1981 XS1100 Midnight Special Slow restoration

[Medumdum]

Hello y’all, I’m new to the forum and Yamahas in general. I’ve worked on a few classic bikes before but they’ve all been Hondas. I haven’t had a bike for the past 2 years after shattering my ankle, but I’ve gotten the itch again so I started looking and stumbled into this absolute treasure.

I saw it for sale and I knew I had to have it. With a jump pack and a shot of starter fluid, bike fired right up. I plan on slowly restoring it while riding it, since most of what it needs are cosmetics. With that being said, it does need a bit of mechanical work before I can get it on the road, namely the calipers are all sticking and the tank was disconnected from the carbs.

I just wanna double check the placement of the hoses coming out of the petcocks. When I picked up the bike the crossover line was connected to the front outlet and the small tube that went to the carbs was on the back outlet. I couldn’t really get them lined up properly in that same orientation with the clamps I have (which I do plan on swapping for more oem style ones later, if someone can let me know what that would be) so I swapped them around. Is there a correct order to them? I haven’t connected them to the carbs yet, I just got a bit of work done on it this morning before work, but I’m getting gas on the way home and going to try and get it to fire up this evening.

Any words of wisdom on how to get the gold accents redone as close to as factory as possible would also be appreciated, but that probably won’t be till after I’ve ridden it for a couple months.

[cajun31]

What you have is the 1981 LH model. This site, although a bit hard to navigate is a great source for you. XJ4Ever Restoration Parts and Supplies Catalog Index. You can get all your gold parts redone by them. Not cheap but what is these days? On top of their price for the parts, they also require you to send good parts back to them so they have parts available. In order to qualify your original parts can not be pitted so badly that they can't redo them. They decide that upon receipt and inspection. I have never heard negative reviews on them so no worries. All the hoses on the bike from the fuel feed side are not under pressure so those c clamps are really not necessary. This search page I did on Ebay shows an assortment of clamps available and are really as close to OEM as you can find. Price is not bad either. Yamaha xs1100 fuel hose clamps for sale | eBay.
On the LH model you have a unified brake system. When you use the front brake you are actually only engaging the front right caliper. When you apply your back brakes you are engaging the front left caliper and the rear at the same time. You will learn to use the rear brake predominantly when stopping. It was supposed to be an improvement from the previous year. There is a lot of debate concerning that but I elected to leave mine original. One of the first things I do when acquiring and restoring is, and you are doing this and common sense dictates, is to get the bike running properly first. Gives you strong incentive to move forward with full restoration. Just looking at the few pictures you posted, I would not hesitate to start planning the full restoration. XJ4Ever has a kit they have put together to help, should you need new rubbers etc. for the back master cylinder. As far as I know you can't source it elsewhere as a kit. You may find individual parts here and there but not complete like they have available. Because of he unified system you have a proportioning valve in between the rear master and front left. Hopefully it only needs to be purged and cleaned because it is an unobtanium item. The front master, the kits are readily available. I like parts supplied by georgefixs Store. The calipers need to be cleaned and I would suggest and advise that you replace the oem caliper pistons with stainless. They don't pit like the oem steel that were original. If your bike has been sitting a very long time you may find they are not in the best of shape. I like BrakeCrafters for the parts. Here is a quick search brakecrafters 1981 Yamaha XS1100L Midnight Special for sale | eBay. I have never had a problem with their kits. Your calipers are different from previous years so make sure your parts sourced fit.
You said the bike started which is a big plus. The carbs still need to be gone through. When buying gas if non ethanol is available go with that. Ethanol is not your friend, especially in carburetors. There are tips in the maintenance section on going through and cleaning the carbs. As for the hose routing here is a diagram on Partzilla that should be helpful. Yamaha Motorcycle 1981 OEM Parts Diagram for FUEL COCK-PIPING | Partzilla.com.
If the tank needs cleaning Apple cider vinegar is great. Just fill the tank with it let it soak, repeat as necessary and finally coat the inside of the tank after drying with a coat of oil. I use marvel mystery oil and slosh it around to coat the entire tank. If you search this site we have had discussions on the procedure. The nice thing about the Apple cider vinegar is that it does not harm paint and slowly but surely eradicates rust. You may not even need to worry about it if your tank is ok. Surface rust is not generally a problem other than needing to be cleaned. It is the pitting and more severe rusting that caused problems.

You will also probably need to rebuild your petcocks and your, what we all call your octopus valve. Many will advise getting rid of that item. Don't listen to them. Parts are available to properly rebuild it and it works great when redone right. One word of caution on the petcock rebuild kits. The rubber o ring supplied for the seal against the tank is usually too small in diameter and will allow fuel seepage around the base that will cause problems. It is especially bad on new paint. Just take those o rings to a local hardware store such as ACE or Lowe's and get a larger diameter. You may also find that you fuel filters are in poor shape, but fortunately they are still available. You can find them on Partzilla. Not cheap but I always replace them.

