Help is my Cylinder RUINED or NOT?

[ResetBTTN]

Many of us have had to rethread the cylinder holes or studs for the exhaust. Here's my nightmare.

Originally I rethreaded both holes to 7mm and that only lasted a little while. The left hole is now an 8mm. The right hole was good until I went to tighten them both back down and there she goes too...stripped. So I tore it apart again to turn it into an 8mm also. Something went wrong and ended up with the crater you see here.
I've searched the forum for repair options and I went with the heli coil repair. I bought the 3/8 16 repair kit and drilled the hole out with a 5/16 drill according to this chart http://www.newmantools.com/tapdrill.htm
Oh I must mention the reason I went with that size is because I was rethreading and tried to hurry the process with a drill. I ended up boring it out completely.

What I'm left with is a huge hole that I believe has ruined my cylinder. Is there any room for repair or should I cut my loss and get a new one?

 

[Desert Rat]

Many of us have had to rethread the cylinder holes or studs for the exhaust. Here's my nightmare.

Originally I rethreaded both holes to 7mm and that only lasted a little while. The left hole is now an 8mm. The right hole was good until I went to tighten them both back down and there she goes too...stripped. So I tore it apart again to turn it into an 8mm also. Something went wrong and ended up with the crater you see here.
I've searched the forum for repair options and I went with the heli coil repair. I bought the 3/8 16 repair kit and drilled the hole out with a 5/16 drill according to this chart http://www.newmantools.com/tapdrill.htm
Oh I must mention the reason I went with that size is because I was rethreading and tried to hurry the process with a drill. I ended up boring it out completely.

What I'm left with is a huge hole that I believe has ruined my cylinder. Is there any room for repair or should I cut my loss and get a new one?

Before tossing it, I would try to tap it any size and fill with jb weld and retap

 

[Kioshk]

I second a JB Weld solution, only don't bother remapping; just put the stud in there with the goop.

 

[Desert Rat]

I second a JB Weld solution, only don't bother remapping; just put the stud in there with the goop.

tapping it whatever size 1/4-20 etc. the threads give the JB something to grip
against then re drill and tap
gooping it in there will result in later failure
which you don't want! it'll just pull out prematurely LOL

 

[bairdco]

i'd just jb weld a new stud in.


then, while waiting for it to dry, order a new jug. they're cheap.

 

[ResetBTTN]

i'd just jb weld a new stud in.


then, while waiting for it to dry, order a new jug. they're cheap.

Thanks for all the suggestions so it seems like JB welding it is the next step. Bairdco what do you mean by order a new jug?

 

[maniac57]

JB weld will not hold very long in this application.
Order a new jug.
Using a stud that big will interfere with the exhaust pipe and will not tighten up since the nut will be rubbing the pipe.
Live and learn. I would also replace the stock studs with higher grade studs since you have to order a jug anyway.
Don't panic though, replacement cylinders are relatively cheap.

 

[bairdco]

exactly what he said above...

jb weld might last you a few days, but it'll eventually pull out. for some weird reason, nothing sticks to these engines, except dirt.

jb weld can probably keep you riding until you get a new jug. i'd make sure you have some kind of bracket or strap to hold your pipe to the frame, too.

 

[agcat111]

Re: I come ome from work and...slience on the forum

I come home from work..looking forward to reading some good stuff and apparently everyone went to bed?

 

[agcat111]

One of the problems might be the opoor quality of the metal holdong the studs?

 

[maniac57]

Take your pick:
Poor quality materials
Poor quality control during assembly
Poor assembly
These engines are made of recycled gum wrappers and the steel is cheese hardened.
Seriously, most problems like this start with vibration loosening the stud which allows the threads to get chewed up. The best way to prevent further issues like this would be to replace the stock kit hardware with better quality parts and learn to look the bike over EVERY ride for loose bolts and vibration related problems. My personal bike has been tight and trouble free for over a year now with several thousand miles on it without a single engine problem. I had to tighten everything for the first few weeks until everything settled into place and has been trouble free since.
I'd guess 75% of the issues people have with these little Asian gems are caused by improper maintenance. I have NEVER had as many failures as I read about here, so my maintenance process seems to be the difference between my experience and the nightmares I read about so much. Keep in mind, these engines are NOT meant to keep up with traffic or run for years without work.
Treat them correctly and you will have years of fun!
Expect too much and you will be disappointed.

 

[biknut]

JB weld won't work, it can't handle the heat. It's pretty much time for a new cylinder.

Next question, what kind of cylinder do you have?

