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Old 01-19-2015, 04:04 AM   #1
mrkennethporter OP
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Joined: Jun 2007
Location: Ireland, Naas
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Sick little 2 stroke. Yamahahaha TY80

Need a bit of advise.

Just rebuilt my first bike. A ty80 .

My son is learning on it. I had him at his first trial yesterday when problems forced him to go home early. It was doing this since the rebuild but it seemed to get worse on the very day we needed it to work .

When the throttle is snapped open to any position it stalls. If I build the revs slow, its fine. Plenty of power at the top and middle range.

What I have done so far.

Taken the carb apart and cleaned everything . Jets blown out, reset float to spec(23mm) , cleaned and set air screw to spec (1 1/4) . Needle set correctly to 2nd groove. Cleaned spark plug. Plug looks fine, maybe a little oily.

Bare in mind everything on this bike is nearly 40 years old.

Problem still exists . It really feels like a fuel problem, but not sure what to do next.

The slide is worn down to brass on one side and there is a little crack on the boot of the choke seal, but I think that seal is just to keep mud out.

The bike was in a damp shed for 25 years , everything was covered in rust and crude.

Any suggestion would be greatly appreciated . Thanks

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Old 01-19-2015, 06:46 AM   #2
wfopete
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Hmmm. I would go back through that carb again. Consider getting it ultra sonic cleaned. I think that motor is a piston port design but you might double check me on that to see if it uses reed valves. If it does check those reeds for cracks or damage. Good luck; nice bike.

Oh yeah, put a new sparkplug in it, just because.

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wfopete screwed with this post 01-19-2015 at 06:53 AM
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Old 01-19-2015, 10:53 AM   #3
Scootern29
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Raise the needle a notch or two. It sounds like it is a little lean when cracked open. Not enough fuel and it hit's a flat spot (bog / stall).
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Old 01-19-2015, 12:01 PM   #4
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Along those lines, another quick and cheap thing you can try is while the engine is running at idle, spray a little WD40 (or the like) around the base and intake gaskets to see if they are leaking. If the motor's RPMs rise when you do this, it indicates a intake leak (and thus a lean condition).
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Old 01-19-2015, 07:58 PM   #5
daviethebiker
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Did you replace the crank seals when you rebuilt the engine ? I know crank seals on old 2 stroke engines dry out.
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Old 01-20-2015, 11:29 AM   #6
mrkennethporter OP
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The bottom half was bought as a rebuilt item. It was only 50 quid of flee bay.

The seller stated it had the big end and seals replaced.

I can not be 100% sure though. I will leave splitting the engine as a last resort .

How would one know if it was the crank seals?

I am waiting on a new plug to arrive and bought a tin of WD .

I have to wait till payday to purchase this next . http://yambits.co.uk/ty80-carb-repair-kit-p-2143.html

I am also going to give this a try over the weekend. Great idea...
https://www.youtube.com/watch?v=R1DtY2VwSyY
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Old 01-20-2015, 11:45 AM   #7
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If it gets worse thru the day, it is likely running lean and getting worse as it heats up.

You should be able to work with what you have and need no rebuild kit to assess the issue.

If there is an airscrew, see that it is turned approx 1.5 turns out from full stop. Set the needle clip to the center position or position 3 (third notch down from the top).

This should get you close to the standard settings as long as the carb internals (jets, etc) are still as standard.

Make sure you have a proper oiled foam element in the aircleaner box.

Hope this helps, let us know how you get on.
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Old 01-20-2015, 12:20 PM   #8
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REALLY clean out the idle jet. It can look clean and air can pass through it but over the years they do get gunked up. I have seen some that could not be cleaned and needed to be replaced.

Just a thought.

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Old 01-20-2015, 01:26 PM   #9
mrkennethporter OP
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Quote:
Originally Posted by pdxjim View Post
If it gets worse thru the day, it is likely running lean and getting worse as it heats up.

You should be able to work with what you have and need no rebuild kit to assess the issue.

If there is an airscrew, see that it is turned approx 1.5 turns out from full stop. Set the needle clip to the center position or position 3 (third notch down from the top).

This should get you close to the standard settings as long as the carb internals (jets, etc) are still as standard.

Make sure you have a proper oiled foam element in the aircleaner box.

Hope this helps, let us know how you get on.
Just did all of this. And I though it was ok. Nice and crisp when cold. Then it heated up after 5mins.

This is it now in this short clip.
https://www.youtube.com/watch?v=m5ypmTdw8DA
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Old 01-20-2015, 05:29 PM   #10
wfopete
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You COULD have a ignition side crank seal leak. Remove the ignition cover and spray WD40 at the seal area while the motor is running and listen for a RPM to rise. Also check the junction at the carb intake area for cracks.
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Old 01-22-2015, 08:30 AM   #11
mrkennethporter OP
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Thanks for all the help.

New plug done. Reeds taken out and gasket surfaces deburred and cleaned.

But I think the real problem was the pilot . A ran one strand of copper wire up it with resistance. After a good reaming out with wire and carb cleaner, I was able to get 3 strands of copper wire through. Hole visibly bigger ..

So I am guessing I had glaze in the hole.

Running fine now. Nice and crisp .
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