What Can I Do?

[JayP]

Hi guys, last weekend my outboard (K&B 8702 7.5cc) was running a bit weird. I noticed that 2 of the head bolts came loose, and a third bolt broke in half! Now I have a broken-off bolt stuck in the crankcase. The are no threads above the bolt inside, so I can't even use a shorter bolt. Any ideas as to my options? I really don't feel like buying a new case right now. Will the head seal with 5 bolts? I have no idea how the bolt broke. I haven't touched the bolts for some time, so the case of overtightening does not apply here. This is something that just happened on its own. Any ideas would be greatly appreciated......JayP

 

[Geraghty]

Hi guys, last weekend my outboard (K&B 8702 7.5cc) was running a bit weird. I noticed that 2 of the head bolts came loose, and a third bolt broke in half! Now I have a broken-off bolt stuck in the crankcase. The are no threads above the bolt inside, so I can't even use a shorter bolt. Any ideas as to my options? I really don't feel like buying a new case right now. Will the head seal with 5 bolts? I have no idea how the bolt broke. I haven't touched the bolts for some time, so the case of overtightening does not apply here. This is something that just happened on its own. Any ideas would be greatly appreciated......JayP

Is any of the cap screw shaft still sticking out of the crankcase?

 

[lohring]

If the bolt isn't corroded in and you didn't put it in with locktite, there are two ways to get it out that I know. Try centerpunching the screw then take a #43 drill in a drill press running backwards and see if the bolt unscrews. Otherwise take a thin disk in a Dremel and carefully slot the head. You may need to cut into the case. Then unscrew the bolt with a small screwdriver. If neither of these work try drilling out the screw with a #43 drill. If you can retap the thread you can still use the case. Otherwise. you need to helicoil the threads or get a new case. Doing the above things carefully is the secret to not wreaking the case.

Lohring Miller

 

[Bob Finn]

Find a shop buddy that can access an ELOX machine. They can burn that bolt(or tap) out and leave the threads intact. I've done it with broken taps a couple of times

 

[Brian Sorgente]

I've done this several times, just center punch the top of the bolt (give it a good punch) and you should be able to spin it out simply by spinning it out with a hobby knife or even with your fingers. Because the screw is being stretched holding the head in place, this wedges the threads in place upward, by punching it, this will break them loose, centering the threads again. so you should be able to spin it out efforlessly as long as the threads arent corroded very badly. If this doesnt work, I would drill a small hole in the center of the screw and buy a set of small screw extractors. They're cheap and work very good. Craftsman makes a good set. I would say drilling the bolt out would be a last resort but if you do, first off I'd use a left hand drill bit, and it better be sharp and straight through the center. Drilling hardend steel in aluminum can be a little sketchy, if the bit walks off the side or goes through the side of the bolt, its not gonna walk right out of the steel into the soft aluminum case.

Hope it works out for ya

Brian

 

[Mike Stewart]

Once you get it fixed, it's a good idea to loosen the head bolts a bit after you clean your engine to keep them from getting corroded into the case. "I haven't touched these bolt's for sometime" was probably the cause of your situation.

 

[Hurricane]

When putting you head bols or any blts back in I use Never Seize and then torque them with a torque wrench in a crossing pattern and that does away with the broken bolts.

Bob what is a ELOX machine?

 

[Chuck Spragg]

I have run the 7.5 k&b with one head bolt stripped with no leaking as a last resort though,

 

[Geraghty]

Once you get it fixed, it's a good idea to loosen the head bolts a bit after you clean your engine to keep them from getting corroded into the case. "I haven't touched these bolt's for sometime" was probably the cause of your situation.

Loosening head bolts,"especially K&B head bolts", after cleaning your motor will completely murder your piston and liner fit.

Everytime you loosen the head bolts on any motor but especially a K&B,you will be asking the piston and liner to break in all over again after you re-assemble.

I recommend that you never lift the head off any motor unless you absolutely have to.The service life of your piston and sleeve will be extended by a ton by leaving the head bolts where they areafter initial assembly.

A good torque wrench is a good idea.Even torque is a must if you want to keep the K&B liners round after re-assembly.If you don't use a torque wrench,not loosening the screws even becomes more important.

"DO NOT" use stainless steel fasteners.They are to soft and will not apply even torque without stretching.

A good grade of carbon steel cap screws are the best.

Treat your head bolts with Corrosion "X" and then assemble with a small amount of anti-seize.They can sit there for years and will still come apart very easily.

The thinner the liner flange at the top of the liner.the more the liner is going to distort when you tighten the head bolts.

Any of you that have run K&Bs for awhile know what I am talking about.When you tighten the head bolts the fit can totally away.

 

[Brad Christy]

Jay,

At one shop I used to work for, we regularly had to disassemble automotive components that had been through an evironmental simulator, exposing them to about ten years of corrosion in a matter of days. This is what we did:

Get ahold of a left handed drill of the appropriate size, C'punch what's left of the screw and carefully start drilling it out. at some point, you will most likely crack it loose and it will back out rapidly, leaving the threads intact. The customer liked this much better than when we initially drilled them out and installed Heli-Coils. Left handed drills are available from most of your industrial supply houses, including MSCdirect.com. Always use the same drill size you would use when drilling a new hole to be tapped.

Worked every time..........

Thanks. Brad.

Titan Racing omponents

BlackJack Hydros

 

[Bob Finn]

I was told that it was similar to an EDM. I didn't see it. He burned the tap out of the A356 casting and the threads were perfect. Saved a brand new homemade crankcase. He worked @ LTV Aerospace.