questions before beginning my first top end rebuild

[Port]

some background
I picked up my first bike, a 1981 xs650-sh a few months ago. It was running when i got it but then a few things happened. First, I popped the clutch and hit a 1" tall brick wall, crushed the header pipe and dinged the left side engine cover. I replaced the exhaust and rebuilt the front brakes. The first time i took it for a ride it was running ok, just a little bit of backfiring and then it just cut out. I got it home and it had no sparks, i've ordered a new wiring harness as the old one was a patchwork mess but, i'm pretty sure something else is wrong with the electrical system but i can't figure that out until i get the new wiring harness in.

Now to the topic of this post
I noticed a pretty bad oil leak after her maiden voyage. It's leaking from both head gaskets but only on the left side (probably shook loose during her introduction to the brick wall). I've got the bike pulled mostly apart at the moment and want some advice as how to proceed.

1. Should I torque down the head bolts/ nuts first to see if that stops the leak once i get her running again?

or

2. Should I pull the engine now and replace those two gaskets before putting it back together?

3. If I go with number 2:
What do I NEED to replace when i open up the engine?
What SHOULD i replace when i open up the engine?
What should i make sure to double check for failure?

4. One of my intake valves has a fair amount of carbon buildup on it while the other one is pretty much clear of any buildup. What can cause this and what should I do about it?

Slightly off topic
5. The starter is also slipping after a couple of seconds of turning over. This can wait, right?

6. Some gas in the airbox is due to malfunction floats, right? If so, how do i adjust the floats? I have had trouble finding something that addresses this specific topic.

7. How the hell do i remove an old exhaust head gasket? (the big metal crush rings)

9. I was only able to remove one exhaust stud when i was trying to replace them. I used 2 nuts, snugged up against each other but wasn't able to work them loose, any tipps?

10. how can i tell if the sump pump filter needs replacing and if it does, should i upgrade it?

 

[xjwmx]

6. Some gas in the airbox is due to malfunction floats, right? If so, how do i adjust the floats? I have had trouble finding something that addresses this specific topic.

7. How the hell do i remove an old exhaust head gasket? (the big metal crush rings)

9. I was only able to remove one exhaust stud when i was trying to replace them. I used 2 nuts, snugged up against each other but wasn't able to work them loose, any tipps?

The gas in the air box is more likely from a combination of leaky petcock and leaky o-ring around the float valve seat. There's a good thread on rebuilding the petcock. Or you can get a manual replacement. Both about the same price. The float needles and seats themselves are probably ok unless they've been in a cornfield for thirty years.

The old exhaust gasket comes out easily if you have some kind of hooked probe to get it started. They're just a plain ring, maybe 1/8" thick. A squirt of PB Blaster wouldn't hurt.

Did you bend the stud when you hit the wall? If not, leave it alone, if so, then the usual route to unsticking reallly stuck parts is heat, usually a torch. Dry ice works too, for places like under a dashboard. A pipe wrench might get it by itself.

Just responding to the questions that might be hardest for you to find answers to on your own.

 

[Port]

I'll check out the leaky petcock and o-ring information. That sounds more reasonable as the carbs seem to be in good condition.

The exhaust gasket on the side i hit the wall with (left) popped out when i removed the old pipe but, the one on the right side is stuck like hell. I don't have a hook to pull on it with, i'll try and find one somewhere.

I didn't bend the studs but they were rusty as hell so i figured i'd replace them. When i couldn't get the other 3 out I said "fuck it" and put the pipes back on with one new stud. I think i'm just going to return the other 3 new ones.

Thanks for the reply

 

[xjwmx]

you can pull the tank and if the petcock drips in the run position with a full tank it needs to be rebuilt. If you can pull the seat out of the carb easily then that o-ring around the seat is bad, otherwise not. Something seems to happen to them after thirty years...

 

[650Skull]

Scroll down to post 17 for a Link to rebuilding BS CV Carbs, and vacuum operated petcocks tutorials

Scroll down to post 28 To the link to fix your electric starter problem. Usually a simple fix.

maybe it would be prudent to get the electrics sorted and re-torque the head. Get the bike running good, (fix carb leak). Do a compression test, that will give you an idea if it needs a tear-down straight away. Try not to do it all at once just take things one step at a time.

Did you find some headers, there are a few exhaust systems for sale in the classifieds. 74-79 Standard headers will fit and 78-83 Special headers will fit. Full Special system HERE and

 

[Port]

The gas in the air box is more likely from a combination of leaky petcock and leaky o-ring around the float valve seat.own.

