Small Bevel Wheel Bolt Keeps Loosening and Stripping

[StevelKnievel]

I have a 48cc Grubee. I am just about done breaking in the engine. During the 2nd tank of gas the bolt that holds the small bevel wheel on came loose and drilled a hole through the cover. I took a bolt from a scrap engine I had laying around and replaced it. Now the second bolt has stripped as well. Fortunately, I heard it rattling around before it could cause more damage. Has anyone else had this problem? What should I do? Thanks for your help!

 

[rustycase]

I have not had that problem, but I have read reports of a Loctite Thread repair product that is supposedly rather good.

It sounds like the internal threads in the crank have been damaged, so you might as well use this 'last resort' product, and hope it works.

Best option if it does not work is to buy a replacement crankshaft unit to install in your cases, I suppose.

Use some JBweld or epoxy product to patch the hole worn in the case.
Put a nickel, your state quarter, or a half, over the outside for entertainment.

Unfortunately, this problem you are enduring is typical of what could happend to almost any buyer of a chinagirl, no matter what the source.

Good luck
rc

 

[Al.Fisherman]

Just this past week I've heard of a bolt problem, this was about a bolt breaking off.

First find out if in fact the threads in the crankshaft is bad or not. This can be accomplished by using a bolt or stud (8 X 1.0). Screw the stud or bolt into the crankshaft, and tighten down to normal torque. Use a grade metric 8.8 or better. If you can tighten and it holds, I'd use blue lock tite to hold the OEM bolt in. If it doesn't, I'd use red lock tite (before buying a crankshaft) to hold it in. Keep in mind that in order to remove the red, heat needs to be applied.

Rusty has the cover solution. One of very FEW uses of JB Weld on these engines. Or you could lay the cover face down on a piece of something like wax paper, fill the hole (the JB will sink with gravity), and fill the hole. After cured, remove the wax paper, sand the cover face on a sheet of sandpaper using a flat surface, and paint.

 

[StevelKnievel]

I have a spare cover from a roached engine I slapped on. I will try the Loc-Tite. Is there something at Home Depot or elsewhere that will suffice as the bolt or should I order a new one? Thanks, guys.

 

[Al.Fisherman]

I have a spare cover from a roached engine I slapped on. I will try the Loc-Tite. Is there something at Home Depot or elsewhere that will suffice as the bolt or should I order a new one? Thanks, guys.

Your problem is finding a 8X1.0mm bolt, as it isn't that common. At times I need to make cylinder studs and I found it hard to come by at a reasonable cost. Home Depot and Lowe's have a selection of metric bolts and nuts, but no 8X1.0 hardware. The problem replacing one (OEM) is that it will be hard to tell if the crankshaft threads are destroyed, and what color lock tite to use. My opinion..... just a nickel's worth.

 

[Venice Motor Bikes]

If the crank threads are stripped beyond repair & or the end of the crank shaft is damaged to the point where it can't be repaired in a propper fashion?
First make sure the gear has NO CRACKS near the woodruff key slot & that the woodruff key is still in place; then tap the gear firmly in place with a soft metal hammer. Then throw a few small tack welds on the seam to hold it on. This will make it so the gear will never again come off again.

Keep in mind that this is a very drastic (& irreversable) solution to the problem & you should try every other fix first before doing this!
I've done this on a few bikes & they have not had any other issues with that gear after welding.

Also... dont weld too heavy or you will damage the crank seal gasket.

 

[Al.Fisherman]

That's more drastic then RED. I got a used engine that the drive sprocket was welded. But I could drive out the clutch shaft without splitting the case.
Although I've never had a bearing go out yet, I'd sure consider changing the cheap Chinese bearings with a better set.