HELP! cooling head screw stripped on an O.S. Engine

tallcracker · #1 01-05-2003, 11:04 AM

my friend has an O.S. .21 engine, i am not sure what model but he has the blue cooling head. the other day he was rebuilding it when he found that one of his screws that mounts the cooling head was completely stripped. he tried going to the hobby shop and getting longer screws to bite the treads below that possibly were not stripped but that didnt work. we are now considering a few options, and i wanted every 1's opinion.

1. To drill and tap out a larger hole and just buy a larger screw

2. try and find a much longer screw, then drill in the good metal below the stripped threads and tap those out with the original threads and just use a longer screw but of the same size and let it bite into the now new threads.

we had considered using something like J.B. weld and putting that in the hole then drilling and tapping that out, but we havent had any real experience with that product and i wasnt sure the metal would be srong enought to support the torq placed on those screws.

i am sure other options are out there, please tell me anything that you think will work. please respond i want to get every 1's opinion. i feel that we have 1 good shot to get this right and i dont wanna screw up an expensive O.S. engine.
thanks guys

Nitromatt · #2 01-05-2003, 11:52 AM

drill it out. Even if you mess up the head its not worse then messing up the whole case.

Pro3/nmt105 · #3 01-05-2003, 12:31 PM

the only solution without any flaws would be buying a new crank case which run about 50 to 70 bux. if u drill deeper into the crankcase u will weaken i alot and if u tap the holes and put in larger screws chances are it wont line up just right and cause problems. I dont think that Jb weld will be able to thake the high temperatures but i dont know for sure.

BurnsDX · #4 01-05-2003, 12:33 PM

I would put in a Heli coil. You can stack them up to get more treads. A Heli coil kit is a little expensive but they work awesome.

ExtremeMT · #5 01-05-2003, 12:51 PM

Do this, craftsman has a drill kit that is made for stripped screws, borrow one or buy one, put it in a drill and put it on the torque setting and set the engine on a table or something, have a friend to hold it in place with all his strengh, use alot of force and push the bit on the screw really hard and start the drill very slowly and it should come out, if it doesnt get a drill bit thats really small or a dremmel and try to cut the head of the screw off, then take the cooling head off and you have the screw sticking up out of the crank case, gets some plyers and turn it out. Hope this helps.

Nitromatt · #6 01-05-2003, 01:25 PM

oops I read your post wrong here is what you do. This happens to me all the time. get drill and a bit the same size as the screw head then drill directly in the center of the screw when you reach the shaft of the screw it will pop of the head then. take off the head and take a pair of pliers and twist out the shaft of the screw no damage done.

tallcracker · #7 01-05-2003, 01:53 PM

hey guys thanks for the replies. i think i may not have stated my problem very clearly, sorry. we can get the screw out of the engine no problem, but when we try and use the screw to tighten down the head the treads are stripped in the crankcase. so the screw is not locked into the hole, the threads on the crankcase are stripped out and the screw cannot get enough bite to secure the head.

tallcracker · #8 01-05-2003, 01:55 PM

can some 1 explain to me what a heli coil is? maybe that ois the answer to my problems, but i dont know anything about them.

hpi#1 · #9 01-05-2003, 02:07 PM

or u could use a dremel to cut off the heade. then use the dremel to cut a slot in each screw. than use a flat head screw driver to unscrew them.

associatedGTguy · #10 01-05-2003, 02:15 PM

besides getting another case i would drill out the hole and the head and retap the threads in the crank case to the next size bigger ..then get a screw that will fit

JFawwaz · #11 01-05-2003, 02:17 PM

so you have no problem getting the screw in or out you just cant tighten it because its stripped?

buy new screws

JFawwaz · #12 01-05-2003, 02:17 PM

so you have no problem getting the screw in or out you just cant tighten it because its stripped?

buy new screws

NitroSafari · #13 01-05-2003, 02:44 PM

Your gona have 2 drill out the hole to remove wots left of the old thread with a drill bit that about the same size as the hole then retap it ud hav 2 find a slightly larger screw thats gona fit the thread though thats all i can suggest hope yhis helps

JIM

Nitromatt · #14 01-05-2003, 03:01 PM

disregard what I said I guess I am blind.

NitroSafari · #15 01-05-2003, 03:10 PM

Quote:

Originally posted by tallcracker
hey guys thanks for the replies. i think i may not have stated my problem very clearly, sorry. we can get the screw out of the engine no problem, but when we try and use the screw to tighten down the head the treads are stripped in the crankcase. so the screw is not locked into the hole, the threads on the crankcase are stripped out and the screw cannot get enough bite to secure the head.

JIM

asc · #16 01-05-2003, 08:52 PM

Tallcracker,

A heli coil (helical coil) is a spring like device that restores - so to speak- threads that have been stripped out. They are often used in automobile and motorcycle engines and transmissions that have stripped threads in their aluminum housings. I don't know if a kit is available for a screw that small. The stripped hole is bored out to the size of the outside of the heli coil and the heli coil is screwed in. The inside of the heli coil then becomes the new threads for the original screw.

If it were my engine, I would get a drill and tap for the next size up from that screw. I believe O.S. engine screws are 2.5 mm. I'd go with a 3 mm that included a drill, tap, and cap screw. You would probably need another drill to drill out the hole in the cylinder head that will accept the larger capscrew. Good luck.