I checked the float valve seats and they just slid right out. So i need replacement o-rings, is (1.5mm thick x 7.5mm I.D) the correct size? And I found a previous thread where you answered this same question. When i opened the float bowl, the gasket had an extra hole for another screw. the hole was on halfway on the outside of the carb and halfway sandwiched between the bowl, there was still enough between the two to make a seal. Is this normal or should i replace the gaskets?

Scroll down to post 17 for a Link to rebuilding BS CV Carbs, and vacuum operated petcocks tutorials

Scroll down to post 28 To the link to fix your electric starter problem. Usually a simple fix.

maybe it would be prudent to get the electrics sorted and re-torque the head. Get the bike running good, (fix carb leak). Do a compression test, that will give you an idea if it needs a tear-down straight away. Try not to do it all at once just take things one step at a time.

Did you find some headers, there are a few exhaust systems for sale in the classifieds. 74-79 Standard headers will fit and 78-83 Special headers will fit. Full Special system HERE and

The thread for those two links is amazing, it answer everything. And yeah, I got a replacement exhaust pipe (header and muffler) but from ebay. It bolted on fine but the previous owner of my bike had drilled out the back-cap the the mufflers so i figure i'll just drill out the back of the replacement too and then eventually replace both of them. There's one thing that worries me, the center pipe on my stock pipes came through the back-cap in the center but the center pipe of the replacement exits the back-cap closer to the bottom of the cap. Are they basically the same or did order something i shouldn't use?

 

[Port]

another random question, where is the regulator/rectifier supposed to be mounted? mine was just wedged into the toolbox cubby by the PO.

 

[xjwmx]

I checked the float valve seats and they just slid right out. So i need replacement o-rings, is (1.5mm thick x 7.5mm I.D) the correct size? ... When i opened the float bowl, the gasket had an extra hole for another screw. the hole was on halfway on the outside of the carb and halfway sandwiched between the bowl, there was still enough between the two to make a seal. Is this normal or should i replace the gaskets?

I'm don't remember the size at the moment. If somebody here said that's the size, it probably is. I got some from cycleorings.com or something close to that. It seems like they were putting together kits but I just told them I wanted two rings for a bs34.

I can't really picture what you're saying about the gasket. Maybe a picture? Regarding replacing the gasket, if you see some way it will leak to the outside, then yes. But the gasket that they came with is excellent so keep it if you can. The replacements that I know about are "cardboardy" and fragile looking. I've had mine apart probably a dozen times and the original gasket it still fine.

The original needles and seats seem to be long lasting too. I replaced them just because of their age but ended up putting them back in when the replacement needle swelled up at the tip. The original parts on these bikes seem to be outstanding quality in general. I'm impressed. Now I keep using the original if possible.

 

[xjwmx]

another random question, where is the regulator/rectifier supposed to be mounted? mine was just wedged into the toolbox cubby by the PO.

It goes on the back side of the "downtube". Lots of pictures of its location around. Removing the little plastic toolbox with help, if it's still there. Just one 10mm bolt holding the toolbox.

 

[650Skull]

I checked the float valve seats and they just slid right out. So i need replacement o-rings, is (1.5mm thick x 7.5mm I.D) the correct size[/COLOR]? And I found a previous thread where you answered this same question. When i opened the float bowl, the gasket had an extra hole for another screw. the hole was on halfway on the outside of the carb and halfway sandwiched between the bowl, there was still enough between the two to make a seal. Is this normal or should i replace the gaskets?



The thread for those two links is amazing, it answer everything. And yeah, I got a replacement exhaust pipe (header and muffler) but from ebay. It bolted on fine but the previous owner of my bike had drilled out the back-cap the the mufflers so i figure i'll just drill out the back of the replacement too and then eventually replace both of them. There's one thing that worries me, the center pipe on my stock pipes came through the back-cap in the center but the center pipe of the replacement exits the back-cap closer to the bottom of the cap. Are they basically the same or did order something i shouldn't use?

Pic of the o-ring sizes for various carb parts.

There was a different placement, (some in the center and some low on the center), for the outlet on the rear of the Special mufflers. I couldn't say if it would make a difference, shouldn't think so.

 

[Mharrington]

Oil leak- did you damage the chrome plated oil supply tube that runs up along the center of the cylinders?

 

[Port]

Link to the album

I can't really picture what you're saying about the gasket. Maybe a picture?

