Rear sprocket bolts Qingqi QM200GY-BA

Following on from message nº10 on this thread concerning breakage of rear sprocket bolts by shearing and their possible replacement for stronger items, I've had a look at what's fitted to mine.

A simple observation of the heads of the bolts shows they're are marked "7ST". This could be something to do with their strengh. To compare, other bolts so marked include the pillion footrest hangers, engine holding bolts, engine guard bolts, etc.

Other screws for light duties like the chain guard are marked "4ST". This looks so far as if it's some sort of Chinese bolt tensile strengh code, but:
Bolts for serious duties like handlebar clamps, brake callipers, fork yokes, etc, ARE marked using the international ISO markings, and they clearly show "8.8", meaning a quite high tensile strengh grade. So, what does "7ST" mean?. Is it better than 8.8 or worse?.

This is a chart showing the US an ISO bolt strengh markings. No "7ST" there!

http://www.telecable.es/personales/a...tstrengths.gif

I removed one of the bolts after bending back the very strong security tab washer and it's a M8x30 mm with a 6 mm long unthreaded shank.
This 6 mm being the width of the sprocket.

One important note about fasteners. The threaded section of a fastener should never be given side loads or shear loads.
The threads will not be as strong as the shank (unthreaded portion), and can also chew away on the surrounding metal.
This should be taken into account on any critical aplication such as Disc brake rotors, drive coupling flanges, sprocket drives, etc,
so they MUST be replaced with a similar bolt with a 6 mm plain shank and a high tensile rating.

I'll visit my friendly screw peddlar tomorrow and see what he's got.

Here's a (bad) photo of the bolt (bloody useless Macro function on my Cannon IXUS 60...):

http://www.telecable.es/personales/a...ocketbolt6.jpg

Have visited my screw supplier today (28th) and they don't have anything like that (I knew it!). Alternatively he can supply me with the nearest thing that can be modified and it's a DIN-931 M8x40 bolt in 12.9 grade (the strongest) and with an unthreaded shank 17 mm long.
This bolt can be first cut down to 30 mm and then a Die used to cut the thread another 10-11 mm along the plain shank until only 6 mm remains.
This is all very easy to talk about, but 12.9 steel is tough and after doing one was exhausted. (It's hot and humid here today). So I did the only thing a red-blooded Spaniard does when confronted with a difficulty ...gave up, drank some wine and had a siesta.

I did talk to a keen bicyclist in the shop and he confirms that the cause of the sprocket bolts breaking is letting the spokes come loose, it happens to bicycles all the time apparently. So I think that I'll just keep an eye on my spokes and see what happens.

Thanks forchetto for the thorough information and research. I had the rear wheel off last night to change the sprocket and tire. I think you can see from the pics that the stock bolts (silver color) do not have a very deep shoulder, even the sprocket is almost resting on the threads.

I had a couple of other bolts lying around to compare, but have not found a perfect match yet. I'm going to measure the hub thread depth and try to have a local screw shop make the correct bolts. I'm thinking that the shoulder that rests in the sprocket and top of the hub should have a slightly larger OD than the rest of the bolt.

http://www.contactdi.com/2008/fix/fix001.jpg

http://www.contactdi.com/2008/fix/fix002.jpg

http://www.contactdi.com/2008/fix/fix003.jpg

Cheers!
ChinaV

Thanks for those great pictures, chinaV, they help a lot, as I only took off a bolt while the sprocket was still on the bike.

I assumed the thread went to the top surface of the hub, but it seems there's something like 6 mm unthreaded. There must be a reason for this, as it entails cutting the thread first and then a second machining operation to remove 6 mm of it. I can't see the reason, although someone suggested it stops the bolt tension from raising the aluminum, making the sprocket seating face not flat.

This means that, as you say, the bolt could have a longer unthreaded shank, and it makes it easier to find standard bolts that could fit. Looking at a chart of preferred sizes of DIN-931 bolts, there's one that requires minimum modification and is a M8x40 with a 28 mm threaded portion. This means it has a 12 mm plain shank, and with just cutting off the surplus 10 mm in length to 30 mm total, would fit and present this plain 12 mm shank to the tab washer (1.00mm), sprocket (6.75 mm) and the remaining plain part (about 4.25 mm) would sit nicely inside the hub, just before the threads start.

