spark plug threads stripped off

[BootScootin'FireFighter]

Has anyone ever dealt with this issue? I had my bike cut out on me, and upon further investigation, the spark plug and cable were wiggling loose. It will run, but after a little time, it will vibrate itself free. It will initially thread in, but once a little snug, start to come loose. It is obviously not reliable or safe to take onto faster roads without a chance to pull over. I am going to call the local shop tomorrow morning and I have ways to get it towed. The replacement cylinder head is $161, but I'd imagine replacing it will end up being almost $500 with labor. I'd like to save that money and do it myself.

So my question is, has anyone ever replaced the cylinder head themselves? What sort of tools would I need and where would I begin?

I also thought maybe it could be re-bored to a larger thread size, and that would involve different spark plugs or some sort of collar to install.

Where to go from here? I really want to take this one on the upcoming cannonball run, but I have another bike as a backup just incase.

[OldGuy]

Does the sparkplug still have its crush washer? This is the thick washer that crushes a little when you tighten the plug.

If the washer is missing, or really crushed flat, you might first try replacing the washer. Long shot, but... Good luck!

[agrogod]

Wow you just seem to be hitting a stream of bad luck these days. First your brakes now your cylinder.
I upgraded my RH last year to a 70cc, and was wondering the same things you have asked.
I found it was just easier to replace the cylinder so there was no need to try and find different plugs. You could try to helicoil repair the threads and would need to get the right kit for your threading.
As for the cylinder replacement its more time involved than anything else, but a fairly easy and straight forward to do job. Just regular tools are all that's needed and patience.
What ever you decide much success to you.

[BootScootin'FireFighter]

I have the time and the tools. Where do I begin? Is it something that needs to drain all the oil out and simply disassemble and reassemble in the same order, or is there something critical and unusual that I need to make sure I do that isn't obvious?

[BuddyRaton]

I have the time and the tools. Where do I begin? Is it something that needs to drain all the oil out and simply disassemble and reassemble in the same order, or is there something critical and unusual that I need to make sure I do that isn't obvious?

Good suggestion to replace the crush washer. I would also make sure that you are actually torquing it down. Some "plug wrenches" that come with scooter tool kits actually change diameters at different depths on the plug. You may need to keep it in the correct position to engage the plug and get it snugged all the way down or get a dedicated plug socket.

As far as replacement look through the posts on installing a big bore kit. Unbolt the rear shock to the head rotates up and you will have plenty of room to work.


Replacing the head is actually pretty easy. You need the usual metric wrenches, feeler gauge for valve adjustment,, a gasket and a torque wrench. Here is a video on a GY6 BBK install. He goes over everything pretty well. One thing I like to do is check the timing marks before dis-assembly. There is a line on the cam that should be perpendicular to the head. Check the timing marks on the flywheel and make a witness mark if you need to.

https://www.youtube.com/watch?v=zCaWK-wIFDA

viewtopic.php?t=15191&highlight=bore

As far as sourcing one I would place a "Wanted" here and on scoot.net. Someone that has installed a bbk and large valve head has a used stock head laying around.

Keep us updated!

[BootScootin'FireFighter]

I saved those links that gearhead posted a while back about disassembling the cylinder head, I will reference them for a later date. In the meantime, I think my best course of action is to drop the entire engine, cvt, rear wheel, shock, and exhaust assembly as one piece and swap it out from the other Buddy to make my primary one reliable again. Thanks for all the feedback and advice.

[RoaringTodd]

It's a good thing you got this before the cannonball. Pulling for ya.

[lovemysan]

I have an extra used head. But you could probably have yours rethreaded at a machine shop for about the same effort.

[jrsjr]

I...I think my best course of action is to drop the entire engine, cvt, rear wheel, shock, and exhaust assembly as one piece and swap it out from the other Buddy to make my primary one reliable again.

I think that's a very good idea considering the epic journey on which you are about to embark. You want everything to be shipshape if not sparkly new when you you hit the road, because WOT all day every day for three weeks is going to take its toll. It might be a good idea to carry a spare stator in your kit, too. You can always get a flywheel puller at any auto part place, but Buddy stators can be a little hard to come by in the sticks...

[thatvwbusguy]

If you can combine two donors to make one franken-scooter, that sounds like the way to go for now!

When time and funds allow, breathe some new life into this downtrodden beast with a Stage2 performance kit and a big valve head. There is no machining work needed for this boost, but the results are pretty impressive. A few hours of quality wrenching time will change the attitude of the scoot completely.

Be careful though, power corrupts and mods start getting expensive once you open the flood gates

[BootScootin'FireFighter]

I think that's a very good idea considering the epic journey on which you are about to embark. You want everything to be shipshape if not sparkly new when you you hit the road, because WOT all day every day for three weeks is going to take its toll. It might be a good idea to carry a spare stator in your kit, too. You can always get a flywheel puller at any auto part place, but Buddy stators can be a little hard to come by in the sticks...

I learned that lesson the hard way in 2012, cost me a hefty day's worth of points. Stator, belt, spark plugs, oil filters, brake levers, headlight, tire plugs, mini air compressor, CDI and coil... all these things will be in the spare kit. Even got my cordless impact wrench with all socket sizes I'd need. I did get a flywheel puller a while back and it's come in handy numerous times. I don't know what it is, but I go through stators frequently.

As for the big bore kit, I don't know how much longer I'll keep the Buddy's, so probably won't be putting a big project like that in. I'm looking towards a dual sport and possibly a Honda Grom for my little bike.

[BootScootin'FireFighter]

Well I was able to do the engine swap. No lift, no help, but like wrestling an alligator to get it up and lined up, then inserting the mounting rod. What a bear! It fired right up, but started to make a clacking sound. I pulled the valve cover, the valve clearance was perfect, oil was good, everything was plugged back in the right way, fuel getting to the spark plug. It was a rough ride in, very clackety, especially at idle. I did the checks mentioned above just now and think it's a bad auto choke. Reason being, the wire for it got snagged during the move and there was a downward pressure pulling on the wire. When I opened it up to check, the stem that goes into the carburator broke of completely. I don't know much about the Auto-choke, but is it safe to assume that is the culprit? That would be causing it to run rich and make that noise on the ride in this morning? It's broke off now, so it's not starting at all. I have the spare bike at home I can strip one off, but that's a $65 replacement part, which sucks of course, but hopefully that's the end of that issue.

Can anyone confirm if they've had similar issues and relate it to the auto-choke?

Scooterloungeonline has it labeled as a "auto bystarter set"

[lovemysan]

The operation of the autochoke is silent. It doesn't make any sounds. Have you verified the noise isn't coming from under the belt cover? Rhythmically Valve train noise occurs at half the engine speed due to gearing.