What to do with a new 66cc engine?

S

Squaredcorn

New Member
I just got my first 80cc (66cc is what it actually is i think?) motor off eBay to put on an old mountain bike to use when i go to college. Well when I'm going through the forums i see many people saying to change the spark plug right out of the box because the one they give you sucks.

Then I've also seen people posting about rearranging a pin under the drive gear, replacing the gaskets, and re-torquing the head before you try to start it.

I was just hoping someone with experience could give me a list of "to-dos" to prep my engine for its first time out.
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First time on the forums btw thanks!!!
 
I pull the head and cylinder on all my new builds to rinse out the lower crankcase and inspect everything. Be sure the piston pin circlips are secure and the rings are properly installed.
If you do not have a torque wrench or the experience to re-tighten the head bolts properly, you may want to skip this.
Pull both sidecovers and grease the bucking bar and ball, and the gears on the clutch side. Inspect the small gear for proper alignment with the clutch gear.
Seal up the case where the mag wires come out. Water in there kills coils!
Be sure all fasteners are tight (like the intake and exhaust)
Most experienced builders will also replace the plug cap and wire with an automotive part. (The stock stuff is junk) NGK bh7es seems to be the most popular plug, but I just run whatever comes with it until it fails.(if it does) I have never had any problems with the stock plugs yet.
 
hard question to answer - seems anyone with good mechanical skills would naturally do the usual stuff, while someone without those skills would quickly get into trouble attempting them

I do a lot of these and usually just fire them up right out of the box to see if anything seems wrong when they run the first time. OTOH, my supplier is very reliable as to kit quality.
 
Haven't had time to work on it since i got it but now i have a free day, I'm gonna do what maniac suggested, i have a snap-on torque wrench and i was just curious what kind of inch pounds people are torquing the heads on these too. also the gaskets look like garbage i was curious if replacing them with high-heat rtv would be better?
 
Messing with the head torquing and gaskets are unnecessary unless they are causing problems such as oil leaking. Most of these tips are just to avoid future problems. The plug wire is recommended to be changed because the stock one has loose parts that fall out (but it works fine until then). The stock spark plug is perfectly fine and I doubt you'll notice anything by switching. I have no mechanical skill, but these things are really not complicated. To reassemble a top end is only a handful of parts. If you are looking to go all out before you fire it up, port your cylinder/manifolds and deck the head. Or build one and then fix your kinks afterwards.
 
You'll get as many opinions as you get replys to your question. Everyone is different. Different perspectives, different skill levels and different experiences.

If you're not concened with any warranty issues you can disassemble the top end and see what lurks in the crankcase but if you've never installed a piston back into a cylinder you need to know that there are tricks to it. Such as, aligning and compressing the piston rings properly. This is where a lot of non-mechanical builders get into trouble.

If you want to assure yourself that you've at least taken care of the weak links, replace the cylinder head acorn nuts with shouldered/flanged hex nuts and use a torque wrench to reassemble. 120 to 140 inch pounds is a good ball park torque value. Note, I said INCH ponds, not foot pounds.

Replace the kit supplied spark plug boot with a good automotive quality item. The wire is okay if it's long enough for your installation. Try the kit plug and it will probably perform just fine but if/when you do replace it there are several options. The NGK B6-HS is one used most by many builders. The 6 denotes the heat range.

Hope we've put you on the right track or at least given you food for thought. Good luck and we're always here to help if you need it. You can also use the search feature to find answers to almost any question you might have.

Tom
 
Maniac's suggestions, and others, are certainly good ones.

But there's another way. This is what I do. I buy an engine and put it on the bike and I start riding. These engines/kits, the china girls anyway, are so inexpensive that I regard them as disposable. I keep a brand new kit on hand (there's one in my attic right now) to be my spare parts store. My bike and engine are approaching two years. My spare kit is approaching one year. I haven't needed to take anything from the kit yet.

I would be wise to take the new engine and do the things that Maniac recommended to it. And I might. But I do have other things to do. And so far this hasn't made it up high enough on my priority list.

Doing it this way, you'd be wise to have backup transportation. I happen to have a car, but I hardly ever use it. That's because I also have a regular pedal bike on hand at all times. And I often ride it just for the exercise and to make sure that it's always in good working shape. So I can afford some downtime.

If one doesn't want a pedal bike or a car, then he could always keep two working motored bikes on hand. Alternate riding them so that you know that they're working.

That's the beauty of these. They're so cheap that you can keep two on hand.
 
I just got done putting it on the bike today, besides the exhaust and the clutch everything is set up to go.

The only reason i was wanting to re-torque the head was because i can see through the cracks to the other side, like the manufacturers hand tightened them, (which i cant complain about the kit was only about $140)

And after seeing all your guys' replies i think ill just run the original gaskets tell one of them blows.

Thanks for the quick replies all of you guys.....Ill torque the head and try firing it up tomorrow, someday if i end up liking the bike allot ill consider porting the intake and exhaust, but in the middle of the quarter in school finding time to do that might be a long ways down the road.

Again thanks for the quick replies its nice knowing there's a helpful and quick responding community out there for new guys like me!
 
Be sure to re-torque the head bolts after a few short rides. Also periodically check tightness of the exhaust, intake and motor mounts. They all loosen after time......
 
Squaredcorn said:
The only reason i was wanting to re-torque the head was because i can see through the cracks to the other side, like the manufacturers hand tightened them, (which i cant complain about the kit was only about $140)
Click to expand...

Yep, noticed the same "see through" issue "right out of the box" with my $140 kit. I also followed the same general "save your engine" advice mentioned in the above posts and other threads in this forum. I also went as far as replacing the bent "out of the box" cylinder studs with upgraded units @ ~ $3 a piece w/acorn nuts.



