Honda NA50 Crank Seals.

So the Express II I just picked up is blowin the white smoke billows when it's cold, and running rough until it warms up. Auto oiler isn't pumping oil yet, so that ain't it. I can only assume it's the tranny side crank seal. I've read several other threads on the issue, and I have the service manual downloaded. It looks like quite a grip of moving parts under the cover, but should be pretty straight forward, right?

I see others have had a hard time finding a clutch puller. Has anybody found a source for one that will work?

Are there any other wierd/special tools I must have?

Any other warnings or lessons you can help me learn the easy way are appreciated.

Re: Honda NA50 Crank Seals.

Jack Rutherford /

if the seal is bad, it will burn 4 stroke oil which smells different than 2 stroke oil and it will usually burn it after 5 or so minutes of riding. if it is smoking immediately on start up, that may be something else.

Re: Honda NA50 Crank Seals.

It can do it fairly immediately if it's pooling in the crank area. The smoke will be foggy and hang in the air for longer than 2t oil also.

Re: Honda NA50 Crank Seals.

It does it right after starting, only when it's cold. Runs rough, and smokes a huge amount of white smoke that hangs in the air for a while. I'm running 50:1 Bel-Ray MC-1 synthetic premix in it. I do have the 2T oil tank full of Lucas 2T oil, but I still haven't gotten a drip out of the outlet line from the pump. I don't know how it could be from 2T oil. But I also don't know why it clears up when it's warmed up. I don't think the auto choke would make it run that rich.

Re: Honda NA50 Crank Seals.

Also, on a totally different issue, but one I'm sure I will run into when I remove the tranny cover:

Something started catching in the transmission. It's clicking when it runs, and if I try to roll backwards it catches, and stops. If I rock back and forth a touch, it frees up, then does it again if I go forward again. Any time I reverse direction of the wheel, it seems to catch.

Time to figure out what's up. Need to find a clutch puller, I guess. I'll start searching, but if y'all know of one that works...

What could possibly go wrong? Lol.

Re: Honda NA50 Crank Seals.

Jack Rutherford /

I found a clutch puller on eBay Australia - $38 shipped. I can look again but it was perfect for the job. If it quits smoking after you run it for a bit then I really doubt it's the seal. Mine would start to smoke after about 5 minutes of running, fog the whole damn neighborhood, spit oil droplets out the exhaust all over the tire and whatever else was in the way, and wouldn't quit smoking until I shut it off. It would even shoot sparks out the exhaust which may or may not have been related but no longer does that after I replaced the seal.

see this thread

and see this link for the eBay clutch puller (edited)

Re: Honda NA50 Crank Seals.

Mine doesn't do that stuff! Just smokes like crazy when I first start it, but clears up after a minute. Didn't do it when I first got it. Just started. Could 2T oil be leaking into the case somehow? It's not coming out the outlet line. But it didn't do it before I put oil in the tank...

Re: Honda NA50 Crank Seals.

The auto choke is actually quite ridiculously rich when cold.

Re: Honda NA50 Crank Seals.

I think you have bad valve stem seals . LOL

Re: Honda NA50 Crank Seals.

> P D Wrote:

> -------------------------------------------------------

> I think you have bad valve stem seals . LOL

Maybe that’s all it is. Because once it’s warmed up it’s great. I sure don’t want to fix what ain’t broke. It’s not low on transmission oil, and it ain’t fowling plugs, so maybe the crank seals just fine and it is just doing what Hondas do Maybe I just want something to tear apart and fix.

Now for the transmission issue. Is it normal for these transmissions to catch a little bit when you switch directions? Is it just those ratchet pawls inside ratcheting , or is it something I need to be worried about?

Re: Honda NA50 Crank Seals.

> P D Wrote:

> -------------------------------------------------------

> I think you have bad valve stem seals . LOL

Probably cause I installed them upside down.

Re: Honda NA50 Crank Seals.

Switch direction? What?

Re: Honda NA50 Crank Seals.

> DPC Ryan Wrote:

> -------------------------------------------------------

> Switch direction? What?

Switch direction: forwards vs reverse. As in, when I stop the bike in front of my garage, then walk the bike backwards into the garage to park it, sometimes something is catching, but if I rock it back and forth, it releases. same if I'm rotating the wheel on the stand, either forward or backward, and then switch directions, sometimes it catches and won't go the opposite direction unless I rock it back and forth. Like a ratchet pawl inside holds it up briefly.

Re: Honda NA50 Crank Seals.

Jack Rutherford /

I've had lawn mowers that would do that - catch and release with rocking. Something is probably wrong with your transmission. You probably need to look inside after all.

Re: Honda NA50 Crank Seals.

The clutch should be completely disengaged and nothing should happen when you move the bike forward or back even when running.

Re: Honda NA50 Crank Seals.

> DPC Ryan Wrote:

> -------------------------------------------------------

> The clutch should be completely disengaged and nothing should happen

> when you move the bike forward or back even when running.

This^^

Looking at the cover screw heads it should be obvious if someone has had the cover off before.

Re: Honda NA50 Crank Seals.

> Pacer Racer Wrote:

> -------------------------------------------------------

> > DPC Ryan Wrote:

>

> > -------------------------------------------------------

>

> > The clutch should be completely disengaged and nothing should happen

>

> > when you move the bike forward or back even when running.

>

> This^^

>

> Looking at the cover screw heads it should be obvious if someone has had

> the cover off before.

