Reseal, Rebuild or Resize?

reseal, rebuild or big bore?

  • reseal

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  • big bore

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sf bay
Hey all,
I have a 1980 xs650 special. I've owned it for a few years. The odometer shows under 9,000 miles and the guy I bought it from says it is original. (I take that with a grain of salt but that's what I've been told and I think it "may" be close to the truth.) I'm running open pipes, rejetted, k&N filters, brass suspension bushings, etc.
My question to all you more knowledgeable than I is, Do I just reseal it, rebuild it or get a big bore kit? To me, this is more of what we use to call "bar hoppers". Great around town and for short bursts. It vibrates quite a bit at higher speeds on the freeway though. (Yes, the tires are balanced etc). I've driven the newer triumphs and loved them on the freeway but way too much $$$ for me. Drove the new 650 royal enfields and liked them(and the price), but they are about as lacking on the freeway as these xs650 are. BUT, I DO LIKE my xs650 and am satisfied with it (except the oil leak). And the few mods I've done to it have helped greatly. It just leaks quite a bit of oil so would like to take what is left of this winter to fix the oil leak. I'm just wondering since I have to probably take it apart at least partially, anything else I should do while I'm in there? Also, a good parts source. I have nothing against mikes but would like to hear of other, reliable parts sources. And if there is good pictorial here or on the web, or even a book (rember those?) that would be immeasurable. I've come across a guide in German but I don't speak German.
The leak seems to be coming from where the top thing (valve cover?) meets the finned part (barrel?) and/or where the finned part meets the case. I've already tried adding the brass washers on top and torqueing them to spec. I've rebuilt several car engines but never a bike engine so I'm not too stupid and feel I should be able to tackle this. And I've had everything from crotch rockets to hogs. I was thinking at the very least since it will be at least partially apart, I could get a nice cam in there (open to suggestions) Nothing too radical and still streetable. I checked the compression a while ago and it wasn't equal. It was a little more than 10% difference which seems to indicate.....However, it doesn't smoke (blue or white). Also, any special valve job (multiangle, etc) that helps but isn't cost prohibitive (titanium, etc if thasts even an option on these, lol) would be appreciated (and who could reliably do it). I could probably do a port and polish/port match myself (is the difference worth it?)
So that's a little about me and what I'm looking for. I'm all ears. Thanks in advance
Welcome to the wonderful world of the XS650.
As far as books, the factory books are available. You can find them used on Ebay and such places. has them as downloads.
Even the Haynes or Clymer books are ok.
There are several threads on here about rebuilds.
I don't think there are many options on cams. There are a couple out there but are more for racing, but some use them on the street.
I have found the 750 kit Mike"s sells is a goo upgrade. I put one on my 75. It gives you more power. What I liked more was the change in vibrations. The high rpm vibe were greatly reduced. The forged pistons weigh differtent. I think thius is what changed the vibes.
On head work, just cleaning up the mold lines in the passages is all you need. The diameters are already a bit big. Even as a 750. About right for some of the 1000 cc builds. European racers build them.
There are larger pistos to build upto 707 cc using the jugs you have.
Once inside the front cam chain guide should be replaced. I have no issues with the one I got from Mike's but orthers have. There is a thread on modding one from another bike to work opn here some where.
Once you have the jugs of the book explains how to check the rods for wear at the bpth ends. If the check oput as ok then you wont have to split the cases.
Oil leaks on the head gasket and base gasket are not uncommon. Just pulling the head and jugs is enough to fix that.
Valves, often just lapping cleans them up enough and is easy to do. Need to check the wear of between the valve stems and guides, If worn enough new guides are not hard to install.
Altering the rocker arms for the Porsche/Volkswagen type floating foot adjusters is not a bad thing.
If you browse the TECH section found up near the top of the page is a good thing to do. You can find things I've mentioned as well as many more.
Just a couple of thoughts
Assuming it is 9000 miles.
I Would not expect much wear and things to do in the engine ..
So opening is besides a lot of work .. It cant be done without taking the engine out
A risk ... causing more problems than fixing

I would try to re torque one more time according to best practice
And recheck a couple of times.
Even if it leaked ( a little ) I would try use it some more before opening.
I have seen many bikes unfortunately being opened and then never back again

