You have been smiled on by the almighty. It seems you avoided a total engine destruction which occurs when these parts break. They break from age rather than miles.

 

Save the pieces to forensically reassemble them after full extraction to determine if you have all the pieces. Also, I think you do still have a boulder -filter for the oil pickup. I think everyone will agree to replace the chain while you're committed to this operation. I think the guide that broke is the one most prone to break, and the one down low on the Pside is the one that lets the chain slap horribly and cause the most destruction. At least you have awareness of the problem. You also have some tools and some mechanical aptitude. I think you're going to be okay in the end. There are a lot of write-ups on this MB issue, so do your due diligence. An important trick is when you're feeding the new chain is to ziptie the chain to both cam sprockets so the chain doesn't jump a tooth, and it will want to with the rotating cam lobes and valve spring pressure.

 

Thanks for helping me look on the bright side @rick ! I'll count my blessings.

@GearheadGreg , what do you mean by "still have a boulder -filter for the oil pickup"?

I'll do some digging for those resources. Please provide your favorites! I have watched @PanzerPuff's video. It's super helpful, but a bit scary too...

 

The oil pick-up won't suck up a big chunk, I believe it has a screen to prevent it. Sand&metal shavings, maybe. Chunks of plastic, no. And if you have another piece of plastic that you never find, consider that if it gets into a spot that's going to specially conflict with other moving parts, those parts will be metal. Metal v. plastic -plastic will loose, as long as it doesn't fall between the chain and a sprocket. A good many R107 owners wish they'd had your luck. 😊

 

Ahh. Someone did you a dis service by replacing the metal rails with the newer self destructing plastic ones. Do you still have the screw in oilier tubes or has that been down graded as well? But I think you will be OK. Be sure to also replace the chain tension guide rail. That is the one that wears and causes the other ones to break.

 

I've been panicking about pieces of the guide rail that are surely lost inside the deep recesses of the engine. That's my single biggest concern. How hard do I need to look? What's the best way to find them? How worried should I be about the pieces I can't locate?

Are you joking with me @roncallo? Aren't all of the guide rails and oiler tube clips plastic?

 

Piece it together and see how big the biggest piece missing is. Keeping in mind the biggest piece missing may be in several pieces, but it will give you an idea. But I wouldn't loose too much sleep over it. I have pulled several engines apart with multiple pieces of valve umbrella seals caught by the oil screen.

Your car was probably delivered with metal baked chain rails and screw in metal oil tube fittings. I'm not sure what year those were discontinued. Says here early 70's

 

Luckily you can see down there with a cheapo USB borescope, Amazon will likely bring you one tomorrow, no oil draining needed, the vulnerable parts are above the tide line and accessed from above.

As others have mentioned you are lucky, go buy a lottery ticket right now! You are also blessed that this happened near the end of the driving season (if you live in a place with winter), now you have lots of time to do it carefully and properly.

 

This is my daughter's daily driver so we don't want it to be sidelined too long. We definitely have winter here in Utah. She plans to drive it year round unless there is a bad snow storm. Do we just need to make sure to wash the underbelly after driving on winter roads to clean the salt off? It's parked in the garage.

So, with the chain in, use a borescope to search around and some sort of grabber tool to pull out any pieces I find. Other than that, just follow Panzer's video? Any other great step by step guides you guys have found?

You all give me confidence and hope. Thank you.

 

So, with the chain in, use a borescope to search around and some sort of grabber tool to pull out any pieces I find. Other than that, just follow Panzer's video?

Correct, the only places there's danger of damage is down where the chain meets the sprocket, if a larger chunk goes around between the two it may disrupt cam timing or damage the chain. Bits in the oil pan don't matter.

 

I'm about to start the same adventure as you but mine haven't exploded yet.
Being a bit scared about what you don't think you know yet is a good thing. You've been given some great advice already. What @GearheadGreg said will get you through it. Just take a deep breath and go one foot in front of the other.
For my 560SL project finding MBZ parts is causing much frustration. I'm finding too many Mercedes NLA parts and parts price gouging.
Keep us posted.

