Scary new problem

[goatman123]

In an attempt to track down any vacuum leaks, I was changing out the o-rings that go between the carb manifolds and the head. The outer screw on the left front carb boot had metal shavings on it as it came out. I am not sure if this is from a previous attempt at a repair and it is part of a helicoil coming out, or if it was just tightened too much and stripped some of the aluminum from the head. Anyhow, it will not tighten up now, and leaks oil profusely on start up. I also worry that some of this metal got into the engine since this is in an oil galley. Does anyone have a suggested way to repair this? Can I tap it out to the next size up? Help!

[dingy]

The screw on the outer right front head, and the outer left rear head for the intakes are a tad different than the other 6.

 

These two are drilled through the head and into the cavity that the head bolt is in. See the picture, arrow points to where it is at. 2nd picture somewhat shows alignment of this hole.

 

If at some point someone put too long of a screw in this hole it could possibly hit the head bolt and be the source of the shavings.

 

The cap screws into these two holes should be 16mm long, the other 6 are 20mm long. You need to put some black permatex (or similar on the threads of these two screws to get them to seal.

 

As far as the shavings go, the oil filter will hopefully do its job and get those very few shavings out. With the way the oil sump is on these bikes, all of the oil will not drain out on a change, so an oil change, while it will make you feel better, will do little good for this.

 

Gary

[goatman123]

Thanks for the reply. I do have the shorter screws in the correct holes, but my main problem now is that the hole is stripped out, the bolt no longer tightens up but just keeps turning.

[MasterGuns]

I had the same problem on the first motor that was in this 86 I ride. I have since then replaced the original motor with an 89. But, like I said I had this identical issue with the same lower bolt on #2 manifold....vacuum leak and a stripped out manifold bolt. I was able to solve the problem by installing another bolt about 3/8 to an 1/2 inch longer than the orginal bolt. First thing I did when considering this as an option was to measure the depth of the hole tapped into the side of the head. To my surprise it was a lot deeper than the original bolt length. So all I did was run a tap down to that depth just to make sure the threads were straight and installed the longer bolt. Was able to tighten it up enough. Worked out for me and no more vacuum leak either.

 

The original motor developed a wrist pin knock after running the bike to Dog Patch Arkansas over 90 mph for a prolonged period of time....trying to dodge thunderstorms.. Rather than address the wrist pin issue, I just installed another complete motor.

 

Just my experience.

[goatman123]

Is it possible though, that a longer bolt would obstruct the flow of the oil? I did screw in one of the longer bolts and it too won't tighten down. Does anyone see a problem with tapping the hole larger and getting a larger diameter screw? I am afraid to go longer and just tap the hole deeper but the factory size, because there has to be some reason they made that screw shorter. Seems either a helicoil (I have no experience using that) or tapping a larger diameter hole.

[Condor]

Thanks for the reply. I do have the shorter screws in the correct holes, but my main problem now is that the hole is stripped out, the bolt no longer tightens up but just keeps turning.

 

Sounds like you've pulled out the helicoil you put in the last time.... It might not have fit perfectly in the threads you taped. You could drill out the hole a bit and install another. Even in SAE. Maybe 1/4x20??

Another thought... You might try using J-B weld around the original 6mm screw. If the inside walls of the hole are rough it may allow enough bite to snug down on the screw a bit after it sets?? Most of these 6mm hex caps say 10ftlbs of torque... which is about a little over hand snug.

[dingy]

The reason these two screws are shorter is that if the head is removed with the intakes still atached, the sholder of the head bolt can not pass the longer screw that is now encroaching into the head bolt cavity. This I know from first hand experience.

If you have stripped it, your options are limited. Helicoil probably being 1st, 2nd drill # tap next size up, be it SAE or metric, with this option you need to have a clean hole no larger than the minor dia. of the thread you opt for. My last choice would be J&B weld. I have seen this stuff work, and not work.

At a minimum, valve cover will need to come off to clean out head bolt cavity off drill & tap chips.

Gary

[MasterGuns]

I had the same problem on the first motor that was in this 86 I ride. I have since then replaced the original motor with an 89. But, like I said I had this identical issue with the same lower bolt on #2 manifold....vacuum leak and a stripped out manifold bolt. I was able to solve the problem by installing another bolt about 3/8 to an 1/2 inch longer than the orginal bolt. First thing I did when considering this as an option was to measure the depth of the hole tapped into the side of the head. To my surprise it was a lot deeper than the original bolt length. So all I did was run a tap down to that depth just to make sure the threads were straight and installed the longer bolt. Was able to tighten it up enough. Worked out for me and no more vacuum leak either.

 

The original motor developed a wrist pin knock after running the bike to Dog Patch Arkansas over 90 mph for a prolonged period of time....trying to dodge thunderstorms.. Rather than address the wrist pin issue, I just installed another complete motor.

 

Just my experience.

 

Didn't know the hole had been retapped and a heli-coil used.

[goatman123]

The bike is new to me, I have not done any drilling or tapping, but maybe PO did, or maybe he just tightened it too much and stripped the aluminum, not sure. Thanks for the replies.

[goatman123]

Just wanted to give an update on this. I went with MasterGuns solution and tapped the hole deeper but the same size (M6 1.0) and got a longer screw. It tightened down, and I used some permatex on the screw, so hopefully when running again it won't leak. I used the 20% off coupon at harbor freight, and got a 40 piece tap and die set for $9.80! Not the best quality I'm sure, but for my limited use of it, a great deal. Thanks for the help.