Ryan, thanks for verifying. Somethings up in there, but I don't know what. Yet.

Pacer, looking closely, there are fresh socket wear marks on the cover. Somedummy's been in there. (Not this dummy. Yet.)

Here we go, wish me luck! How bad can it be?

Looks simple compared to a ZA 50. I ain't touchin that sumbitch

Re: Honda NA50 Crank Seals.

Planetary 2 speed clutch is a little complicated but overall the whole drivetrain is very stupid simple.

Re: Honda NA50 Crank Seals.

I wish I had added transmission repair to the title.

The cover is off. Here's my initial observations:

Starter gear has been damaged and welded. Still missing one tooth.

image.jpg

The chain tensioner spring tab was not seated in its groove, but may have come unhooked during disassembly.

The large gear at the rear has a couple of chipped teeth, likely caused by the broken starter gear tooth.

image.jpg

Other than that everything looks normal. There was only one or two tiny metal shavings in the bottom of the case, and the oil looks new.

I think I'll put it back together and run it. It's just mopeds.

What could possibly go wrong?!

Here's the whole picture:

image.jpg

Re: Honda NA50 Crank Seals.

But I'll wait to hear some advice from y'all first. It's lunchtime anyway, got to go make some steak and eggs.

Re: Honda NA50 Crank Seals.

Could be the chain slapping with the bad tensioner, or the teeth clicking past. Either way you aren't getting parts without getting basically a whole engine, so run it til it pops. Then you choose to get another (different) bike or attempt to swap an engine on. All depends on how much you end up loving the bike and whether it's performance ceiling was where you wanted to be.

Re: Honda NA50 Crank Seals.

Upon closer inspection, this is what I found. I found the missing tooth. I'm going to put it under my pillow, and hope the tooth fairy comes and brings me a new Tomos.

That tooth floating around in there was surely causing the catching, when it gets in a bad spot. I'm really lucky to have such minimal damage inside. I'm going to rinse it out with brake clean and slap it back together. Then I'm gonna run it till it pops, and sell what's left for parts.

image.jpg

Re: Honda NA50 Crank Seals.

So I found a broken wave washer in the bottom of the case right below the driven sprocket. It looks to be the same diameter as the driven sprocket shaft, so I can only assume that there is supposed to be a wave washer behind it to preload it. I'm going to try to find one, but what happens if I can't? Can I put it back together without that wave washerand be OK? How imperative is it?

image.jpg

Re: Honda NA50 Crank Seals.

This has been put in wiki.

Honda express transmission.

Re: Honda NA50 Crank Seals.

Jack Rutherford /

get a new wave washer. it is imperative unless you want other odd noises coming from your transmission.

Re: Honda NA50 Crank Seals.

> Seth B Wrote:

> -------------------------------------------------------

> So I found a broken wave washer in the bottom of the case right below

> the driven sprocket. It looks to be the same diameter as the driven

> sprocket shaft, so I can only assume that there is supposed to be a

> wave washer behind it to preload it. I'm going to try to find one, but

> what happens if I can't? Can I put it back together without that wave

> washerand be OK? How imperative is it?

> >

I'd take that shaft to your favorite hardware and find a 12mm wave washer to fit .

Running without the wave washer could easily allow gears and such to run close enough together to catch and lock . Then you'd have to rock the bike back and forth to get them to return to unlocked position , until the next time . ;)

Parts diagram :

https://www.hondapartshouse.com/oemparts/a/hon/506cc71af870023420a436cc/clutch-drive-chain-final-gear

Re: Honda NA50 Crank Seals.

> P D Wrote:

> -------------------------------------------------------

> > Seth B Wrote:

>

> > -------------------------------------------------------

>

> > So I found a broken wave washer in the bottom of the case right below

>

> > the driven sprocket. It looks to be the same diameter as the driven

>

> > sprocket shaft, so I can only assume that there is supposed to be a

>

> > wave washer behind it to preload it. I'm going to try to find one, but

>

> > what happens if I can't? Can I put it back together without that wave

>

> > washerand be OK? How imperative is it?

>

> > >

>

> I'd take that shaft to your favorite hardware and find a 12mm wave

> washer to fit .

>

> Running without the wave washer could easily allow gears and such to run

> close enough together to catch and lock . Then you'd have to rock the

> bike back and forth to get them to return to unlocked position , until

> the next time . ;)

>

> Parts diagram :

>

> https://www.hondapartshouse.com/oemparts/a/hon/506cc71af870023420a436cc/clutch-drive-chain-final-gear

Thanks for the diagram, but the part is obsolete. I've been to the local Napa and they can't find one. I've looked around online, and requested a quote from Hubbard Spring. We will see if they reply. it has to be very precise dimensions, to fit in the recess where it goes, so something off the shelf at a small town hardware store isn't likely. I will source one, somehow, because it looks like I don't want to put it together without it.

Re: Honda NA50 Crank Seals.

By the way, those dimensions are 12 mm ID by 16.5 mm OD by .016 inch thick, if anybody's lookin.

I found some on Amazon that are 12 mm ID by 18 mm OD, but that's as close as I've come. I suppose I could stick one on a bolt with a nut, and stick it in a drill and file it down to the right OD. Make my own.

Re: Honda NA50 Crank Seals.

Youre not looking very hard.

As far as it purpose:

Helical cut gears have axial loads.

The wave washer cushions that load to prevent the gear from slapping the case.

Re: Honda NA50 Crank Seals.

I wouldn't rule out Mom & Pop .

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