My stupid CS-490

[TLG]

Hey Bobby, Sorry about your issues. But just a suggestion to prevent a repeat failure. If you do a gasket delete you need to verify the crankshaft counterweights are not interfering with the bottom of the cylinder. The part that goes into the lower riser. You don't know the bottom of the cylinder may have been cut lowering it lower into the rotating crankshaft. As far as keenserts go McMaster Carr has thin wall 5mm that use a 8mm tap to install. Good Luck. TG

 

[Bobby Kirbos]

@TLG
Any reason to not use the helicoil type thread repair inserts? I don't know how much meat there is to drill into and the coil inserts need a way smaller pilot hole.

 

[TLG]

I seem to have trouble with the helicoil style retaining in the material. screws tend to loosen a touch, helicoil is never tight again. It's a loose worm in the hole so to speak. Threadlocker does not work as both the screw and insert are as one. The keenserts I threadlock and they also use two small stakes to lock into the material. Check McMaster Carrs site and see what I'm talking about.

 

[James Miller]

Sorry Jim, I'm fixing it. I don't really know if the base delete is worth the hassle of a temperamental machine, so I ordered the $1 gasket.

As expected. Cant blame a guy for trying. Wish 490s showed up on cl as often as 400s.
As to the BG delete being worth the hassle. The exhaust numbers on the 490 are so low that pulling the gasket will gain a little compression but probly not show any gain due to lowering the exhaust even more. Short of machine work and porting your probly better running the gasket.

 

[drf255]

@drf255
I noticed that the holes for the jug bolts are through holes. Do you happen to know where the other side ends up? Do they go into dead space or do they go through into the crank case?

Sorry pal, can’t remember.

 

[Bobby Kirbos]

Sorry pal, can’t remember.

Thanks, but I realized that I asked a stupid question. I had a bolt missing. If the hole ended up into the crank case, the saw would not have run this far; into the gas tank would have been a mess. My bet says dead space.

 

[BGE541]

So, how well will a chainsaw run when there are 3 bolts holding down the jug, when there should be 4 bolts?

And, what are the odds that simply bolting the cylinder down will solve the problem ... without needing to pull the thing apart and put in new sealing goop?

I would pull it, clean it and put some Dirko in it... an hour of your time is worth the $149 you’ll spend for an OEM P&C IMHO. And you get a chance to grind on it if you want while you’re in their but that’s just me.

 

[Bobby Kirbos]

@James Miller
Pics below.


The missing bolt was on the intake corner of the flywheel side. This crack is on the exhaust corner of the flywheel side. I think the above damage may have been a function of the 4th corner (intake side) not being held down.

I took a look at the saw this morning. The bolt holes are through holes on an external flange. If I wanted to, I could pull the flywheel and use a through bolt with a nut on the bottom. But first, I'm going to try fixing it the "right" way. A helicoil thread repair insert for an M5 bolt would need a hole tapped for a 6 x 0.8mm thread. I'll just tap the hole for an M6 bolt. The pilot hole for M6 is 5mm. The original bolt size is an M5 which is now stripped. I already have the needed pilot hole "drilled".

If that doesn't work, an M5 through bolt with a nut on the bottom will be the fix.

...the saga continues.

 

[pioneerguy600]

I don`t see why tapping it for the next size up is an issue, we do it all the time when building hybrid saws and I have yet to see a failure. If the bigger screw won`t go down through the existing holes in the cylinder fins then just drill out these holes, its very easy to drill out aluminum a bit bigger , the fins won`t care if you do.

 

[Bobby Kirbos]

I don`t see why tapping it for the next size up is an issue, we do it all the time when building hybrid saws and I have yet to see a failure. If the bigger screw won`t go down through the existing holes in the cylinder fins then just drill out these holes, its very easy to drill out aluminum a bit bigger , the fins won`t care if you do.

The good thing is that this bolt is accessible from the side without needing to install it through the fins.

 

[pioneerguy600]

The good thing is that this bolt is accessible from the side without needing to install it through the fins.

Ya, all the better and I did see that but thought to add that drilling out the existing holes down through the fins is easily accomplished also. In your case makes it easier to get the base screw in place, just watch for side clearance between the screw head and cylinder case, have needed to do a bit of relief grinding on several cylinder casings when upgrading/ up sizing screws.

 

[James Miller]

Did you order a new cylinder?

 

[Bobby Kirbos]

Did you order a new cylinder?

Yes. I ordered it last night, along with a new base gasket. Just under $100 including the ride.

 

[Kostas]

The cylinder is a little expencive,at least now you will make your saw like it is meant to be.I started my 490 for the first time yesterday and i must say i am impressed.When i got it,i did the muffler mod and remove the limiters.It is a 2018 model and i must say its tune was spot on out of the box.Anyway,i see the aluminum front handle from the cs 500 on a European warehouse for 7 € (original price was 20€),really cheap.Will it fit to the 490?

 

[Bobby Kirbos]

Fixed it. New jug and base gasket. I retapped the 1 hole for M6x1mm. All the rest are M5x0.8mm. There is just enough clearance between the jug body and the bolt head, but it does clear. It's amazing how well it runs when it's not leaking air in from the side.

I did a small amount of sanding on the intake port, but not much. It is more smooth than it started, but it's not polished to a mirror finish. I get what I get. It's a runner.