As you suggest, it would be ideal if the plain part fitted better inside the holes. It would have to be made specially and look something like the bolts that are used as handlebar lever pivots:

http://www.mettec.com/images/YZ250F%...0PIV%20016.jpg

Hey Guys,

I found some possible replacement bolts for the QingQi 200gy rear sprocket.

These come from the excellent Mcmaster-Carr company in the US. They have a partially threaded M8, 30mm, 1.25pitch, Class10.9 cap bolts which I think may work.

They are about 12.00USD for a pack of 25 zinc plated and 9.00USD for black finish.

- Click image for site link and search "Metric cap screw" -
http://www.mcmaster.com/library/20050125/91310A538L.GIF

If anyone is serious about trying these, let me know.

Paz,
CC

I've just received my genuine Suzuki 44 tooth sprocket to replace the stock 48 tooth and so raise the gearing. It's a Suzuki part number 64511-48001 made to fit models DS100, DS125, TS100, TS125 (1978-79).

If you prefer JT Sprockets have an equivalent listed with reference number JTR 809.44

Site at: http://www.jtsprockets.com/

Some of us, in this and other forums, have had trouble with sprocket bolts shearing or threads in the hub stripping. We've speculated about the bolt steel quality, poor hub alloy, etc, but I think I now have the answer and it agrees with ChinaV's suspicions also. (See post number 2 on this thread).

At the same time as I ordered the sprocket I ordered a set of genuine Suzuki bolts, according with the parts catalogue where I found the sprocket. Their part number is 09100-08094. They come as a set of six.

On opening the packet, the difference is obvious, they're M8x30 grade 8.8 (marked "7" as per Japanese practice) same as the Qingqi's but, the unthreaded shank is 14 mm long rather than 6 mm.

Good engineering practice advises not to let a bolt work in shear load, only in tension, but if the designer chooses to do so, to ensure two things:

1- Ensure the tensile load applied to the parts by the bolts is sufficient to stop relative movement between the parts and so avoid movement and the transfer of the shear load to the bolts.

2- If this happens through overload or under-torquing of the bolts, then the shear load must not fall upon the threaded part of a fastener.

This is the reason why there's an unthreaded portion in the bolt holes of the hub. (see ChinaV's photos in post 2).

The idea is to use a bolt with a plain shank that will go through the tab washer thickness (1 mm), the sprocket thickness (7.2 mm), and have the remaining plain portion sufficiently long to penetrate the unthreaded hub portion.

In one South American forum they thought that this unthreaded portion in the hub meant that threads had been stripped and have carried out a repair using a thread insert threaded right to the top surface. This is wrong.

In normal usage and with the bolts torqued up correctly, the two parts (sprocket and hub) should not move relative to one another. This can only happen if the bolts come loose.

The recommended torque for these bolts is 22Nm (16 ft.lbs.). The procedure I would use is to torque the bolts, wait a while before bending up the lock washer tabs, to allow the joint to settle, re-torque and bend the tabs over one of the bolt head flats.

http://www.telecable.es/personales/a...ketsection.jpg

That makes sense! I'm sure it will be a great improvement over the stockers.

How deep is the unthreaded portion of the QingQi hub? From ChinaV's pics it's didn't look as deep as indicated in the drawing. Would you have to countersink-drill it?

Also, cool illustration! I didn't know you were also an artist! :icon10:

CC

Nice work forchetto,:thumbsup: Who needs shop manuals when you have forchetto the artist at MCM :mwink:

Cheers
ChinaV

Thank you, thank you. I thought the drawing was rubbish really. I do have a little chap at work that can work an AutoCad program to do it properly, but being another Spaniard all I got was: "Mañana..." and I wanted to publish it as quick as possible.

By the way, the bit about not working fastener threads in shear was more than confirmed by the NASA Fastener manual RP-1228 which states on page 24:

"Standard design practice is to choose a grip length such as the threads are never in shear".