This should get you started and I am sure others will chime in as well. Don't be bashful about asking questions and posting lot's of pictures as you work. One last thing ... spooge hole. Look that up on this site and make sure yours are clean when doing the brake master cylinder cleaning.

[Medumdum]

Thanks! I think my octopus is already gone, or maybe my eyesight is instead, haha. Where exactly on the bike would it be if I still have it? I stumbled upon that same diagram earlier but I could not find the diaphragm, nor did I have any T fittings anywhere, I could only see 3 fuel lines on the bike, one long line that’s perfect length to go from one petcock to the other, and two short ones that are the right length to go to the fuel inlet on the respective side carb.

I’ll definitely have to drop the carbs to take a look, as when I tried to fire it up on its own gas today it fired for a bit then died. I tried a couple more times to get it actually running, and I saw fuel pouring out of the air box so I quickly shut off both petcocks and dropped the box. The foam in the filter got soaked and destroyed, so gonna have to order one of those too. I’m guessing the needle and seat are gone, dunno what else would cause the carb to overfill so badly. The tank is mercifully in decent shape, it’s been lined already and still looks to be holding up. Hearing it run, for however briefly, was a very happy moment for sure.

As far as breaks go, I’m definitely going to rebuild the calipers, since faulty front breaks were how I shattered my ankle two years ago and I do not want a repeat of that. Thanks for the link to the rear rebuild kit, I’d already found the BrakeCrafter kits for the front but didn’t know if I was gonna replace the cylinder or not, now I’m definitely leaning towards getting the stainless replacement but I’ll disassemble it, inspect it and go from there. Also gonna do a bit more research on that proportioning valve and the spooge hole while it’s slow at work tomorrow.

The pitting on some of the gold parts is pretty bad, so it will have to wait till I have enough to spend on the bike that I can stomach not getting the deposit back. The bike is a cool survivor for now at least. It even has the original tool kit, which I’ve never had for a bike before. Makes me glad I got it, as the seller said he had some people that messaged him that wanted to turn it into a cafe racer. Nothing against cafe builds, or any custom builds, but doing it to this bike would have been tragic.

[Tematt]

Welcome to the forum! You have a winter project I see. As it goes, the deeper you dig, you'll find things you will want to do, as did I, lol. Here's the upside, you will have a tank when you are done and will know more about your vintage bike. I have rebuild the carbs, valve cylinder, brakes, electrical, and next debating on pulling the jugs to rering the pistons all in the past month. At my pace It may be a total restoration lol. The members are very knowledgeable and responsive. Good luck on your journey, can't wait to see your progress. Xj4ever is very good if you have patience with the site. Jbm is the only good place you'll find replace diaphragms for the carbs... Trust me, you will want those. Don't think ebay or a knock off carb kit with them in it will have the correct sizes for aftermarket. Also, if your jets are not damages and can be cleaned up, stay with them (bad experience with a ebay carb rebuild kit taught me) for now focus on disassembly and cleaning while you source parts. Bag, label, take pictures of everything.

[Tematt]

For youtube there's a few I recommend. https://youtube.com/@ANDY5?si=ovIQyzKTIeP2ZYwo
Andy's mortacycle obsession he has a xs Playlist about 7 years old but talks alot about xs1100 knowledge & https://youtube.com/@Steptoexs11?si=_SPFY9nEXkKPiRjS steptoexs11 both good..

[cajun31]

JBM is a good option JBM "How to measure" the motorcycle CV carburetor diaphragm goove. (jbmindustries.com). TX, SX650, KZ750, Carburetor Diaphragm Mikuni BS38, BS34 SS, BS32 (jbmindustries.com).

Not the only option though. These you just have to replace the components from yours to finish these . Same costs. 80-81 YAMAHA XS1100 CARBURETOR SLIDE PISTON & RUBBER DIAPHRAGM | CRUZINIMAGE.NET.

When cleaning your carbs, while apart take a strong flashlight and shine it on the diaphragm while looking at it from the other side and inspect for any signs of holes or problems. If none are present then they are probably fine. If you do find holes then replace them. Some have tried to repair them with different solvents or glues. My experience with repairing them is they just stiffen where that is applied which affects their flexibility. Cheap enough to replace them. As Tematt implied if parts are required for you carbs try to stick with Mikuni oem parts. Aftermarket cheap chinese made parts cause more problems then remedies. You stated the bike ran so hopefully your carb cleaning won't be that involved. They do however, need to be disassembled and thoroughly cleaned and inspected. Before removing the idle jet screws, lightly seat each one counting the number of turns and writing that down. Set them back to those turns when reassembling. Generally the small orings installed become hard and need to be replaced. If they are original they will definitely need to be replaced. Most carb kits include them. Be sure you get the old rings out, they can sometimes be hard to see down those tunnels. I took a straight pick and bent a small hook on the end to use to fish those out.

