CB360 box build - Project Junebug
- Thread starter plagrone
- Start date
Trevor May
Been Around the Block
Re: CB360 box build - nearing completion
I can actually offer a technical suggestion! A mechanic once told me you can easily diagnose low compression by putting compressed air into the spark plug port. If you hear air coming out of the exhaust, exhaust valve. If you hear air in the carburetor, intake. Air from the oil fill port, rings. That way you know if you need a valve job or a cylinder job.
I can actually offer a technical suggestion! A mechanic once told me you can easily diagnose low compression by putting compressed air into the spark plug port. If you hear air coming out of the exhaust, exhaust valve. If you hear air in the carburetor, intake. Air from the oil fill port, rings. That way you know if you need a valve job or a cylinder job.
Trevor May
Been Around the Block
Re: CB360 box build - nearing completion
I used Google voice to post that last bit. Instead of valve job I had said head valve. Google heard hand job. I typed the correction myself, just in case.
I used Google voice to post that last bit. Instead of valve job I had said head valve. Google heard hand job. I typed the correction myself, just in case.
plagrone
Coast to Coast
Re: CB360 box build - nearing completion
Okay, I'm trying to make a checklist to figure out what all I need, and what all I need to do. I'm thinking a hone for the jugs (if that's all that's needed), new rings, new valves, new valve seals. I already have a gasket kit.
Do you guys think the old valves will be able to be reconditioned or should I just buy new ones?
I'm starting to wish I hadn't sold my spare head.
Okay, I'm trying to make a checklist to figure out what all I need, and what all I need to do. I'm thinking a hone for the jugs (if that's all that's needed), new rings, new valves, new valve seals. I already have a gasket kit.
Do you guys think the old valves will be able to be reconditioned or should I just buy new ones?
I'm starting to wish I hadn't sold my spare head.
Re: CB360 box build - nearing completion
I don't think you'll be able to make a decision about any of those things until you get the engine apart and specced out.
Worst case scenario is you have to bore the jugs, get bigger pistons and rings, recut the valve seats, and get new valve. Best case scenario is hone the bores and get new rings, and lap the valves. Reality is likely to be a mix.
I don't think you'll be able to make a decision about any of those things until you get the engine apart and specced out.
Worst case scenario is you have to bore the jugs, get bigger pistons and rings, recut the valve seats, and get new valve. Best case scenario is hone the bores and get new rings, and lap the valves. Reality is likely to be a mix.
plagrone
Coast to Coast
CB360 box build - nearing completion
Ah, well I don't know much about valves so I assumed they would have to be replaced if compression was this bad... I didn't realize how serviceable they were, thought they were more of a "if it's bad, replace it" type of part.
But yea, I figured I'de need a day with the head off and some calipers to figure out exactly what I need to do. I'll get everything off sometime this week and get some pictures up. I'm praying the valves will be serviceable and cylinders within spec. I'll also have to be getting some of these guys, I reckon: http://www.ebay.com/itm/HONDA-CB360-CL360-CJ360-CB-CL-CJ-360-VITON-VALVE-SEALS-/230985117239?pt=Motorcycles_Parts_Accessories&hash=item35c7c92e37&vxp=mtr
Thanks, and here's to hoping reality involves honing and lapping.
Sonreir said:
Ah, well I don't know much about valves so I assumed they would have to be replaced if compression was this bad... I didn't realize how serviceable they were, thought they were more of a "if it's bad, replace it" type of part.
But yea, I figured I'de need a day with the head off and some calipers to figure out exactly what I need to do. I'll get everything off sometime this week and get some pictures up. I'm praying the valves will be serviceable and cylinders within spec. I'll also have to be getting some of these guys, I reckon: http://www.ebay.com/itm/HONDA-CB360-CL360-CJ360-CB-CL-CJ-360-VITON-VALVE-SEALS-/230985117239?pt=Motorcycles_Parts_Accessories&hash=item35c7c92e37&vxp=mtr
Thanks, and here's to hoping reality involves honing and lapping.
plagrone
Coast to Coast
Re: CB360 box build - nearing completion
I haven't removed the valves yet, but the cylinders are smooth as glass and there's no condemning wear or deterioration on piston heads or combustion chambers.