So all those billions you've spent on Space work are useful eh?. We're always told that a by-product of the US Space program is the non-stick frying pan. I ask myself: Surely the one thing you don't want in space is a frying pan that allows your sausages to fly off in zero gravity all over the capsule?. One that would encourage the food to stick would be far more useful to your astronauts...:icon10:

Quote:

---

Originally Posted by CrazyCarl

How deep is the unthreaded portion of the QingQi hub? From ChinaV's pics it's didn't look as deep as indicated in the drawing.
CC

---

Have now done the sprocket fitting and proper measurements. The sketch has been edited to read 7mm deep unthreaded portion of the hub, and the Suzuki bolt has a 14 mm plain shank rather than the 15 mm stated previously. The chain had to be reduced by 1 and 1/2 links.

Not road-tested yet, as bike still on the work bench waiting for a chain tensioner that I'm hoping to adapt to the swing arm.
This mod was carried out by "frog" in http://www.chinariders.net forum and apparently transforms the feel of the transmission in exchange for a very modest outlay. The universal tensioner shown is only about $10.

The swing arm has some brackets welded on that hold some sort of chain guiding loop near the sprocket. I can't really see what it does, so I'll try to fit the tensioner to those brackets.
Will report on progress.

http://www.telecable.es/personales/a...tensioner2.jpg

Additional findings for the pedants amongst us ::icon10:

Everytime I work on this bike I never fail to be impressed by the design, fit and finish, and build quality. It feels just like working on a Jap bike. I can think of no higher praise.
However, I have noticed yet another error in the rear axle shaft. This is entirely decorative-chromed throughout its length: head, shaft, threads, nut, the lot.

I have never seen this done on any Jap, Italian or British bike I've ever worked on. The reason being what is known as "Hydrogen embrittlement".

Hydrogen embrittlement (or hydrogen grooving) is the process by which various metals, most importantly high-strength steel, become brittle and crack following exposure to hydrogen. It's caused by the Hydrogen evolved during electroysis being, to some extent, absorbed into the crystal structure of the steel at its surface. It has a tendency to increase crack propagation sites in steel due to the micro cracked structure of the coating . There is also a drop in the fatigue strength of the material which can be as much as fifty percent.

Well known examples of this error were those special bikes in the past with chromed or nickel-plated frames, they were discontinued due to this weakening of the material leading to breakages.

Let us pray that it's strong enough...

Hey Forchetto,

First post for me, but can I just say thanks for the excellent tips regarding Qingqi 200S.

I'm in the UK and own an RMR200 that I'm really happy with although I have suffered from the shearing bolt problem from the rear sprocket. I've just collected my swingarm from the welder as the stud left behind once the bolt head had sheared, worked it's way out and cut a gouge in the swing arm!

I'll be ordering the 44T sprocket for a bit more poke but will definitely order the suzuki bolts you specified as well!

Thanks again for the info about these fine bikes.

Cheers

Ian

Thank you for your comments. Have you done a tour of the forum yet?. There are quite a few bits and pieces concerning our bikes here.

Also, I've just found out the reference number for an equivalent sprocket from JT Sprockets, reference nº JTR 809.44 . Put that reference in the buyers guide search box that appears and it goes straight to the right sprocket:

http://www.jtsprockets.com/61+M54a708de802.0.html

The Suzuki bolt only just fitted in the hub. Before you do the final fitting, run the screws into the holes to ensure they will fit without bottoming and no metal has to be removed to accomodate the plain shank section.

The dimensions of the drillings on the Qingqi's hub are as follows:

Overall depth of hole 32 mm
Depth not threaded 7 mm
Depth threaded 15-17 mm

If you find the bolts bottom out due to the unthreaded shank touching the start of the thread you may have to remove one or two of the first threads in the hub with an 8.2 or 8.3 mm drill. There's plenty of thread left.

Just for the record, did you manage to retrieve the broken bolt?. I'm curious to know where about its length it sheared. This might confirm our findings. Also have a look at the remaining bolts to see if there's any sign of strain somewhere along their lengths. What tends to happen is that the sprocket moves slightly and, due to tolerances, not all screws take up the shear strain equally. One of them will do that first and that will be the one to shear first followed by the next one that touches the side and so on.

I was able to retrieve what was left of the stud...it was pretty mangled but from what I could tell there was no shank left and it did look as though it might of broken at the top of the threaded section as you suspect.

