Aliexpress Sprag DC4127(3C) Width?

Edfury828

Edfury828

VIP MEMBER
Joined
Jun 21, 2023
Messages
115
Country flag
Comparing my stock original sprag to the DC4127(3C) sprag Aliexpress sent me, I am seeing a 0.119" larger difference in width. Does anyone know if this even could be right? It does not look right to me. I am thinking they may have sent me the wrong one?

I'm pretty sure it has been the cause of much unpleasant experience since installation. On the up side, I am getting really good at tearing apart MK III primaries!
 

Attachments

  • Aliexpress Sprag DC4127(3C) Width?
    20240522_175106.jpg
    156.4 KB · Views: 43
Edfury828 said:
Comparing my stock original sprag to the DC4127(3C) sprag Aliexpress sent me, I am seeing a 0.119" larger difference in width. Does anyone know if this even could be right? It does not look right to me. I am thinking they may have sent me the wrong one?

I'm pretty sure it has been the cause of much unpleasant experience since installation. On the up side, I am getting really good at tearing apart MK III primaries!
Click to expand...
We just did a sprag change on a friends MK3. The Aliexpress sprag was identical to what we removed. Unkown if that was original or aftermarket installed by a previous owner.
Your image does not look right at all, even the dogbone "rollers" look different width. Confirm if there is a stamped part identifier with what you ordered.
 
Tornado said:
We just did a sprag change on a friends MK3. The Aliexpress sprag was identical to what we removed. Unkown if that was original or aftermarket installed by a previous owner.
Your image does not look right at all, even the dogbone "rollers" look different width. Confirm if there is a stamped part identifier with what you ordered.
Click to expand...
There is nothing stamped on the sprag, or the box it came in. The bubble pack the box was in had the right part number, as did my receipt.

The ID fit real tight too, but it went on by pressing with thumbs and it rotated CCW with some drag as is said to be right...

I am assuming my old sprag to be original. Bike has 17,000 miles.
The width for this sprag number is supposed to be 13.5mm or 0.531". My old one as measured with caliper is 0.510. The Ali is 0.629".
 
I have placed another order with Ali. Vendors name was in Chinese so I couldn't read it, but it was a different link so hopefully a different vendor than before and from a different batch of parts. These sprags seem to be working great for everyone else, so I'm hoping for the best!

I also included a note to seller to "please verify correct part, last order was wrong part".

I am still very curious to verify if anyone has a measurement of their Aliexpress sprag width. Maybe if your friend, (Tornado) still has his old one he could measure it when he has time? I take it, his new one is working fine?
 
One Aliexpress listing has the size 'DC4127(3C) sprag free wheels One way clutch needle roller bearing size 41.275*57.935*13.5mm STARTER CLUTCH SPRAG BEARING'

So you have been sent the wrong Sprag.
 
As I suspected... I guess I already knew the answer, Those dimentions are all over the internet for sprags of the same part number. It's just hard to accept that such a stupid thing could randomly happen to you.

Being ignorant of Nortons and Sprags before buying my MK III, and considering the universal acceptance of the Ali sprag for MK III's, I thought maybe somehow this sprag and the engine sprocket it rides in may work together... even though it didn't!

Luckily my replacement efforts were pre-emptive, so my old sprag should still work fine until the new one arrives. When it does, I will post its actual dimentions... Hopefully a little closer to the 13.5 mm / 0.531" spec!
 
I bought 2 from Ali Express .. The first one has been in for a few years .. This is my spare . OD . 57.6 ID 44.1 W 13.3
They came in plain white boxes with no identification on the box or bearing.
 
Last edited:
Thanks Ron, I appreciate the effort! That not only absolutely verifies my wrong part, but adds great reference information for posterity :)

BTW, my bubble wrap package had the part number in really tiny micro charectors. I had to take a pic and blow it up to read!
 
Edfury828 said:
Thanks Ron, I appreciate the effort! That not only absolutely verifies my wrong part, but adds great reference information for posterity :)

BTW, my bubble wrap package had the part number in really tiny micro charectors. I had to take a pic and blow it up to read!
Click to expand...
Your 13.3 mm Ali width (= 0.523") is pretty close to my old (assumed original) sprag width of 0.510"!
 
Edfury828 said:
Comparing my stock original sprag to the DC4127(3C) sprag Aliexpress sent me, I am seeing a 0.119" larger difference in width. Does anyone know if this even could be right? It does not look right to me. I am thinking they may have sent me the wrong one?

