Moped Issues - easy fix im sure

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Old 06-14-08, 11:07 AM
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Moped Issues - easy fix im sure

Ok guys

I have a Moped with 1000 miles on it from 2000
A Kinetic TFR

one night riding it around for fun ran fine - parked it
next time i tried to run it wont stay running without the Choke on

--- here is a list of done things

Cleaned all air filter, housing, etc..

Cleaned Carb inside and out about 5 times now - Float is fine, needle is fine, jets are clean, looks brand spanking new

Took Exhaust pipe completely off motor check it over - its got air flow and the exhaust port is cleared

Fuel and all Fuel Lines are good to go - clean and flowing fine

spark plug is fouled a bit but still sparks just fine and gapped

NOW here is the possible issue
I can place my thumb into the Plug Hole and have someone sit and pedal the moped - and it doesnt push my thumb off the hole -- i can feel a bit of a push - so im afraid its lost compression!!!


now there are 4 bolts holding the head on this moped -- if its indeed compression can I just pop the head off and replace the piston ring?

or should I try to replace the spark plug thats fouled first -- its fouled but Does Spark

let me know i was selling this to my brother for 350.00 but if it doesnt run i cant sell it -- and I definetly need money


its also got sort of a rubbing noise going on when I pedal the moped -- this wasnt there before -- is it possible a piston ring broke and is grinding the sides of the chamber?

Thanks guys
Sangrelx
 
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Old 06-14-08, 04:48 PM
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oddball

Bump

This post isnt showing on the main list 1-33 being shown but this post isnt in the list? ?

I need help

ADDED - Weird it shows up now but this reply didnt until I refreshed the page?
LMAO -- please read original question as I still need help
 
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Old 06-15-08, 07:20 AM
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If you can't feel any compression with your thumb after kicking it over three or four times, you have probably lost the compression. To replace the rings, the cylinder would have to be removed as well as the head. If you can look into the exhaust port, shine a light into it to look at the cylinder walls and check the sides of the piston as well through the port. If it looks like there is significant scoring, it will probably take a new cylinder, piston, and rings to fix it. If that's the case it wouldn't be a cheap fix.

Hope this helps,

Bob
 
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Old 06-15-08, 11:34 AM
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hrm

I have the Exhaust off the engine - ill have to take a light and look into the port and see if thats what it is

it has a Decomp lever ill check over all those connections too

worse comes to worse I giuess i have a dead moped sitting in the yard

I dont have time to tear it totally apart to fix it
 
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Old 06-17-08, 07:26 PM
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By all means check your decompression lever.

With your spark plug in place, and turning the motor, it should suck air in through the carb, and putt air out the exhaust.

If your decompression lever is stuck, it will do neither.

If your rings went out, you'd be seeing blue smoke coming out the exhaust before they went. I've never seen rings go without warning.

Are there any metal shavings in your oil? This is also important. Strange you never mentioned oil...

Also, try a new plug. I've had plugs crack LENGTHWISE as to allow no compression. The spark should be BRIGHT blue in direct sunlight and not a dim thread you only see in the shadows. It's tougher for it to spark in a pressurized fuel/air mixture.

Checking compression with your finger is too subjective on such a small motor. Borrow a gauge.

Usually, the 'Choke' problem you mention is common to carb maladjustment. It tells me you are running too lean a mixture. Perhaps your idle set screw is too far in.

Flywheel Key.... Flywheel Key... Watch out for that one too.
 
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Old 06-17-08, 07:34 PM
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wobweeder

Hey Wobweeder please read this thread for more info and such on this problem

I had posted again here
http://forum.doityourself.com/showthread.php?t=349339

cuz its a small motor section -- and i wasnt getting help in this section

but please read there for the most up to date on what ive got done
 
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Old 06-19-08, 07:23 PM
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OK.. read your messages.

First of all, you should be seeing a cross-hatch scratch pattern inside your cylinder walls. This allows the piston rings to be oiled properly.

There is a special (expensive) machine for precisely doing this, but when I'm in a hurry, I use COARSE sandpaper and lightly scratch diagonally both ways. If your cylinder walls are dull grey mirror clean, without these scratchmarks, your piston rings won't last long. It shows it ran out of oil, and the rings wore the walls smooth.

The exception is if the walls are PLATED. If the walls are plated, disregard the above statement. The walls would not be 'dull grey', but silver mirror.

If you think your jug is leaking: Finding leaks in heads is the same as in tires. Spray with soapy water and look for bubbles. Block the exhaust with an oiled sponge for back-pressure and go to work. Remove the spark plug wire. Pedal it a bit and see where the air comes out.

If you find no air bubbles coming out, you might want to revisit your intake manifold -- carb rubber boot. This one has put me in a quandry many times, especially when it only happens as the engine warms. Try some marine grade grease on the O rings.
 
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Old 06-19-08, 08:21 PM
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woobweeder

cylinder is in great shape - its a 2 cycle engine so oil is mixed in the fuel -- and it has 2 ports inside the cylinder that allow the fuel mix to also lube the piston rings

-- after talking to others and examing things - we have concluded that air is leaking in somewhere!

I have ensured its not leaking where the little boot for the carb is and i will be replacing a gasket that was basically non-existant due to old age it had burned away

i believe that the air leak was from this gasket - thats why it ran when i choked it - because it was getting decent air flow in from this leak and from the choked carb -- when i released the choke it got too much air and wouldnt burn

if this fails ill be back - but i am replacing that gasket and ensuring a tight seal with the carb - and replacing spark plug

we will see what happens I just cant order things until tuesday so its gonna be a bit before i get this done

thanks for your advice
 
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Old 06-20-08, 07:22 PM
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Valves were mentioned earlier so I assumed it was a 4-stroke.

Some 2 stroke motors still have lower engine oil, but probably not one this small.

If someone ran regular gas, that'll also kill it like you are seeing. The cylinder will be worn smooth, and your rings will quickly dissolve. You DO need a hatch on your cylinder. They also call it 'Deglazing'.

I have a hone set that mounts on a drill-press for doing small to medium cylinders (spring mounted stones). For my stuff, I oil it up, let it take off the shiny stuff for a few seconds, then re-hatch with coarse sandpaper. For other people's stuff, I take it to a machine shop.

Reeds... Reeds... Reeds... How are your Reeds?
 
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Old 06-20-08, 09:29 PM
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valves

The Valve you are talking about was the Decompression Valve - -- dont worry about that its not even attached now


-- I think your not reading what I posted properly because you keep stressing how important the groves to allow oil to lube the piston rings are

-- I already mentioned the Cylinder has Ports that allow the Fuel/Oil mix to cross over the piston rings to lubricate the rings

the rings and cylinder are fine - we have concluded that the Crankcase/Base Cylinder Seal being so worn down caused air leaks & the Spark plug being so old and fouled (its been in the block since 2000 and had 1000+ miles usage) - that the most likely issue is Air Leak & Fouled Plug -

So i am tuesday ordering a New Gasket and a new plug as well as some other odd parts to restore this moped

I appreciate your help
Thanks
 
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