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Seal and Coil replacement complete!


Finally received the rest of the parts I needed (exhaust gaskets) to complete the rebuild, everything looks great, ran it around the block and it’s running like a champ. I did notice that the right side rockers are making a bit of noise, so I’ll adjust those again, soonish, that said, the bike sounds great and is running wonderfully.

CX500 stator and seal replacement part 2

With all the seals in hand, and a few hours of work today I was able to actually finish most of the engine work on the CX500.

IMG_20140419_105336The new stator is in place and the CDI advance pulser has been removed. I was also able to significantly reduce the number of wires coming out of the back of this engine. So now I have 1 ground, 2 pairs of high speed coil wires. 3 power wires off the stator coil and the neutral indicator switch!

IMG_20140419_105324New oil seal is installed… This was a bit of a pain. the various ’79 microfiche indicate a totally different seal size, so I had to track down the right seal for the job (what a pain!)

IMG_20140419_105415After closer inspection, the shift cam tensioner spring was a bit tired, so when I ordered the new water pump oil seal I also ordered a new spring

IMG_20140419_105443Since I was trying to reduce the amount of oil leaking out of this thing (which wasn’t much) I took the opportunity to replace the shift shaft oil seal. This is primarily where most of the oil drips would come from, that said, it wasn’t much at all and I would only find a few drips after a long ride and allowing the bike to sit in place for a few days.

IMG_20140419_105933IMG_20140419_105941Also, when I scraped off the old rear engine cover gasket I noticed that coolant had penetrated it. This was due to the o-rings which you see above (new ones installed in these pictures). So those got replaced as well.

IMG_20140419_111153New gasket is installed. Time to button her up.

IMG_20140419_114731One thing I should have noted here (which I didn’t get a picture of before reassembly) is that if you have a failed mechanical seal on the water pump, NOW is the time to replace it. It can be replaced while the engine is on the bike and rear cover is on, however it’s not a simple job.

With the rear of the engine back together it’s time to address the oil leak out of the clutch arm on the front of the engine.

IMG_20140419_121324This little seal, no bigger than a dime has been a massive annoyance to me. It weeped oil out right at the clutch arm shaft and would end up coating everything behind it (due to wind blowing it everywhere)

IMG_20140419_121318The seal took all of about 2 minutes to replace, and another half an hour scraping the old gasket off.IMG_20140419_172607You can clearly see where it was leaking…. How annoying.

Any who, with some effort I was able to reinstall the engine on the bike by my self.

IMG_20140419_172624Next step is to torque everything down, reinstall the radiator. oil and coolant, etc. Likely this won’t happen this weekend as I’ve decided to replace the exhaust gaskets as well. They look alright but probably will leak a bit, so I’ve got another set ordered and they should be here shortly.

CX500 stator and seal replacement

The CX500, minus just about everything!

CX500 /wo engineAs you can see, the engine is removed! Over the summer I noticed the stator got worse and worse until I nearly ended up stranded with a dead battery. So the first step is to remove the tank, side panels, foot break, carburetors, electrical etc. etc.

CX500 radiator /w sensor and electric fan modI was pretty pleased to see that the electric fan modification I did on the radiator is holding up well. The paint is holding up pretty good as well, although some has been scratched off around where the radiator inlet pipe is.

CX500 M.A.C. 2-IN-1 titanium wrapped exhaust and headers The other thing was pretty happy about was the condition of the M.A.C. exhaust system and how well the titanium wrap job is holding up.

CX500 engine with rear cover off

Got the engine up on the bench this morning and popped the rear cover off. Man theres a lot of bolts on this thing. While removing the cover was mindful not the disturb any of the seals for the final shaft, shifter, or oil and mechanical seal on the water pump shaft. That said, I’ll need to order a new shifter seal, as well as new copper washer for the water pump (If I can’t find one) and possibly two new o-rings for the cylinder jacket what pass through pipes

CX500 starterAs you can see, the starter gear is in great shape. This reduction gear on the engine is also in nearly new condition, which is really nice to see on a bike this old!

