Author Topic: 750: too much HP for spokes?  (Read 2587 times)

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Offline Garage_guy_chris

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750: too much HP for spokes?
« on: May 06, 2016, 05:10:52 PM »
So I seem to recall reading on here that the stock spoked rear wheels will start having problems in the mid 80 hp range. I just sorta filed this fact away and haven't thought or worried about it that much.   

Last fall which was just 6 weeks after finishing the bike and getting maybe 750 miles on it while putting it away i noticed a broken "TUP" tension under power spoke. I didnt think a whole lot of it just figured i over tightened it or a bad spoke or whatever, I bought a new set from the same place and replaced it.

Today while taking a break on my ride i noticed a spoke that didn't look quite in pattern, I touched it and sure enough its broken at the bend going through the hub. Again it is a "TUP" tension under power  I wasn't very happy and slightly concerned so i zip tied it to the other spoke it crossed to keep it from flopping around and gingerly headed home.

Now that im home and took a quick look at the wheel i found another one that was 1/2 cracked right at the same bend and again a TUP spoke. A few light turns with a spoke wrench and it snapped without much effort

So thats three outside "TUP" tension under power spokes in 1600 miles. Now my bike is 836cc, has cam, stainless valves,mild head and port work and its likely making mid 70's maybe low 80's power. I figured i was ok power wise for a spoked rear but?????

I have the remainder of spoke kit I bought to replace the one last fall, but im a little concerned just replacing them is setting me up for a total failure of the wheel which is likely to result in a hospital stay and a destroyed bike...

The thing running through my head is that maybe these NON-OEM aftermarket spokes aren't as strong as OEM or other aftermarket options?

Here are the offending spokes they were bought through Vintage CB750 but i also see them come up at Part's N More which are the same parent company. I suspect other places sell them too but can't identify the manufacturer. all the packaging says is "Made in Taiwan and 19-7502


-Is it likely Im making too much power for a spoked wheel entirely

-Are there any better options something like Buchanan's spokes, going to hold up better or should I be starting the restore process on my Lesters?

-Also is a double disc front wheel likely to cause the reverse problem of too much tension under braking ( a front wheel failure would be really really bad )






« Last Edit: May 06, 2016, 05:22:11 PM by Garage_guy_chris »
1971 Cb450 Cafe  (on the road)
1974 Cb750 Restomod (on the road)

Offline Retro Rocket

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Re: 750: too much HP for spokes?
« Reply #1 on: May 06, 2016, 05:13:44 PM »
Plenty of bikes with 80+hp running spokes Chris, I'd be looking at the quality of the spokes... ;)
750 K2 1000cc
750 F1 970cc
750 Bitsa 900cc
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Offline Swoop

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Re: 750: too much HP for spokes?
« Reply #2 on: May 06, 2016, 05:28:27 PM »
Or ...how are you riding?
Hard?

Offline Garage_guy_chris

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Re: 750: too much HP for spokes?
« Reply #3 on: May 06, 2016, 06:02:35 PM »
My riding is a real mix sometimes im just cruising enjoying the ride, other times Im definately enjoying most if not all those 836cc's through back road twisties. No crazy stuff though, no burnouts or wheelies or anything
1971 Cb450 Cafe  (on the road)
1974 Cb750 Restomod (on the road)

Online calj737

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Re: 750: too much HP for spokes?
« Reply #4 on: May 06, 2016, 07:36:05 PM »
Spoke material, not power related. Switch to Stainless from Buchanan's and throw those away.
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Offline Flyin900

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Re: 750: too much HP for spokes?
« Reply #5 on: May 06, 2016, 07:38:59 PM »
Chris,

I have posted about these guys before and you may have missed it under the cam chain tensioner issues. I didn't have an issue with this item but responded to the seeming failures and subsequent recall of said item.
I am a local ON guy and have had a number of dealings with both these companies. I refuse to buy anything else from them, as I find the quality of a large part of their goods are price driven not quality driven.
I have had issues with tools, fork seals and wrong engine seals and frankly found they are not very knowledgable on the parts they sell.

