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Oil leak Crankshaft seal I guess???

esmith250624

esmith250624

Veteran Member
Joined
Nov 2, 2023
Total Posts
238
Total likes
242
Location
Prescott AZ
See the before photo and after photos. First ride today on the CB400T rode great shifts through all the gears just fine. Had a blast, after 10 min of fun, pulled into the driveway and noticed a leak. leaking from the bottom bolt of the flywheel cover, I'm guessing that means crank case oil seal. I will remove it tonight to take a look. I will start looking through the archives to see what's out there, But i assume this one needs the cases separated and probably not a quick fix then if that's the case. I will try to confirm the location and let you guys know........Bummer!

Before photo all put together (almost) and ready to ride. looks pretty goo from 20ft, but don't get too close!
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The after photos.....
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I took the flywheel cover off and the flywheel is not covered in oil which was what I was scared to see. there is only about a teaspoon of oil left in there and maybe about a tablespoon came out. should I pull the flywheel and stator to look at the seal and get some photos?
 
The crankshaft seal has an external lip that fits into a groove in the upper and lower case halves. To properly replace that seal requires the crankshaft to be lifted out of the case to slip the seal over the crank and seat it into the groove. Of course this means the cam chain has to be removed from the cam gear so the camshaft can be removed and so on. Gets to be a major operation real quick.
I can say I have cheated and cut the lip off the seal to install like a typical seal, only took 3 seals to get it done. Not a recommended permanent fix but when on the road thousands of miles from home you do what you have to.
 
Breaking apart the cases requires a good attitude and a lot of clear-headed thinking. I’ve done it twice; the second time to retrieve a dropped head bolt washer.

Guess it goes without saying it’ll be a good opportunity to inspect any moving parts for wear and replace ALL seals. My suggestion is to NOT touch the counterbalance assembly. It wasn’t easy for me to reset the timing on those chains and gears.

I took the opportunity to put in new overbore pistons. The pistons were cheap and the boring cost $100 per cylinder.

Good luck!
 
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There are 3 different part numbers listed for this seal. any suggestions which one is correct. and it does not look like it has the lip on the edge. Partszilla has one also but I would need to know the correct number.

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LongDistanceRider said:
91204-350-005 is the shift shaft seal
91201-323-005 is the crankshaft seal
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Thanks, I see that 4 into 1 has an aftermarket seal that looks like a press-in type. I am considering do this to see if I can delay putting an OEM seal in later this year. I know you said not recommended for long term. I will probably get one of each, the aftermarket one is only $4 so might as well try it right....:confused:

Talk to me about removing the seal without splitting the cases, did you have to cut the seal because of that LIP on the edge?
 
While you are down in there, make sure your shift lever seal is not leaking too. You may want to change it anyways if you have everything apart. It leaked on my 79 and took an awful lot of fussing around to track down the source of the leak. Its an easy fix though, and cheap.
 
aeron said:
While you are down in there, make sure your shift lever seal is not leaking too. You may want to change it anyways if you have everything apart. It leaked on my 79 and took an awful lot of fussing around to track down the source of the leak. Its an easy fix though, and cheap.
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Will do thanks. I actually already have that seal and the kick start seal. as you can see in the pics the oil is not even discolored yet, its still clean, I was going to drive a few miles then do and oil change, changing those seals at that time. Plans change I guess.
 
esmith250624 said:
Thanks, I see that 4 into 1 has an aftermarket seal that looks like a press-in type. I am considering do this to see if I can delay putting an OEM seal in later this year. I know you said not recommended for long term. I will probably get one of each, the aftermarket one is only $4 so might as well try it right....:confused:

Talk to me about removing the seal without splitting the cases, did you have to cut the seal because of that LIP on the edge?
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Yes, I trimmed the retaining lip off the seal so it resembled a conventional seal like the one being sold by 4into1 for $4.
Removal of the original seal is tough due to the retaining lip. You'll want to drill a 1/8" hole in the body of the seal, there's steel inside to drill thru. Then insert a wood screw in the seal and pry like this
GEDC2244.JPG

Under NO circumstances try sliding a tool between the crankshaft and seal to pry, You will leave a gouge on the crank resulting in a permanent leak.
The reason I don't consider this a permanent repair is that under certain circumstances the crankcase pressure can be enough to blow the seal out, typically with backfires thru the carbs. But I can say that when I did it I was in West by god Virginia and rode without leaks for another 10,000 miles before rebuilding the engine and fixing it right.
It did take 3 attempts to get it right with a new seal each time.
 
HMMMM! still not sure, I rode for about 10-15 min, and did not see any leaks, but after it sat for about 30 min after the ride I saw 1 tiny drop of oil. when I put the stator cover on it was coated in oil, I quickly wiped it out, there there may have been enough oil to drip a little bit out once warmed up. More testing is needed I think.