 

MountOlympus

Before you start I suggest you review:

TonyLiveTV

Welcome to TonyLiveTV! This channel follows the restoration of my 1987 Mercedes-Benz 560SL, a project that began when I purchased the car at an auction in 2006. From 2006 to 2008, I rebuilt the entire suspension, including the differential, using only genuine Mercedes parts. I also replaced the...

www.youtube.com

You will find detailed videos of all the things you need to do to install the guides, tensioner, chain including tips regarding removing/installing the guide pins, removal and install all the front end components ect.

Search through the numerous videos and collect the ones that apply to removing the components like alternator, fan, PS pump ect INCLUDING the tools and part numbers of the parts you will need.

Be very careful removing the tensioner ...you need to follow his method to preclude stripping the tensioner bolts.

Insure you have really good quality hex sockets and wrenches to insure you don't strip the hex screws and bolt heads.

Good opportunity to clean up the front of the engine as well.

 

Don't be afraid to tackle the timing chain and guide rails yourself. It's not as bad as it looks. Do take your time. I know your daughter wants her car back but since this is your first time, go slow. This isn't really a hard job, just tedious. You do need to remove almost every accessory from the front of the engine except the AC compressor and water pump. Removing the radiator will give you even more space but you might be creating new problems. As others have said, keep two zip ties on the cam sprocket at all times as you're feeding in the new chain to prevent it from jumping. Watch the panzer puff and tony liveTV videos multiple times to familiarize yourself with the components. Good luck

 

Thank you @dave_socal , @steve86 and @clinton66. I appreciate that video resource and your encouragement and advice!

I will take my time. I think I would be happy if it was on the road again by labor day.

Steve, When you say clean up the front of the engine, do you just mean scraping and scrubbing off any grime that has accumulated through the years from dirt and oil leaks?

Since the car runs hot and I've already replaced the water pump and thermostat, I wondered if this would be a good time to take out the radiator. If I take it to a shop could they tell me if it needs to be cleaned out?

Clinton, What additional problems might I encounter if I try to take it out?

 

Thank you @dave_socal , @steve86 and @clinton66. I appreciate that video resource and your encouragement and advice!

I will take my time. I think I would be happy if it was on the road again by labor day.

Steve, When you say clean up the front of the engine, do you just mean scraping and scrubbing off any grime that has accumulated through the years from dirt and oil leaks?

Since the car runs hot and I've already replaced the water pump and thermostat, I wondered if this would be a good time to take out the radiator. If I take it to a shop could they tell me if it needs to be cleaned out?

Clinton, What additional problems might I encounter if I try to take it out?

What's the history of the radiator?
If you don't know.....then I would definitely take it out and bring to a shop. You have metal tanks so a re-core if needed can be done.
And now you have a bit more room to do the timing chain etc.

 

How many miles on the car ?...................

Car runs hot ? How hot is hot; what is gauge reading ................and outside ambient ...............
Did you flush the cooling system after the pump/TS replacement ?................

While you have plug wires off and after front end components out good idea to perform a smoke test. Smoke machines available @ Amazon not too expensive and will pinpoint vacuum leaks that are one of the largest contributors to poor engine performance.

When you have spark plugs out number them, take pics and post so we can advise what we see..................

Do you have records of work done by PO, if so post so we can comment.................

How has car performed ? Cold start............., warm start............, throttle response .................upshift/downshift...............
engine noises..............

Once car together if you haven't test duty cycle.
Do you know how to test duty cycle........... and have you done one.......results................

If car is to be her daily best to check all this out now while things apart and before she depends on it especially if she will run it year round!

 

The job is harrowing but doable by anyone with some common sense and mechanical aptitude.

I collected a dump of relevant links when I did the job:

https://www.benzworld.org/threads/chain-tensioner-guides-link-dump.3041701/

 

Yep, "journey of a thousand steps." None hard but it's easier with some special tools. I might be able to find the little tool that pulls the pins and loan it to you. Hopefully someone here has the cover / guide that bolts on top of the cam gear so the chain does NOT slip a tooth during installation.
It's been several years since I did the M117 engines in my 560SEC and 560SEL, the same engine as in the 560SL, but I can discuss with you how this goes. Call if you'd like. Las Vegas (PDT) 702 four hundred and ninety four, eighty and a fifty six.

 

Thanks for the great collection of knowledge @tonk560!

@nobby, I don't know the history of the radiator so I'll have to find a local shop.

@Steve86560sl, The odometer shows 178k, but hasn't worked for some time. It might be in the high 180s now.