No phone, no real tech support and US dollar purchases plus HST and shipping in US dollars equals no business from me!
Common sense.....isn't so common!

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Offline madmtnmotors

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Re: 750: too much HP for spokes?
« Reply #6 on: May 06, 2016, 07:45:52 PM »
Spoke material, not power related. Switch to Stainless from Buchanan's and throw those away.


+1


My 40 year old stock Honda spokes are tolerating some moderate abuse:






and yes, the front wheel is off the ground. The angle of the photo makes it difficult to tell, but I could tell!    8)  8)  8)
TAMTF...


Wilbur



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Offline SOHC4 Cafe Racer Fan

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Re: 750: too much HP for spokes?
« Reply #7 on: May 06, 2016, 07:53:49 PM »
Stainless!
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Offline BomberMann650

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Re: 750: too much HP for spokes?
« Reply #8 on: May 06, 2016, 08:07:47 PM »
Spoke material, not power related. Switch to Stainless ...

+1

I've only ever laced bicycle wheels myself.

Is it possible to run a longer spoke with a multi-cross lacing pattern on these?  That would toughen up any wheel...in theory

Offline grcamna2

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Re: 750: too much HP for spokes?
« Reply #9 on: May 06, 2016, 09:24:03 PM »
Get oem Honda spokes or Buchanan's,no more worries.
75' CB400F/'bunch o' parts' & 81' CB125S modded to a 'CB200S'
  I love the small ones too !
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Offline Garage_guy_chris

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Re: 750: too much HP for spokes?
« Reply #10 on: May 06, 2016, 09:35:09 PM »
A little update on the spokes

My father which is a metallurgical engineer with 40 years experience had a look at two of the broken spokes and had a few comments. He is suggesting it is a manufacturing defect with either bad raw materials or bad manufacturing process. He said that the raw materials may have been too hard to work properly and during the heading or bending the steel has developed cracks that are propagating outward through the stress of use until it fractures. He also commented it could have to do with stress relieving / annealing or hardening after the spoke is shaped.

On my wheels I may replace the two broken spokes to get by for a couple weeks but I don't intend to keep using them for very long.  I have two options:

1. Restore the set of Lesters I bought over the winter and put them into service,  they need modded for the dual disk speedo drive, bearings, paint and polishing... 

2. Rebuild the existing spoked wheels with better quality spokes. People have suggested Stainless i assume they are recommending Buchanan's as they are the only manufacture making stainless spokes or I would also consider regular plated steel spokes from a reputable manufacture in the States or Japan, none of this Taiwan or China crap

Chris,

I have posted about these guys before and you may have missed it under the cam chain tensioner issues. I didn't have an issue with this item but responded to the seeming failures and subsequent recall of said item.
I am a local ON guy and have had a number of dealings with both these companies. I refuse to buy anything else from them, as I find the quality of a large part of their goods are price driven not quality driven.
I have had issues with tools, fork seals and wrong engine seals and frankly found they are not very knowledgable on the parts they sell.

No phone, no real tech support and US dollar purchases plus HST and shipping in US dollars equals no business from me!

Oh I saw, read, panic'd, had a "wanna put a rag in the tank filler and light it moment" then checked my E-receipts and purchase history on those cam chain tensioners... Luckily i did not buy mine for them!

In Ontario and maybe else where, these guys have a paper catalog any powersports dealer can order out of here they are "MC distributing" I have been to there building on a trip through Stratford, I thought I would pick up a few things and save some shipping since i was there anyways. They wouldn't have any of it and refused to sell anything this way. they refered me to there website. Now about the website there are 3 i know of

www.vintagecb750.com
www.partsnmore.com
www.xs650direct.com

if you look they all have the same address:

79 Linton Ave
Stratford, ON N5A 2S3
Canada

Now im not gonna directly throw them under the bus. The reason being is they aren't manufacturing these parts they are merely distributing them. I would hope they pay more attention to what they are selling and listen to customer complaints and input. On that thought i can't comment as I donno there inter company workings.