Btw, 1 foot pound of torque = 12 inch pounds (you probably already know this, but I thought I'd mention it anyway). Note: be very careful when using foot/pound calibrated torque wrenches while working on small engines and/or fasteners (this can be especially true with "click" type torque wrenches). Inch pound wrenches are the best way to go imo. Also keep in mind that, generally speaking, you want to stay away from using the very lowest and the very highest torque ranges on any torque wrench.

Meanwhile, you might also consider pulling the (R.H.) clutch cover off so that you can apply a little grease to the helical gears. While you're in there, make sure that the small crankshaft mounted drive gear is correctly aligned and fully engaged with the large "clutch basket" driven gear (just search "small beveled gear" in this forum for more info on this).
 
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I installed mine right out of the box and used lock tite on all nuts and bolts. I did though change the spark plug wire after installing it. The only troubles I've had were plugged up exhaust after breaking it in,a faulty spark plug and the outer crankshaft seal was not secured in place tight causing oil to get at the magneto and wires.
But since installing it this past spring, I put on almost 1300 miles. Others riders probably have more.
 
this has been said before....

pull the top end and port your jug, dont go crazy just a moderate port

deck the head down on some glass and sand paper to up the comp to the desired lvl

deck the jug slightly to get a better gasket mating surface

get a nkg or champion plug

get a new plug wire and boot

cut ppiston skirt so it does not cover intake at TDC then grind ramp for transfers and exhaust port to correct timing

port match exhaust header and intake

extend intake to 7-8in from piston face with auto radiator tubing

adjust clutch properly and oil the gears and pin and arm

get a better 410 or 415 or #41 chain ... anything is better than what they give you !!! it will break rats nest up and crack your case !!!

most important !!!! tighten your chain properly so that you almost do not need the tentioner !!! i do not runn the tentioner !!! i just adjust the chain so i do not need it by adding or taking away links !!! the tentioner if not properly mounted and adjusted will cock sideways and ruin your day !!! it will flip into your spokes and tear up your rear tire snding you flying into a skid !!!

look into chain tentioner mods to see how to fix this issue !!!

with all that done you will have yourself a powerfull reliable lil motor !
 
rogergendron1 said:
this has been said before....

pull the top end and port your jug, dont go crazy just a moderate port

deck the head down on some glass and sand paper to up the comp to the desired lvl

deck the jug slightly to get a better gasket mating surface

get a nkg or champion plug

get a new plug wire and boot

cut ppiston skirt so it does not cover intake at TDC then grind ramp for transfers and exhaust port to correct timing

port match exhaust header and intake

extend intake to 7-8in from piston face with auto radiator tubing

adjust clutch properly and oil the gears and pin and arm

get a better 410 or 415 or #41 chain ... anything is better than what they give you !!! it will break rats nest up and crack your case !!!

most important !!!! tighten your chain properly so that you almost do not need the tentioner !!! i do not runn the tentioner !!! i just adjust the chain so i do not need it by adding or taking away links !!! the tentioner if not properly mounted and adjusted will cock sideways and ruin your day !!! it will flip into your spokes and tear up your rear tire snding you flying into a skid !!!

look into chain tentioner mods to see how to fix this issue !!!

with all that done you will have yourself a powerfull reliable lil motor !
Click to expand...

Wooooo, all that just made me a bit dizzy :-{ All that would put a lot on a first time builders plate.......at that rate I'd scrap it and get a small 4-stroke ;)

But of course, that's just me rotfl

Like Tom was sayin'.........
 
"extend intake to 7-8in from piston face with auto radiator tubing"

not good idea in my opinion, the fastest motors normally use the shortest intakes, I tried to extend the intake on an engine that had room issue on the bike I put it on, never did run right with that extension, put a shorty Manic billet intake on it problem solved run like it should then.

my recommendations for the noob would be more down these lines.

1.] replace spark plug and boot, (NGK B6HS or B7HS plug and NGK boot or automotive wire and boot)

2.] use loctite on all fasteners and use lock washers under mounting hardware, exhaust and intake nuts or bolts.

3.] mix up some 25:1 or 32:1 good quality 2 stroke oil/gas mix in a gallon jug, run all of it through the engine, and then because it will be running rich as most all of them do, put a smaller jet in the carb to get the 4 stroking way down, which will increase power and top speed. do plug checks according to info you will find here on forum to know when you have a good tune on the carb by getting the plug color to a nice medium brown color.

4.] if better performance and power is desired consider a better free flowing exhaust from one of the vendors here on forum, like SBP expansion exhaust which themselves and several other vendors carry, its a great choice if you dont have the tools and know how to build your own.

Deburring the ports in the cylinder is a great upgrade that will help with performance, but that is something that doesn't have to be done straight away, I have two engines that have had no port work done to them at all and they both run good and will cruise at 30-34MPH all day long without a problem, they would do better with port work of course but do just fine like they are also.

upgrading the upper wrist pin bearing would be a good idea if the jug is pulled for porting after break in also, this bearing is the one most likely to fail.

This how I would direct the noob on their first build, keep it simple and they can improve things as they go.

Map
.we.
 
Hey there! I did forget one thing that I'd recommend for a new engine. One of the posters above reminded me.

Improve or replace the gaskets on the clutch cover and the magneto cover.

I consider this a must. Water will get in there otherwise. And it's likely to not take long.

I use red Permatex. I just lay a bead on the edges of the covers and press them in place. Make it thin, though. You don't want much of that stuff squeezing into those spaces.
 
I just spray my gaskets with a good coat of copper coat spray let the gaskets hang over night and then place them and tighten good, you will have an excellent seal.

Silicone does work but I never liked all that mess squished out our things on my engines.

But it does do the job no doubt.

Map reddd
 
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