It seems like the longer the drive the hotter she gets. She might get to 230ish Fahrenheit on a 30 minute drive. We haven't done a drive longer than that. She's gotten that hot on drives between 60 and 100 degrees. Ambient air temp didn't seem to make a big difference. I did just repair the aux fan, but didn't get a chance to check it. I did flush the coolant and replaced it with G05 when I did the water pump. I haven't used a temp gun to confirm the gauge readings, but my gut feel is that the gauge is accurate.

I have the service booklet from the first owner, but nothing really from the second owner who had it for 20 years. For the last 10 years it was driven sparingly - just to get emissions done or for parades. It's always lived in Southern California and toasty Arizona.

I've only taken out one spark plug so far (#4). It smelled like gas. I have new plugs to put in at some point. I'll share pics of the old ones when I remove them.

I don't know anything about duty cycles.

To me the car has shifted well and the engine sounds good. It usually takes 8-10 seconds of cranking to start up whether the engine is hot or cold. Although it has sometimes started faster. It started better than that when we first got it. If I start it up right after turning it off, she starts up immediately.

I have a timing gun and compression test kit, but haven't used them yet.

Good idea to do the vacuum test while I've got more space to work.

 

In addition to getting a smoke machine to test for vacuum leaks get a vacuum gauge to test vacuum.

You do the smoke test when engine NOT running so you can do anytime while the front end is apart.
Let us know where any smoke issues from and we can help target fixes.

Vacuum test of course needs to be done with engine running (should test at idle with the vacuum line connected to the AC components connected and then disconnected (difference if any will show if the vacuum components of the AC controls are leaking vacuum.

Read up on "duty cycle" when you have a chance...lots of diagnostic uses.
When you figure you want to check it the best meter (a Snap On MT471) presently available on Ebay for < $60...will give engine RPM and duty cycle readings
BUT, check with seller to insure it is working

Pardon Our Interruption...

I have 2 of them bought @ Ebay and both work great
Test @ connector X11 (driver side fender about mid way with round screw cap, under the cap 8 connection points use #3 for duty cycle if using the MT471

 

FYI the OP's car is a '76 450, it has fully mechanical CIS injection & idle speed control. No lambda system, no duty cycle adjustments. Fuel mixture is adjusted by CO readings from the exhaust.

 

Thanks for the great collection of knowledge @tonk560!

@nobby, I don't know the history of the radiator so I'll have to find a local shop.

@Steve86560sl, The odometer shows 178k, but hasn't worked for some time. It might be in the high 180s now.

It seems like the longer the drive the hotter she gets. She might get to 230ish Fahrenheit on a 30 minute drive. We haven't done a drive longer than that. She's gotten that hot on drives between 60 and 100 degrees. Ambient air temp didn't seem to make a big difference. I did just repair the aux fan, but didn't get a chance to check it. I did flush the coolant and replaced it with G05 when I did the water pump. I haven't used a temp gun to confirm the gauge readings, but my gut feel is that the gauge is accurate.

I have the service booklet from the first owner, but nothing really from the second owner who had it for 20 years. For the last 10 years it was driven sparingly - just to get emissions done or for parades. It's always lived in Southern California and toasty Arizona.

I've only taken out one spark plug so far (#4). It smelled like gas. I have new plugs to put in at some point. I'll share pics of the old ones when I remove them.
View attachment 2945422


I don't know anything about duty cycles.

To me the car has shifted well and the engine sounds good. It usually takes 8-10 seconds of cranking to start up whether the engine is hot or cold. Although it has sometimes started faster. It started better than that when we first got it. If I start it up right after turning it off, she starts up immediately.

I have a timing gun and compression test kit, but haven't used them yet.

Good idea to do the vacuum test while I've got more space to work.

The plug electrode is telling you the fuel mixture is very rich. My 560SL looked like that at 114k miles on the clock. I was also only getting about 9MPG gas milage. After spending a couple days here reading up on rich fuel mixture, low compression and fuel injection, I decided to replace everything on the fuel pump cluster and fuel injectors, injector manifolds etc. My old injectors looked like this:

Judging from all the gunk built up on my injector tips it appears they weren't producing a fine fuel mist anymore but just squirting a fuel stream into the combustion chamber and leaving plenty of unburned fuel. So I figured it was a no-brainer to replace the injectors.

