[Pablo españa]

Hello and thank you for accepting me in the forum, first of all I apologize, I do not speak English, I am Spanish, and I just purchased a Royal Enfield bullet but I do not know the model, can you help me identify which model it is?  Thank you!

[Adrian II]

That is a 4 speed, 500 Bullet deluxe, chromed fuel tank and mudguards, (or gas tank and fenders), other models just had these painted. Known as the iron barrel Bullets in the USA because of their cast-iron cylinder barrels. With a few changes these are broadly similar to the British-built royal Enfield Bullets from the mid 1950s, with the addition of 12V electrical systems, a twin leading shoe front brake and, in this case, an electric starter as well as the kick start.

This model has its own section on the forum. Meanhwhile the AVL-engined Bullet or Electra-X Royal Enfield as it was known in Europe has a different engine, and the cylinder is cast alunin(i)um, not cast iron.

I hope this helps.

A.

[Bilgemaster]

Welcome aboard! That's a very fine looking Bullet with many desirable features such as a right-hand shifting gearbox and a proper crankcase breather properly located at the lefthand base of the cylinder.

My chief advice to you as a new Bullet owner would be to avoid using the electric starter. They are extremely prone to failure because of a poor design with a weak "sprag clutch" (Español: "embrague de patín"). Search the Forum Archives for the word "sprag" for further details. You would be very wise to learn how to kickstart your Bullet and NEVER use its electric starter!

Let's see a photo of its righthand (pretty) side too!

[Pablo españa]

Thanks a lot!  If I have started it and I am polishing it, the starter is faulty, the advice is late, now I am looking for a replacement to fix it

[Pablo españa]

Welcome aboard! That's a very fine looking Bullet with many desirable features such as a right-hand shifting gearbox and a proper crankcase breather properly located at the lefthand base of the cylinder.

Thanks a lot!  the promised photo, here it just arrived at my house after years of standing, I promise to upload a photo when it is fixed


My chief advice to you as a new Bullet owner would be to avoid using the electric starter. They are extremely prone to failure because of a poor design with a weak "sprag clutch" (Español: "embrague de patín"). Search the Forum Archives for the word "sprag" for further details. You would be very wise to learn how to kickstart your Bullet and NEVER use its electric starter!

Let's see a photo of its righthand (pretty) side too!

[Bilgemaster]

Thanks a lot!  If I have started it and I am polishing it, the starter is faulty, the advice is late, now I am looking for a replacement to fix it

It is best to remove the sprag gear cluster and the starter (to save weight), and then close the hole with one of our Forum host's "Starter Motor Blanks" (https://accessories.hitchcocksmotorcycles.com/accessory-shop/crankshaft-engine/21512). Some owners have "fixed" the starter many MANY times, but it is such a poor design that it is almost guaranteed to fail again. What happens is that if the engine kicks back, or even rolls back gently, it breaks the sprag clutch.

There are some things you can do to try to avoid problems: always have a perfect battery that is fully-charged, use the decompressor when first pressing the starter button to allow the engine to gain a little speed, always stop the engine with the decompressor, and use about 800ml of automatic transmission fluid (like "F Type" for Fords) instead of the original 420ml. But none of these hopeful techniques worked for me. My sprag still died although I hardly ever used it.

Hitchcocks does sell a very expensive "Starter Upgrade Kit" for about £700 (see: https://accessories.hitchcocksmotorcycles.com/accessory-shop/ignition/34789), and you would also still need a new sprag. I do not know how effective this kit is. I do know that I don't miss my "electric leg", and here is what I did with its button, relay, etc.: https://youtu.be/Xcfo30h-0N0

[richard211]

 I have been curious for a while as to why exactly the sprag clutch fail. I am aware the sprag clutch quality is not the best. Earlier on my AVL 350 it used to have a low speed stalling issue and the crank used to roll back when it stalled. Every time it happened the sprag clutch would spin the starter motor. But it never blew up. Given that the engine was a 350cc and had a 8kg crank, the shock transmitted through to the sprag clutch and starter motor is considerably less compared to a 500cc with a 10kg crank. I wonder if part of the issue causing the sprag clutch failure would have been a starter motor that was seizing up. Does anyone who has had a sprag clutch fail and still have their starter motor laying around be able to check whether the pinion on the starter motor spins freely without binding or seizing up?

 The logic I am trying to apply is if the starter motor was seizing up and a kick back or roll back occurred, the weakest link obviously is the sprag clutch that has to take the brunt of the kick back / roll back. Its just something that I have been wondering about for a while.

