repair threads in MS290 plastic crank case

[Stihlofadeal64]

Repairing a clamshell 029 super. The crank case is plastic and after getting everything repaired and in the process of reassembly I discovered the previous person who has worked on this saw evidently stripped out the holes for the coil body mount. Since the crank case is plastic what are the best options for repairing this area.

I thought of drilling and tapping and putting a metal insert in, but was not sure that would hold. I would probably have to super glue the insert in to get it to remain. It seems I saw a thread years ago where there were inserts that you could use to repair plastic applications like this that were very sturdy and durable over the long term. Thanks in advance for your help.

 

[Whiskers]

Just get an epoxy fill the hole drill it out slightly smaller than the screw. The screw will make its own threads.

 

[Stihlofadeal64]

Just get an epoxy fill the hole drill it out slightly smaller than the screw. The screw will make its own threads.

Could you recommend an epoxy, I'm not familiar with what would be best for this application. Thanks so much!

 

[Big_Wood]

An epoxy would have to be pretty tough to hold up in that application. JB would not work. About the closest thing I can think of is marine Tex but even that I'm not sure. Have you ever worked on the smaller poulan/huskies like a 240? For the top cover screws the plastic case has inserts that are course threaded on the outside for the plastic and fine thread for a 5mmx 0.8mm bolt on inside. Best option for you otherwise use bigger bolts.

 

[Whiskers]

I believe I used this stuff last time and it worked pretty well.

 

[Whiskers]

It wasn't in that location though, it was where an av mount attaches. I suppose it could be different here having to torque it down.

 

[grizz55chev]

It wasn't in that location though, it was where an av mount attaches. I suppose it could be different here having to torque it down.

Trusting an epoxy in a critical area is not a reliable fix. Some people have used the method of melting plastic into the hole and retreading but in the case of a coil mounting would suggest a metal insert. I have also used a zip tie inserted into the stripped thread and retread the screw into the hole for a quick fix. Good luck !

 

[tickhound93]

I've used the zip tie method, it works.

 

[RiverRat2]

Belzona 1111 Super metal epoxy will work....

Engineering grade repair system.

A two-component paste grade system based on a silicon steel alloy blended with high molecular weight reactive polymers and oligomers. When cured, the material is durable yet fully machinable . the rear Motor mount bolt up connection point on my work cars transmission is held in by it has been for 5 years.



Applications include.

Shafts
• Hydraulic rams
• Bearing housings
• Keyways
• Engine blocks
• Casings
• Pipes
• Tanks
• Flange faces



you must clean the area then abrade the application surface, mix the epoxy per direction, let it cure about 4-6 hrs . when cured to ambient it is fully machinable ( a zip tie would be much cheaper) Send me your shipping addy via PM and I will send you enough to fix your coil mount

Compressive Strength:
Tested per ASTM D695
914 kg/cm2 (13,000 psi)
when ambient cured

 

[fearofpavement]

In that situation, I just put in a few strands of copper wire the length of the hole's depth. How many strands depends on how stripped out it is. I don't often encounter stripped holes on this series, more often on the 1128 series.

 

[Chris-PA]

It's not loaded like a bar stud, but I just put 6 5mm x 0.8 helicoils in my Craftsman/Poulan case. The 4 recoil screws and the 2 coil mounting screws had stripped out from repeated disassembly. It worked great and the inserts show no signs of spinning.

 

[Stihlofadeal64]

All good information -- keep the cards and letters coming!

 

[a. palmer jr.]

A Helicoil might work in that situation but you might have to change the mounting bolt to regular threads and then glue the Helicoil in.

 

[Definitive Dave]

they sell a slightly oversized bad stud for repairing this

Use over sized bar stud
1127 664 2410 front bar stud on MS 290/310/390
For back bar stud you must use helicoil because the stud goes into engine pan


1123 664 2405 front and back oversized bar stud for:
MSE140C, MSA160C, 017/018, MS170/171/180/181, 019,
MS191/192, 021/023/025, MS210/230/250/251


9795 003 0840 converts damaged 4mm DG threads to
4mm machine thread

9795 003 0353 converts damaged 5mm DG threads to
5mm machine thread

 

[a. palmer jr.]

Dave, I think the one he wants to repair is the one that holds the coil on if I read it correctly. A slightly oversize bolt might work if he drilled out the coil frame also.

 

[Chris-PA]

Given the way the helicoil is made, the insert is a spring and the kit contains a tool that essentially stretches the coil to a smaller diameter for installation (using the tab that you break off afterwards). Once you remove the tool it expands, and I think it would be near impossible to get back out without melting the case or some such.

I ordered a box of 5mm cap screws from McMaster-Carr and will be using this method to repair/replace stripped plastic thread screws. I also did the carb support mount on my Earthquake this way. It's nice having fine thread machine screws going into steel threaded inserts rather than the coarse thread cutting plastic screws - especially for screws on parts like the recoil cover that is removed often.