Frustrations Rebuilding a 440

[litefoot]

I finally got around to looking for the air leak. It was coming out of the bottom of the cylinder. As soon as I saw the soap bubbles, I had an "Ahah!" moment. I hadn't trimmed the crankcase gasket at the cylinder base. Anyway, I trimmed back the gasket, but the two crankcase halves are not perfectly flush at the cylinder base. Is this abnormal and do I need to apply some sealant? Thanks my friends. See how nice I can be when I "need" something.

 

[pioneerguy600]

I finally got around to looking for the air leak. It was coming out of the bottom of the cylinder. As soon as I saw the soap bubbles, I had an "Ahah!" moment. I hadn't trimmed the crankcase gasket at the cylinder base. Anyway, I trimmed back the gasket, but the two crankcase halves are not perfectly flush at the cylinder base. Is this abnormal and do I need to apply some sealant? Thanks my friends. See how nice I can be when I "need" something.

Did you drive the two dowel pins back in place before tightening the case screws? The two halves should line up closely to flush under the cylinder.
Pioneerguy600

 

[Lakeside53]

They are machined as a pair, and will be perfect... if they were a pair.. and if the pins are in. If the pins are not set, loosen the case screws before tapping them in.

 

[litefoot]

They are machined as a pair, and will be perfect... if they were a pair.. and if the pins are in. If the pins are not set, loosen the case screws before tapping them in.

I remember reading in the service manual about tapping in the dowels before torquing the case screws to spec. I did set them, and they did drive in, so I'm wondering why there's a mismatch? I mean, if they're in, shouldn't the cylinder base halves be matched up. Is it possible I tightened the screws a little too much before driving in the dowels?

 

[Jacob J.]

silly question(?) can the crank develope a groove from the seal?
i know you said you had a low hour saw but could there have been a little grooving?

Nah. The steel in those cranks is case hardened to many thousands of degrees harder than the rubber seals. I've never seen a seal groove a crank in the 20 years and 800 or so saws I've been through.

I remember reading in the service manual about tapping in the dowels before torquing the case screws to spec. I did set them, and they did drive in, so I'm wondering why there's a mismatch? I mean, if they're in, shouldn't the cylinder base halves be matched up. Is it possible I tightened the screws a little too much before driving in the dowels?

Dowels first before tightening anything. Like Andy said, those case halves are machined as a pair at the factory and they're tested before assembly.

 

[BarkBuster20]

hey if i could pick up a "blown" 046 for 50 bucks or under would it be a good deal? worth doing?

 

[Lakeside53]

worst case you could sell the tank for $50

 

[BarkBuster20]

well it was running and a friend recently told me he "blew it"

 

[bigbadbob]

Great thread, great reading, good info!!!

 

[litefoot]

OK, I got the air leak fixed. The cylinder base alignment wasn't bad. I just needed to trim off more of the crankcase gasket. Both pressure and vac tests were good. Yeah! Well, almost done. Here's a look with everything back together:

I still have one problem. She fires on the first pull at full choke, but instead of the expected "cough", the cord just stops dead in my hand without the usual sputter. I then go up to fast idle and it starts on the 2nd pull without problems. It runs and accelerates very nicely. I expect maybe this damage to the IM (FW rubbing against it after the crank bearings went out) is causing a timing/spark problem.

 

[litefoot]

Great thread, great reading, good info!!!

Thanks for saying that. I traded a 361 for this saw thinking I was getting a good deal. Well, after the piston, cylinder, crank bearings, seals and now a possible bum ignition module...I have to say it was not "materially" a good trade.

But there's no denying the education I have received in this whole process. I never thought about this thread being helpful to others. I just hope my fumbling and bumbling hasn't discouraged others from thinking about doing their own repairs. I just ran into more obstacles than I anticipated.

 

[litefoot]

OK, guys. I'm just about ready to throw in the towel. I'm a patient guy, but this is getting ridiculous. Did some test runs with the saw today running Ultra at 40:1. It ran OK, but it didn't feel like the compression was that great. I tested it and it read 125 psi (143 corrected for altitude). I re-checked the tester with my 034...it read nearly 170 psi corrected.

Pulled the muffler. Light vertical scratches on the intake side of cylinder. I don't know if these were leftover from the bearing failure, but I thought I had inspected the cylinder closely.

But I know I cleaned out the crankcase (Heck, I split the frickin' thing) and I did clean out the cylinder before bolting it down.

Anyway, I guess I've got to try and sand out some more scratches. What do I use?

Thanks for you help and thanks for letting me bellyache. I just feel like such a dumba$$ right now.

Yours truly,
Master Chainsaw Rebuilder
(Master of Disaster, that is)

 

[2000ssm6]

Is the same piston and rings in it that were used since post #1? OEM kit right? You should have more compression than 142, if you have good rings and a good cylinder surface to seal to. I'd check those rings again after pulling the jug.

I clean cylinders with muratic acid and a q-tip, might use some steel wool if needed.

 

[redunshee]

Nah. The steel in those cranks is case hardened to many thousands of degrees harder than the rubber seals. I've never seen a seal groove a crank in the 20 years and 800 or so saws I've been through.



Dowels first before tightening anything. Like Andy said, those case halves are machined as a pair at the factory and they're tested before assembly.

These guys know alot more than me but I failed the pressure test once and found I had overtightened the cylinder and as a result caused the gasket to misform.

 

[Ax-man]

That module is probaly OK. Your pic is showing the iron core of the module. All that thing does is set-up a magnetic field for spark when the magnets in the flywheel go zipping by it ,nothing more, it will work just as good dirty as it does clean and abused a little. That core has nothing to do with timing. Just make sure you have enough air gap between the flywheel and that core. If your timing was off the saw wouldn't run right.

