Any one ever rebuild a CB650? Looking for sugestions on how to do it

[layback209]

So my hawk started burning oil 60000km on her, she has served the P.O. well but is giving out on me.

What kind of costs am i looking at if i take it to a bike place to have this done?

Is this something a weekend wrencher could handle over winter?

What sould be done? I was thinking
-new piston rings
-new pistons and rods (if they don't cost more then i paided for the bike)
-"Machine the Cyclinders???," Deglaze???, Bore them out a bit???

Should you do anything to the valve train and cylinder head?

I love this bike, I dont want to sell it. Any ideas, sugestions, rebuild advice would be appreciated :)

Cheers,
 

[Bumblebee]

Are there any exterior oil leaks? Is the oil level too high with the excess oil getting pushed back into the breather tube and being burned that way? (Overfill will leave the heads via the breather tube to the air box then into the cylinder and be burned there which can appear to be a ring problem)

If you have basic mechanical skills, good tools and a manual, not in a hurry, a top end overhaul is fairly easy and straight forward.

Start by finding the source of the problem. Except for excess oil or external leaks it'll likely be rings or valve guides. What is the oil consumption rate? A leaking head gasket can also leak oil into the #1 or #4 cylinders. If something major (cylinder) is cracked that could leak but it's rather unlikely unless the engine has been abused. Which cylinder is the source of the problem? Not sure why you would need rods unless it's bent or out of specifications. Machining the cylinders or machining in general? Are they scored or is something warped?


As for price, no real clue other than my head gasket leak years ago. I picked up the parts (gaskets) which came to a whopping $55 total. Just for fun I walked into the shop next to the parts department and told them what the problem was. The same $49 gasket that was in the bag I was holding in my hand was going to be $125, the other gaskets ran another $100. They couldn't get me in for 3 months and it would take 2 weeks. Labor $400. A couple other shops had said basically the same thing. I went home and pulled out the wrenches. Six hours later and the $55 total cost it was done and I KNOW the job was done right along with locktite on the cam gear bolts and a very close inspection for any other problems as well as a good cleaning. When the last bolt went into place, I know all the insides were at nearly new specifications. Pulling the cylinders and installing new rings would have taken about another 4-5 hours the way I do maintenance.

[gammer]

I agree, top end overhauls are not too hard to do. Just take your time and have a shop manual handy.
A top end gasket kit will be a must and will probably run you between $100-$150.
If the cylinders and pistons look good, then I'd just replace the rings and get the cyls honed out.
But if specs are way off on the cyls, then you will have to get 'em bored a bit and over size the pistons. This will obviously cost you more. Also note, that sometimes when you bore and oversize, you will need to re-jet the carbs.

You might want to do a valve job while you have the top end off too.

[layback209]

Are there any exterior oil leaks? Is the oil level too high with the excess oil getting pushed back into the breather tube and being burned that way?

Yes there is one comming from behind the midle of the headers, i think its the head gasket thats leaking there.  And no i don't believe i overfilled the oil.  I always check it on level ground.  I believe i seen the breather tube open to air in a kind of "dump vapor" position under the bike.  I will have to confirm with the manual if this right for this bike.  The ccv set up on my truck goes to the air box.

Sweet advice now i know what to look for when i take this bad boy apart.

My timing chain "i think" makes a good ratlte noise every once in awhile.  Do these chains stretch over time? I cant rember for sure but i think i may have read in the manual that they can be re-tensioned.  Be anought thing to check out when i do the top end.

You might want to do a valve job while you have the top end off too.

I don't know much about valve trains what is all involved here?

Thanks for the help,

[gammer]

My timing chain "i think" makes a good ratlte noise every once in awhile.  Do these chains stretch over time? I cant rember for sure but i think i may have read in the manual that they can be re-tensioned.

Yep, they do stretch with time. However the cam chain tensioner automatically adjusts to keep tension on the chain. If you suspect that it is making noise, then it is possible that the chain is stretched beyond what the cam chain tensioner can provide tension for, or your cam chain tensioner is not functioning properly.
If that is the case, then you will need a new cam chain and/or tensioner

[Bumblebee]

Different year models vary however:
The crankcase breather tube should go from the top of the center head cover to the airbox. The vent line underneath should be the excess gunk dump line from the airbox.
It sounds like the head cover (cylinder head cover with the rocker arms) has a leaking seal. That upper seal is prone to leaking if the bolts aren't torqued down properly. The main head gasket is below the level of the spark plugs where the large finned piece attaches to the cylinder jug case. There is no pressurized oil at the head gasket area between the cylinders - it' gravity drop between #2/#3 down to the crank case.
If you're taking the heads off, save yourself a lot of hassle and just get all the rubber seals that are involved in the dissassembly and replace them as you go. Look close at the manual. On mine there are two tiny rubber O-rings at the head gasket level outboard of the #1 and #4 cylinders. That's the path where the oil comes up from the oil pump to the heads. Those O-rings are essential to keep the oil from leaking.

If there's the occasional strange chain/metal type rattle from the center of the engine between the #2/#3 cylinders, it's probably the cam chain.

If that is the case, then you will need a new cam chain and/or tensioner

Or use the pennytech fix procedure that's in the manual:
Transmission in netural.
Ignition and kill switch off.
Remove pulse generator cover.
Loosen camp chain tensioner lock nut. (located on the lower back of the cylinders between #2 and #3)
Tighten the cam chain lock nut while slowly rotating the crankshaft clockwise. (cam chan locknut torque = 7-10 ft/lbs)
Reinstall pulse generator cover.
Done.

If that doesn't fix it, then you're into replacing the tensioner and/or chain. The tensioner comes out the top easily. Replacing the cam chain is MAJOR surgery and involves splitting the case.

Note that if you're taking the heads off, retensioning is in the reinstall procedure when hanging the cam chain on the valve cam.

[gammer]

If that doesn't fix it, then you're into replacing the tensioner and/or chain. The tensioner comes out the top easily. Replacing the cam chain is MAJOR surgery and involves splitting the case.

I have heard of folks replacing their cam chains by popping a link out then joining the end of the old chain to the new chain. Pull the old chain out and at the same time it pulls the new chain through. Then join the new chain with a master link.
You will need a chain breaker for this and of course the new chain will have to be aftermarket, as the oem cam chain will be all one piece.

[Pizzmeister]

Keeping in mind I know nothing about replacing the cam chain (other than having mine replaced a number of years ago), couldn't you get the OEM chain, connect it as you indicated, pull it through, disconnect old chain, and then just use the master link on the new OEM chain?

[gammer]

Most of the aftermarket cam chains come with a master link. The OEM's do not.
I guess technically you could pop out a link in the OEM and then use the master link from an aftermarket to join it back together.