I did find out that my vent hole on the gas cap is plugged, I ran the carbs out of fuel, so then I have to stop and crack the gas cap to vent it and refill the carbs. I guess it worked better with the leaky gasket i had on it on the first ride, I put a new gasket on and it seals up too good.

Edit: i left the stator cover gasket off for now so I can easily check for leaks.
 
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So far unable to clear the vent hole, if that is really what it is. I soaked it in vinegar overnight, a bunch of rust bits came out of it. I stuck my pick down the hole (No Laughing) and it felt like it broke through one layer at a slight angle and then hit a hard stop. I'm curious if anyone else has tried something that worked. What happens if I drill through that next layer?

I looked online for aftermarket caps, and not finding one that looks like the right fit due to the gas cap "FLAP" on the tank that will only close once the cap is turned straight "in line with the bike"

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I would use compressed air with a rubber tip on that hole, but not drill it. There is a one way valve of sorts that should allow air in but not out. I have the same one on my T2. Maybe try some WD40, let soak, blow it with at least 100psi., repeat until it unplugs. I've taken apart the older style ones by using air to separate the pressed together parts, cleaned it out good then pressed back together, but not this type and not sure if it's possible.
 
ballbearian said:
I would use compressed air with a rubber tip on that hole, but not drill it. There is a one way valve of sorts that should allow air in but not out. I have the same one on my T2. Maybe try some WD40, let soak, blow it with at least 100psi., repeat until it unplugs. I've taken apart the older style ones by using air to separate the pressed together parts, cleaned it out good then pressed back together, but not this type and not sure if it's possible.
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Ok, thanks, I will keep trying to clear the blockage. (at least for another day or two!!)
 
I just looked at mine. It is a pressed together unit and if one was really desperate, I guess trying to uncrimp the outer/top half to blow it apart for the ultimate clean out would be extremely difficult but possible.
I'd keep soaking and blowing, even a gasoline soak, but it's probably mostly rust so vinegar should do it.
I just tried sticking a couple flat blades under the spring ears to see if the valve/flap whatever it is, could be freer for an easier blow through. Maybe...
 
@ballbearian Its pretty stuck, i heated up a piece of tubing and formed it around the hole to make a good seal, I can hold it against the hole at 80 psi and nothing, i will try to soak it again in vinegar, and try again. but I saw a matching gas cap on ebay for $5 and $6 shipping so that is on its way just in case. it looks much cleaner than mine except for the black paint on the top. I will strip off the paint if the vent works.

my compressor is set at 80 psi I will see if it goes higher, but still working on it.

On another subject, I rode 10 miles on the bike today, I know 10 miles is not a lot, but I am branching out slowly. don't want to get to far away from home just yet. But everything worked great. still a single drop of oil 30 min after the ride, it actually did not even drip into the pan it was just hanging on the lower bolt. I will keep testing but if it keeps leaking I do have the other oil seal I can try. I installed the aftermarket one from 4 into1, the other one is a Honda OEM seal. I left the gas cap loose so it would vent and fill the carbs.
 
Just wanted to wrap up some loose ends on my project. and give some updates on where I am on this project.

1. I tried clearing out the gas cap vent but could not clear it, The ebay cap that I bought works great though so I kinda set this aside for now.
2. I have gone 100 miles on the motorcycle now, and the crankshaft oil leak has stopped leaking. I did not do anything since my last post other than ride it. It stopped on its own.
3. Sunday I replaced the fork seals and refilled with ATF, (That is a dirty, messy, smelly job) they now look better and work much better.
4. I made an adjustment to the fuel mixture and went for a ride, After a few miles I was getting some weird idle symptoms. I went back home and started checking things. I thought maybe my mixture adjustment threw something off, so I set it back to where it was. (Turns out that this was unrelated... but I will get to that) Anyway while idling I pulled the sparkplugs off one at a time and found that right cylinder was not firing, or at least very intermittent, but it would kick in if I gave it some throttle. I pulled spark plugs and tested each one and swapped them to see if anything changed and what I noticed was a very weak spark on the right side. The right side spark plug wire seemed to be the issue, so I removed both Wires and proceeded to resolder them both. Well they were never really soldered to begin with (just crimped) so I soldered them, I did find the right cable had a poor connection to the spark plug cap, which was likely causing my weak spark. Re gapped the spark plugs to .035 (Dyna Coil....ask @Maraakate ) Then rechecked Spark.... All good now. Started it up and still getting some fluttering and spitting which I am contributing to the right side cylinder. So I tried not to panic and took a day off to think about the problem.

