Crank Seals Vs. Rich Running

[lakehouse]

I've been fighting a rich running condition with my SB50 stock motor that is NOT carburetor related. (There is no debris, plugged passages, etc. in the carb. I am 100% sure of that.) When I pulled the left side cover off where the belt drive is, I found a light residue of burned oil "dust" that had developed within the past 50 or 60 minutes of static run time, doing various run intervals and durations. (I recently cleaned the cover so this is new "dust".) Our local motorcycle mechanic said that I probably have a leaking crank seal, which in turn, could possibly cause the motor to run too rich. (Let me say that I have had the carb off and apart so many times that I can't count them. I've tried new bistarters, with and without the airbox on and off, and adjusting the carb screws has no effect on the way it runs. Also, it will only idle at 1/3 throttle without dying. I cannot get the motor to lean out no matter what I tried. I'm running the stock jet, 115psi compression cold, good spark, flywheel key is OK too and no vacuum leaks.) I'll agree that there is a good chance I have a seal that is leaking, but how would this, or would it even cause, a rich running condition? I am aware that the crankcase is pressurized during the run cycle but how would it cause an excessive amount of fuel to be drawn through the carb? Can this seal be replace without removing the engine from the frame, and/or would I have to do a complete rebuild on it? (It has less than 500 total miles on it since new.) I've been struggling with trying to figure out the problem here for too many months, and had to let it sit since before Christmas just to retain what little sanity I have left. Anybody have any ideas?

[bfowler]

I'm in the same boat as you so I'm really interested to hear what people have to say. My build hasn't been running very well and I think the crank seals are leaking. Been looking to replace the seals but I don't want to have to do a full rebuild.

[lakehouse]

We're on the same page then. I'm anxious to see if anybody has run into this problem before and found the cure. There will probably be a lot of speculation forwarded to me, and I appreciate that folks are trying to help. I have worked as an auto mechanic in the past many years ago, and have a decent feel for what's going on, I think. I'm still trying to figure out why the engine would respond with a rich condition if a crank seal isn't allowing pressure in the crankcase to build up. Plus it seems to be exhaust that is leaking by judging from the "dust". I know that's not right under any circumstances. But then again, this is a 25 year old seal that's trying to do its job. I'm guessing that it has to do with port timing, which for all practical purposes, is fixed and cannot be altered without some serious grinding. Keep watching this posting to see if our hero steps out of the woodwork somewhere, and solves our problem. All we can do is hope I suppose.

[ped]

hi. your jet may be too big. what size is it? you can change the seals by removing the fly wheel and variator. use a pick hook to pull them out. and, a long pipe same size as seal, to install.
I have seen a rich condition caused by big jet. 1. faulty float valve (replace).2 float valve seat may need cleaning. ( i have used a toothpick with buffing compound then clean with carb clean.) 3. no power going to bystarter or bad bystarter. 4. carb air jets clogged. 5. check or replace air filter. 6. float level may be too high (adjust). hear are some things that i would check. give us detail if nothing works. good luck .

[lakehouse]

Thanks for the reply, ped. I do appreciate the shout and the thoughts, and the info on replacing the seals. For starters, I have the stock OEM jet in the carb. I am the first person to go into the motor and/or carb, as I got the bike from the original owner. I believe it's a #68 jet. I never did write the size down anywhere but I think I am correct. Let me address your suggestions one by one as you numbered them.
#1 - Float valve works perfectly. I quadruple checked it and am positive on that fact.
#2 - Float seat is clean and does not leak fuel. I even tried a different float needle and it's the same thing. I checked it with a jeweler's magnifying glass set up.
#3 - Both bistarters work the same and one is brand new. No problem with either as I bench checked them as well as on the engine too, All measurements were well within the specs.
#4 - Jets are clear as I can pass light through them, as well as a 0.020 copper wire. Plus they readily flow carb cleaner when shot through them. In fact, ALL passages flow nicely with the carb cleaner (aerosol type).
#5 - No air filter in airbox. At half throttle with airbox removed, the engine dies when airbox is attempted to be installed. (Light air pressure from my compressor shot at carb intake drastically increases the RPM. Finger choke kills it!)
#6 - Preset float level is non adjustable, and is at the spec set forth in the service manual. I used dial calipers to get my measurements.