If you are sure that is done and over .it needs to be done I would go for stock
Inspect the cylinder + heads and so
The vibrations can be reduced with another carburetor jetting.
It can be difficult to get that right but here are extremely competent persons
( I dont say that often )
That perhaps can give advice.
Wow, what a great (and knowledgeable) group. Just posted a few hours ago and already got some good responses.
- Leo, thanks for the welcome! And all the info. Went to biker .net and got a wealth of information! On your 750 kit, did that come with all the pistons, rods, wrist pins balanced? Is that why you have fewer vibrations? And I'm assuming you had to go to bigger carbs?
And by getting the bigger pistons for the jugs I have, I'm assuming that means boring them out? Any reliability issues with that(cracking, warping, etc)?
So I can check BOTH ends of the rods without splitting the case? Nice.
I did a search for "Porsche/Volkswagen type floating foot adjusters" and "Altering the rocker arms" on this forum and the only hit I got was this thread?
Jan_p - I did try retorqueing about three or 4 times with the brass washers. Seemed to help at first but eventually went right back to where it was(not the torque, the oil dripping). Lol, funny you mentioned rejetting helping the vibrations. I thought the bike seemed to vibrate a lot less after rejetting but chalked it up to my imagination. Couldn't think of a logical explanation. Lol, glad you mentioned it. I rejetted a lot of bikes in the past but was out of practice when I did this one. But little by little it came back to me. I had forgoten how much fun it was swapping out pilots, mains, adjusting idle jets, etc, then taking it out for test runs and trying different rpm ranges. Oh and putting smiles on the nieghbors faces in the process ;) lol
marty - This is kind of where I was leaning towards. Check the bores, hone the cylinders, lap the valves(haven't lapped valves by hand in a long time neither), clean up the flashing, port match,etc. I'm assuming you have 3 0r 4 rings and you gap them and stagger the gaps on reassembly? Leo mentioned the front cam chain guide also. Any other parts? I can't believe your bike has 57,000 miles on it ?!?!?! That REALLY motivates me to get this done!

Question for all you gurus. On reassembly do you recommend putting the gaskets on dry, with some type of sealer (if so, which one) or using both? I know I've used permatex aviation sealer and won't get any leaks but it is a bitch to take off if you have to open something up again. I've also used the newer permatex black and grey with mixed results.
Welcome to the forum. I'll be the first to say it.... we like pics here. The more the merrier... show us what ya got. :D
Permatex Aviation is my go to. Yeah, it can be a bitch to remove, but done right, how often do you have to do a teardown?
Have a read here on top end buildup. It's in the Tech section. I've never used it, but I hear it's a passable how-to. :rolleyes:
Oh..... and may the force be with you. :sneaky:
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Welcome to the 650 madhouse ob1

There were 2 models in 1980 and they are completely different cosmetically. Pics will tell us what you have but a vin no will confirm the models as a lot of time these bikes are sold buy the production date. The production date spans 2 years so if the bike was produced after July then it is classed as the next years model.......Say a Date of Sep 1980 it will be an 81 model.......small thing but can make a difference when people post information for you, or you want to buy parts.

Check this mob out for engine pistons and a couple of other parts they supply. Cheep but a lot of people from here have used these guys with good resaults as well as Honda and suzuki guys from where i have read.

A couple of links about their pistons

Thread on rings and placement

Downloadable service and parts manuals. The pre 80 ones have clear diagrams and pics and the engine is pretty much the same from 74-84, with just carb and cam-chain adjuster differences...........a lot of other great XS650 info on thexscafe as well
Are you kidding me?!?!?!? That is a Frickin AWESOME write up Jim!!! That must have taken you foreever to photograph, document, upload and do the work. HUGE Thanks on my behalf and all those who have and will use it. That is amazing.
So, you're modest, knowledgeable, and funny. If you're ever in the San Francisco Bay Area, let me know. We'll go have a drink or two. Or go pick some up and bring them back here if we're still on covid lockdown.

I'll try and throw some pics up this weekend.

By the way Jim....confronting our dragons allows us to grow. If we so choose ;)
Thank you 650skull. Good to be here. I didn't know there were different xs650 models in 1980. Good to know. I'll try and get some pics up this weekend. Those are some great links that answer some of my questions. Got the downloads from the last link too. You must have some really organized bookmarks ;) So I guess wiseco pistons aren't what they used to be? I don't mind paying a "little" more for quality, especially on stuff like this. I definitely don't want to have to do this again anytime soon. But I also don't have deep pockets neither. I have cruzin image bookmarked and it's on my radar. Especially if others here have used them with good results. Thanks!
Hi, you will have noticed by now from the answers above that to do any dismantling in the top-end area - cam cover, cylinder head, barrels - the engine needs to come out. And it's heavy. Hope you have a good workshop or other place to work if you are going to open things up. Also, hope you are strong, or better still have a helper who is strong, or better still have a chain and pulley. But as you have worked on car engines, I guess you have all that sussed.

In case you didn't pick up on it, get a manual.

Good luck whatever you decide on. Oh, and pictures . . .
The need for a rebuild on most of these now is due to their age, not so much the mileage wearing them out. Things like gaskets, seals, and that front cam chain guide that was mentioned are starting to routinely fail. Yes, try a few more head re-torques, it certainly can't hurt. But, sometimes the head gasket does fail badly and replacement is the only option. If it only really does have 9K miles on it, sounds like it spent lots of time sitting. The rings may need to seat in again so put some more miles on it. Check the compression again after running it some more and it may be better.
As promised.....




And here are the tabs I welded on to the frame to mount my rearsets


I removed the dummy lights to clean up the dash a little


The offender


Another project in the works



I'm not happy with the profile so will be doing it over. Also, it must be able to be removed easily and replaced with stock seat easily and be able to fit Without cutting the rear hoop on the frame. And I need to work on where it meets the rear fender as I want to keep the rear fender. (my own requirements) If I wasn't so picky and demanding, it would VERY easy to cut the rear frame hoop and remove the rear fender and be done with it.

