Topic: 750 Main Bearings Bolts - Leak...

[Johnie]

CB750KO - Under the crankcase, left side just above exhaust pipe #1
are bolts that drip.  Before I try to remove them I thought I better ask if there is any damage I can do by removing and installing new oil rings.  Are these long enough that I have to remove the exhaust to get them out?
Thanks

[scondon]

 Here's a pic from CMSNL site that shows what the whole plug looks like. It is the same part as the plug on the side of your engine so you can easily remove the side one and measure if you would like exact dimensions.

http://www.cmsnl.com/products/cap-oil-path_15331300000/


  Just about any leak in your motor can end up dripping from those plugs since they are one of the lowest points on the motor. Be sure that it is the source of your leak.

[andy750]

Yeah mine leak as well (no surprise there since my whole engine seems to leak!) - Im also interested Johnie in how you get on....keep us posted!

cheers
Andy

[Bob Wessner]

Mine leak as well, but John's bolts look nicer. Mine seem more corroded and felt trying to remove them could lead to a real disaster so I thought I would live with the drip now an then until something major needed to be done with the engine.

[Kevin D]

Johnie,
 
The bolts you are pointing at clamp the main bearings. There is no seal on the bolt, and they are plenty long, 8x120mm, or 4" if you prefer.

I'm sure there are members on board who have had success repairing leaks here. Maybe fit a fat o-ring on the bolt after the flatwasher??

The two oil passage plugs are a little further back, on either side of the pan, and have an o-ring, easy fix.

And.........No.........I didn't put the case in the washing machine to clean it up. It's my impromptu work bench and photo studio.

[Sweep]

If you're splitting the cases you can put hd crank studs on there instead of stock.

[Johnie]

Johnie,
 
The bolts you are pointing at clamp the main bearings. There is no seal on the bolt, and they are plenty long, 8x120mm, or 4" if you prefer.

I'm sure there are members on board who have had success repairing leaks here. Maybe fit a fat o-ring on the bolt after the flatwasher??

The two oil passage plugs are a little further back, on either side of the pan, and have an o-ring, easy fix.

And.........No.........I didn't put the case in the washing machine to clean it up. It's my impromptu work bench and photo studio.

Now that this KO restoration is pretty much done and on the road, it is time to tweek some things.  This post goes back to February and I think Kevin has it right.  Looks like these are for the main bearings.  Long bolts too.  The bolts I am pointing at in the pictures - the one on the right leaks when riding only.  It does not drip when sitting.  I have to try to stop that leak as I hate it when it gets all over the lower muffler.  Anyone ever fix this?  I did put a cut rubber hose around it and will try then to put a clamp on it.  But I thought it may be better to drop the bolt a half inch and slip a flat rubber gasket over it and retighten?  But concerned there is a torgue for that bolt since it is for the main bearing?  Or can I just give it a good snug pull to tighten it?  Give me your ideas or how you fixed yours...Thanks...

[mazingerzeca]

The washers for the cylinder head studs are made of copper. Given that copper is softer, they can be made of this material to seal the studs on the cylinder head an prevent oil leaks. Would it be possible to use copper washers in the crank studs too and avoid oil leaks?

[Johnie]

Copper washers...not a bad idea.  The reason I was going to try rubber is then I would not have to take the bolt all the way out.  I could just drop that bolt enought to slip it over the bolt and tighten.

[754]

I take it you made sure they were toequed (overtightening not a good idea)

I say soft metal washer, is the way to go, if you make them out of alum sheet try to find soft aluminum or anneal them.

It seems to me that the thin smear of sealant on the case halves must be missing at these bolts to allow the oil out, or the seating suface under the bolt heads has a gouge or nick..

[Johnie]

I take it you made sure they were toequed (overtightening not a good idea)

I say soft metal washer, is the way to go, if you make them out of alum sheet try to find soft aluminum or anneal them.

It seems to me that the thin smear of sealant on the case halves must be missing at these bolts to allow the oil out, or the seating suface under the bolt heads has a gouge or nick..

754...what is the torque for these bolts?  The engine is all OEM and I have not touched the bolts yet.  They are tight when I put a wrench on them.  I have not tried the torque yet as I have to remove the exhaust to get at it.  Thanks for the input as I know Bob and some others are having leaks from these same bolts...

[Gamma]

http://i192.photobucket.com/albums/z293/galaxy8155/img019.jpg[/img]]

[Jerry Rxman Griffin aka MuthaF'er]

I think Sparty had this issue after his engine was reassembled but I'm not sure if he found a cure. He did however use heavy duty crank studs so I'm not sure if the same cure would apply since the heavy duty replacement is studs with nuts that can easily be removed as opposed to long bolts.

I believe I would make damn sure that this is where the leak is coming from rather than running down from somewhere else. If so I would probably try to torque all 10 bolts in the proper sequence so it doesn't create a leak at a different location. What surprises me is that there is not a higher torque value for the 8mm bolts than the 6mm bolts.

[MRieck]

I think Sparty had this issue after his engine was reassembled but I'm not sure if he found a cure. He did however use heavy duty crank studs so I'm not sure if the same cure would apply since the heavy duty replacement is studs with nuts that can easily be removed as opposed to long bolts.