[Medumdum]

Thanks for all the advice guys. I haven’t gotten too much done on the bike because I spent most of time just getting this garage tent thing built so the bike would be out of the elements. I don’t have a proper garage so this is the best I could do.

Anywho, I got the carbs off today. Previous owner claimed a shop had gone through them two years ago and got them rebuilt and tuned correctly. With how easily everything came undone I believe it, didn’t even have to tap out the aluminum rods holding on the floats, I was just able to pull them out. The slides and diaphragms were still in great shape, some of the jets were clogged but nothing a bit of chemtool and thin copper wire couldn’t solve.

My main concern now is that the needles and seats didn’t look to be in too bad of a shape. With how badly the carbs flooded, I imagined they were going to look a lot worse. I did already order a replacement for them regardless, but is there anything else that would cause the carbs to flood to the point of also flooding the intake box?

I also pulled the air box itself because I was still looking for the octopus, does not look like this bike has it still. Guy I bought the bike from did say he also has a parts bike I can bring home, so I might try and grab that next week and hope that it still has its vacuum system. In the case that I cannot easily obtain one, how should I hook up the fuel lines so that it’ll still run at least? From what I read on posts where people delete their octopus, I should maybe just cap off the “prime” outlet on the petcock and run the fuel line from the “on” outlet straight to the fuel inlet on the carb?

New air filter, front pads and front rebuilt kit with the stainless cylinders from breakcrafters is also ordered and on its way.

[DEEBS11]

This is a quality Japanese kit that I am presently running in my XS11.

https://www.ebay.com/itm/352927647481

[DEEBS11]

And these are genuine Yamaha seats. Arguably the most important part in the carb. Do NOT use aftermarket.

https://www.ebay.com/itm/29316334171...Bk9SR9iNuraTYw

[DEEBS11]

I agree when restoring a bike if it comes to you stock then you should leave it stock as so many bikes are ruined by amateur modifications. However, in the case of your missing "Octy" you may want to replace the petcock with a simple manual unit. These only the fit Specials with no air box if that is what you presently have. (I do see a stock air box in your photo so if you keep it this part would not work. It would hit the airbox.)

https://www.ebay.com/itm/23320042039...Bk9SR-TukLeTYw

[cajun31]

And these are genuine Yamaha seats. Arguably the most important part in the carb. Do NOT use aftermarket.

https://www.ebay.com/itm/29316334171...Bk9SR9iNuraTYw

I had to do my research on this. K&L is a company based in California. You can google them and actually can download their catalog. The company that lists these parts in this particular Ebay listing is just sourcing and reselling the same parts that come in the K&L carburetor kits. Such as these that GeorgeFix sells. The seats and needles and filters are the same in the K&L kits. They are all made in Japan. Stating they are Mikuni in this listing is just a way to make people believe they are different. If they are indeed different the kits say as good as oem. These kits 4 Carb kits 81 XS1100SH SPECIAL 80-81 XS1100LG XS1100LH MIDNIGHT SPECIAL 18-2606 | eBay have those same seats and needles included in them as well as everything else needed for the carbs. The only things I don't use out of these kits are the jets. I have tried them just as an experiment to see if I could make them work and they do, but the carbs are just easier to tune and synch with original jets sourced from places such as JetsRus.

[LAB3]

If there isn't any heavy corrosion or other physical damage the o-rings and bowl gaskets are all you really need.

[DEEBS11]

I stand corrected Cajun31. The main clue is the superimposed part number on the photo. it crosses to a K&L part. Japanese made but not OEM Yamaha.

[DEEBS11]

OK These are OEM Yamaha/Mikuni.

https://www.partzilla.com/product/ya...7a911be38f78bb

[cajun31]

Thanks for all the advice guys. I haven’t gotten too much done on the bike because I spent most of time just getting this garage tent thing built so the bike would be out of the elements. I don’t have a proper garage so this is the best I could do.

Anywho, I got the carbs off today. Previous owner claimed a shop had gone through them two years ago and got them rebuilt and tuned correctly. With how easily everything came undone I believe it, didn’t even have to tap out the aluminum rods holding on the floats, I was just able to pull them out. The slides and diaphragms were still in great shape, some of the jets were clogged but nothing a bit of chemtool and thin copper wire couldn’t solve.