I've just ordered the sprocket and bolts and hopefully it'll be a straight fit. Will let you know...did you have to remove some of the thread or did you get away with it?

I've had a good look round the site now and it's excellent - just the sort of resource I was looking for to get more info about my latest bike. I'm certainly enjoying the lower running costs of the RMR compared to my GSXR! I'm definitely a convert to the China Moto way of life!!:thumbsup:

I did some measuring of the holes with the depth probe of a vernier calliper, and mine was just right, but the holes differed slighly and so I tried the bolts on first before torquing up. Mine were just OK, but with tolerances, etc, other bikes might not be and require slight metal removal.

The weather is so crap here at the moment that I still haven't been out to test the new gearing...will report as soon as I can.

My fuel consumption is around 3.1 litres/100 km or something like 76 miles/US gallon, 91 Miles/ UK gallon. I'm not a fast rider though, others may not be as economical.

One important thing to consider with this and all other Suzuki or Suzuki-derived singles up to 250 cc, is to keep an eye on the oil level. The sump only holds about a litre, about the same as a Honda 50 Super Cub, and if the level drops only a bit, lubrication is compromised.
First thing that suffers are the camshaft bearings. Their plain bearings running straight on the cylinder head alloy will start to wear prematurely.

The oil change intervals in my handbook are at 4000 km. I believe this is far too long for such a small quantity and would recommend changing sooner. At about 2000 km. What do others think?.

Thanks for the words of advice about the oil Forchetto. I always tend to change the oil on my bikes more frequently than recommended. Worthwhile, especially if it's such a small amount.

You had a chance to try out the new sprocket gearing yet? Mine arrived today but won't get chance to fit it for a while. By the way, I can recommend Wemoto in the UK for suzuki spares....I ordered yesterday lunchtime and the sprocket arrived today! Great service.

Haven't tried it yet. Hasn't stopped raining for weeks...At the moment I'm trying (without much success) to adapt a chain tensioner to mine before I take it out.

I'm surprised by the quick sprocket service, specially as this is from a fairly rare and old models. I got mine from a very large Dutch spares specialist:

http://www.cmsnl.com/search.php

But they took several weeks to supply. I'll make a note of Wemoto for the future.

The sun finally came out today and I was able to have a decent ride on the Qingqi, now fitted with a 44-tooth wheel sprocket rather than the 48-tooth that came as standard.

I was worried that pulling away from standstill would involve a lot of clutch slipping with the higher overall gearing. This was not the case. The initial impression is that first gear is now useful. Before this, it was just a gear for pulling away and changing a microsecond later. Now it's a useful gear, even goes up to more than 30 kmh if you want to. Much better for slow city work where you were either screaming in first or bogging down in second.

Overall the bike feels more "long legged" and far more relaxed without noticeably losing any of the instant pulling power that a low geared box gives you. The torque spread of the engine means that you can still potter along country lanes in 5th at 2500 rpm if you want, without any transmission snatch, and now reach a top speed of around 125 kmh (Indicated). You can cruise at max torque at 7000 rpm with the speedo showing 115 mph leaving another 1000 rpm before the power peak at 8000rpm.
The rpm readings are at best approximate as the rev-counter has tiny, not very precise calibrations, and I can hardly read it without my bi-focals...it's the age you know! (mutter, grumble...).

I did a highway run against a rather strong head wind and in a slight up gradient the revs fell off to such an extent that I had to drop a gear to get back up to a reasonable speed. I don't think it would have been much different with the original gearing.

The vibration that sent my hands to sleep after a few miles is not there anymore. There's vibration, but not so noticeable now. This could be due to the gearing shifting the vibration period further up the speed scale as well as the silentblock vibration damper now fitted between the new P&P exhaust can and the chassis. I have found this to be efective on other vehicles too.

As an aside, I can't recommend the P&P exhaust can enough. Apart from the gorgeous sound it produces, it has perked up the mid range power no end. The removal of the catalyser built into the factory silencer is responsible for the extra power. The efficiency improvement of the new can was evident from the first start up: The idling speed increased and needed to be reduced straight away, proof of combustion efficiency. You often get this effect, without touching the carb settings, with the engine running, as you carry out such adjustments as the timing advance (on systems where you can do this), carburettor synchonisation on multi-cylinder machines, etc. The revs rise as the combustion improves using the same carb settings.