Right now, it is just in the mock up stage. Once everything on the bike is where I want it, I will take it apart, detab the frame, sand blast etc.

BUT, I still NEED to be able to ride it (I'm addicted to bikes). So once the engine is out, the work done, it will be going right back in so I can ride it while I get everything else done. That's why I do one thing at a time as time and money permit. Even though in the long run, it is way more work.

And, I'm including this last pic ONLY to keep me honest. My garage is currently a pig stye. It USED to be THE garage my friends would bring their friends to see. But I'll have to clean it up to get this project done. And I'll have to see it everytime I come to this post. :((frown face refers to the garage, not this post. Obviuosly)

Looks like good bones to work with. I've always liked the Special II. For starters, you'll want to ditch the K&N pleated filters. They've been known to not play nice with the CV carbs.... harder to tune.
After you get that place cleaned up, you'll have a well provisioned shop for a rebuild.
On the throttle cable, there is a sort of half moon shaped washer formed onto the elbow. This locks the cable in when mounted so it points at the headlight. To redirect it for better routing with lower bars, file some of the washer off. Here's mine with that bit of filing done so I can direct the cable to point straight ahead .....

650skull - You ROCK! you know where ALL the good , important information is on this board (and elsewhere). Do you or someone else around here happen to have the pics of the porting job? I have to tell you, you are just a wealth of pertinent information. THANKS for sharing!
So, it's an 80g Special II. What does that tell you/me? Pros/cons? Things to look out for? Anything specific about them?
p.s. - You don't happen to have a bookmark for an xs650 engine stand that fits in to a regular engine stand, do you? Or a good one that sits on a bench?

Raymond - Some good points. You can't do the job if you don't have the tools/equipment. Fortuneately, I think I should have some/most of what I think I will need for this. I may need to go get some small stuff (like tips/stones for the dremel, etc). I also have a pretty solid engine stand I fabbed eons ago. (I've rebuilt several 427(iron blocks) on there so it should suffice.) What I would LOVE to find (or fabricate) is something that I could place in my engine stand to hold the bike engine. I came across a few designs last year when I was going to attempt this but most were angle iron welded up that you place on the bench. I "think" I remember one somewhere that went in an engine stand so you could easily turn it for access to all parts of the engine? Barring that, I think somewhere on the net was one that sat on a bench but it did rotate for easier access. I'll have to work on that. I'd like to say I'm still as strong as I used to be but....worse case scenario I'll get a buddy or 2 and we'll have a couple of brews. After ;). And I do have a cherry picker but not sure how/if I could postion that to pull the bike engine?

5 twins - I kind of figured any gasket, seal etc that fails on this bike is due more to age. Anything 40 yrs old is going to start breaking down. heat/cold cycles and especially if it sat around (which I'm sure it did) because it would dry out. But I think if it was the rings, I'd be getting blue smoke, wouldn't I? So you think it's the head gasket? Would you still recommend taking the barrels off and replacing the gasket that goes below that? Is that a common failure also? Hmm, just thinking about that. I'll just do it anyway as this bike is 40 yrs old and would rather not have to worry about it for quite some time (at least the engine). LOVE what you did with your cable/routing it. I do remember when I was doing it trying to reroute it. Unsuccessfuly. I'll definitely be trying your mod. The simplest solutions are usually the best. Thanks for sharing.

Jim - "Good bones". Lol. That's "exactly" what I thought when I bought it. Funny you mentioned the k&n and cv carbs. I thought this bike was more finicky than others I've done when I was tuning it/syncing the carbs. I did get on the www and to look for answers and figured I would go back to a stock style(1 piece) filter if I had too. But knock on wood, seems fairly decent right now. And are these bikes sensitive to the weather more than most? Especially heat(100 plus degrees)? I know most carbureated stuff is. Simple science. Ah, the front forks. Yes, noodles is a good description, lol. I did stiffen and put uprated springs up front (and brass bushings in the rear) but stopped short of doing the needle bearings in the neck(but may do it on FINAL reassembly). I was originally was going to shave off the tabs for mounting the front fender to clean up the forks a bit but just painted them black instead. Just in case. Glad I didn't. Do you think putting the front fender back on would help in the twisties? This bike definiteately doesn't inspire confidence on more challenging turns/uneven pavement. If not, any recommendations on braces(or other solutions?) Also, what's your favorite engine stand(s) for this? That is something I will definitely need.
It worked. After taking the picture of my pig stye and looking at it online, I had to go out and start cleaning the place up. Makes a big difference having something in your face or if it's something you just pass through and see occasionally. Spent most of yesterday (Saturday) cleaning/organizing my garage.

Jan p - You're right. It was on both sides. But after I did the brass washer mod and did a few retorques, the one side was much better and actually stopped leaking. Unfortuneately, can't say the same for the other.

Thanks again to ALL for your support and sharing your wealth of knowledge and experience. I should of done this a long time ago. If I can ever return the favor, just let me know.