Can a cylinder body be replaced without special tools?

Nashville Kat

Nashville Kat

Well-Known Member
Had a stud break problem trying to shift from a sleeve carb-

if I replace the cylider body, do I need any special tools?

Do the rings fit in by themselves?
Does the cylinder body just slip off the sleeves after the head is removed?

Over two years now and never torn one down the least bit.

P.S.- Dont recommend "sleeve carbs" the steel rods it sits on -"the sleeves"- are not spaced apart the same as most studs and carb intakes-

and the sleeve rods themselves are thinner than the normal stud- what a mess!

that "anti-spacing" kinda deal to drive you crazy and buy more stuff I guess-

:-||
 
If I catch your drift you want to change out your jug for a new one? No special tools except for two 1/2" x 1/2" sticks that are about 6" long. These you slid under the piston with the sticks parallel to the direction the crank turns. First, though, I sand the bottom of the cylinder jug. There's an angled forcing cone that helps to guide the cylinder over the rings. Use oil and 220-320 grit wet/dry sandpaper to smooth the angle out so the rings slid into the cylinder easier. The 2 sticks keep the piston in place as you wiggle the cylinder over it. The piston has pins in the groove to stop the rings from rotating. You have to kinda squeeze the rings a bit to get them going into the cylinder. Rocking the cylinder fore and aft(from intake to exhaust side) slips the piston in. If the jug is not machined on the top(some arn't :P ) then you need to do the sandpaper/glass thing and sand down the mating surfaces on top the jug. 400 grit is good for that. It just needs to be smooth and flat for a good seal. I like useing white lithium assembly grease rubbed onto the piston and cylinder walls when you put it together, lubes the rings good, too.

What you need to do a replacement is:

rings
gasket set (top and bottom gaskets)
new jug
depending if the piston is wasted a new piston
torque wrench
white lithium assembly grease

Depending on parts price not all that much, really. A new piston isn't all that much and most come with rings. Look around on eBay. Some of the packages have the parts needed so you don't have to get them individually.

I'm thinking all you need for under $40.dance1
 
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Well I got the new jug with the standard intake studs- a broken carb "sleeve" stud still remains in the other, and even thinner than standard studs- defying extracting- looked at a set of easy-outs- it ddn't appear they had one thin enough- I'll probably try to drill it anyway- and only the sleeve carb wil fit- and it's been malfunctioning-

Getting it all apart was no problem, and the old piston pulled out quite easily- I thought it was going to be easy- but the part I feared most- getting the piston and rings inside the new cylinder has proven difficult- I shoulda ordered new rings, but they weren't listed with yearlybird when I ordered the jug- the motor doesn't have 25 miles on it so I'm trying to use as much of whats there as I can-

the top gasket is practically flawless- the bottom one I got off and am reusing- but ordering new ones is a recommend here- it was touchy removing the flimsy old bottom one-

I was surprised at the amount of carbon in the cylinder- and some had built up under the dome near the plug in the 50 slant head- I had not been getting great performance and had checked and cleaned a plug that was too dark- this was not oily residue, though that was the cause- it was baked on. A less oily gas mixture has been getting a better running motor, so that's how I'll stay.

so anyway I struggled for a time with the rings, until I broke the top one- new ones will have to come and I'm tired of messing with it right now- the 66 will have to run!
I was having some better luck compressing the rings with a hose clamp before I broke the one- I guess on cars there's a tool to compress the rings- I had a good start on them once, but couldn't get them further up- and then my fingers got tired of compressing them-

oil and light lithium grease are obviously necessary- better luck next attemp I hope-

the other "good" news I guess is that the new jug is for some reason much lighter weight than the old one- so the build is basically about keeping total weight down anyway- a cruiser with 700 C wheels- and I'm glad to drop a little more weight cause I have to take it up and down a flight of stairs with a landing turn in the middle.

a lot of these vendors are not listing the parts for 50cc as much anymore- I get the feeling the 66 is becoming the standard- so you might keep that in mind when ordering a motor or kit.
:-||
 

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Anyway- this all started with carb float problems and I thought it would be nice to put my old longer billet (I cut it shorter) intake on with the standard NT carb that originally came with my 66- after I put the billet on it was running pretty good but I had also ordered a Speed carb that is working really well on the 66.-

The "sleeve carb" resisted the change with thinner studs spaced wider apart

I thought I may even eventually put a speed carb on the 50cc- which would surely work well,- but now after spending money on these repairs that is not gonna happen soon- the old stock NT on a billet will have to do-
 
Also wondering about " the pistons has pins in the groove to stop the rings from roatating" ????

did'nt see any pims in the ring groove- they seem to rotate freely, at least when I move them- so I was womdering- where do the ring gaps go? should they be lined up or staggered? should they go into the fore and aft sections first, which hang lower?

I'll look again, but I neither saw nor felt pins or anything that kept the rings from rotating.
 
There are pins for the ring ends on each side of the intake port.
They are staggered so they don't line up.

If you did not line the pins up with the ring ends that is why you broke your rings

You do not need or want to use a ring compressor.
Fingers work best with the right technique.

Stock base gaskets are junk. Make your own from auto part store
gasket material.
Download the pattern from SickBikeParts.com

http://www.bicycle-engines.com/2stroke-engine-kits-c-1.html
Seems to be one of the only ones to have 50 cc 2011 EPA motors
 
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Great, thanks for the tip- I'll look for the pins again.

(LATER)

Yes- I found the pins- they are very small- can barely see them, and they only affect the rings when the rings are squeezed tight

the remaining ring goes right up then- this is a crucial-

I don't think I'll have any trouble with the repair now- the ring pins must be accounted for and make all the difference
 
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before you install your rings and new jug, tug on the ring pins with some needle nose pliers and ensure they do not pop out. if they do, jb weld them....i've now have had 2 failures-granted in the past 7 years- from the retaining pin falling out and causing rings to catch a port.
 
Yeah, well, don't have a welder so I'm not pulling on anything with pliers-

Got the new rings and, paying attention to the pins, got the cylinder on over the piston- not then as easy as I'd hoped, but not that difficult either- you really have to line the gaps in the rings on the pins.

I found that blocking the back wheel with a couple of solid objects stopped the piston from moving up and down, and also supported it on both sides with the plastic ends of some medium sized craftsmen screwdrivers.

Just got to hook up the clutch cable and put the carb and twist grip on- not in any hurry- may try to start her tomorrow-

I may go out on something else today- but too stiff to pedal and it's mid 90's here.
 
Not a welder !!!!

Next time Use an epoxy called JB WELD.

To extract a flush stud from a china girl head or block.
Slot the center of the flush stud with a dremel, about 1/8 to 1/4 deep. Using a screwdriver slightly smaller than the stud unscrew the stud.
 
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