Retaped Head studs to 3/8" But still more problems!

Discussion in 'General Questions' started by SEGACDX, Jun 24, 2016.


    SEGACDX Member

    Geez It's like waking up on a bed of spikes with these engines. nothing is ever good enough for these picky little things!

    So as you know I've retapped to 3/8" from 8mm because of stripped threads, I happen to have the stupid 1.00 M8 studs which it just great because no one carries heli coils in that size. So I said fuck it! They sell 3/8 rod, they got 3/8" taps, they got 3/8" heat nuts, they have it all here at princess auto!

    But as usual nothing is ever simple, I knew I had to drill out my head and cylinder to fit and so I did with my drill press. What a "fun" time that was my 3/8's drill bit was all bent up after but it was the biggest one I had.

    It seems like china need to go back to engineering school because the stud holes are unevenly placed making it very hard to put the cylinder on and the head, I ended up cracking two fins and having to WB weld them to keep them from cracking any more. I have to use a mallet and a rubber wrench handle to get it on by hammering the center of the cylinder where the gasket goes.

    I recently rebuilt my engine AGAIN with new gaskets because this crank it to wide for the case and without a crank case gasket it rubs and makes lots of heat nothing like my old GT5 which was great up until the ring bearing on the crank exploded, I had to replace a bearing on one side it looked like it got no oil while the other was saturated in oil I have never seen that before, the thing was black and sooty.

    Anyways I noticed cracks on two side of the studs in the crankcase so I have patched them up with High temp putty for now, I also noticed small holes in places where the drill must have gone to far but form the looks of it they didn't macine it right to begin with so I patched it with high temp putty as well, but my god worst engine I have ever had so far nothing but bullshit and problems from the start.

    I want to know if anyone else has retapped and what they have done to make things go more smoothly.

  2. 45u

    45u Active Member

    How are you stripping the cases are you over torquing the head nuts? When ever I get a new engine one of the things I do is take the motor completely apart as every one I have done I found a LOT of grit and trash in the including the Grubee GT5A. One of the things I do is in the case where the cylinder studs go is make sure the holes are taped all the way to the bottom using a bottom tap. Then I thread lock the studs in the case. If I where to srtip one I would not over size I would put a thread insert in like a Heilcoil and put back it back to stock size. So far I have never stripped one as I torque my head nuts to proper torque.

    SEGACDX Member

    It is odd isn't it? This engine is the only one I have ever done this on, but it was both on the same side. I think they fucked up the threads on that side because the other side was solid.

    I would have helicoiled but I had M8 1.00 studs not the 1.25, so I would have to get some new head studs and I just wasn't having that and the helicoils where expensive.

    Next time I won't have this problem I am sure this engine is just a bad one.
  4. 45u

    45u Active Member

    I bought a 2 sets of NEW case with all hardware and side covers for $30 so I have plenty of spare case and always keep many spare parts around. I hate having to wait on parts! Like I said I always check the stud holes on every motor I do and make sure the thread are good and all the way to the bottom of the hole. I do the same for my motorcycle being it is my only transportation besides my motor bike. Helicoil kit are available for 8mm x 1.00. I have much money in my tools, machines, heilcoil kits and much more as I have been wrenching for well over 45 years and much of the time as a living. I have more in just hand tool and special tools not counting my machines and so on then I do this and I have a lot in my daily ride. I never rig anything I always have the correct tool and if not I buy it.

    Last edited: Jun 26, 2016
  5. crassius

    crassius Well-Known Member

    on a side note about your drill bits failing - several friends have called lately about that - seems chinese steel is getting to be a real problem in tools as well as in these bikes
  6. HeadSmess

    HeadSmess Well-Known Member

    its aluminium? how the $%^ do you bend a 3/8 drill drilling aluminium?

    you know they come already pretwisted? its why they call em "twist drills" :D

    rather than bagging out the asian engineers, from the sounds of it i think someone else should go back to engineering school...

    lets see now...

    what did you expect to happen after removing the crankcase gasket?

    that also changes the stud position, slightly. but hey, hammers fix all problems, huh?

    sometimes a good engine is purchased by a bad owner... maybe just as often as a bad engine is purchased by a good owner...

    poor lil china girl :(
  7. Nanonevol

    Nanonevol Member

    You need a metric hammer otherwise you'll strip it.

    SEGACDX Member

    I used my drill press and I think the bit got bent getting stuck after a lock up but it also could have been bent before hand, yes I used lots of cutting lube and made sure to let the chips break out and come up the bit, I also used air to clean the chips out every so often.

    What I expected was for it to be made the same or even similar to my old GT5 that game me many years of good service. The problem is not that the gasket keeps it from rubbing it the fact I got a badly machined engine. I've used RTV on my old engine many times as gaskets and they worked better than anything else. I've replaced the gaskets now but I still have the same rubbing problem.

    I'd still say the chinese quality control is abysmal we all know that but I am just sick of it honestly.

    This is not my first engine not by a long shot, but this was just a bad engine from the start. It was picked up for cheap mostly new not used used for long but missing a few parts.

    I do not feel bad for this engine one bit but it would have been nice if it would have been as good as the first crappy engine I got from gas bike many years ago.

    SEGACDX Member

    When you live in Canada everything is metric, it what we do best bud. ;)

    SEGACDX Member

    I just don't get it, why do the chinese well they need to not only make shit that doesn't work but shit that doesn't work for a high price. Everywhere seems to have tools made in china and they are not cheap like you would think sometimes as much a good quality tools just because they have a fancy label but that's what we get I guess.
  11. James L

    James L Member

    I didn't retap head studs, but I retapped my rear motor mount hole. I broke a threaded rod, I tried left hand bits no go.

    So I drilled out the remaining threaded rod. I don't have expensive tools and am not going to buy any lol. I took a 6mm bolt and 2 cycle oil and rethreaded the hole with it. The threaded rod is holding 10x better then the original hole. The threaded rod has not have me any issues since.

    I have rode close to 100 miles in 2 days and am so happy now. Oh I used a 13/64 drill bit, a 6mm bolt and a ratchet.

    SEGACDX Member

    I'm glad it ended up working out for you. I had a thread on my first engine cylinder on the intake side strip out, I used a trick with wire wool to keep it in place, you just pack some in to hold it in by friction temporarily. You can also use JB weld High heat since it's not a high torque stud. Somehow it ended up not coming out ever again so I got lucky.