Link to can seller: http://xian.west-wire.co.uk/index.ph...d&productId=13

Details can be found on this thread: http://www.mychinamoto.com/forums/showthread.php?t=499

My PGO (Quadzilla in the US) mini-buggy rattled away merrily until I fitted a new can with a similar anti-vibration mounting. The difference was astonishing.

Have I mentioned the beautiful handling, suspension action and slick gearbox of this bike before?...it takes me 10 minutes to stop smiling after a ride on our mountain roads.

Hello Forchetto,

Thanks for the excellent write up...I'm itching to get back out on my RMR again now! The weather actually improved enough at the weekend here in the UK to let me do some spannering on my bike, but there's still too much salt on the roads to take it out yet...I'd watch it disintegrate in front of my eyes judging by the damage a couple of trips in December did!! Perhaps corrosion prevention is the next goal for the Chinese manufacturers (although the japanese bike firms still have some way to go yet!). A thorough clean up has been carried out over the dark winter months and any removed bolts had a generous blob of copper grease before refit.

Anyway,managed to get my swing arm painted and refitted following the repair, my new sprocket is on and also the P&P can that I bought last month (these seem to be standard mods for 200GY owners eh!!:icon10:) All I need to do is take a couple of links out of the chain (this weekend weather permitting) and I'll be all set for spring.

How many links did you remove from your chain by the way?

Thanks for the links...here's a couple for the parts I ordered - my sprocket was from www.wemoto.com - excellent service, and I ordered M8x30 bolts from www.stagonset.co.uk - again, quick delivery and they were 34pence each as opposed to 1.50 Euros each for the Suzuki items! Hope this is useful. :thumbsup:

I removed 1 and 1/2 links, three rollers. This got the chain back up to the beginning of the adjustment range.

Interesting about the bolts. Our local specialist supplier of hardware swore they didn't exist with that overall length and that unthreaded shank...gits. Mind you I can't find that combination in that fasteners page either.

I did pay 1.50 each to Suzuki. For that price I expected them to be made of titanium or myrrh...:icon10:

The fasteners page is fantastic, by the way. Really well laid out and informative.

About the corrosion, one of the few defects I find on this bike is the frame paintwork. It's really thin all over and hardly has any gloss.

Keep the roller bearings and linkages of the (rather complicated) rear suspension well greased. They're very exposed to road crud, but they look well made.

Hi Forchetto, Ian,
Thanks for the valuable info on drive sprockets, links and exhaust cans. I am a Brit living in France and ride a GY200 around the French Pyrenees. I too plan on changing the rear sprocket for reasons already mentioned in this forum.
I thought I would join this discussion as my bike seems to have a different rear wheel hub. The bike is from Shandon Pioneer (supplier of Pulse brand in the uk) and is factory supplied with 15/51 tooth sprockets. The rear sprocket is held in place by four studs/nuts instead of the six you describe.
I haven't yet stripped down the rear wheel but will investigate this further and share the information here.
Just wanted to say hi and à bientot !

Welcome to the forum.

It's very strange this, Jinan Qingqi and Shandong Pioneer appear to be two different companies and yet they're in the same province: JINAN, and they make virtually the same bikes. On top of that Shandong Pioneer on their website : http://www.xfmotor.com.cn/en/ claim the same history as Qingqi, started in 1956, link with Suzuki technology, blah, blah, blah...Perhaps Crazy Carl or someone else that's lived in China can explain the relationship between those two companies.

You might find the reason for the sprocket teeth discrepancy is because your bike has a 520 size chain rather than my Qingqis 428 size. Check this by measuring the pitch, it should be 5/8" between pins or rollers and 1/4" wide rollers, if it's a 520 size.

The 428 size will be 1/2" pitch and the roller width is 5/16".

The rear hub differences are interesting, take a photo of it if you can. My bike has the sprocket held by six bolts with locking tab washers.

Its a 428, I had already checked and there are no tab washers. I am not sure if the sprocket is held in place by four bolts coming from behind the sprocket or if they are studs. Anyway I will check at the weekend and let you know. I'll upload some photos early next week.

forchetto,
Did you change the front sprocket as well?