My main concern now is that the needles and seats didn’t look to be in too bad of a shape. With how badly the carbs flooded, I imagined they were going to look a lot worse. I did already order a replacement for them regardless, but is there anything else that would cause the carbs to flood to the point of also flooding the intake box?

I also pulled the air box itself because I was still looking for the octopus, does not look like this bike has it still. Guy I bought the bike from did say he also has a parts bike I can bring home, so I might try and grab that next week and hope that it still has its vacuum system. In the case that I cannot easily obtain one, how should I hook up the fuel lines so that it’ll still run at least? From what I read on posts where people delete their octopus, I should maybe just cap off the “prime” outlet on the petcock and run the fuel line from the “on” outlet straight to the fuel inlet on the carb?

New air filter, front pads and front rebuilt kit with the stainless cylinders from breakcrafters is also ordered and on its way.

Just wanted to specifically address some of your questions. Looking at the pictures you posted one of the needles looks like the pin in the end of it is stuck down. That happens when varnish gets in them. You stated you will be replacing all of those anyway. When those pins do not compress and release properly they can cause float level / gas level issues. If you have not already done so make sure you read the carb cleaning tip that is posted in the carburetor repairs section Carb Cleaning 101 - XS11.club Forums. Your float heights should be set at 23mm or just go by what Kat says about the plastic floats. the key is to set them all with the float bowl gasket removed. There is another method to set the fuel level and there is another tip Setting the Carburator Float Height - XS11.club Forums but requires additional equipment to accomplish. Hopefully you are keeping the parts from the carbs from getting mixed up. Keep all the parts separated by carbs as you work through them. Float heights, stuck floats open, etc... are the main reason for flooding. Do you park your bike on the center stand or side stand. Parking on side stand can make the floats stick open too, if they are not clean and operating correctly. Your octy is gone by your description so you need to get into the habit of immediately turning your petcocks off when you get done riding. I mean even when you just stop for a minute. Having the carbs cleaned and set up right will help but there will still be no guarantee that the carbs may not still flood. Just doing the simple turn the petcocks off will eliminate that. Like I said in an earlier post your bike looks very nice and if it were me my goal would be to get it back to original. That would include acquiring the parts necessary. The octy can sometimes be found on Ebay. Just buying that part is not all you would need though. You also need to make sure you have the mount bar that installs on top of the number one carb to be able to secure the octy. Here is the octy for sale on Ebay rare OCTY "OCTUPUS" vacuum FUEL SHUTOFF--- for 1980 1981 YAMAHA XS1100 SPECIAL | eBay. You also need the bar you see on the left of this picture mounted on the top right of the number one carb.

Of course you will also need the 8mm screw/bolt washer to secure the Octy.
Why do I suggest the Octy you might ask? If working correctly as the Yamaha engineers devised, it will serve as a shut off for the fuel. When working correctly when you start the bike the diaphragm opens and allows the fuel to flow. When you shut the bike off and lose vacuum the diaphragm closes shutting the fuel flow off. The standard model xs1100's have this same diaphragm built into the petcocks and functions in the same manner. From what you have thus far described you no longer have the octy and it has been bypassed. The long fuel hose from petcock to petcock serves that purpose. If you elect to put the bike back to original the diagram on fuel cock piping Yamaha Motorcycle 1981 OEM Parts Diagram for FUEL COCK-PIPING | Partzilla.com shows you exactly how to route your lines. You will need to also purchase two of these plastic joints Yamaha 3H3-24376-00-00 - JOINT PIPE | Partzilla.com along with the clamps etc. that I posted earlier.

One other tip, When you start on the brakes, do the rear master cylinder first. If you can get it working correctly you can use it to remove the pistons from your calipers. You will see a larger bolt on the side of the master cylinder and you can actually remove it and still operate the rear brake lever to pump brake fluid. The fluid will not just shoot out of the hole but allows you to keep adding more fluid as you need to. I use a cajun injector syringe to squirt more fluid in as needed. Those calipers can sometimes be pesky to remove. I have found this method helpful. The calipers have quite a ways to travel before they pop out. Here are a couple of listing from Ebay that could also help when doing the brakes. Brakecrafters Motorcycle Brake System Reverse Bleed Kit Non Pneumatic Bleeder | eBay, I prefer a mity vac or something similar but it looks like this could work. I also always use some of this grease when reassembling everything. It does not hurt rubber Brakecrafters Red Rubber Grease For Hydraulic Motorcycle Brake Systems Repair | eBay and it also keeps everything coated to eliminate moisture. Just get in the habit of replacing the brake fluid every couple of years because dot 4 brake fluid is hygroscopic (attracts/absorbs water).

Good luck and keep us posted on your progress.