I took lots of pictures and went through one side at a time. It took me a day and I didn't have any extra pieces left over. It started back up after a few cranks which I thought was a miracle.
Long story short the plugs now look clean and I'm getting 16MPG.

You may want to consider replacing your injectors while you have the engine unbuttoned.
One less thing to do later down the road.

For me, it's back to the Timing Chain project.
YMMV

 

Thank you Dave, what do you need to remove to do the injector job?

 

As I recall there wasn't a whole lot of stuff that needed to be removed.
1. The air filter assembly had to come off which is easy.
2. There is a double hose metal bracket at the driver side intake manifold that needed the fastening bolt removed to move the hose assembly around a little bit.

3. The fuel injectors have brackets that lock them in place and need to be removed. The hard fuel lines needed to be disconnected at the fuel injector nozzles and loosened at the fuel distributor.

4. The big injector rubber manifolds connecting the four injectors on each bank along with the plastic connecting pieces had to be pulled off.

The rubber manifolds were likely the originals and were difficult to pull off. I used 10" hose pliers and wiggled them loose and they did come off. The passenger side was much easier than the driver side. All in all it wasn't very difficult.

There were other bits and pieces that needed to be loosened or removed but were all minor.
The main thing for me was to be careful, take my time and not break anything else.
Document everything as you are already doing and be sure to not have any extra parts left over when you're done.
YMMV

 

Oof. What a bummer of a Saturday. The mission for my daughter and I was to replace the valve cover gaskets to address oil leaks. While in there we thought we might replace the oiler tube clips and inspect the guide rails. I was hoping I would find the rails in good condition because replacing them seems like a pretty big job. Ha! Boy were we in for a nasty surprise. Any help would be greatly appreciated!

Unfortunately, when we lifted the valve cover a couple of pieces fell out - pieces of the guide rail. The top inner rail is completely broken off and missing some chunks. I don't know how long it's been like this. We've had the car for 4 months a driven it a few hundred miles. Other than starting slow and getting hot it has run well.

Will you help me formulate a plan of action? We don't have the money to turn it over to a mechanic. I've enjoyed working on the car and have replaced the water pump, hoses, belts and fuel intake distribution system, but really have limited mechanic experience, skills and tools. I can't pull the engine out, open it up and find every little piece of plastic. What should we do? I was not planning on replacing the chain, but maybe I have to now? That job seems like a big stretch for me. Do I also need to drain the oil and examine the engine innards with a borescope? I've never used one. Does the chain need to be out of the way for that inspection? What do I do based on what I do or don't find?

Obviously, we need to replace the guide rails. I have them along with a guide and pin puller bolts and sockets from Mercedes Source. I also have the tensioner guide rail, but haven't looked into how hard that one is to replace. Do I have to do all this to replace the rails?

1. Remove fan and shroud
2. Remove alternator and belt
3. Remove power steering pump and belts
4. Remove distributor (all of it or just the cap?)
5. Remove valve covers
6. Remove chain sprocket and lift chain
7. Replace rails and put it all back together - I don't really understand how the pin pulling process works yet.

It's all pretty overwhelming. Maybe I could do most of the work, but find an expert to do the trickiest parts.

The biggest chunk. It wasn't totally loose so I haven't pulled it out yet. I don't want any more parts to break free.
View attachment 2945357

The pieces that fell out when we removed the valve cover.
View attachment 2945356
Video of the oil by the valve cover.

Oof. What a bummer of a Saturday. The mission for my daughter and I was to replace the valve cover gaskets to address oil leaks. While in there we thought we might replace the oiler tube clips and inspect the guide rails. I was hoping I would find the rails in good condition because replacing them seems like a pretty big job. Ha! Boy were we in for a nasty surprise. Any help would be greatly appreciated!

Unfortunately, when we lifted the valve cover a couple of pieces fell out - pieces of the guide rail. The top inner rail is completely broken off and missing some chunks. I don't know how long it's been like this. We've had the car for 4 months a driven it a few hundred miles. Other than starting slow and getting hot it has run well.

Will you help me formulate a plan of action? We don't have the money to turn it over to a mechanic. I've enjoyed working on the car and have replaced the water pump, hoses, belts and fuel intake distribution system, but really have limited mechanic experience, skills and tools. I can't pull the engine out, open it up and find every little piece of plastic. What should we do? I was not planning on replacing the chain, but maybe I have to now? That job seems like a big stretch for me. Do I also need to drain the oil and examine the engine innards with a borescope? I've never used one. Does the chain need to be out of the way for that inspection? What do I do based on what I do or don't find?