CX500 engine starter reduction gearBoth gears on the starter reduction gear on in nearly perfect condition.

CX500 engine lower rear CX500 engine gear selector starThe gear selector and selector star are both in great shape. This is an interesting design for a selector star, usually you don’t see them with pins to provide the indexing. That said, I guess such a system would probably last a whole lot longer.

The other thing I noticed (which is hard to see). Return spring on the selector shaft came (the shaft which protrudes through the rear of the engine) appears warn, so I’ll order a new one of those, hopefully it tightens up the gear selector a bit.


Timing chain tensioner CX500 Timing chain CX500Checking on the timing chain things look good. You can see, given the position of the cam chain tensioner that the chain will need to be replaced in the next 10K miles, so another job for another time. There is still some room on the tensioner (though not much) and there is zero slop on the chain.

CX500 engine final shaftThe final shaft, with damper assembly is in great shape. The lobes on the damper cam show very light ware, the shift is nice and tight and I expect many more years out of this.

CX500 engine G47 state /w pulsers CX500 engine G47stator /w pulsers (2)The offending unit. Here’s the old G47 stator and pulser assembly. The first thing that failed on this stator was the source coil (which you can see by it self on the stator assembly). These G47 style stators are extremely complicated with a bit of a mess of wiring.

The new stator will be a G8 style unit from a newer bike. Normally you can’t run these in the old CX500’s with CDI control systems, however I’ve replaced the control system with a much better Ignitech black box.


CX500 engine rear cover water pump, oil and mechanical sealYou can see that the oil seal has seen better days so I’ll replace that while I’ve got the rear engine cover open.

CX500 G47 stator (removed)After some quick work with the air tools and some wire cutters,  I was able to extract the old G47 stator core from the rear cover.

CX500 G47 stator and pulser wiring harness

Next task is to figure out how much of this wiring bundle I can do away with. I suspect given that the Ignitech only needs pulser data, I will be able to get rid of quit a few of these wires.  This will be nice as it reduces the overall clutter, it also takes the weigh down a few onces 😉

Shimmed and Ready

Got the new shims in the mail today; ordered them from Thunder Valley Powersports and they were good about keeping me up-to-date on where my order was at.  With parts in hand I set about correcting my valve clearances.
Using my spreadsheet from before, I was able to easily decide which shims to reuse and which to replace with new ones. While relatively easy, the entire process is extremely messy.
To keep the bike somewhat under control, I continued to have it supported mostly upright by my ladder. This bike has no center stand (one of the previous owners ripped it off) so this sufficed in the meantime.
After all was done, I went through and re-measured my clearances. Things definitely look better than they were.

Cylinder Original Clearance (mm) New Clearance (mm)
1 Intake A 0.25 0.08
B 0.13 0.06
Exhaust A 0.15 0.10
B 0.18 0.08
2 Intake A 0.2 0.10
B 0.15 0.10
Exhaust A 0.18 0.08
B 0.18 0.10
3 Intake A 0.18 0.08
B 0.13 0.10
Exhaust A 0.13 0.13
B 0.2 0.10
4 Intake A 0.2 0.13
B 0.13 0.06
Exhaust A 0.2 0.13
B 0.2 0.13

Prior to putting the cylinder cover back on, I inspected it and found a ton of residual silicon all over where the old gasket was.  I’m guessing someone didn’t quite know how to get the gasket back on, so they went with adding more gunk.  I cleaned it off as best I could, installed a new gasket and closed things off.  One issue is that around the opening where the tachometer cable plugs in, there’s no gasket (and none seem to be available).  I’m going to have to silicone that as soon as I can.

I was able to test fire the bike after buttoning back up.  Things seem to actually be running a little bit better, but I can’t really tell until I take care of the opening near the tach cable outlet.  It was spewing oil all over from that location, so I need to fix it before I can tell what’s going on.  The engine definitely seemed happier than it was, though.