I have tried a variety of situations with the bistarter in place, but not wired up; bistarter removed completely, bistarter in place and connected as it should be with voltage going to it; plus any other combination you can think of, but makes no difference in the running condition. I don't think the engine is reaching anywhere near max RPM and is rough sounding throughout the limited RPM range that I have. It cold starts fine when fuel bowl and chamber is full of fuel. Adjusting carb screws has no effect whatsoever on idling, or the way it runs. The "dust" is the belt cover is the only clue I am getting of an abnormality. I have even flushed out the crankcase to rid it of any possible build up of oil as suggested by our local motorcycle mechanic who has been working on bikes for nearly 50 years, and is one of the best. He maintains our police dep't.'s bikes, he's that good.

Now what? Still don't know if a bad crank seal would cause the problem of running rich or not. Your thoughts are???? The bike ran perfect for the original owner from the day he bought it until it was parked about 10 years ago. This one is eating my lunch.

[ped]

hi lakehouse.
I can understand how you feel. I'm not a expert. but those are things that i would check. there are a lot of knowledgeable people on this forum. that have years experience. let see if someone can help. so that we both can learn something.
to answer your question I don't know. I never had a leaking crank seal. I had a intake leak that allowed extra air in. making a lean condition. I also had a jet too big. and was not able to make idle adjustments. it takes a while to do tuning . but once you get it you'll be happy.
is that right you don't have a air filter? that is part of tuning. some scoots won't run right without a air filter. check the air box tube see if it's clogged.
let see if someone can help.

[paulpauly7]

crank seals leaking will give a lean condition .Have you run it with the air box installed with a genuine new honda filter with a properly sealed lid ? you cant just use any faom in the airbox .Have you done a plug chop with a new plug ? Have you checked that the muffler isnt partly blocked ?Have you checked for carbon build up on the top of the piston and on the head also the exhaust port?

[lakehouse]

I have tried running it with and without the muffler, but it makes no difference. And no, there is no blockage of any kind in the muffler. And as far as a new, OEM air filter goes, the engine stalls out from being flooded with just the airbox being installed. (There are NO blockages or restrictions anywhere in the airbox or drain tube.) A filter of any kind would only create more of a choking effect. A brand new spark plug (correct number and gap) makes no difference from the old plug. And I agree with paulpauly, that in analyzing the situation, a leaking crank seal would make for a LEAN running condition. But I thought I would pose the question to those who have more experience with these engines than I do. Also, there was no carbon build up in the muffler inlet, or the exhaust port, that would cause a restriction of any kind. Therefore, I didn't see a need for pulling the head off since I didn't have any indication that it would reveal any abnormality. And I doubt that there would be carbon build up on an engine with less than 500 miles on it.

The original owner said that the bike has always run perfect since the day he bought it new. He used it mostly for his grandkids to ride around his 2 acre lot, but parked it one spring when the battery became dead. I think he got tired of watching them lay the bike down on its side breaking things (light lenses, mirrors, fairings, etc.) and buying a battery every year. That's when it was parked outside, uncovered, until it was gifted to me. (It's a 1989 Elite E, and was parked for about 10 years or so.)

What size jet would be a good guess to try if what I have is a #68, and take into consideration that this is the jet that Honda installed and I have a 100% stock engine? I've even tried lowering the carb needle as low as it would go, but could not tell any difference. It still won't idle without about 1/3 throttle.

Thanks for the suggestions, guys, but something is causing the richness that's way beyond the basic things to look for. I've tried to get another carburetor to rebuild "just for grins" to see if it would make any difference. But the folks who have one and are willing to part with it don't seem too eager to work with me. I even bought a brand new carb, but it was for a different engine and won't bolt up due to the location of the bistarter. I need a carb with an outboard bistarter, and the one I bought is inboard and interferers with the rear suspension.

Do women like bald headed men, as this one has me pulling the hair out of my head!

[lakehouse]

I agree with all of your statements. But I am at the point that I will try just about anything, as I am out of ideas as to what to try next. Thanks for your input though.

[paulpauly7]

search muffler cleaning then follow the instructions .also remove the head and check for carbon build up .Stop asking for majic answers untill you have done these things.Blowing into the muffler with your mouth is not a test and dont run it without the muffler.And also you didnt answer the question did you do a plug chop with a new plug to confirm the rich running .Google plug chop to know how to do it right .The colour on the tip is NOT what you should be looking at you need to look for the ring at the bottom of the porcelin

[lakehouse]

Did you put your fuel/vac lines on right? Is the lower hose from the diaphragm going to the manifold, and the upper going the the correct spot on the carb?