Next day what I came up with is I am going to pull the gas tank and recheck the valve adjustments. I reset the valve clearances, (right side Exh was a little to tight, but everything else seemed ok. Set them to .006 intake, .008 Exh a little on the loose side as was suggested on here. Then I had another thought related to the throttle plates in the Carbs, Remembering that I bench synced these and tried to get both throttle plates to completely close at the same time, but with these symptoms I thought it might be possible that the right carb is choking off too much air at idle, but it recovers once you give it throttle. (So some of you guys are going to say DUH you need to sync the carbs on the bike), well I don't have a sync tool at the moment, but I thought since I already have the tank off I will try to do it by ear.

I made a note of the starting position of the sync screw, then loosened the lock nut, started the bike set the idle rpm screw to idle at about 1200 rpm and slowly turned the adjustment screw back and forth to find which way it was going to be happy. I was glad to find out that opening the right side throttle a little is where it was happy (confirming my suspicion). I went back and forth a few times turning the sync screw, then back down the idle screw until I felt it was sounding good. I then put everything back together and went for a ride. It is much happier with this adjustment and the idle has significantly improved. less than a 1/4 turn is all it really needed.


Things next on the list to do.
1. Rebuild front brake caliper. (already cleaned up and re-assembled, but leaks fluid. Parts will be here this week)
2. Find or Make a air box lid. not happy with the ebay prices for a full airbox assy. I just need the lid.
3. Fix Battery+ connection. I have a non standard size battery so I need a different wire to put everything back to stock location. Or just get the right battery...:unsure:
4. Properly route wire harnesses/cables to correct locations.
5. Fix tail light housing with epoxy paste and threaded inserts, Like @Slofun did! (or get a cm400t tail light assy, since I don't have a grab bar to mount the rear turn signals. I have them mounted in the fender holes.)
6. Missing the "GRAB BAR" that mount around the seat. I keep looking for a "DEAL" on ebay.
7. Repair the original seat. I have the original seat frame with the old foam. it will need some work and a seat cover.

Edit:
8. And a better fuel line setup with filter.
 
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The oil you were getting after the seal replacement was likely old oil that was flung into the stator and eventually dripped out.
I'll have to look but I may have saved the grab bar from the T1 that was damaged, replaced it with a perfect one.
 
esmith250624 said:
Hearing all the good news about these bikes getting saved and put back on the road. I wanted to post an update that I just passed the 1000 mile mark after getting mine back on the road. Thanks to everyone on here that provided advice and/or encouragement. Here's to another thousand!!
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Congratulations, esmith, well done, and great to hear!
 
You’ve been very diligent in going after every little issue that’s come up. I’m very happy for you that the results have been so positive. You’ve got a great, fun, comfortable bike to go out on now. It’s a great feeling knowing your’re personally responsible for putting it back on the road, right?
 
esmith250624 said:
Things next on the list to do.
1. Rebuild front brake caliper. (already cleaned up and re-assembled, but leaks fluid. Parts will be here this week)
2. Find or Make a air box lid. not happy with the ebay prices for a full airbox assy. I just need the lid.
3. Fix Battery+ connection. I have a non standard size battery so I need a different wire to put everything back to stock location. Or just get the right battery...:unsure:
4. Properly route wire harnesses/cables to correct locations.
5. Fix tail light housing with epoxy paste and threaded inserts, Like @Slofun did! (or get a cm400t tail light assy, since I don't have a grab bar to mount the rear turn signals. I have them mounted in the fender holes.)
6. Missing the "GRAB BAR" that mount around the seat. I keep looking for a "DEAL" on ebay.
7. Repair the original seat. I have the original seat frame with the old foam. it will need some work and a seat cover.
8. And a better fuel line setup with filter.
Click to expand...
From my previous to do list back in Apr, the only two things left on the list are 5, and 8. here are some photos of the new seat cover grab bar and air box lid. Seat cover is from Sirius Consolidated Inc, thought I could salvage the old strap, but turned out to be to brittle, So I will work on a new seat strap next.

The before photo of the seat is at the top of this post.... Well the other seat not this one. Still have the other as a backup. This seat got stripped down to the pan, soaked in vinegar (leftover from the tank treatment.) and after 2 days the original paint just rubbed off with my fingers and a bristle brush. Some rust pitting was on the pan. it was sanded down and wire wheeled as good as it was going to get. then primed and painted. Had to build up a few sections of worn out foam. Cut out 2 large sections of foam and glued in some replacement foam from a cushion I got at the thrift store. $5 worth of foam. Then fitted the cover.

I know there is a decent priced air box on ebay right now but I blew my budget on the seat cover, grab bar, and new set of gauges. So the air box got a band aid fix for now. Don't know what to call it yet.... Maybe a PAC-MAN Air flow Mod! Kegerator Beer/fuel line is holding up ok. starting to get a little bit hard, and losing some flexibility, so trying to finish the season with that before I change it.

I have been testing different settings on the airflow, No lid was running good but too lean and too hot, this engine seems to like the air dam set right at half way open.


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