« Last Edit: May 06, 2016, 09:41:35 PM by Garage_guy_chris »
1971 Cb450 Cafe  (on the road)
1974 Cb750 Restomod (on the road)

Offline grcamna2

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Re: 750: too much HP for spokes?
« Reply #11 on: May 06, 2016, 10:05:35 PM »
The oem Honda spokes and some Buchanan's are a 'butted' spoke:the part w/ the bend that fits into the hubs has a larger diameter and fit's tighter than the straight gauge aftermarket spokes avail. from most distributors.The hooked ends that fit into the hub holes is where the most stress is;you want a tight fit into the hub holes so the spokes don't squirm around in there and break.

The other thing is,when you build the wheel make sure you have even torque on all of them so that they all work together to bear the strain put on the wheel.  ;)
« Last Edit: May 07, 2016, 08:46:33 AM by grcamna2 »
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Re: 750: too much HP for spokes?
« Reply #12 on: May 07, 2016, 02:39:38 AM »
The other benefit about Buchanan's is they know your bike. When you order spokes, they have OEM replacement spokes based upon your model (front and rear) and rims. You get everything in nice little baggies complete with lube. They like a glove, and they last like an STD.
'74 550 Build http://forums.sohc4.net/index.php?topic=126401.0
'73 500 Build http://forums.sohc4.net/index.php?topic=132935.0

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Offline bwaller

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Re: 750: too much HP for spokes?
« Reply #13 on: May 07, 2016, 08:11:06 AM »
It seems you've come to the correct conclusion on your spoke issue. Too bad.

This doesn't apply in your case, but most broken spokes result from being under torqued, not over.

Offline 754

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Re: 750: too much HP for spokes?
« Reply #14 on: May 07, 2016, 08:38:28 AM »
 I bet its as simple as the bend radius or the bending method...
if 20 spokes are holding the loadat anygiven time its only 20 lbs per spoke, string should almost hold..
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Offline Henning

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Re: 750: too much HP for spokes?
« Reply #15 on: May 07, 2016, 11:45:52 AM »
Stainless itself is not a better material for spokes; plain steel like the OEM spokes will be more forgiving and tolerate more abuse. Still, lots of people here running stainless spokes without problems so it points to a bad batch or another issue with the spokes.
71 or thereabouts 750 K1 - this one should have been put down

Offline przjohn

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Re: 750: too much HP for spokes?
« Reply #16 on: May 07, 2016, 01:21:10 PM »
I bought some reproduction spokes for a 72 Kawasaki H1B restoration a couple years ago. I just noticed a couple of the nipples are starting to rust, WTF  >:( they have been installed for only 2 years. It is my own fault for taking the easy Ebay way out. Time to order a set from Buchannons and grab a six pack. The guys that have built a few wheels will know what I am talking about, it is kind of monotonous, hence, the six pack.

Moral of the story, Buy Buchanons or stock.
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Offline Dunk

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Re: 750: too much HP for spokes?
« Reply #17 on: May 08, 2016, 06:08:15 AM »
Mine is stock displacement but has some port work. No issues with Buchanan spokes. I got them for stainless to not worry about rust, but they appear quality and have a larger OD near the hub so may be stronger.

Offline MRieck

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Re: 750: too much HP for spokes?
« Reply #18 on: May 08, 2016, 09:57:49 AM »
 Use straight spokes...not tapered ones. I had just 100HP and I believe the rears are straight 10 gauge stainless spokes.....no problems
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Offline Garage_guy_chris

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Re: 750: too much HP for spokes?
« Reply #19 on: May 08, 2016, 01:12:58 PM »
Im hoping Buchanan's still has these kits available. they are heavier than stock which will help. I was also thinking the hubs may need to be drilled to accommodate the larger diameter but in my case this would be a good thing because drilling this particular hub would help clean up some elongated and messed up holes.  Otherwise I was thinking I should find a better rear hub which i thought I had and I do but it turns out its off a later 79+ DOHC bike. I will have to check my stash because i seem to remember buying a rear wheel for the sole reason it looked like it had a good hub...

« Last Edit: May 08, 2016, 01:17:30 PM by Garage_guy_chris »
1971 Cb450 Cafe  (on the road)
1974 Cb750 Restomod (on the road)