[Bilgemaster]

I have been curious for a while as to why exactly the sprag clutch fail. I am aware the sprag clutch quality is not the best. Earlier on my AVL 350 it used to have a low speed stalling issue and the crank used to roll back when it stalled. Every time it happened the sprag clutch would spin the starter motor. But it never blew up. Given that the engine was a 350cc and had a 8kg crank, the shock transmitted through to the sprag clutch and starter motor is considerably less compared to a 500cc with a 10kg crank. I wonder if part of the issue causing the sprag clutch failure would have been a starter motor that was seizing up. Does anyone who has had a sprag clutch fail and still have their starter motor laying around be able to check whether the pinion on the starter motor spins freely without binding or seizing up?

 The logic I am trying to apply is if the starter motor was seizing up and a kick back or roll back occurred, the weakest link obviously is the sprag clutch that has to take the brunt of the kick back / roll back. Its just something that I have been wondering about for a while.

After removing my sprag and its fragments and related gear cluster I rode around for a couple of months with the starter motor filling the hole until I got that Hitchcocks blanking plug. The motor would still spin merrily. With mine at least the sprag was definitely the culprit, and I fished many of its fragments from the primary.

[Pablo españa]

It is best to remove the sprag gear cluster and the starter (to save weight), and then close the hole with one of our Forum host's "Starter Motor Blanks" (https://accessories.hitchcocksmotorcycles.com/accessory-shop/crankshaft-engine/21512). Some owners have "fixed" the starter many MANY times, but it is such a poor design that it is almost guaranteed to fail again. What happens is that if the engine kicks back, or even rolls back gently, it breaks the sprag clutch.

There are some things you can do to try to avoid problems: always have a perfect battery that is fully-charged, use the decompressor when first pressing the starter button to allow the engine to gain a little speed, always stop the engine with the decompressor, and use about 800ml of automatic transmission fluid (like "F Type" for Fords) instead of the original 420ml. But none of these hopeful techniques worked for me. My sprag still died although I hardly ever used it.

Hitchcocks does sell a very expensive "Starter Upgrade Kit" for about £700 (see: https://accessories.hitchcocksmotorcycles.com/accessory-shop/ignition/34789), and you would also still need a new sprag. I do not know how effective this kit is. I do know that I don't miss my "electric leg", and here is what I did with its button, relay, etc.: https://youtu.be/Xcfo30h-0N0

Thank you very much, your contributions are very interesting

[richard211]

After removing my sprag and its fragments and related gear cluster I rode around for a couple of months with the starter motor filling the hole until I got that Hitchcocks blanking plug. The motor would still spin merrily. With mine at least the sprag was definitely the culprit, and I fished many of its fragments from the primary.

I read a post on another forum where an automatic transmission repair specialist had found out the RE sprag clutches were a cheaper copy of a Borg Warner sprag clutch and using the Borg Warner sprag clutch resolved the issue. Does anyone have the Borg Warner part number?

[Adrian II]

This came up on H's forum some time ago, Borg Warner T-35 torque converter is what the sprag clutch is out of, but there was no mention of a separate part number for the clutch itself.

A.

[Bilgemaster]

The BorgWarner part that 'Richard211' and 'Adrian II' mention is probably the one described in the old thread about my own Bullet's "Spragtastrophe" here: https://forum.classicmotorworks.com/index.php?topic=26991.msg309194#msg309194.

As you can read there, I did actually try contacting Borg-Warner for more details about their sprag (BorgWarner Part No. BW-SP-2--Also mentioned is the German-made Stieber Clutch Part No. DC-4127-N [3C]), but I never received the kindness of a reply. Since I already decided to remove the starter and had hardly ever used it anyhow, I never bothered following up.

[richard211]

Adrian and Bilgemaster thank you for sharing the Borg Warner transmission information. I have been going through a few Transmission Catalogues and the Borg Warner sprag clutch PN# BW-SP-2 which may have started it life in the 1960's in the BW T35 transmission its still a very common part thanks to a partnership between Borg Warner and Asin (being in use for over 50+ years). There is a transmission called the AW TF-80SC ( AW stands for Asin and Warner), this transmission is a very common Front Wheel Drive Transmission used worldwide.