I believe I would make damn sure that this is where the leak is coming from rather than running down from somewhere else. If so I would probably try to torque all 10 bolts in the proper sequence so it doesn't create a leak at a different location. What surprises me is that there is not a higher torque value for the 8mm bolts than the 6mm bolts.

He solved it using an oring and some silcone sealent. It can be tricky as you don't want to much sealant on the main bearing tower because it can easily push into the main bearing. Also assembly lube can interact with the sealant and not cure properly.

[mark]

I think Sparty had this issue after his engine was reassembled but I'm not sure if he found a cure. He did however use heavy duty crank studs so I'm not sure if the same cure would apply since the heavy duty replacement is studs with nuts that can easily be removed as opposed to long bolts.

I believe I would make damn sure that this is where the leak is coming from rather than running down from somewhere else. If so I would probably try to torque all 10 bolts in the proper sequence so it doesn't create a leak at a different location. What surprises me is that there is not a higher torque value for the 8mm bolts than the 6mm bolts.

He solved it using an oring and some silcone sealent. It can be tricky as you don't want to much sealant on the main bearing tower because it can easily push into the main bearing. Also assembly lube can interact with the sealant and not cure properly.

I kinda remember that one. The thread died really quick, too. Didn't get my 2¢ in then so here it is now:



Wavy spring lockwasher and cap nut instead of split washer and plain nut.


Happy trails.

[paulages]

I think Sparty had this issue after his engine was reassembled but I'm not sure if he found a cure. He did however use heavy duty crank studs so I'm not sure if the same cure would apply since the heavy duty replacement is studs with nuts that can easily be removed as opposed to long bolts.

I believe I would make damn sure that this is where the leak is coming from rather than running down from somewhere else. If so I would probably try to torque all 10 bolts in the proper sequence so it doesn't create a leak at a different location. What surprises me is that there is not a higher torque value for the 8mm bolts than the 6mm bolts.

He solved it using an oring and some silcone sealent. It can be tricky as you don't want to much sealant on the main bearing tower because it can easily push into the main bearing. Also assembly lube can interact with the sealant and not cure properly.

I kinda remember that one. The thread died really quick, too. Didn't get my 2¢ in then so here it is now:



Wavy spring lockwasher and cap nut instead of split washer and plain nut.


Happy trails.

it's a bolt, not a stud. a cap nut won't do anything. i just had one leak on an engine i rebuilt. luckily it was on of the end bolts, so i was able to back it out without the frame or exhaust being in the way. i put some 1104 sealer around the last inch or so of bolt before the head, and some more behind the head, so that it squeezed up and sealed when retorqued. worked fine.

[mark]

I think Sparty had this issue after his engine was reassembled but I'm not sure if he found a cure. He did however use heavy duty crank studs so I'm not sure if the same cure would apply since the heavy duty replacement is studs with nuts that can easily be removed as opposed to long bolts.

I believe I would make damn sure that this is where the leak is coming from rather than running down from somewhere else. If so I would probably try to torque all 10 bolts in the proper sequence so it doesn't create a leak at a different location. What surprises me is that there is not a higher torque value for the 8mm bolts than the 6mm bolts.

He solved it using an oring and some silcone sealent. It can be tricky as you don't want to much sealant on the main bearing tower because it can easily push into the main bearing. Also assembly lube can interact with the sealant and not cure properly.

I kinda remember that one. The thread died really quick, too. Didn't get my 2¢ in then so here it is now:



Wavy spring lockwasher and cap nut instead of split washer and plain nut.


Happy trails.

it's a bolt, not a stud. a cap nut won't do anything. i just had one leak on an engine i rebuilt. luckily it was on of the end bolts, so i was able to back it out without the frame or exhaust being in the way. i put some 1104 sealer around the last inch or so of bolt before the head, and some more behind the head, so that it squeezed up and sealed when retorqued. worked fine.

[paulages]

I think Sparty had this issue after his engine was reassembled but I'm not sure if he found a cure. He did however use heavy duty crank studs so I'm not sure if the same cure would apply since the heavy duty replacement is studs with nuts that can easily be removed as opposed to long bolts.

I believe I would make damn sure that this is where the leak is coming from rather than running down from somewhere else. If so I would probably try to torque all 10 bolts in the proper sequence so it doesn't create a leak at a different location. What surprises me is that there is not a higher torque value for the 8mm bolts than the 6mm bolts.

He solved it using an oring and some silcone sealent. It can be tricky as you don't want to much sealant on the main bearing tower because it can easily push into the main bearing. Also assembly lube can interact with the sealant and not cure properly.

I kinda remember that one. The thread died really quick, too. Didn't get my 2¢ in then so here it is now:



Wavy spring lockwasher and cap nut instead of split washer and plain nut.


Happy trails.

it's a bolt, not a stud. a cap nut won't do anything. i just had one leak on an engine i rebuilt. luckily it was on of the end bolts, so i was able to back it out without the frame or exhaust being in the way. i put some 1104 sealer around the last inch or so of bolt before the head, and some more behind the head, so that it squeezed up and sealed when retorqued. worked fine.

ooooooooooookay.... i guess i didn't catch that you were trying to help sparty out with his problem he already fixed rather than the question actually posed in this thread.