid, but this works so good I left it.

I'm committed to using 7.4 "unleaded" pistons. Will be interesting to see what they weigh compared to current 8.6. How will that effect factor??

I seldom exceed 5000 either. When I do it's only for a few moments accelerating.
Don


1973 Tiger 750
Re: Cali. crank balancing companies?
MarksterTT #796141 01/20/20 11:36 pm
Joined: Jun 2007
Posts: 6,923
Likes: 16
Britbike forum member
Offline
Britbike forum member
Joined: Jun 2007
Posts: 6,923
Likes: 16
I haven't ever built a 750 from the bottom up so I've never had the chance to play with balance factors. I believe that the factory changed the 85% BF of the 650's to around 70%. Others will perhaps know exactly when this was done. I'm not sure what they were after, but apparently it didn't work or only partially worked. According the HB, 85% would probably be a bad move. That leaves moving to a lower BF as an option. My balancer did ALL Triumph street motors at 58-62% but I'm not sure that takes into account the chassis or not. It seems to me that 750 frames are a bit more rigid than earlier frames. At this point we need more info on the effect of different balance factors for 750's short rod motors in OIF type of frames. If someone here has done this, it would be good to hear from them.
Cheers,
Bill


Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Black Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
Re: Cali. crank balancing companies?
MarksterTT #796301 01/22/20 6:12 pm
Joined: Feb 2005
Posts: 730
Likes: 2
Britbike forum member
OP Offline
Britbike forum member
Joined: Feb 2005
Posts: 730
Likes: 2
TR7RVMan...I believe T140/TR7's are balanced at 74% from factory. Balance factors were chosen after test riders were given various factored bikes to ride and then chose the most popular...so I've read, different frame designs, attachments, engines (short rod engines have heavier pistons/pins and rods then 650's) all make a difference in perceived vibration.

You mentioned going to 7.4-1 pistons, the stock dia. 7.9-1's weigh 261-264 gr. bare and just for comparison I weighed up a few items.

Pistons bare; T120...242 gr.,.... pin 54 gr.,.... assy. minus rings 296 gr....9-1 cr. (.688" dia.pin)
T140...261-264... " 71 gr. " " " 335 gr.....7.9-1 cr. (.750" dia.pin)

Forged MAP pistons

3.0" T120...254 gr...…pin. 60 gr.,...…assy. minus rings 308 gr......9.5-1 (older 2618 alloy, latest design/alloy closer to 234 gr.)
3.128" " ….269 gr......."....60 gr.........." " " 329 gr......9.5-1 (825cc older 2618 alloy)

3.0" T140.... ? ........ ? .... forged 7.5-1, 9.0-1 & 10.5-1 available but point being the 7.5-1 should be significantly lighter then stock T140

*notice that largest 825cc forged 9.5-1 MAP pistons weigh less than the stock bore T140 assy. and I can still get a few more grams off the MAP pistons but not so
easy under stock cast pistons.


Rods, minus shells;

Late T120...419.1 gr. stock............MAP 429.5 gr.,....4340 steel H beam
T140...427 gr. stock .............MAP 425.0 gr.,... " " " "

*notice that MAP steel rods in T140 size weigh less than stock T140 alloy and only 10 gr. more than stock T120 alloy

Above info just to think about if you're interested in going lighter and/or lower compression or will be rebuilding a performance engine and think that all big bore or steel rods are big heavy things to avoid...in the olden days forged big bore pistons and steel rods were significantly heavier.

I think with the lighter 7.5-1 cr MAP pistons and balanced crank (dynamically) you'd probably have a pretty sweet running T140/TR7

Last edited by MarksterTT; 01/22/20 7:48 pm. Reason: change and add info
Page 1 of 2 1 2

Moderated by  John Healy 

Link Copied to Clipboard
Home | Sponsors | Newsletter | Regalia | Calendar | Bike Project | BritBike Museum | Spiders Cartoons | DVD- Manuals & Parts books
Upgrade to: Premium Membership | Gold Membership | Life Membership | Vendor Membership | Site Sponsor Membership
Powered by UBB.threads™ PHP Forum Software 7.7.4