 The second sprag clutch made by Stieber PN# DC-4127-N [3C] is a bit bigger than the Borg Warner sprag clutch in most of its dimensions. I don't think they could be interchanged. The Stieber sprag clutch seems to have been used on The Norton Commando mk3, seems like they too struggle to keep their sprag clutches intact, but going through their forums they seem to have some luck with the $17 sprag clutches off aliexpress .

Adrian and Bilgemaster, would you happen to have the gear and engine sprocket where the sprag clutch sits so we could confirm some dimensions?

The dimensions for the Borg Warner Sprag Clutch are
Width: 0.336" / 8.53mm
Race Outer Dia.: 2.747"/ 69.77mm
Race Inner Dia.: 2.087" / 53.01mm

[Adrian II]

I do still have the remains, but I think they're buried under junk in the garage, I'll try and remember to look tomorrow unless B.M. beats me to the draw.

A.

[Bilgemaster]

Adrian and Bilgemaster thank you for sharing the Borg Warner transmission information. I have been going through a few Transmission Catalogues and the Borg Warner sprag clutch PN# BW-SP-2 which may have started it life in the 1960's in the BW T35 transmission its still a very common part thanks to a partnership between Borg Warner and Asin (being in use for over 50+ years). There is a transmission called the AW TF-80SC ( AW stands for Asin and Warner), this transmission is a very common Front Wheel Drive Transmission used worldwide.

 The second sprag clutch made by Stieber PN# DC-4127-N [3C] is a bit bigger than the Borg Warner sprag clutch in most of its dimensions. I don't think they could be interchanged. The Stieber sprag clutch seems to have been used on The Norton Commando mk3, seems like they too struggle to keep their sprag clutches intact, but going through their forums they seem to have some luck with the $17 sprag clutches off aliexpress .

Adrian and Bilgemaster, would you happen to have the gear and engine sprocket where the sprag clutch sits so we could confirm some dimensions?

The dimensions for the Borg Warner Sprag Clutch are
Width: 0.336" / 8.53mm
Race Outer Dia.: 2.747"/ 69.77mm
Race Inner Dia.: 2.087" / 53.01mm

Since I basically fished out the fragmented remains of my sprag clutch piece by piece, I am afraid that all I have left for the next owner, should they (I believe foolhardedly) wish to resurrect it, is the starter motor and the removed part of the gear cluster corresponding to the not entirely accurately depicted items 8, 9, 12 & 13 shown in the Hitchcocks Parts Book diagram here: https://www.hitchcocksmotorcycles.com/partsbook-pages/2410. The now harmless rest is still in situ on the bike.

Sadly I lack any Vernier Calipers for the sort of exacting measurements down to the thousandth of an inch or hundredth of a millimeter as you have provided. I'm afraid that the best I can offer for some scale of my debris in attached photos is the metric side of a purloined Ikea measurement tape still smelling vaguely of meatballs. As well as an overall photo of this general section of the laid-up gear cluster without its sprag, I will try to show the details if items 9 ("PART No. 560017 GEAR, CLUTCH DRIVEN, 500+535cc, E-START ONLY" also shown here: https://accessories.hitchcocksmotorcycles.com/10401?qty=1&continue_url=https%3A%2F%2Fwww.hitchcocksmotorcycles.com%2Fpartsbook-pages%2F2410), 12 (PART No. 560008 CLUTCH DRIVING GEAR, 500+535cc, E-START ONLY" also shown here: https://accessories.hitchcocksmotorcycles.com/10382?qty=1&continue_url=https%3A%2F%2Fwww.hitchcocksmotorcycles.com%2Fpartsbook-pages%2F2410) and 13 ("PART No. 560009 SPINDLE, 500+535, E-START ONLY" also shown here: https://accessories.hitchcocksmotorcycles.com/10384?qty=1&continue_url=https%3A%2F%2Fwww.hitchcocksmotorcycles.com%2Fpartsbook-pages%2F2410) with the measuring tape for at least some  sense of scale.

[richard211]

Thank you Bilgemaster for the photos, looking at the dimensions it looks like the Borg Warner sprag clutch BW-SP-2 is way too big for the Royal Enfield application.
 I did find an aftermarket supplier with a fairly decent reputation in India that sells sprag clutches for the older bullets.

[Carl Fenn]

Incidentally Tetrosyl UK have started making that read semi hardening gasket compound again it’s red and goes under the name of gastite not RTV you can apply with paper gaskets easy to get old gasket off and resistant to oil petrol steam and antifreeze excellent when it comes to removing gaskets and cleans off with meths bit like wellseal.