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Discussion Starter · #1 ·
I figured it's time for me to start documenting my humble build thread in the hope that it can share some knowledge as I've been helped immensely already reading through everyone else's build threads on this site.

I have a 1978 CX500 Standard that the previous owner had started a scrambler build.

Here is the bike as I bought it with only the addition of the vinyl on the seat so that I could ride it a bit before the snow started:
Land vehicle Vehicle Motorcycle Motor vehicle Car

Land vehicle Vehicle Motor vehicle Motorcycle Car

Land vehicle Automotive tire Vehicle Tire Motorcycle

Land vehicle Tire Automotive tire Vehicle Motorcycle
 

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Discussion Starter · #2 ·
My plan is build a Brat/Cafe style bike. I was drawn in by the Moto Mucci build then discovered Mike's CX500RR which blew me away. I'm aiming for somewhere in between!
The bike ran OK when I bought it but after discovering some things the previous owners have done I have decided to strip the bike and rebuild the engine as I'm not comfortable with the quality of work that had been done.
The frame has been hacked just a bit where some tabs were added and then the original tabs cut most of the way through on the seat support:
Motor vehicle Auto part Wire Automotive exterior Bumper

The radiator has been JB Welded in several spots on the back:
Grille Metal

After flushing the cooling system I found a half-dollar sized chunk of silicone from the radiator.
The front engine hanger bolts were loose.
The wiring had been hacked a bit, etc.
 

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What do you mean by rebuild the engine? If you mean complete disassembly, be sure to check on the availability of replacement parts. My recommendation would be to adjust and check the cam chain for wear, do the resistance measurements on the stator, do an oil and filter change and examine filter for metallic bits. If it passes these tests and is running well, I'd suggest to think twicw about engine disassembly. Just my opinion for what it's worth.
 

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If it runs OK and passes a few tests leave it be.

If it runs make all the necessary checks and adjustments.

If it doesn't, diagnose the problem.

Pulling one of these apart too far can get expensive and bearings in particular are hard to come by depending on grade fitted to your motor.
 

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Discussion Starter · #5 ·
Thanks for the heads-up!

I should have clarified that I am not doing a total rebuild. My leak down test had a lot of air escaping into the crankcase past the rings and a bit past the exhaust valves. I am planning on a valve job & replacing the piston rings only. I am not wanting to get into the lower end of the engine and have to wrestle with bearings that are NLA.

The previous owner stated he had done the triple bypass with G8 stator, cam chain/guides, & mech seal but with some of the items I was finding on the exterior I want to see these internal items for myself as I'm not sold on the quality of work done. I would rather take a bit more time & money this winter to ensure I won't being doing this stuff down the road during riding season.
 

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Discussion Starter · #6 ·
I had some time to get back to work on the engine. I removed the heads in preparation for a valve job and I what I found wasn't too good. There was coolant in one of the left head bolt holes in the block and coolant in two of the right head bolt holes in the block. Auto part


Left head gasket: Auto part Bicycle part Metal
Auto part Bicycle part Metal


Right head gasket: Auto part
Auto part


I don't know what I'm looking for in regards to blown head gaskets but the gaskets look to be intact.
 

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Discussion Starter · #7 ·
Here are the left head valves.
Auto part Automotive engine part Circle Engine Metal


The intake valve area is deeply pitted on the left head
Auto part Metal
Auto part Tire Automotive wheel system Wheel Automotive tire


Here are the right head valves.
Auto part Automotive engine part Engine Metal


The intake valve area on the right head doesn't look too bad to me.
Auto part Metal Automotive wheel system Circle Rim


Do these heads look OK?
 

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Discussion Starter · #8 ·
Last batch of pictures for today.

