MS460 PTO Crank Seal Problems

[drf256]

Common newbie mistake is using the longer m4 screws for the upper fly side 1128 AV mount on the oil pump in error. They are longer and will punch through the crankcase. I did it once and never made that mistake again.

 

[jacktheripper]

Yep, I made sure not to do that. Also, there is no definite "punch through" damage on either side of the case. Just a strange, small leak.

 

[Woodwackr]

And then there's a loose bearing seat...

 

[Basher]

The screw on Jacks saw is not punched through, his saw is leaking around the steel insert where it meets the crankcase. I think this crack appears due to the difference of expansion rates from heat, I have sealed them up with 309 using vac pulled it in and the saws have sealed and stay sealed for years now, the precleaning to rid it of oil took some time as nothing will seal up an oily surface.

 

[jacktheripper]

I heated up the clutch side case with a heat gun under pressure and vacuum in an attempt to get the air leak to show. It didn't. I still think that it probably needs a clutch side case, but maybe I'm missing something. Who knows, maybe I'm just experiencing carb nozzle issues or something. It definitely is still acting like it has an air leak, but I can't pin it down. I'm going to replace the fuel filter and see if anything happens. What is strange is that it fires up and runs fine for a minute, then starts stumbling over itself and going lean. Then it becomes very reactive to the fuel screw and either tunes too rich or too lean quickly. I ran it with the gas cap off to check for ventilation issues, but it didn't make a difference.

I think I just need to move on from this project - just listed it as is for $500. Just want to get my money back out of it.

 

[jacktheripper]

I am beginning to wonder if it might actually be the carb. I had a bad nozzle on three wt194's from three 026's in a row. They would start up and initially run fine, and then lean out and act erratically. That is what is happening to me with this saw...

 

[Basher]

This chainsaw repair hobby can become a bit expensive when one needs to keep buying swap out parts just to try to overcome a running problem. Many turn to using the cheaper AM parts and that works sometimes but often it just causes another problem. Have a case on point, my next door neighbor on the lake was having issues with his Jonsered65 cc saw and he is a bit of a handy fellow mechanically. He spent several months tearing his carb out cleaning and adjusting each weekend. He finally brought it over to me and told me what was happening, my diagnosis was that the coil/ module was packing it in when it heated up but he wouldn`t believe that since it had spark when tested when cooled down so he kept up the tear apart clean and adjust over and over until we got a cheaper AM module just to try, voila the saw ran great again. Now it has a new OEM module in it and the point of my long post is sometimes it makes sense to try a cheaper AM part as a diagnosis tool. I would personally have skipped the AM coil but his cheap ass philosophy prevents him from overspending on any issue.

 

[jacktheripper]

I ordered an aftermarket carb, and will ultrasonic clean the OEM carb in the meantime and try both. Maybe it's just the carb after all...

 

[JIMG]

I have had issues with carbs on high hour old saws being worn out at the throttle shutter shaft to carb body bearing area. No amount of cleaning will remedy that.

 

[Woodwackr]

I have had issues with carbs on high hour old saws being worn out at the throttle shutter shaft to carb body bearing area. No amount of cleaning will remedy that.

Yup, do a pressure test with the carb installed…soapy water…watch all the bubbles

 

[jacktheripper]

I cleaned the OEM carb in the USC and fully rebuilt it again. Installed it on the saw, and the saw was still running weird. Today at lunch I got a Duke's chinese carb in the mail and installed it - also running weird. Then I fully vacuum and then pressure tested the saw while turning the crank, and there was no apparent leak, again.

I'm back at work until this evening, but now my mind is wandering back to the fuel line and filter. I've tried two different filters, but not fuel lines. Maybe there's a pinhole in the line inside of the tank...

 

[Basher]

I cleaned the OEM carb in the USC and fully rebuilt it again. Installed it on the saw, and the saw was still running weird. Today at lunch I got a Duke's chinese carb in the mail and installed it - also running weird. Then I fully vacuum and then pressure tested the saw while turning the crank, and there was no apparent leak, again.

I'm back at work until this evening, but now my mind is wandering back to the fuel line and filter. I've tried two different filters, but not fuel lines. Maybe there's a pinhole in the line inside of the tank...