Calculating New Valve Shims

Went back into the cylinder head and took some measurements. Dirty work, but had to be done. I used metric feeler gauges to find the clearance and a digital micrometer to find the thickness of the current shims. The manual mentions that the shim thickness should be between 0.06mm and 0.13mm. I calculated for middle of the road (0.095mm) to find the new shim thickness. The current layout of the bike is:

Cylinder Clearance (mm) Current Shim Thickness (mm) New Shim Thickness (mm)
1 Intake A 0.25 2.589 2.75
B 0.13 2.693 2.75
Exhaust A 0.15 2.585 2.65
B 0.18 2.581 2.65
2 Intake A 0.2 2.49 2.6
B 0.15 2.544 2.6
Exhaust A 0.18 2.593 2.7
B 0.18 2.586 2.65
3 Intake A 0.18 2.765 2.85
B 0.13 2.767 2.8
Exhaust A 0.13 2.634 2.65
B 0.2 2.592 2.7
4 Intake A 0.2 2.568 2.65
B 0.13 2.7 2.75
Exhaust A 0.2 2.61 2.7
B 0.2 2.616 2.7

The result of this is the need for the following shim sizes:

New Shim Thickness Count
2.6 2
2.65 5
2.7 4
2.75 3
2.8 1
2.85 1

I have placed an order for the shims I need (reusing some of the old shims where I can). Hopefully the new shims will get here soon and I can see how things go.

Clean Carbs But Still No Love

Finally had a chance to button up all the carbs and get the pack rebuilt.  My attempts to fix the stripped air mixture screw all went poorly, so ultimately I picked up a replacement off of Ebay and cleaned it up.  Things are looking pretty clean and came together quite well.

Clean Carb, Bottom Clean Carb, Throttle Clean Carb, Choke

Placing the carbs back on the bike went pretty well and I just had to test it.  I put some fuel in and checked for leaks; happily everything seemed to be holding pretty well.  Started up the engine (with my fingers crossed) and things fired up, but still having issues with carbs 3 and 4.  Doing a temperature test at the headers, cylinders 1 and 2 read around 250+ degrees F while cylinder 4 was at 83 degrees F.  Not good.

After stepping back and trying to figure out the next plan, I decided to go ahead and revisit the compression and ignition.  To rule out “no spark” problems, I went ahead and did an ignition test as well as a spark test; both seemed to pass for all for spark plugs.  Pulling them I did notice that cylinder 3 and 4 were both “wet” compared to 1 and 2.

Spark Plugs

Next up was the compression test.  The Clymer manual says to try a normal compression test (crank the engine a few times) and a wet compression test (add a tablespoon of oil to the cylinder and retry the compression test).  I found the following:

Cylinder Dry Compression (psi) Wet Compression (psi)
1 120 210
2 97.5 270
3 105 150
4 97.5 165

The low compression readings seem to be within reason (the Clymer manual says that ~100psi is good enough to get the engine going), but the worry is that with the additional oil, cylinders 3 and 4 didn’t significantly change.  This could point back to needing to finish the valve shim adjustment I mentioned in an earlier post.  Perhaps in doing that I can correct some of these compression issues.  To do so, I’ll need to order the following 25mm valve shims:

Shim Thickness Number
2.6 2
2.65 5
2.7 5
2.75 1
2.8 1
2.85 1

After putting all the spark plugs and re-wiring, I decided to fire the bike up one more time (this time with the oil still in the cylinders).  I expected quite a bit of smoke, which is what I got, but was also pleasantly surprised to notice all 4 cylinders seemed to be firing.  Seems the added compression from the oil has helped a bit; furthering the idea that the next step is to finish the valve adjustment.