Both the left & the right cylinder water jackets had a bunch of white, crystalline crud in the bottom. This is even after flushing the cooling system with vinegar and distilled water with a pump & hoses for 30 minutes a few weeks ago. The liquid that I got out of the system didn't look out of the ordinary. Here are pictures of the water jackets: Auto part Wheel Tire Automotive wheel system Automotive tire
Auto part Tire Wheel Automotive wheel system Automotive tire


Left cylinder condition - it looks fairly deeply pitted to me. I'm assuming this cylinder is too far gone for a simple de-glazing.: Metal Auto part
Tire Automotive tire Metal Automotive wheel system Wheel


Right cylinder condition - this one doesn't look so bad but there is some vertical scoring: Metal Cookware and bakeware Circle
Metal Cookware and bakeware Circle
 

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Discussion Starter · #9 ·
What is the verdict by looking at these pictures? The engine ran what I thought was well before the tear-down. The engine oil I drained did not look milky or bad in any way. Same for the coolant that I drained.

I have new piston rings & valve guide seals ready to go but I don't want to proceed any further with this engine if it is too far gone. I would rather purchase a lower mileage example and do this right one time.
 

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Discussion Starter · #12 ·
The bike has an Ignitech unit. I thought this negated the pulser coil at the rear of the engine? Or are the pulser coils not what is under the pulser cover?
 

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Pulsers are inside the motor in the rear cover on a CDI motor. Under the small rear cover if TI and if CDI the small rear cover houses the advancer plate.

If your bike has an ignitech it no longer uses the advancer but does use the pulsers to tell the ignitech when to fire.

I think the coolant in the bolt holes was residual from tear down. I don't really see any evidence it was getting into the cylinders.
 

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Discussion Starter · #14 ·
I've never torn into one of these engines before so all information is helpful. The bolt holes that didn't have coolant in them were full of sludgy oil. I just don't know what is normal and expected with these engines when tearing them down.
 

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Discussion Starter · #15 ·
Here are the stator test results with the engine sitting on the workbench:
1/5 = 104.0 ohms
2/5 = 88.2 ohms
3/5 = 199.0 ohms
4/5 = 104.0 ohms
6/5 = 87.7 ohms
7/5 = 199.0 ohms
No 8 or 9 as I have the Ignitech
Which numbers correspond to the Pulser Coils?
 

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Because of the cylinder slope the bolt holes generally fill with oil and coolant when the heads are lifted.

Make sure to clean and dry them or they hydraulic lock and you will never get a true torque reading when retorquing the head bolts.
 

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Discussion Starter · #19 ·
I got the pistons removed and the cylinders de-glazed with a Flex Hone. Here are the results.
Left cylinder before: Tire Automotive tire Wheel Auto part Rim
Tire Automotive tire Auto part Wheel Automotive wheel system

Left cylinder after: Wheel Auto part Tire Automotive tire Rim
Auto part Tire Wheel Circle Automotive wheel system


Right cylinder before: Auto part Wheel Tire Automotive wheel system Automotive tire
Auto part Automotive engine part Wheel Engine Metal

Right cylinder after: Auto part Automotive wheel system Wheel Automotive tire Muffler
Auto part Automotive wheel system Circle Metal Wheel


The left cylinder still has some pretty severe pitting at the top. The right cylinder doesn't look too bad except for some vertical scoring still visible.

Here is possibly the worst part: Mason jar Metal Glass
The right piston is cracked.

I've got two more engines that I picked up with cheap parts bikes that I now need to tear into to see if I have one good block and another good right piston. The project must continue. I'd really like to have my bike ready for April/May.
 

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Discussion Starter · #20 ·
Resurrecting my old thread as I've finally had some time to get back into this project after a few years! I got down to the block of the 1982 CX parts bike that I picked up back in 2018. The pistons & cylinders are OK although there are some other issues.
Damaged camshaft:
Office supplies Writing implement Writing instrument accessory Material property Font

Writing implement Wood Office supplies Automotive design Automotive tire

I'm hoping I can use the camshaft from the original engine I have.

Bad rod bearing:
Gas Auto part Machine Machine tool Metal


The exterior of the block needs some attention which is where I am currently with the engine.
Automotive tire Motor vehicle Table Bumper Wood

Motor vehicle Automotive tire Wood Automotive design Hood
 
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