Yes. No problem there because the oil line is connected to the port on the intake manifold. I even replaced both lines with new ones to eliminate any problems that may be caused by old lines. I doubt that it would even start if the oil line was connected to the carb fuel supply port. Thanks for the idea though.

[paulpauly7]

Exhaust?
Carbon build up?

[lakehouse]

how are you not noticing a prolbem with no slack in your throttle cable. you told me in a pm that, your screw settings are stock, 1 7/8, 2. ok. on both.

2 for idle stop. idle stop is 1800 rpms

2 isnt a real number, from where? in? how do you find wher it starts?

then out? ????? nah you shouldnt do that. if you are doing that, your thorttle cable, will have a lot of slack. and letting off would not affect it.

maybe check the case for a hole, cause the carb would have to be open to suck gas into it, and no gas it wouldnt run.

and your sayign 1/3 throttle keeps it running.. ?? RIGHT!? alright. are you chasing your throttle cable or something? alright.. alright.
waiting for fixed updates.

The "1 7/8" came from the Honda service manual in the carburetor section. The "2" is from bottoming out the speed screw and unscrewing it outwards. Fellow knowledgeable readers suggested that this would be a good starting place, and that was how many turns it was when I initially disassembled the carb. (I always check and record adjusting screw settings when rebuilding carbs during teardown as a good starting reference on reassembly.) I didn't notice any slack in the throttle cable at all during any of my testing and adjusting regardless of screw settings. If you were to bottom out the idle stop screw, it would raise the slide up as high as it would go at an idle position, assuming you held the throttle wide open when bottoming the screw out correct? And twisting the throttle would still raise and lower the slide. At that setting when I let go of the throttle, the engine should maintain a high RPM because in actually, the idle is really set way too high. But when I let go of the throttle, the engine dies virtually instantly. That's why I say that I have to give it about 1/3 throttle (1/3 of the total amount of rotation available to increase RPM's) to make it "idle". I cannot tell you what RPM that is, as I don't have a suitable tach to give me that information. I will also add that throughout the RPM range that I am able to achieve, the engine doesn't sound like it is running "clean" and crisp, and is a bit gurggly and rough. Also, gaining RPM is quite slow, and not like other bikes I have owned.

Wouldn't a hole in the case cause a lean running condition? I would think so. But an ever so slight finger choke over the carb causes it to stall out (flood). And injecting a small quantity of compressed air at 10 or 15 psi from 12 - 18 inches away, causes the rpm to increase instantly and significantly. Both those factor points to a rich condition. If I were lean, the effects would be just the opposite. I just don't know where that extra fuel is coming from. Remember, this is a 100% stock motor that ran perfect from day one until parked 10 years ago.

[lakehouse]

Did you buy this bike this way? Have your ever had it running right?

The bike sat up for 10 years, outside, uncovered, without ever being started. Per previous (and original) owner, it had always run perfectly and never gave any trouble. I have been fighting this rich condition from day one of my ownership. I planned on doing a restoration, but want to make sure the engine would run like it should (and like it used to) before getting too deep into it. Although, I have bought new tires, tubes, seat cover, battery, and misc. parts for it already. Maybe I should have waited on those items.

[lakehouse]

My point is you never witnessed it running correctly. How do you know if you have the correct needle/slide? Did you run the numbers to see if you have the right carb/jet sizes? As far as you know the prev owner installed a carb or slide/ needle from a different bike...

I have learned after several failures, its easy to overlook the obvious.

I wholeheartedly agree with your comment regarding overlooking the obvious. Anyone who has played with mechanical devices for any amount of time has done it sooner or later. I know I have.

The previous owner was and elderly man in his 70's when I got the bike from him. He had an extremely limited aptitude for anything mechanical, and the bike never left his house or his possession. He had zero interest in making it faster, or changing out any component. In fact, I had to show him where the spark plug was. About all he ever did was add oil and gas to the reservoirs, and buy a battery every spring. (I couldn't talk him into removing the battery and putting a maintainer on it during the cold months.)

The only numbers on the carb were casting numbers, and I never saw any on the slide needle. The only number I could identify with is the #68 (if I remember correctly) on the main jet. And from what I am discovering, This '89 Elite E was not the most popular bike, and used carbs are hard to find. As stated in previous posts of mine, the bystarter is on the outboard side, and it's the only one that will bolt right up without changing intake manifolds (or making custom modifications).

You posed some good questions though. Probably the same ones I would have asked too.