353 Fail

[Stump Shot]

When I finished machining the base on a 353 I could not remove the mandrel, it was stuck hard. Finally after some persuasion with a plastic tipped hammer did it come off. Turned out the odd shaped bump out in the lower transfers had caved inwards on both sides. After some reflection I decided that I didn't quite know what was going on, but if the inside moved it had to take the outside with it and that would spell a leak.
In the end I bagged this one not trusting it to be of any use of any kind. Ordering a new OEMu 346xp ne cylinder kit seemed to be the order of the day

Highlighted and pointing to afflicted area

 

[redline4]

Both sides, opposite corners or both side, same side corner?
If that makes sense..

 

[Stump Shot]

Both sides, opposite corners or both side, same side corner?
If that makes sense..

Uh huh, both sides that little area sprung in.
I've done a bunch of these before without this issue. I dunno...

 

[Ketchup]

I’ve seen AM cylinders do that when you raise the cylinder flange at the lowers. Could taking the transfer covers off be part of the issue?

 

[thedude74]

Does the 353 use the same cylinder as the 45mm 350? Sure looks the same.

 

[Stump Shot]

I’ve seen AM cylinders do that when you raise the cylinder flange at the lowers. Could taking the transfer covers off be part of the issue?

All I can say is it hasn't been up until now.

 

[thedude74]

I’ve seen AM cylinders do that when you raise the cylinder flange at the lowers. Could taking the transfer covers off be part of the issue?

Is that limited to removable transfer cap cylinders?? Or others as well? Just wondering if they're plated with the caps in place causing stress/tension that is relieved once the caps are removed.....The caps causing tension that is, not the plating process.

 

[Stump Shot]

Does the 353 use the same cylinder as the 45mm 350? Sure looks the same.

Its 45mm for sure. @Woodrow is the resident 3xx specialist, he can maybe chime in.

 

[Stump Shot]

Is that limited to removable transfer cap cylinders?? Or others as well? Just wondering if they're plated with the caps in place causing stress/tension that is relieved once the caps are removed.....The caps causing tension that is, not the plating process.

With the caps removed I could slide the mandrel in and back out again effortlessly. After machining the mandrel would slide a little until the edge came in contact with that area. So some stress was relieved or some such thing while machining.

 

[Woodrow]

The 350 and 353 closed port 45 mm cylinders are indentical. The only difference is the dished piston in the 350 vs the flat top piston on a 353.

 

[Stump Shot]

The 350 and 353 closed port 45 mm cylinders are indentical. The only difference is the dished piston in the 350 vs the flat top piston on a 353.

Thanks Dan, every 350 I've ever received already had the cylinder replaced with the 346xp of one type or another.

 

[bigbadbob]

I had a 353 with a dished piston, AFIK it was factory it had the green fuel cap as well.
Swapped it out for a flat one. The jug was a closed port

 

[pbillyi69]

that doesnt really make any sense to me at all. why would cutting material off the base change how that part of the jug is shaped at all? is there any visible signs of damage?

 

[Stump Shot]

that doesnt really make any sense to me at all. why would cutting material off the base change how that part of the jug is shaped at all? is there any visible signs of damage?

No damage, again the mandrel would slide all the way in and all the way out before machining as I had to find the correct mandrel out of the pile. Only after machining would it not fit properly any longer.
I can't say that it makes much sense, however after talking with another porter this evening, he had a couple cylinders warp out of round over the years after porting them. The only thing I can think is that there is stresses cast into the metal when made and removing some metal relieves the stresses and hence the metal moves. Kind of a strange thing to wrap ones head around, no doubt.

 

[pbillyi69]

so making to bottom thinner made it tweek a little where the transfer ports are is what your thinking is. huh that is interesting

 

[huskihl]

Any chance it happened when you were cutting the band? It’s much more likely that the bolts pulled the corners up, which could potentially push the middle in

 

[Stump Shot]

Any chance it happened when you were cutting the band? It’s much more likely that the bolts pulled the corners up, which could potentially push the middle in

I cut the band first, then the base. Combo deal?

 

[huskihl]

I cut the band first, then the base. Combo deal?

Idk. I have seen changes in roundness at the bottom of the cylinder while tightening the bolts for squaring up the band but wouldn’t have figured a base cut would do it. But anything is possible, I suppose.

 

[NateSaw]

I don't know the plating process.. But it seems a sound theory to me that could have been the culprit. I mean, certainly the nikasil has more tension in it than the aluminum, otherwise, how would it be harder and facilitate cylinder longevity? The way plating "runs away" from the am cylinders if not chamfered delicately when porting, seems to indicate it has shrunk, or sprung during the plating process, perhaps when cooling. Oem adhesion is definitely strong at least on the Stihl's cylinders. So if the nikasil has a memory towards shrinking, and is well bonded to the more ductile aluminum, then said aluminum is thinned, or weakened, seems to me it could yield to the tension in the nikasil, rather than the nikasil pulling off the aluminum. If that theory is true, I'd imagine we're at the mercy of the process. Proper heating and cooling down times? Idk. Just a theory.

 

[Moparmyway]

Did you cut the base outward or inward ?

I’m wondering if you cut in, mayhaps the pressure of moving in towards the center helped move the thinned material ?

Second thought is that cylinder extension looks like you cleaned it up a little. Maybe the slap of the start of the interrupted cut pushed some things around ?