The first picture in the album shows my float bowl gasket. The "extra hole" i was talking about is in the top right corner, it's the same on both carbs. The PO replaced the floats with plastic ones, and i think he replaced the needles too but, i'm not positive what the original ones look like.

Pic of the o-ring sizes for various carb parts.

There was a different placement, (some in the center and some low on the center), for the outlet on the rear of the Special mufflers. I couldn't say if it would make a difference, shouldn't think so.

Thanks for verifying the o-ring size. I took some pictures of the exhaust outlets, they are in the album. I dont think it will make a difference either but, but i wanted to see what others thought.

Oil leak- did you damage the chrome plated oil supply tube that runs up along the center of the cylinders?

No, the only damage to the engine was a nick on the left side engine case but, i think the jolt of the impact may have caused the gasket to leak. There's a picture in the album showing the leak. both of the head gaskets leak, the top one more so.

 

[xjwmx]

The first picture in the album shows my float bowl gasket. The "extra hole" i was talking about is in the top right corner, it's the same on both carbs. The PO replaced the floats with plastic ones, and i think he replaced the needles too but, i'm not positive what the original ones look like.

That's the hole I thought you might be talking about. I never paid any attention to it, but it's normal.

The floats in the '81 are normally plastic, if you were expecting brass. Plastic is much better to have. Look at the plastic floats where the pin goes through and there should be a sleeve there. There are some cheap aftermarkets without sleeves and the ones I'm thinking about, at least, are supposed to be no good.

The original needle seat will have a Mikuni logo stamped on it. Not sure if the needle is stamped, but if the seat is original chances are good the needle is too.

 

[Port]

The floats in the '81 are normally plastic, if you were expecting brass. Plastic is much better to have. Look at the plastic floats where the pin goes through and there should be a sleeve there. There are some cheap aftermarkets without sleeves and the ones I'm thinking about, at least, are supposed to be no good.

The original needle seat will have a Mikuni logo stamped on it. Not sure if the needle is stamped, but if the seat is original chances are good the needle is too.

Neither the seat nor the needle were stamped but, the seat sure does look old. I have a hard time believing its not the original, but, i guess it doesn't really matter. right?

Any tips on removing the old o-rings?

And, i'm still not sure where to mount the regulator/rectifier. it was in the void behind the batter in the batter box, the triangular cubby. I searched the forum but could only find threads about alternative places to mount it.

 

[5twins]

Honestly, I don't think you're in the position, knowledge-wise, to be doing a motor rebuild. You're VERY short on the facts about this motor. It really shows with all the other unrelated (to a motor rebuild) questions you're asking. Study up and learn some more, seriously .....

 

[Port]

I have to start somewhere

 

[xjwmx]

^Read through all the material, especially the rebuild section of the factory manual. Plan in your head what you're going to do, what you will need to buy, what you will want to outsource and where. Spend a couple of weeks on that, and then have at it. You'll do alright. This kind of stuff is all in the planning.

 

[650Skull]

Scroll down to post 17 for a Link to rebuilding BS CV Carbs, and vacuum operated petcocks tutorials

Scroll down to post 28 To the link to fix your electric starter problem. Usually a simple fix.

maybe it would be prudent to get the electrics sorted and re-torque the head. Get the bike running good, (fix carb leak). Do a compression test, that will give you an idea if it needs a tear-down straight away. Try not to do it all at once just take things one step at a time.

Neither the seat nor the needle were stamped but, the seat sure does look old. I have a hard time believing its not the original, but, i guess it doesn't really matter. right?

Any tips on removing the old o-rings?

And, i'm still not sure where to mount the regulator/rectifier. it was in the void behind the batter in the batter box, the triangular cubby. I searched the forum but could only find threads about alternative places to mount it.

In the link to the manual/ID thread it also has an engine tear-down and rebuild in post 4. This has been around for eons now and is a recognized self help engine rebuild. This thread and the Tech menu is the best information out there and couple that with the expertise of several of the regulars here will have your brain busting with information and skill

Before thinking about doing anything along those lines just work on the easy stuff, it doesn't matter where the Reg/Rect is mounted as long as it is secure and the couplings have no tension on them.

Again re-torque the head, it was probably not tight and the knock just shifted things. It may be all it needs, and if it works go back to the carbs, (learn), and any other small issues, connections, charging system, compression test and take the time to learn and work out a program so when/if you do thew tear down then it can be done with confidence