I'm pretty sure it has been the cause of much unpleasant experience since installation. On the up side, I am getting really good at tearing apart MK III primaries!
Click to expand...
I've spent years at this. I have bought around 15 altogether, 5 being from rgm and andover. The later ones lasted for about 3 starts on average! Yes, I had renewed the other components . Changed to an rgm belt drive kit, now unavailable, and no better ! So then, source from China. Got 3 from one company direct but no better, but no worse ! Then got 10 for 118 dollars from another company and ,yes, slightly wider. Had the pulley very slightly machined to fit and the internal tolerance left. One lasted around 40 starts and the second, so far, is still working. Minefield indeed. I can also strip down the primary roboticaly now but fingers 🤞. At least cost wise I have a boxfull left. Roy.
 
The yaki said:
I've spent years at this. I have bought around 15 altogether, 5 being from rgm and andover. The later ones lasted for about 3 starts on average! Yes, I had renewed the other components . Changed to an rgm belt drive kit, now unavailable, and no better ! So then, source from China. Got 3 from one company direct but no better, but no worse ! Then got 10 for 118 dollars from another company and ,yes, slightly wider. Had the pulley very slightly machined to fit and the internal tolerance left. One lasted around 40 starts and the second, so far, is still working. Minefield indeed. I can also strip down the primary roboticaly now but fingers 🤞. At least cost wise I have a boxfull left. Roy.
Click to expand...
I believe CNW has an upgraded sprag and assoicated parts kit for upgrading the MK3 starter mechanism. The same bits are used in their complete estart kits. Spendy compared to the AE sourced sprags, but if youve had so much bad luck in past it may be your path forward.
 
My sprag was from Andover Norton and has done over 150 starts I'd guess (3 years, 5,000 miles). The advice I followed was to replace everything the sprag is in contact with, when replacing the sprag, never just the sprag. I was also super careful to clean everything in the primary, even the chain tensioner reservoir, clutch etc. and the inside faces of the cases. I change the primary oil every year, 1500 miles, once it has warmed through from a ride, to have a chance of holding any contaminants in suspension.

I may be on borrowed time on mine now, but I hope not 🤞. Not a job I enjoyed.

It does seem there are some poor quality replacement parts, but I also suspect contamination may cause some failures.
 
I had the same advice to " replace everything" from Norvil after my Norvil sprag let go in about 4 starts.
That seemed an expensive proposition at the time so I went back to kickstart for about ten years.
Finally , as an experiment, I decided to try one of the Sprags advertised on Ali Express without changing any other parts. I figured I could handle the $17 loss if it didn't work.
Several years and several hundred starts later it still works nicely.

Glen
 
Tornado said:
I believe CNW has an upgraded sprag and assoicated parts kit for upgrading the MK3 starter mechanism. The same bits are used in their complete estart kits. Spendy compared to the AE sourced sprags, but if youve had so much bad luck in past it may be your path forward.
Click to expand...
I found today that the CNW sprag kit is made by another company for them. CNW is presently sold out, but British Cycle Supply also sells them, and presently, has one kit in stock!

I think The Yaki, post-11 had an interesting approach, and worth noting that he too got sprags that were somewhat wider than stock, machining his crank gear to accomodate!
 
The reason to replace everything is that the original engine sprocket is made from a material with a soft core so even with case hardening they will eventually fail. The change to material with a tougher core was one of the first changes I made when I joined AN and all our MK3 engine sprockets are made from the tougher material and have been for 8 years. There are also small differences in the working envelope for the 18 sprag to work in. The Chinese sprags for reason seem to work in anything, mine is now 5 years old and still working fine, as yet I have not heard of one even failing though I have heard of a bike where a Chinese one would not fit but when fitted to another MK3 worked fine.
 
It seems I exaggerated. $119 whatever that is ? $9.00 per unit? Grief. I'll stick with Ellen. Prices will have risen I presume. Roy.
Aliexpress Sprag DC4127(3C) Width?
 
kommando said:
One Aliexpress listing has the size 'DC4127(3C) sprag free wheels One way clutch needle roller bearing size 41.275*57.935*13.5mm STARTER CLUTCH SPRAG BEARING'

So you have been sent the wrong Sprag.
Click to expand...
Is the above number the CORRECT one for MKIII?

Link please?

Thank you.

Edit: found it, all set. 👍🏻
 
Last edited:
You must log in or register to reply here.
Back
Top