Quote:

---

Originally Posted by david3921

forchetto,
Did you change the front sprocket as well?

---

No. I would have preferred to do so rather than the wheel sprocket but I came across some problems of space and availability of alternative sprockets.
See this thread for an explanation:

http://www.mychinamoto.com/forums/showthread.php?t=534

Hi forch, i been reading some post elsewhere and according to them the fron sprocket of the Suzuki SX125 is compatible with the QM200 (The name in Chile for que QM200 is Euromot GXT200). Its a 16T sprocket and the only detail is that it is a little wider in the middle but is easily solved.
The 2 first links are for the post I was telling you about (in Spanish) and the 3rd one is the detail of the sprocket they mention it

http://www.adach.cl/foro/topic.asp?TOPIC_ID=48319
http://www.adach.cl/foro/topic.asp?TOPIC_ID=46567
http://www.jtsprockets.com/fileadmin...rge/jtf416.jpg

Cheers.

PD: If any one is interested in some specific part of this post and don understand spanish i'll be glad to help, but please don't ask me to translate everything.....:icon10:

Thanks Chinipan. I'll read through that forum a bit more. Looks useful.

Right, this is for the Sherlock Holmes amongst you. Here are some pics of the rear sprocket belonging to my Pioneer GY200. The number stamped on the back is 428-51T, pretty obviously a 428 pitch chain with a 51 tooth sprocket!
The hub houses four rubber bushes. Four studs of 8+mm diameter are secured to the sprocket with nuts and ample amounts of locktite. The sprocket just plugs into the bushes and is held in place by one large circlip.
Can anyone identify with this type? The rubber bushing no doubts cushions any shock treatment transmitted through the drive chain, synonymous with a Suzuki design. I want to source a smaller sprocket for reasons already explained on this post.

Just a few more details to add on the rear sprocket: the four holes are on a 90mm diameter, 64mm between centers and take what appears to be an 8,2mm stud. I have scanned the drawngs in the 125cc Suzuki section of JT Sprockets with no luck. I'll keep looking.......
Any suggestions would be gratefully received. Cheers!

Thanks for the photos.

Another mystery to solve in the never-ending quest to understand the thinking of Chinese makers...

Curiously enough one of our posters, LuisCarlos, from Brazil, is looking for a cush drive rear sprocket hub to stop the possibility of the bolt breakages we've been hearing so much about.

This is the thread: http://www.mychinamoto.com/forums/showthread.php?t=510

The hub on your bike seems a superior arrangement to the one our Qingqi comes with and I'll bet it's interchangeable with ours. A rubber-cushioned cush drive like yours should feel a lot smoother and be easier on the transmission. On top of that the fixing of the sprocket will not shear as easily as just bolts.

Have a look at these drawings taken from JT Sprockets. I had a look for components with a 4 hole 90 mm pitch circle diameter like yours and it appears that several versions of the Honda CB125, CB175, and CG125 use that.

The only data missing from yours is the diameter of the centre hole. All these are 58 mm, is yours the same?.

Notice that these sprockets have two sets of holes, four with 8.2 mm diameter and 4 with 10.5 mm.

Honda CB125
Honda CB175
Honda CG125E
Honda CG125 Brazil


http://www.jtsprockets.com/fileadmin...rge/jtr269.jpg

It looks like the closest could be the CB125. Take a look at how similar the rear wheel assembly of it is. Note the rubber cush drive bushes, four hole sprocket, large circlip fixing etc, on this drawing:

http://images.cmsnl.com/img/partslis...F4113_5988.gif

Quote:

---

Originally Posted by forchetto

Welcome to the forum.

It's very strange this, Jinan Qingqi and Shandong Pioneer appear to be two different companies and yet they're in the same province: JINAN, and they make virtually the same bikes. On top of that Shandong Pioneer on their website : http://www.xfmotor.com.cn/en/ claim the same history as Qingqi, started in 1956, link with Suzuki technology, blah, blah, blah...Perhaps Crazy Carl or someone else that's lived in China can explain the relationship between those two companies.
...

---

In different place : Shandong Pioneer-Rizhao /Qingqi-Jinan

The Pioneer history (in Chinese) machine translated