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Enduro Engine - 2 stroke Cylinder, Piston, Tranny, Bearings, Clutch, Pipes & Silencers, etc.


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Old 11-24-2023, 03:51 PM
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Default Crank seal leak - installation question

Hey guys!

TLDR version. I've replaced a right side leaking crank seal with a new one and replaced an o'ring behind it on a crank shaft. After placing everything back on the crank and tightening the nut at the top of the crank shaft drive gear I ve reperformed the leak down test and the seal appear to leak even worse than before.... What may cause that?

Long version :

I am new to two strokes and got myself a 2014 ec300r used sometime ago. After inspecting a spark plug it looked like bike was running very reach and was really hard to start. Needed like 20 kicks at least. So I figured I would check condition of the top end after making sure that the bike has a spark and clear air ways.
Bike happened to have a brand new top end although previous owner didn't mentioned that. I ve checked the bore size and a piston with the rings and everything is well within specs.
After cleaning a power valve which were heavily carbonized (the valve actually couldn't move in full range since one of the ridges that goes across the valve and host ones of the rods had so much carbon that it blocked the rod from moving in the full range. Anyways after making sure that top end is in a good order I scouted this forum for other potential issues and decided to do a leak down test that is recommended in many other cases.
So after installing a leak tester I got it 6psi and were losing about 2 psi in 5 min which I guess is not too bad. It took me a while to locate the leaking point at the clutch side of the engine really close to the frame at foot peg level. So my immediate suspect was the crank seal, which seems to be one of the common leak points.
After getting to the crank seal while fighting a rusty pin by the water pump to to get the cover along the way, I ve managed to plug the power valve outlet and redo the leak down test to reconfirm that the crank seal is actually leaking which it was. So I ve proceed to a tedious seal extraction process which involved taking off a crank nut by jamming a cylinder with a rope through a spark plug hole and a lot of cursing followed by drilling and tapping an old seal with a wood screw to extract it.
Then it was time to get the new seal in which really didn't want to get into place so I had to heat up the area and slowly tap it in place. While doing so I didn't realize that the slider that is mounted on the crank and slides on the inside of the oil seal and the little metal bump key is on the crank that holds that slider are actually removable. Anyways after realizing that I took the key and slider behind it off to access the o ring that sits at the base of the crank shaft bearing to replace that as well.
After that it was time to get everything back together, so I thought to double check the new seal with a leak down to make sure that it works... And it was worse... Way worse than before. The new seal was leaking between it's rubber part and the slider in several places. So I took everything off the crank shaft again to double check if I am missing anything or damaged the seal or the slider which both looked OK to me with no damage.
Now the bike is just sitting and driving me crazy. I have cleaned, assembled and leak tested that thing for several times and it keeps loosing air sometimes more sometimes less and most of the time in multiple different places around where slider connects with the rubber part of the seal.
So is there something I am missing or have I damaged something during installation? I suspect that while extracting the old seal I may have poked the rubber on the bearing behind it but it looks that I scuffed it rather than made a through hole. Also I think if I've damaged the seal while installing it onto the hot slider and the crank shaft housing... Or maybe I leave some tiny debris between the seal and the slider and that makes it fail.... Although I tried to wipe everything and apply assembly lube every time I tried to make it work.
Anyways I am a bit desperate now and would appreciate any thoughts on what may be the issue here.

Thanks!


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Old 11-28-2023, 01:56 PM
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Did you try another seal? And then install it cold without having the slider present on the crank?

I have never done it like you have tried, I have always split the cases to install new seals (and bearings) so I cannot comment on best practice. But applying heat isn't a method I would use for seals. They should normally go in without applying too much force.

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Old 11-28-2023, 03:47 PM
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Aside from your method of installation, I would consider the spacer to be suspect. The ends maybe not be square to the bore or the OD may not be true.

The left side crank seal can be replaced without splitting the cases, so your method for the right hand side should be possible. Install the seal into the case (cold), then install the spacer with oring. I'm not directly familiar with the assembly so this could be bad advice. The spacer may have to be in place first.