Further Carb Work

Finally got some time to get back to the surprisingly clean carbs from the CB900.  I went through the various air and fuel passage ways with some carb cleaner and all the pathways seem pretty clear.  Piece by peice I started reconstructing the carbs replacing all original bolts with stainless socket button-head screws and also replacing all O-rings, diaphragms, and gaskets.  As this bike is already running with an aftermarket exhaust (and I plan to run without the airbox initially) I also applied the DynoJet Stage 3 (which included a new needle and larger main jet set to DJ130 from stock 105).  The Stage 3 also calls for the air mixture screw to be backed out 3.5 turns (instead of the stock 2.5); and that’s where my problems started.

I already noted that there were a number of problems with carb 4 on this bike, especially with the air mixture screw.  While attempting to install the air mixture screw I found that the carb body is stripped (looks like someone was trying to dig out the air mixture screw at some point).  The result is that I can’t install the air mixture screw anywhere near the correct back-off.Stripped air mixture hole.

In an attempt to fix the problem, I’ve filled the upper part of the hole with JB Weld and am letting it set for the next 24 hours.  Hopefully it’ll harden enough that I can drill out and thread the hole and start moving forward again.  If not, I’ll probably look for a replacement body on Ebay.

While waiting for the JB Weld to set, I went ahead and put the remaining 3 carbs togetther.  I was able to put carb 1 and 2 back together.

XS400 Sold!



Well it’s sold! Made a few bucks on it, covered the parts I put into it and moving on.

Based on my experience finding XS parts, and the build quality in general I think I’ll stick with Honda’s in the future.

That said, the next owner is happy with the bike and will enjoy it until he’s ready for something a little more powerful.

Tearing Down the Carbs

Finished tearing down the carbs to prepare them for a cleaning.  Found a missing washer (carb 4) on one pilot/air mixture screw and a missing O-ring (carb 1) on another.  The missing O-ring likely explains the amount of fuel build up on the number one carb.  In addition, the primary main jet emulsion tube has noticeable stripping on the head; someone was trying to play with the jets at some point.  Lastly, the bellows for the accelerator shaft was missing.  All of these should be included in my Randakk’s DOHC rebuild kit, so shouldn’t be a problem getting things back together when it shows up.


The first round of cleaning was done using a 96oz can of Berryman Chem-Dip followed by a dunk in a 1-to-2 part mixture of Simple Green and Water in an ultrasonic cleaner.  The carb bodies I placed in the Chem-Dip for 30 minutes and into the ultrasonic cleaner for 20 minutes followed by a rinse of water.  The combination of the carb cleaner and a run through the ultrasonic cleaner did a decent job of cleaning things up.  Hitting it with an air compressor I was able to blow out the passage ways and make sure everything was dry.


Doing some research about the problems the CB900 is having, it seems that with aftermarket exhausts the carbs start running extremely rich.  This was very apparent by the amount of fuel build up and the color of the spark plugs.  I had previously purchased a stage 1 & 3 jetting kit from Dynojet and realize now is the time to go ahead and put it into place.  I haven’t decided on what to ultimately do with the airbox, but either way I should have jets that are ready.  One step is to drill out the vent holes in the slides, so I went ahead and did that now.


The overhaul clean is pretty much done, the next step is to get into the smaller passage ways and make sure everything is really nice and clean.  That’ll be another day, hopefully when I get the rebuild kit in the mail.

Beginning the CB900C Carb Rebuild

It’s been a while since I’ve done some work on the bikes (winter time projects were in the way).  Bringing the CB900C back to the middle of the garage, I fueled her up to see where the project was left off.  Engine started after a bit but still running rough.  Taking some quick temps, I noticed that the header off of cylinder 4 was much colder than the other 3, so it’s time to pull the carbs, give them a clean, and see what’s really going on.

After pulling off the carb pack, I started breaking things down to single carbs.  After stripping a few of the screws on the braces I finally started getting into the single carbs but needed to break for the night.  Found a great reference for breaking these carbs down here:


Definitely will be making my way through that document in hopes of getting them back together.  Will post more and pictures as the project continues.