removing 348 barrel

[darren1967]

Hi all

I have removed my 348 cylinder head (think its a 76 ,Malcom Rathmel). Looking into the holes holding the barrel on cant make out what bolts are used ,they look like a allen bolt with a small torx fitting in the center of each bolt. Any ideas what tool I should be using.

Thanks in advance

[topcat]

Hi all

I have removed my 348 cylinder head (think its a 76 ,Malcom Rathmel). Looking into the holes holding the barrel on cant make out what bolts are used ,they look like a allen bolt with a small torx fitting in the center of each bolt. Any ideas what tool I should be using.

Thanks in advance

7mm allen key

[portman]

Hi all

I have removed my 348 cylinder head (think its a 76 ,Malcom Rathmel). Looking into the holes holding the barrel on cant make out what bolts are used ,they look like a allen bolt with a small torx fitting in the center of each bolt. Any ideas what tool I should be using.

Thanks in advance

They should be allen socket headed sleeve nuts, but you need a 7mm allen key/driver, which is not a popular size.

The torx "fitting" you can see is probably from how the nuts were forged should not perform any function.

Once you've got the nuts off there are some slim washers underneath which soemtimes lodge in the holes and can make life removing the barrel a trifle tricky.

[darren1967]

thanks both

[nh014]

Hi all

I have removed my 348 cylinder head (think its a 76 ,Malcom Rathmel). Looking into the holes holding the barrel on cant make out what bolts are used ,they look like a allen bolt with a small torx fitting in the center of each bolt. Any ideas what tool I should be using.

Thanks in advance

With due credit to John Haberbosch of Rocky Mountain Montesa ...

Sleeve Nuts

Beginning about 1968 engine designs changed. Up to this time most models had long studs that were used to retain both cylinder and head. These 10mm bolts were quite long. Due to expansion rates for the aluminum of the cylinder and head versus the steel stud the torque values on a cold engine were light. The engine casting was unable to handle much torque and would distort slightly and/or the stud would want to pull out. This torque value was 11 to 15 lbs. ft. To have a more secure fastening of the cylinder to the engine, shorter and thinner 8mm studs were fitted and the cylinders were modified to accept a sleeve nut.

This nut (part #3360.161) was sized to fit in the 11mm hole. To accommodate a tool one end was made to accept a 7mm Allen wrench. These sleeve nuts also have the torque of 11 to 15 lbs. ft. but they only have to hold the cylinder to the engine cases. They don

[dadof2]

Its a long time since I have done this and I thought the AF size was 9mm not 7mm but anyway the usual problem is rounding out of the socket in the screw. You can make this less lkely by grinding an oversize allen key down until it is a tight fit (has to be tapped into) the head of the screw. Then at the same time as applyying about 20 ft/lbs torque sharply strike the top of the allen key (copper face mallet) to send a shock through the thread.Repeat quite a few times.

Cheers

[darren1967]

thanks for the info.and I thought this was going to be simple