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1150 cam tower collapsed on #4 exhaust

Carter Turk

Carter Turk

Forum Sage
Charter Member
Was retorquing head bolts and checking valves, putting the cover back on, when two cover bolts kept spinning.
Cover back off helicoiled 2 cam towers, cover back on, last bolt was still spinning again.
Thought about running to see if oil would weep through or not.
Decided to take it off a third time and found three large chunks of the cam tower thread had crumbled off.
Probably all my fault, maybe the depth of coil was too high or I forgot to knock out the tang.

If these things are line bored from the factory, I can't just buy one tower can I ?
It's the small 2 bolt on the end of #4 exhaust, think it has the "D" triangle stamp on it.
Sorry no pictures, but I managed to get another coil in there deep enough for the coil not to have any exposed threads.
I got the shouldered cover bolt to snug down without spinning, but not to 96 in.lbs like the others.

Note this not the part of the tower holding down the cams, but the threads on top to hold the cover on.

Would it be possible to buy one used cam tower and run it? Thanks for any comments
 
Carter Turk said:
Was retorquing head bolts and checking valves, putting the cover back on, when two cover bolts kept spinning.
Cover back off helicoiled 2 cam towers, cover back on, last bolt was still spinning again.
Thought about running to see if oil would weep through or not.
Decided to take it off a third time and found three large chunks of the cam tower thread had crumbled off.
Probably all my fault, maybe the depth of coil was too high or I forgot to knock out the tang.

If these things are line bored from the factory, I can't just buy one tower can I ?
It's the small 2 bolt on the end of #4 exhaust, think it has the "D" triangle stamp on it.
Sorry no pictures, but I managed to get another coil in there deep enough for the coil not to have any exposed threads.
I got the shouldered cover bolt to snug down without spinning, but not to 96 in.lbs like the others.

Note this not the part of the tower holding down the cams, but the threads on top to hold the cover on.

Would it be possible to buy one used cam tower and run it? Thanks for any comments
Click to expand...

I think if you can find one at a decent price it's worth a try. So is having the hole welded shut and re-tapped although that may warp it as well. Tale it down to the local automotive machine shop and see what they say. My feeling is that if the cam still turns freely with the cap torqued down you are good.
 
I wouldn't try to weld it, without it bolted it down. even then....?
Drill and tap to a larger size then then plug it with an aluminum plug then drill and tap the plug to 7mm. (or helicoil the plug right off the bat if there is enough material) I've done that sort of thing before, I used a NPT thread on the plug and hole I thought the tapered thread would hold better, I put threadlocker on as well, it seems to work.
Is there enough material to use a Wurth Timesert? (basically what I am describing)

If you can source a used replacement it's probably worth a try, compare it closely to the old one and check for clearance with plasti-gauge. fixing the old one would be my preference.
 
Thanks for replies, this head has a ton of miles, the cams have seen better days, so I thought maybe a used tower would suffice, If I can find it or maybe a 1100 one.
 
Carter, you can also use the cam caps from an 83 750 or the 85 700. Same caps. 1100 caps do t have the threaded bung on top. Then just get a flex hone ball hone to fit that new cap.
Ray.
 
I unashamedly used three caps
from an alternate head on my bike about 20000 kms ago
no visible wear or performance problems.

Whats the wear range on these things anyway? One assumes that the cams and the holes wear evenly but do they?
 
rapidray said:
Carter, you can also use the cam caps from an 83 750 or the 85 700. Same caps. 1100 caps do t have the threaded bung on top. Then just get a flex hone ball hone to fit that new cap.
Ray.
Click to expand...

Thanks for the tip Ray.

Would the hone ball be twirled around on the base journal and cap with exhaust cam out or just the cap?
 
With the cap bolted & torqued on the head. Pull the rockers & install the cam & new cap first to see if it rotates freely without needing honed.
Ray.
 
Went on a 70 mile loop the other day and no oil is weeping through cap.
I would like to find another tower eventually.
 
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