MS 290 cylinder-thread pitch

[anderson3754]

Putting my MS290 back together with a meteor cylinder and piston big bore kit, this cylinder is not tapped for the 4 holes. What size tap is needed to tap the 4 cylinder base holes . My intent is to use the 4 OEM Stihl bolts. Looked for approx 45min and cannot find reference to this size tap.

Thanks

 

[anderson3754]

On mine the bottom pan has the through holes and the cylinder has the tapped holes. The bolts are installed from the underside of the chassis through the bottom pan, and then threaded into the cylinder to secure the engine assembly securely into the cradle/chassis.

 

[JP56]

As stated above, they most definitely are through holes on the base that thread into the top end and hold the entire assembly into the case. The only difference you MAY find (I have not used a Meteor so I don't know for sure about that brand) is that the threads in the top end MAY be different then the OEM threads.

 

[Vintage Engine Repairs]

You are absolutely right, my memory isn’t the best clearly!

 

[67L36Driver]

As stated above, they most definitely are through holes on the base that thread into the top end and hold the entire assembly into the case. The only difference you MAY find (I have not used a Meteor so I don't know for sure about that brand) is that the threads in the top end MAY be different then the OEM threads.

The original threads Stihl used are a corse pitch self tapping. The aftermarket cylinders come tapped for standard 6mm machine screw threads.

I avoid using the Stihl screws. Plus they can shake loose.

 

[anderson3754]

The original threads Stihl used are a corse pitch self tapping. The aftermarket cylinders come tapped for standard 6mm machine screw threads.

I avoid using the Stihl screws. Plus they can shake loose.

Interesting.... I'm learning something here. My cylinder is a Meteor it is not tapped, just drilled holes. My original plan was to tap for the OEM screws.
(What screws are you sourcing out as replacements.)
My OEM screws do not appear to be self tapping, and I tried to see if they would self tap a thread or 2 but stopped. The drilled hole to me is to small, and I'm fearful I would snap off a corner of the jug

 

[SteveSr]

Putting my MS290 back together with a meteor cylinder and piston big bore kit, this cylinder is not tapped for the 4 holes. What size tap is needed to tap the 4 cylinder base holes . My intent is to use the 4 OEM Stihl bolts. Looked for approx 45min and cannot find reference to this size tap.

Thanks

Just use the original screws to tap new threads! That's how Stihl does it! Do it on the saw to make sure that they go in straight.

 

[anderson3754]

Just use the original screws to tap new threads! That's how Stihl does it! Do it on the saw to make sure that they go in straight.

Are you sure on that. This seems like a very tight drilled hole to run those OEM screws into ??

 

[stihl86]

9075 478 4735
Pan head self-tapping screw IS-D6x52

That's the OEM screw. What the aftermarket cylinder uses, I don't know.
There is no tap. They are thread forming screws.
New screws have a wax like lube on them to aid installation.

 

[anderson3754]

9075 478 4735
Pan head self-tapping screw IS-D6x52

That's the OEM screw. What the aftermarket cylinder uses, I don't know.
There is no tap. They are thread forming screws.
New screws have a wax like lube on them to aid installation.

Thanks...... I'll go back to HL's site and see if I can get the correct screws/bolts for the Meteor Cylinder

 

[kuhndog]

Sent a PM but will post here. Because of failures on AM I got some Meteors. I just checked on my kits hole is bigger then OEM but metal must be harder than Stihl and I slightly enlarged and used original screws with Dirko .Have 2 kits left and left note to check muffler bolts and for loose impulse. Was a new mold and muffler bolts don't fit. Was bad grinding on saw. Also I reused bottom pan because new pan has 4 holes that run through the pan in the sealer path. David

 

[anderson3754]

Kuhndog thanks on the PM just read it. I'll check the items you mention.
I also thought about using the Stihl pan over feeling it was a better casting, we'll see.
This rebuild I started it last night, and my first attempt with a new cylinder. Do you recall the drill bit size you used to open up the cylinder holes ?

Regards

 

[kuhndog]

No I do not. I just held a bit up to screws to be under edges. And put muffler bolts in and try to mount up muffler, I had to grind. Enjoy.

 

[anderson3754]

Found it. For tapping a conventional 6mm hole the drill hole size is .19685 (.196-.197) I'll check with that drill bit size for clean up of the holes

 

[anderson3754]

No I do not. I just held a bit up to screws to be under edges. And put muffler bolts in and try to mount up muffler, I had to grind. Enjoy.

Oh......... I can see this is just going to be a whole bunch of fun. Now to find a 5mm drill bit to check the hole diameters.

 

[irhunter]

Kuhndog thanks on the PM just read it. I'll check the items you mention.
I also thought about using the Stihl pan over feeling it was a better casting, we'll see.
This rebuild I started it last night, and my first attempt with a new cylinder. Do you recall the drill bit size you used to open up the cylinder holes ?

Regards

Before I would start drilling...I would check with HL or Meteor to be sure you don't have a defective jug.

 

[SteveSr]

Oh......... I can see this is just going to be a whole bunch of fun. Now to find a 5mm drill bit to check the hole diameters.

I would also look up the DG screw thread specification. It may tell you the starting hole size for the original screws which you can verify (or not). This may provide a percentage of thread depth vs. starting hole diameter. Sort of like with regular taps.

 

[stihl86]

I took a quick look last night. Didn't find anything. The people who sell it should be able to tell you??
Again, the info I posted was for the Stihl part that goes into a Stihl saw.

 

[stihl86]

Thanks...... I'll go back to HL's site and see if I can get the correct screws/bolts for the Meteor Cylinder

This is the best option, IMO.

 

[anderson3754]

Found it. For tapping a conventional 6mm hole the drill hole size is .19685 (.196-.197) I'll check with that drill bit size for clean up of the holes

I would not use the above drill size of .196-.197 as a base line for these holes in the cylinder.
I made a couple of pin gauges this morning .224-.225-.226 . All 4 holes accepted .224. 1 hole just accepted .225 and 3 holes accepted .226 with one hole being hard push in fit at .226 . I accepted .226 as the nominal diameter. The OEM bolts measured .237 (.011thou ).
I placed the pan and cylinder assembly in the chassis put the bolts in through the bottom to keep the bolts aligned straight, then turned them in by hand with a T27 screw driver about 1/2 way in, 1/4 turn then backing off a 1/4 turn etc. Then used a 12 volt 1/4 inch impact driver slowly, till fully seated and it finished out nice and tight. Additionally I did use Bee's wax on the threads for a lubricant, but numerous substitutes would also work.

So with this Meteor Cylinder and the OEM Stihl bolts it worked just fine. Now to obtain a proper fit for the muffler bolts into there slots, their close but not quite right. Some minor fitting to get the bolts into slots correctly will be needed.