Screwing Cylinder to Crankcase

[robert1]

On another thread I described the trouble I am having working on my 410. I am not a chainsaw mechanic. I had loow compression so I replaced the piston and now got a brand new cylinder (referred to as "Jug" in my other thread)  and gasket also but now I'm trying to screw the cylinder back onto the crankcase and some of the screws don't seem to catch on any threads in the crankcase. Is there some nut or something that dropped down inside the crankcase when I backed the screws out to remove the cylinder when I first took it apart? I don't see them on the illustration in the parts manual. any help appreciated.

[undee70ss]

Checked to see if the threads are stripped.

[robert1]

Thanks for the reply! The two holes on the left hand side (as you hold the saw in front of you)  have threads that catch the screw. The two on the right don't seem to. I cant see any down the holes. I did nothing to damage the threads. Just backed out the screws. That's it. The hole on the right closest to the operator does not appear to have ever had threads. The screw threads are perfect. No damage, No filings on threads. Nothing. It's almost as if there was a nut that dropped down into the saw body but I don't see that in the service manual. I don't see that in any parts diagram. 

[w30bob]

Robert,

If you look at the first 410 IPL in Leon's list, go to page 4, Fig 3, and look at part numbers 42 and 43. One is a nut and the other is a retainer, and it shows them going under the hole in the crankcase that's for the lower left cylinder bolt, from the way you are viewing it. If you look at the quantity of each by the part number it shows 4 of each. I would assume each cylinder bolt threads into those nuts being held on the crankcase by those retainers. Check it out. Then the question is.........where are yours??



regards,
bob

[robert1]

Bob- I am gradually learning my way around this website. Thanks for the tip on Leon's . Those diagrams are same as the others I've looked at. The screw I am talking about is #38 and the flat washer I have is #37. If you follow the line down to the crankcase there is no nut or retainer illustrated there. Are you pretty sure 42 and 43 you reference mate with 38?NEVER MIND. I can see you are correct. On the outside of the crankcase (thank God) there are holders for the nuts. Now I just have to clean off my bench and look for them. If I can't find then I hope I can find on line or at the hdwe store.

[w30bob]

Hi robert,

I hear ya, but look at where 42 and 43 go. They sit under the crankcase edge where the other corner of the cylinder bolts to. So if those parts are used in that corner, and the IPL says there are 4 required.......they must sit under every corner. So although they only show one 38 bolt (and not all 4), they also only show one nut and retainer, 42 and 43. Typically with drawings like this they don't show multiples of each part, just one and you have to make assumptions about the other duplicates. The other thing is when you design machinery it's considered a no-no to use threads in aluminum/magnesium if they're in tension. It's been done a lot, but it's not a smart thing to do, and most modern machinery acknowledges that. Typically in a tension situation, like with a bolt, Heli-coils are used.......or a nut is placed on the backside of the piece to catch the bolt. Aluminum/magnesium threads have very poor strength, but like I said.......it's been done. It's just a sign of poor design. Back to your situation.......I looked at a 410 crankcase on eBay, you can see it here:

www.ebay.com/itm/352693024143?hash=item521e24758f:g:R5EAAOSwjvxdBbnc

It clearly shows the deck the cylinder bolts to is very thin, too thin to be threaded for cylinder bolts for sure.  And you can see a ledge under each bolt hole where the nut and retainer I mention would sit to catch the bolt.  So I believe you DO need PN 42 and 43 under each cylinder bolt.  But you do need to find where yours went to, or they could really ruin your day when you go to start it.  

Hope this helps,
bob

[bobby167]

In the IPL you have, look at # 43 & # 44. # 44 is retainer for the nut. There are 2 of them. Located in IPL towards rotor side.

[robert1]

I see on the outside of the crankcase there are little "shelves built in to hold the nuts etc. At least I know they are not in the crankcase. That's a relief! Now to clean my bench and garage floor. If not there then maybe get on line or at hardware store. I will keep you posted. Thanks for your help.