Too much crap no 3

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glassdoctor
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Too much crap no 3

Post by glassdoctor »

Hi all.
Too much smoke black liquid coming out of no 3.
So much so it splatters.
Is this too much oil? Using top of range castrol. How can you adjust. Other 2 pots seem ok.
Dave

AHAMAYfrank
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Re: Too much crap no 3

Post by AHAMAYfrank »

Dave,

I have just purchased my NS a couple of weeks ago and I noticed that activity here is very low. I have a fair amount of two-stroke experience with other brands but this one of my early posts here.

The primary drive gear on the right side of your engine connects the crankshaft to the clutch. This system is under the clutch cover and runs in transmission oil. If you have been riding it like this for a while, you may notice a dropping of the oil level in the sight glass. You may not notice a level drop, as it wouldn't take much transmission oil to make a good bit of smoke.

Looking at the part information, items 20 and 21 are a seal and an o-ring that have the purpose of sealing the crankcase from oil entering from the clutch area. The o-ring goes around the end of the crank sealing the shaft to the collar. There is a seal pressed into the crankcase that seals the outside of the collar. A nut holds the primary gear tight on the crank pushed up against this collar.

My guess is that you could replace the seal and o-ring after removing the clutch and the primary gear. You should also get a clutch cover gasket in case it gets damaged during surgery.

Usually a seal like this survives until a crank bearing becomes loose in a bike that is ridden quite a bit. For me some of my older bikes sit for quite some time un-ridden, so I would think this may be your cause.

Maybe someone will chime in with direct experience with this symptom.

Frank S.

glassdoctor
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Re: Too much crap no 3

Post by glassdoctor »

Hi thanks for this.
So theres no way this could be no 3 recieving too much two stroke oil?.
You think its transmission oil. Any certain way of telling?
Dave

Paul-IOM
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Re: Too much crap no 3

Post by Paul-IOM »

Hi Frank, it's years since I last split the cases on mine but I'm fairly sure you can't change the gearbox side crank seal without splitting the cases, I think it has a middle lip sitting in grooves in the cases, but I could be wrong.

You are definitely right about it being a weak point on many 2 strokes though, they tend to suck gear oil through a worn or hardened seal, and if the motor sits for too long the seals can stick to the crank and then tear, I turn my motor over by hand every month or so to help prevent this.

AHAMAYfrank
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Re: Too much crap no 3

Post by AHAMAYfrank »

Dave,

I believe the injection pump is a positive displacement pump that displaces oil to all three cylinders equally.

When I got my bike a couple of weeks ago, the previous owner was running premix. I put the injection pump back on. I filled the lines with oil but had some air bubbles still in the lines. I held the cable open to move the oil through the lines quicker. I used clear lines so I could see if the pump was working. It appeared that each time the pump pulsed oil and air bubbles, all 3 lines moved the fluid at the same time. That implies to me that the pump could not over oil just one cylinder.
Paul-IOM wrote:
Mon Nov 18, 2019 9:14 pm
Hi Frank, it's years since I last split the cases on mine but I'm fairly sure you can't change the gearbox side crank seal without splitting the cases, I think it has a middle lip sitting in grooves in the cases, but I could be wrong.

You are definitely right about it being a weak point on many 2 strokes though, they tend to suck gear oil through a worn or hardened seal, and if the motor sits for too long the seals can stick to the crank and then tear, I turn my motor over by hand every month or so to help prevent this.
I think Paul has some great info here. You could confirm the existence of a lip on the seal if you just ordered your parts in advance.

Of course, the best way to do the job is to split the cases if the seal has a lip but I believe you could do it without. You may be able to remove the seal lip, use a semi hardening sealer like Yamabond#4 (Honda probably has a similar type but do not use silicone seal) around the outside out side and push it evenly into place. The seal will most likely be secure just like that but, you could put 3 or 4 small dimples in the case right at the edge of the seal (after it is installed) using a center punch. One pop with one of those automatic jobs would probably do the trick. It wont need much help to hold it in. It would need just a small dent inward toward the seal to do the job.

This may sound like somewhat of a hack, but I think it would work.

Frank S.

Alastair
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Re: Too much crap no 3

Post by Alastair »

As mentioned above, likely source is jiggered crank seal. You can do a leakdown test to see if seals have gone.

At this age, I'd just tear the motor down and have the crank rebuilt as all seals will be goosed. Ignore the bodges suggested, split the cases. Inner seals are available from www.classicracereplicas.com as are outer seals.

Have a look under engine and gearbox sub forum for thread on NS at 30, 000 miles

viewtopic.php?t=3865

Channel Hopper
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Re: Too much crap no 3

Post by Channel Hopper »


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