Obviously, we need to replace the guide rails. I have them along with a guide and pin puller bolts and sockets from Mercedes Source. I also have the tensioner guide rail, but haven't looked into how hard that one is to replace. Do I have to do all this to replace the rails?

1. Remove fan and shroud
2. Remove alternator and belt
3. Remove power steering pump and belts
4. Remove distributor (all of it or just the cap?)
5. Remove valve covers
6. Remove chain sprocket and lift chain
7. Replace rails and put it all back together - I don't really understand how the pin pulling process works yet.

It's all pretty overwhelming. Maybe I could do most of the work, but find an expert to do the trickiest parts.

The biggest chunk. It wasn't totally loose so I haven't pulled it out yet. I don't want any more parts to break free.
View attachment 2945357

The pieces that fell out when we removed the valve cover.
View attachment 2945356
Video of the oil by the valve cover.

Great video of a guy doing it on YouTube on a 117 motor. I used that and the people here. It’s only Time. Really not too bad. And you’ll get to do some preventative maintenance while
In there.

plan on dropping the oil pan for piece recovery. May as well replace the screen and pressure sending unit.

Harbor Freight for the long handled ratchet and plenty of cardboard to protect the radiator fins and front bumper/fenders.

You did dodge a bullet.

 

Are you referring to the Panzer or Tony videos?

 

Does the chain really need to be replaced? The guides are pretty easy, I would get those done and then check for play in the timing chain. Don’t replace it if you don’t need to. To quote Pierre Hedary, “ I don’t care if it has 400,000 miles on it, [if the free play is within specification] don’t replace it.”

 

Once you get this opened up, you’ll
Consider replacing connecting rod bearings.
Start a shopping list. It’s a great opportunity to close the book on many things you’ve been looking at.

 

The Metal chain rails were stopped at the end of the W108-109 models. I've worked on a lot of these engines and never seen W107 and W126 V8's with the metal rails. John Green in Canberra ACT,Australia sold them as a replacement years ago for those worried about losing that left hand rail.
Drop the oil pan ,which is just a steel pan on the bottom of the engine.Any stray parts will be down there ,laying in the sludge. It takes less than an hour to remove , clean and replace the pan. No need to strip the entire front of the engine,just take off the distributor, alternator and power steering pump.
I also remove the rocker arms ,mainly for convenience sake to roll the engine over to replace the chain. I have the tool to do that,which makes life easier.

 

The Metal chain rails were stopped at the end of the W108-109 models. I've worked on a lot of these engines and never seen W107 and W126 V8's with the metal rails.

The early Djet 107s do have metal backed guides. 1971/72 and maybe early 73?
Orignal guide - my 72 350SL 4.5L

 

How many Mercedes mechanics does it take to change a lightbulb..?

 

107. But the bulb is NLA.

 

Wow, project creep much?
Since the guide is not metal backed odds are good the chain has been done, a master link would confirm that. Fish out the bits between the chain and sprocket, install a new guide or three and drive.

 

I’m just quoting this for emphasis. No wonder people are scared of these cars. He needs to replace the guides, an inexpensive job that can be done in a day, and we’ve gone from that to tearing off the front cover to replacing bearings.

Yes, replace the guides, button it up and drive the car.

 

Are you referring to the Panzer or Tony videos?

Jeez. I think I can say he was “Asian”. Had music going and did it in less than :30.

My first Merc: nothing straightforward.

If not for this forum, and , the Asian guy, don’t think I’d have done it.
Now?

Fuel pumps, and the whole kit back there.

Nylon shift linkage bushings

Injectors

Air lines

Fuel spider

etc

After “The Chain”? Tip to Fleetwood Mac, you’ll be unstoppable. Alert your wife.

I have the pin puller if you can’t find one. eBay should you want your own.

 

This is what I used to remove the pins for the guides. Works great and cost almost nothing. I like it much better than the special tool. One or 2 had use the special washer I made with my grinder.

