Paused for help before I screw something up

Homeless Bob

Homeless Bob

New Member
Well... before I do irreperable damage to a perfectly good new engine... What's the best/easiest way to pull the jug on one of these 66cc engines? I'd really like to polish up the insides, but I don't want to damage the jug...

Since it's never been run, do I need to change the rings when I pull the piston? Just how "forgiving" are these little critters?

Also...

What's the recommended torque for the head when I reassemble it?

And...

If anyone has any suggestions of what needs to be done prior to reassembly, please let me know.

My hope is that this little engine purrs and lives forever.
 
If you don't even know how to take the jug off without damaging it, what makes you think that you will know how to polish up the insides without doing damage??? (& what makes you think that it even needs it??)
My advice to you is to just run it like it is & don't mess with it.
You're probably gonna do more damage to it than good, & end up with a engine that breaks down a lot sooner than if you just left it alone.
Your first sentence of "before I do irreperable damage to a perfectly good new engine...", should be thought about very carefully before you mess with it!! ;)
 
Venice Motor Bikes said:
If you don't even know how to take the jug off without damaging it, what makes you think that you will know how to polish up the insides without doing damage??? (& what makes you think that it even needs it??)
Click to expand...

Just because I've never stripped down this specific engine does not mean I have no idea about what I'm doing... I'm shop trained to do aircraft work. I'm used to having plans and drawings and such... unfortunately, these little critters don't come with much documentation and I thought it wise to ask before just wrenching into it... foolish me, huh? I guess it shows more "smarts" to just hack into one blindly.

Venice Motor Bikes said:
My advice to you is to just run it like it is & don't mess with it.
You're probably gonna do more damage to it than good, & end up with a engine that breaks down a lot sooner than if you just left it alone.
Click to expand...

I sure hope that people flying in the commercial jetliners I've had my hands inside of have more faith in my ability than you do.

Venice Motor Bikes said:
Your first sentence of "before I do irreperable damage to a perfectly good new engine...", should be thought about very carefully before you mess with it!! ;)
Click to expand...

Ok... let me rephrase it for you... "...before I end up doing something stupid and preventable by asking a simple question and have to buy a new jug or whole new engine..."

Is that better?
 
Yes... thanks Nougat. Very constructive.

This is more than I got in the kit and I tried a search online and couldn't find any exploded drawings.

Now if I just had definitive specs for head torque, etc. I'd be all set. (Or are these so tolerant that head torque isn't important?)

Thanks again.
 
I'm sorry, I didn't mean to hurt your feelings... :(
It's just that when someone named 'Homeless Bob from Louisiana' asks a bunch of losers on a motorbike board how to take the jug off of the simplest engine on earth, the last thing I'm gonna think is that he's a aircraft mechanic!

I still find it very hard to believe that someone who claims to be a aircraft mechanic would ask a question like "Since it's never been run, do I need to change the rings when I pull the piston?"
It seems to me that any mechanic of moderate training would know better.

That's where I'm coming from... Again, sorry for hurting your feelings.
~Norm
 
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I would normally automatically replace everything... but I've been lurking and reading here for a couple of weeks before buying the engine to soak up all of your expertise and the "bunch of losers on a motorbike board" keep talking about how tolerant they are...

So it prompts me to ask... "Self, is it really necessary to replace the rings on it ... hummm?"

It seems that everything about these critters is speculation and opinion with very little else... I'm a "by the specs" kind of guy... so I have questions. Sorry. I'll try not to bother you further...
 
you don't have to replace the rings unless you mess one up. i've had my motor apart a few times, and it's still going strong. just make sure you align the rings with the "keepers" on the piston. easy enough.

you can squeeze the rings by hand to put the jug back on. just take it slow, don't force anything, and it should be fine.

the transfer ports need the most clean-up. port-match those with the case, and get inside as much as you can. the case has a lot of metal on it, so you don't have to worry about going too far and grinding away too much.

the intake and exhaust ports, from my experience, usually need a light filing to de-burr the openings at the cylinder side. not much else you need to do.

check the head also, since you have it off. sometimes the threads for the plug can be sharp. one of my motors, i took the head off (before running it) and there was a fingernail clipping sized chunk of metal that broke off the threads and was just waiting to do some damage.

when re-assembling, i pour a little 2stroke oil in the case and work the rod around, then after putting the jug back on, i put a capful of oil on top of the piston, too.

as far as torque specs, i use a small 10mm wrench and tighten it up till i know it's not gonna go anymore. y'know, it's that "feel" you get when you know to stop.

after the first run, while the motor's still warm, i go back over the head bolts with the wrench, and "check" them for tightness. if they don't wanna turn, i don't force them.

good luck.
 
I torque mine between 12-15ft.lbs

And I always torque at least three times like 5 first then 10 then 15 in a cross pattern
 
I can recommend changing your head stud's if you intend to go anywhere near the recommended torque. I have snapped a 6mm chinese stud at 4 ft/pds. I had read that i needed to torque to 12ft/pds. I'm sure the 8mm studs are a bit stronger.
When putting the jug back on pay close attention to the little lugs where the gaps on the rings goes, very easy to snap a ring if you ignore them.

hope this help's, i'm not a mechanic just learning as i break stuff.
 
To all... thanks for the info.

I've been looking over the exploded diagrams and there doesn't seem to be any "gotcha's" anywhere.

Tonight I'm picking up a 20" frame that I'm going to mount in my shop and cut up to make an engine stand. After I finish cleaning and polishing up inside the case, I can assemble the bottom of the engine and mount it on the stand to work the top end.

I'm also going to mount the rear end as a wheel truing stand. (Might as well use as much of the "donor frame" as possible.

After that... time to get out the gasket material and cut a couple of sets of gaskets.

BTW... thanks for confirming no need to replace the rings.

The hardware I've been warned about is all going to be replaced. That is the only thing that may prevent me from having the work all done and the engine reassembled this weekend.

Is it best to buy hardware kits online or to match the hardware locally? Never mind... I'll just make some orders online tonight.

Thanks to all again for the constructive words...
 
i go to specialty fastener stores like McFadden-Dale or Fastenal.

I changed out every bolt (including all the carb bolts, and the different sizes i needed for custom motor mounts, intake and exhaust bolts, everything...) with grade 8 allen head socket caps.

bought enough to do 3 motors, plus extra bolts for fenders, chaingaurds, etc, for under 15 bucks at McFadden-Dale.

and don't get stainless steel. it eats aluminum and it's brittle.
 
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