Stud pulled out during top end replacement

[Jes_KX5]

I recently replaced the top end. When putting the cylinder back in, I noticed that one of the four studs felt weird when I was putting the nut on it. I rode anyway  and later noticed that it was leaking at the base gasket. I went to tighten the nut and the stud pulled out of the crank case.

How should I go about fixing this problem? I am thinking tapping the crank case hole to M12. Then spinning an M12 bolt on a lathe so that I can cut the upper part of it with an M10 die. This would save me the trouble of drilling the stud hole in the cylinder to 12mm. I would appreciate any other suggestions. Thanks.

[KXcam22]

Jes,
  Your are lucky (or observant) that you noiced it right away. Your way would work but an M10 helicoil might be the easiest fix.  Cam.

[5dracing]

Jes,

I used to race offroad in the buggies. I've fixed a similar problem on an air cooled VW head. A VW shop that carries aftermarket parts may have the exact bolt you want to make. I'm not sure if the length would be correct, but it might be worth checking. Teh stud I replaced was the exhaust bolt.

[Jes_KX5]

Thanks for the info.

Cam, where could I buy or order a Helicoil that I could have by this weekend?

[hughes]

Try your local auto parts stores for the heli-coils.

[mikesmith]

Or go with a timesert,helicoil works as mentioned to.

[John]

Jes,

It would be more expensive to buy the kit and do it yourself than to leave it to a workshop. Most car workshops have the tools to do this. Ask around at your local shops.

//John

[Brett]

Yep a helicoil or recoil would de the best option or worst case (generally after these options have also failed) you could loctite a press fit aluminium sleeve with the M10 thread in it.  Interesting note on helicoils did you know that using them for repair of spark plug thread you should use a colder plug due to bad heat transfer through them. ie change from NGK B8EGV to B85EGV

[KXcam22]

John is right. It would be cheaper to let a shop put in the helicoil.  I bit the bullet along time ago and bought a full metric helicoil kit - I have had it forever.  I worship it as it has saved me many, many times (my threads only seem to pull out at 2am with a big ride the next morning). Cam.

[gowen]

Yes, it is alot cheaper to have a dealer repair this, I also just bit the bullet a few weeks back on a metric set, due to stripping alot of bolts and it adds up. But just for one repair, the cost is next to nothing compared to buying your own set.

[demographic]

Interesting note on helicoils did you know that using them for repair of spark plug thread you should use a colder plug due to bad heat transfer through them. ie change from NGK B8EGV to B85EGV

That is an interesting point, I will remember that one.

Makes sense to me though

[hughes]

Yep a helicoil or recoil would de the best option or worst case (generally after these options have also failed) you could loctite a press fit aluminium sleeve with the M10 thread in it.  Interesting note on helicoils did you know that using them for repair of spark plug thread you should use a colder plug due to bad heat transfer through them. ie change from NGK B8EGV to B85EGV

Brett, Both of your plugs listed bove have the same heat range or am I wrong but both plug have an 8 for heat range.

The B is for thread diameter.

The 8 Heat rating.

The E is for thread reach

The GV is for racing plug. Elctrode is made of precious metals.

Your second plug numbers doesn't look right. B85EGV. Double check.

[Brett]

hughes the plug heat range i refer to is a half increment heat range ie from hot to cold series goes 8, 85, 9, 95, 10, 105.  In australia i have raced twostroke gokarts for about ten years and we only ever used either of the following : B#EGV or B#EV in racing.  Worst case you may have to buy a B#ES if that is all available.  Sparkplugs rarely ever die just get wet/fouled nothing that a bit of contact clean cant fix.  Depending on whether the motor we were using was air cooled or water cooled and how much power we were putting out would determine which heat range we would use.  In the case of KX500 i reckon an 8 heat range plug is perfect as the motors don't rev stuffall and often are off the throttle (to get the front wheel down) and i am sure the power output versus the capacity (specific power) is quite low compared to modern 125's and 250's.  Anyway you can buy buy ngk plugs that go up in half heatranges, here i haven't seen any bike shops that stock them but nearly allgokart shops do.

[hughes]

That's cool I never even though about that but after some reseach on the internet I found some info about heat ranges in half increments. Just never heard of them or saw anybody running them. I guess we have them in the U.S.A.