You might have to tear the saw back down to the crankcase. Is your crank centered???? I don't know if it is possible to actually put it back together with the crank not centerd but anything is possible.

Larry

 

[Martinm210]

Pulled the muffler. Light vertical scratches on the intake side of cylinder. I don't know if these were leftover from the bearing failure, but I thought I had inspected the cylinder closely.

I would try and figure out what the source of the intake scratches are. Was there some sand or dirt or anything in the carb/intake boot that could be causing this. Intake side scratches are generally debris from the intake. If it was something in the crankcase it would generally appear either at the transfer or exhaust port areas.

I know there is some debate regarding scratches/scoring repair. Some will say use a ball hone to clean things up, others will say do nothing and simply replace the rings, preferrably with some cast iron types. I'm a follower of the do nothing more than maybe a scotchbright pad at most, hones are meant for brand new cylinders or sleeved cylinders and could cause more harm than good.

I'm my limited experience a saw will generally run fine regarding compression unless the rings have been worn to the bone (rare) or because it has lost compression due to stuck rings(common). The stuck rings are usually due to some sort of debris that caused damage to the ring seats in the piston.

I would suggest pulling the piston and cylinder and take a better look. Also look very closely at the piston and rings and make sure the rings slide around and move in/out of the piston ring seats smoothly. Check out that intake side carb/intake boot very closely for possible debris coming from something.

That's what I'd do, but I'm a rookie compared to most of the guys in these forums.

Don't give up, that's a beautiful looking saw

 

[litefoot]

Is the same piston and rings in it that were used since post #1? OEM kit right? You should have more compression than 142, if you have good rings and a good cylinder surface to seal to. I'd check those rings again after pulling the jug.

I clean cylinders with muratic acid and a q-tip, might use some steel wool if needed.

2K,
Yes, it's the same OEM P&C from the beginning. I just pulled the jug and the rings were positioned properly and moved freely. Looking through the exhaust port, I see light scratches on the intake side. They may have been there since the bearing cages made there trip up into the cylinder and out the exhaust. I just didn't notice them when inspecting the cylinder from the bottom. Would light scratches be enough to reduce comp this much?

That module is probaly OK. Your pic is showing the iron core of the module. All that thing does is set-up a magnetic field for spark when the magnets in the flywheel go zipping by it ,nothing more, it will work just as good dirty as it does clean and abused a little. That core has nothing to do with timing. Just make sure you have enough air gap between the flywheel and that core. If your timing was off the saw wouldn't run right.

You might have to tear the saw back down to the crankcase. Is your crank centered???? I don't know if it is possible to actually put it back together with the crank not centerd but anything is possible.

Larry

Thanks.for the advice. I used a business card to adjust the gap to .012. It was actually doing this before I split the case, so I'm guessing there was an issue beforehand. Someone else posted a question similar to this one (start cord jerking out of your hand on cold start, but working fine on all warm starts) a few weeks ago, but I can't find it.

I would try and figure out what the source of the intake scratches are. Was there some sand or dirt or anything in the carb/intake boot that could be causing this. Intake side scratches are generally debris from the intake. If it was something in the crankcase it would generally appear either at the transfer or exhaust port areas.

Don't give up, that's a beautiful looking saw

Martin,
Thanks for the compliment. She's a sweetie on the outside, but a devil inside. LOL. I haven't pulled the intake boot off of the cylinder to look at the exhaust side, so I can't say for sure that the scratches are only on the intake side. I did inspect the inside of the muffler and saw no debris or grit.

I think a lot of my problem has to do with my eyes getting old. Man, I hate not being able to see.

 

[2000ssm6]

2K,
Yes, it's the same OEM P&C from the beginning. I just pulled the jug and the rings were positioned properly and moved freely. Looking through the exhaust port, I see light scratches on the intake side. They may have been there since the bearing cages made there trip up into the cylinder and out the exhaust. I just didn't notice them when inspecting the cylinder from the bottom. Would light scratches be enough to reduce comp this much?

Hard to say without seeing and feeling them in person. If your finger nail catches the scratch, it's usually too deep. You might just have to run it for a few tanks and check again. 10-12 tanks should have the rings broke in good. That's a bunch of sawing. Sounds like you are sure that there is no more foregin material left. I have a spare oem 440 jug you could borrow to rule out a bad "ring to cylinder wall" seal. From all you have gathered and what I read, put some more tanks through it....

 

[Martinm210]

Martin,
Thanks for the compliment. She's a sweetie on the outside, but a devil inside. LOL. I haven't pulled the intake boot off of the cylinder to look at the exhaust side, so I can't say for sure that the scratches are only on the intake side. I did inspect the inside of the muffler and saw no debris or grit.

I think a lot of my problem has to do with my eyes getting old. Man, I hate not being able to see.

It wasn't fun for me when I pulled the muffler on my 044 build and found pieces of piston rings either, but in the end I figured it out, learned alot from the little mishap, and the saw runs great now.

When you split the case did you replace the bearings/seals?

It seems like I read a thread a while back where someone was having similar problems and it turned out the bearing casing was falling apart.

You'll find it...scratches means debris...coming from somewhere.

 

[Junkwrencher]

Put mine in the pot.

I too would say run it more before taking a final compression reading.As far as the module/ignition problem,was the flywheel key replaced or the old one used?I've experienced problems with keys in the past and learned to replace them with a new one.Same to the compression release,new or old,these go bad in time.I once had a 394 Husky that took a load from flywheel to clutch(a large white-oak) and it displayed similar symptoms before the connecting rod bearing went and the piston turned in the cylinder.