One thing to keep in mind is that the spring inside the seal (that tensions the seal) can be dislodged easily during installation. Any edge that the seal goes over needs a significant taper to ensure the seal goes in perfectly straight. Any canting will let the inner spring pop away from it's seat.

So maybe the spacer should be in place first with a guide device at the end to let the seal slide over smoothly. An example is the waterpump seal on a KTM RFS engine. A guide is needed to cover the clip groove. I tried it once using a piece of heat shrink tubing, but the inner spring would come out going over the end of the shaft. With a machined guide having a long taper, the seal went in perfectly.

EDIT to add: I always coat the ID of the seal lips with grease before installation.
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Old 11-29-2023, 05:36 PM
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Thanks for your reply folks! I ve ordered a new seal and an o ring to rule these things out.
I've also researched a bit more in this topic in general and it looks like the seal should be vacuum tested instead of pressure testing, since transmission oil or air that messes up the carburetor air fuel mixture are sucked in when piston travels up. At least that's how I understand it...
Unfortunately I have no equipment for a vacuum test to see if the seal leaks inside towards the crankshaft bearing.
As soon as I get the replacement parts I ll reinstall everything w/o heat and center spacer on the crankshaft and update on the results of a leak test.

I've also suspected the spacer that sits on the crankshaft and seals against the lip of the oil seal to may cause a leak due to wear. However when I run a leak test and rotate the crankshaft at the same time it keeps leaking from the same spot. So I assume if the spacer is indeed the problem the leak should have traveled with the rotation of the spacer against the seal.
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Old 12-06-2023, 12:03 PM
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Ok, a quick update on the crank seal leak. I've got a replacement seal and pulled the faulty one out. After a close inspection it appears to be slightly uneven which made it canted which apparently made it sit unevenly and allow a leak.

I've installed a new seal with no heat and having the crankshaft slider removed, which made it quite a bit easier. I used crankshaft sprocket as a guide to push it inwards which applied even pressure and worked well for me. Previously I used a PVC pipe but the power valve sprocket was getting in my way so the crankshaft sprocket worked better.

Anyways, I doublechecked new seal for leaks and it's air tight. I still need to cut a new gasket for a clutch cover since the one that I got in a rebuilt kit does not match. I ll update on my results when I put it back together, leak test it and try to run.
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Old 12-15-2023, 10:24 AM
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A quick update.

I ve got the bike back together now it starts but runs rich and does not idle. It only idles with the throttle slightly open. I run it without an air box just to test so is it a possible cause?
Also after each short test I open a crankcase drain plug to drain about an ounce of gas out. So it appears that carb is dumping fuel into the crankcase. I ve also noticed that choke does not seem to have any effect on how bike idles , meaning that I can kick bike into life on a second kick without touching the choke and keep it alive just by holding throttle 1/10th of the way open. If I pull choke in it does not seem change bikes rpm.

I tried cleaning the carb and adjusting the float level slightly. Since this was not a problem before, I just don't want to reset old float setting to not mess it up further.

Anyways looking forward for any advise on the matter. Meanwhile I ll take carb off and see how float needle moves. I haven't noticed any obstruction last time but will buff it a bit with something soft just in case I ve missed something. Also will look into how choke sits and if it maybe stuck or something.
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Old 12-19-2023, 11:53 AM
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Float valve sticking is the usual cause. Make sure the carb is level side to side so the floats don't drag. Never hurts to replace the float valve and seat if there is some wear.
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Old 01-07-2024, 06:22 PM
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I was having a similar issue and realized that the seal should drive in to the stopping point and not riding on the groove and the gear collar. Seems to be fine now. You might consider that when installing. I included a photo to show how mine is installed.
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Old 01-08-2024, 01:24 AM
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Quote:
Originally Posted by Neil E. View Post
Float valve sticking is the usual cause. Make sure the carb is level side to side so the floats don't drag. Never hurts to replace the float valve and seat if there is some wear.
Wot this guy sez.

No choke is obviously an indication.

PWK carbs are great. But needle valve is 5 year sort of deal.
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