 

This is how I did my first timing chain on Delilah 20 years ago. But it didn't work for others. I remember recommending it on peach parts and someone starting a new post saying "help, I followed Roncallo's procedure and now I have a broken bolt stuck in the guide pin." It will work but you need to be a mechanic and have to have a good feeling for whats going on. Know when to hold and know when to fold.

In this thread, I demonstrate the old way it was done using a home made version of the MB slide hammer. This is a fairly cheep to make tool. I will add that this slide hammer with its long flexible screw alleviates problems others have with the expensive Baum tool version of it that breaks the studs off in the guide pin.

https://www.benzworld.org/threads/the-old-way-to-pull-timing-chain-guide-pins.3076668/?post_id=18227239#post-18227239

In this thread I used both the pin removal tool and the slide hammer in post #32. The pin removal tool does save time in that certain parts don't have to be removed to gain access.

Delilah Not Running Well and Time for a Timing Chain and...

Apparently coming out of Covid with minimal driving done, Delilah did not fair well. I took her on a 500 mile trip to Western NC a few weeks back and thought long drive with several bottles of Techron might do the trick. No it actually got worse and I decided to put her down until I had a chance...

www.benzworld.org

Baum tools slide hammer

Mercedes Baum Tool B116-2033 Chain Rail Pin Puller Baum Tools BM.116.2033 BM 116 2033 BM1162033 | Pelican Parts

Baum Tools Baum Tool B116-2033 Chain Rail Pin Puller Sliding Hammer Type. Call (310)626-8765. May Qualify For FREE SHIPPING. Parts# BM 116 2033 BM.116.2033 BM1162033.

www.pelicanparts.com

 

I'm getting started on this project this weekend. I thought it would be nice to have the car up higher so I didn't have to bend over as much and wouldn't bang my head as often on that dang grill so I bought a floor jack. For other jobs I've been able to just drive up on ramps. Thank you all so much for your help. Here are some questions I have after reading enough to be dangerous. Please help if you can. It may interest you to know that there is a patch on the left valve cover (pic at end). Maybe a broken chain in the past? I'm not sure if/how that affects this project.

1. Do I only need to replace the sprockets if they look worn and the timing marks on the cams don't line up?
2. Do I only need to replace the chain if the timing marks on the cams don't line up, it's loose, and/or there isn't a master link (indicating previous replacement)?
3. Do I just pull straight up on the chain to see if it's loose?
4. Do I need to remove the tensioner to replace the guides?
5. How do I know if I should replace the tensioner?
6. Is it possible to replace pins without removing the sprocket for certain models?
7. Do I need a special tool like Panzer's wheel puller to remove the sprockets? Is that dependent on whether or not I remove the tensioner?
8. Do I need to put motor assembly grease on the guides?
9. Does it matter which side I do first?
10. Should I be able to remove all 3 upper guides and the tensioner guide with this (pictured) pin pulling set or do I need to borrow yours @JHTx? I still can't quite visualize the process. Is the process for the tensioner guide different than the other guide rails?

 

I'm getting started on this project this weekend. I thought it would be nice to have the car up higher so I didn't have to bend over as much and wouldn't bang my head as often on that dang grill so I bought a floor jack. For other jobs I've been able to just drive up on ramps. Thank you all so much for your help. Here are some questions I have after reading enough to be dangerous. Please help if you can. It may interest you to know that there is a patch on the left valve cover (pic at end). Maybe a broken chain in the past? I'm not sure if/how that affects this project.

It'll be interesting to see the inside of that patched cover, if something damaged it from the inside it would have been very catastrophic.
Remove the covers and perform the stretch test to see where the balancer stops when the RH cam is on the mark, many of your sprocket and chain questions will depend on the result of that. Sprockets never look worn even if they are, and even a brand new chain has slack, how the marks line up is the way to judge condition.
The sprocket(s) have to come off the end of the cam to get the guides past, lots of ty raps and upwards tension will prevent the chain from falling off the lower sprocket.
The sprockets may require a 2 or 3 jaw puller to get off the cam, they all fit differently, a long brass drift and a hammer from the rear would also do in a pinch.
It doesn't matter which side you start on.
No need for lube on the new guides, they are already slippery and the chain gets oiled constantly.
Tensioner replacement depends on if it bleeds down overnight, if you are hearing the death rattle when you start it and the chain passes the stretch test the tensioner is the next suspect.
Removing the tensioner will allow for more slack which you might need to get the sprockets off.