The compression ring and second ring in the right cylinder were seized.
That appears to be the cause of my compression woes.
Interestingly, the valves on the right cylinder look beautiful. The valves on the left side look rusty and corroded.
Lesson learned. If your going to build a bike for six months, don't take anyone's word on the condition of your engine internals.
I haven't removed the valves yet, but the cylinders are smooth as glass and there's no condemning wear or deterioration on piston heads or combustion chambers.
The compression ring and second ring in the right cylinder were seized.
That appears to be the cause of my compression woes.
Interestingly, the valves on the right cylinder look beautiful. The valves on the left side look rusty and corroded.
Lesson learned. If your going to build a bike for six months, don't take anyone's word on the condition of your engine internals.
plagrone
Coast to Coast
Re: CB360 box build - nearing completion
I wouldn't say there's NO wear in the combustion chamber. Looks like someone got a little overzealous while cleaning corrosion and also something metal found it's way into right cylinder at some point. Might be a good idea to get the head resurfaced.
First two pictures are the right, second two, left.
This is the spot that makes me think head needs to be resurfaced. Spot is ~40 degrees in from exhaust valve on right cylinder. Metal is raised probably .8mm from whatever impacted it.
Removing valves today.
I wouldn't say there's NO wear in the combustion chamber. Looks like someone got a little overzealous while cleaning corrosion and also something metal found it's way into right cylinder at some point. Might be a good idea to get the head resurfaced.
First two pictures are the right, second two, left.
This is the spot that makes me think head needs to be resurfaced. Spot is ~40 degrees in from exhaust valve on right cylinder. Metal is raised probably .8mm from whatever impacted it.
Removing valves today.
crazypj
Split personality, I fake being smart
Re: CB360 box build - nearing completion
Not a problem, skim 0.010" off head, mount on a rotary table and re-machine the 'squish' band.
I've done CJ250 (56mm bore) to 70mm bore that way
If you had clearance on intake valve seat you could just flycut the clearance to get back to bore size
Not a problem, skim 0.010" off head, mount on a rotary table and re-machine the 'squish' band.
I've done CJ250 (56mm bore) to 70mm bore that way
If you had clearance on intake valve seat you could just flycut the clearance to get back to bore size
plagrone
Coast to Coast
Re: CB360 box build - nearing completion
If I had the tools or the money, this is the route I would take, along with a rebore to 378, a valve job, and some work on these ridiculous cam journals. That was bad tech in the 70s... What were they thinking?
crazypj said:Not a problem, skim 0.010" off head, mount on a rotary table and re-machine the 'squish' band.
I've done CJ250 (56mm bore) to 70mm bore that way
If you had clearance on intake valve seat you could just flycut the clearance to get back to bore size
If I had the tools or the money, this is the route I would take, along with a rebore to 378, a valve job, and some work on these ridiculous cam journals. That was bad tech in the 70s... What were they thinking?
plagrone
Coast to Coast
CB360 box build - nearing completion
What would we do without cardboard? I'm heading down to the base again this weekend, and I've got my 3/8ths inch slab of aluminum marked up to have side covers and a gauge mount cut out.
For my gauge mount I'm using these little L brackets to give me an easy mounting point off of the top triple clamping bolts while also serving to drop the gauges a little. The position they will ride in looks very good. Lower, yet rider oriented.
The side covers are going to look awesome I think. They're not so much side covers as "battery hiders"... They will also have an angled cut out giving clearance for the K&Ns.
What would we do without cardboard? I'm heading down to the base again this weekend, and I've got my 3/8ths inch slab of aluminum marked up to have side covers and a gauge mount cut out.
For my gauge mount I'm using these little L brackets to give me an easy mounting point off of the top triple clamping bolts while also serving to drop the gauges a little. The position they will ride in looks very good. Lower, yet rider oriented.
The side covers are going to look awesome I think. They're not so much side covers as "battery hiders"... They will also have an angled cut out giving clearance for the K&Ns.
