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-   -   Decent two stroke mechanic (http://www.biker.ie/forum/showthread.php?t=245608)

Mr Snapped Banjo String 10th September 2018 01:56 PM

Decent two stroke mechanic
 
Have a vintage two stroke dirt bike... 1980 yamaha gt 80... i just cant get the bastard right... time to hand it to someone with a little more knowledge than me...
Any body know of anyone... closer to dublin south the better.. but can travel

chopper 10th September 2018 05:34 PM

Re: Decent two stroke mechanic
 
Whats it doing on you

Mr Snapped Banjo String 10th September 2018 05:51 PM

Re: Decent two stroke mechanic
 
[quote=chopper;3551501]Whats it doing on you[/quote]

Running lean... bogging down.... wont take full acceleration

me2 10th September 2018 09:51 PM

Re: Decent two stroke mechanic
 
I know nothing about your specific bike.

On two Smokes the combustion oil is variable in delivery in keeping with acceleration, this may be achieved by a splinter on the throttle cable, one side to the carbs and the other to the oil pump. I've heard of peops premixing oil with petrol, not something I've done or recommend as a general rule.

Ya might know that oil starvation in the piston would give the other two symptoms ya mentioned, as in it could be threatening to seize up. Best of much with it.

fatbast 10th September 2018 10:24 PM

Re: Decent two stroke mechanic
 
[quote=Mr Snapped Banjo String;3551472]Have a vintage two stroke dirt bike... 1980 yamaha gt 80... i just cant get the bastard right... time to hand it to someone with a little more knowledge than me...
Any body know of anyone... closer to dublin south the better.. but can travel[/quote]


Eddie Laycock laylaw racing. knocklyon area. They know classic two strokes. Appointment only .

REDLINE-0 11th September 2018 11:07 AM

Re: Decent two stroke mechanic
 
Ger Byrne.GB motorcycles.naas-newbridge

chopper 11th September 2018 01:40 PM

Re: Decent two stroke mechanic
 
[quote=Mr Snapped Banjo String;3551503]Running lean... bogging down.... wont take full acceleration[/quote]

Have ya tried lift the needle ?

Mr Snapped Banjo String 11th September 2018 01:53 PM

Re: Decent two stroke mechanic
 
[quote=chopper;3551572]Have ya tried lift the needle ?[/quote]

No place on the carb to lift the needle... its preset

chopper 11th September 2018 01:57 PM

Re: Decent two stroke mechanic
 
[quote=Mr Snapped Banjo String;3551574]No place on the carb to lift the needle... its preset[/quote]

Can the needle be removed and a washer put under it? Whats story with bike? Has it been rebuilt or anything ?

Dmac 11th September 2018 08:54 PM

Re: Decent two stroke mechanic
 
Could be intake air leak or crank seals - gives these symptoms too.

Mr Snapped Banjo String 11th September 2018 10:20 PM

Re: Decent two stroke mechanic
 
[quote=Dmac;3551628]Could be intake air leak or crank seals - gives these symptoms too.[/quote]

Air intake is new... the crank seal were replaced i think there may be a very slight difference in one of the seals.... how would you test the crank seals? Leak down test?

DavyH 11th September 2018 10:45 PM

Re: Decent two stroke mechanic
 
You need a 2 stroke specific leak down tester, why was a crank seal with a discrepancy fitted?

Mr Snapped Banjo String 11th September 2018 10:52 PM

Re: Decent two stroke mechanic
 
[quote=DavyH;3551641]You need a 2 stroke specific leak down tester, why was a crank seal with a discrepancy fitted?[/quote]

Was all that was available at the time.... i think it should be replaced with the proper seal... maybe that would be a start...

Dmac 17th September 2018 01:10 PM

Re: Decent two stroke mechanic
 
You need to plug the exhaust port, then bung the inlet and add some air. it should be fairly easy to see if it's not holding air and go from there.

You could use a old inner tube and a piece of wood to plug the exhaust port -

Put the rubber sheet in first and then a close fitting plug. Something similar for the inlet - and use the tube valve to add air - with a bicycle pump. Don't use a compressor:woots:

A squirty bottle of soapy water will show up external leaks, you may be able to hear crank seal leaks from the magneto side or through the oil filler.

The dodgy seal might be ok, worth testing first. :thumbsup2:


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