Clamp off one end of the fuel line and apply vac or pressure on the opposite end, that will tell you if there is a leak, the line can stay in the saw, just need to remove the carb, clamp at the filter end. Hemostats work great for that, apply vac or pressure at the carb nipple end.

 

[jacktheripper]

That's exactly what I am planning to do. Will get back soon about this.

 

[jacktheripper]

No leaks in fuel line. I even tried a different coil and still no difference. I'm going to just bite the bullet and snag the carb off of my NOS 044 and throw it on just to see.

 

[huskihl]

That's exactly what I am planning to do. Will get back soon about this.

Does fuel spray out of the line if you shake it with gas in the tank and pop the end of it off the carburetor? I have no idea what makes it do it or not, but sometimes on poor running saws, I will lay them over on the side and fuel will trickle out slowly but do nothing when I shake it. If I install a new filter and line, fuel sprays out of the end of the hose like mad

 

[jacktheripper]

Does fuel spray out of the line if you shake it with gas in the tank and pop the end of it off the carburetor? I have no idea what makes it do it or not, but sometimes on poor running saws, I will lay them over on the side and fuel will trickle out slowly but do nothing when I shake it. If I install a new filter and line, fuel sprays out of the end of the hose like mad

I got gas in the face after pulling off the carb more than once, if that's what you're asking lol.

 

[Woodwackr]

I've had to UST carbs 3-4 times to get them to work right. sometimes all it takes is some tiny spec of crap in some passage...
but, seems you've eliminated that issue by swapping carbs, so...
I have a ms250 I just built with 'issues'. It runs ok but not quite the way it should. I had tried two carbs I had and no joy. I ordered a used carb from a running saw and that's what's on there now, after a rebuild. I have a brand new OE that will be the next swap to see if it ain't the carb in the first place

 

[Maintenance Chief]

A booger in the impulse line will wreak havoc, I've had them partially blocked and the saw will start and idle fine because of the choke but a load or rpm will cause it to lay down.
I use brake clean to find mysterious leaks on a running saw alot.

 

[jacktheripper]

Ok, so even with the carb from the 044, it still stumbles. I pulled the clutch and oil pump out, and ran the saw with bare crank sticking out the clutch side. I hosed down the whole area with carb cleaner while running, and that did not get it to alter the idle. However, after shooting the cylinder base area near the muffler for more than a couple seconds, I got the saw to die. I replicated this three times.

I did delete the base gasket on the saw, and resealed it with Motoseal when I rebuilt it. I did this twice, since I have now split the cases and rebuilt the saw two times. It makes me wonder if I am just causing the carb cleaner to evaporate and be aspirated into the saw's intake when I shoot the cylinder base area.

Regardless, I am going to put the factory gasket back on and reseal the base and see what happens. While I'm at it, I'll replace the impulse line. Maybe there is some kind of molding flaw inside of it, causing the passage to be blocked somewhat.

What a strange deal...

 

[jacktheripper]

Ok, more intel:

Pulled the jug. See photos.

You can see the area around the clutch side bearing sleeve insert where the paint is missing. I'm lead to believe that it is simply just that: the paint is missing. I may have chipped it a bit when cleaning or something like that, but I cannot believe that this is the source of an air leak, because I was literally soaking that area on the outside with carb cleaner while the saw was running, and the saw did not respond to it.

Also, bearings look great and crank spins freely.

The impulse line is flowing freely. I put an air gun on the carb end of the line and blew through the line and the nipple in the case and nothing came out. I blew through the impulse line with my mouth as well, and could not feel any resistance.

The intake boot to intake port fitment can cause issues with fuel puddling, as I have experienced on 026's firsthand. So, I wanted to check that. The bottom of the boot fits tightly at the same level as the bottom of the intake port. There are no real casting lips that would cause puddling either. However, the top of the boot doesn't really match the port well. The boot is definitely more restrictive than the port is, as shown in the photo.

The cylinder base sealing surface did not show any obvious signs of the sealant allowing fuel or air to blow through. I used a straight edge to check flatness of the cylinder base, and I found that the corners are raised slightly near each of the four bolt holes. Just enough for me to see some light between the straight edge and the cylinder base. Now there's something.

I will use Dirko this time and reseal everything with a factory metal base gasket. Dirko should be better at filling any potential openings in the sealing surface, as it is recommended for clamshells and Motoseal is technically not.

More to come...