What kind of cylinder are they selling you? (Whoever)

Are they the same?

 

[ResetBTTN]

Take your pick:
Poor quality materials
Poor quality control during assembly
Poor assembly
These engines are made of recycled gum wrappers and the steel is cheese hardened.
Seriously, most problems like this start with vibration loosening the stud which allows the threads to get chewed up. The best way to prevent further issues like this would be to replace the stock kit hardware with better quality parts and learn to look the bike over EVERY ride for loose bolts and vibration related problems. My personal bike has been tight and trouble free for over a year now with several thousand miles on it without a single engine problem. I had to tighten everything for the first few weeks until everything settled into place and has been trouble free since.
I'd guess 75% of the issues people have with these little Asian gems are caused by improper maintenance. I have NEVER had as many failures as I read about here, so my maintenance process seems to be the difference between my experience and the nightmares I read about so much. Keep in mind, these engines are NOT meant to keep up with traffic or run for years without work.
Treat them correctly and you will have years of fun!
Expect too much and you will be disappointed.

Thanks for the rambling rambler but it just seems like you have some animosity towards the Chinese lol. Hey that's my bread and butter and maintenance upkeep happened after every ride. And I'm something like a perfectionist so I made sure I took care of mine. Tighten these and make sure those are tightened too after every shutoff.
So don't assume I just ran it into the ground and thought it would break buckle or burn then just fix itself. I'm still on my break in stage so I haven't even pushed it to wide open yet.
I don't mind a little trial and error..it builds knowledge for the next trial and makes for conversation pieces.
So thanks for the suggestion but hit the back space on those assumptions.
Happy riding rider.

 

[ResetBTTN]

JB weld won't work, it can't handle the heat. It's pretty much time for a new cylinder.

Next question, what kind of cylinder do you have?

What kind of cylinder are they selling you? (Whoever)

Are they the same?

I bought the kit from pedalchopper.com; a trust worthy source and I've done plenty of business with Jim there before and after the build.
It's a 66/80cc Skyhawk Grubee GT5

I haven't looked into JB welding it because after looking at it more its jus a temporary fix...who wants that. So this newbie is gonna get a new one and lock it in the first time with some thread lock.

 

[biknut]

I bought the kit from pedalchopper.com; a trust worthy source and I've done plenty of business with Jim there before and after the build.
It's a 66/80cc Skyhawk Grubee GT5

I haven't looked into JB welding it because after looking at it more its jus a temporary fix...who wants that. So this newbie is gonna get a new one and lock it in the first time with some thread lock.

A SkyHawk cylinder is different all the others.

I've had one exhaust stud strip. The best was to fit it is with a 6mm helicoil. That will be stronger than stock. Any other repair is questionable.

 

[biknut]

SkyHawks aren't really the best motors. Get a Flying Horse. They have japanese bearings, and the pistons are lighter.

 

[ResetBTTN]

Yea that's why I'm hunting the google pages for an exact replacement cylinder. I don't wanna mix and match manufacturers.

Singing the song " I can't wait to get back on the road again" lol

 

[Desert Rat]

JB weld won't work, it can't handle the heat. It's pretty much time for a new cylinder.

Next question, what kind of cylinder do you have?

What kind of cylinder are they selling you? (Whoever)

Are they the same?

Oh my I didn't know it wouldn't handle the heat!
so I guess 8 months of running my motor 10 to 20 miles a day in arizona
with a piece of watertight flexduit JB welded to the spud of my old exhaust
pipe just shouldn't be holding up without leaks or movements.
Hum someone should tell the JB weld that LOL


Never tell a machinist what can't be done!!!

 

[biknut]

Oh my I didn't know it wouldn't handle the heat!
so I guess 8 months of running my motor 10 to 20 miles a day in arizona
with a piece of watertight flexduit JB welded to the spud of my old exhaust
pipe just shouldn't be holding up without leaks or movements.
Hum someone should tell the JB weld that LOL


Never tell a machinist what can't be done!!!

Try it without the hose clamps and get back to us.

JB Weld can handle 500 degrees barely, but that not going to be enough for holding exhaust studs.

 

[bairdco]

jb weld works on a case by case basis. i've used it on a leaking gas tank stud for 3 years with no failures, but an exhaust stud lasted a few days.

sometimes it'll last forever, sometimes it doesn't work at all.

for the OP's problem, i wouldn't risk it.

plus, a new jug with shipping costs about the same as helicoils, drill bits, jb weld, studs, etc, and much less in time and frustration.