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Yamaha t80 t50 carb difference ?

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Yamaha t80 t50 carb difference ?

Post  JasonBG on Wed 22 Jun - 9:09

Hi is there any difference between the carb of Yamaha T80 and T50? I have Yamaha T80 and my carb is broken so I want to replace it with T50 carb. Will it work fine or it will be smaller and the bike will lack power ?? Or will it be able to fit properly ?

MANY THANKS !!!
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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Thu 23 Jun - 8:05

JasonBG wrote:Hi is there any difference between the carb of Yamaha T80 and T50? I have Yamaha T80 and my carb is broken so I want to replace it with T50 carb. Will it work fine or it will be smaller and the bike will lack power ?? Or will it be able to fit properly ?

MANY THANKS !!!

Yes the carb on T50 is smaller bore but will fit as flange is same. However expect a drop in performance at top end.
You may care to read a previous thread on the subject http://yamahatownmatet80.forumotion.co.uk/t742-another-new-t80-carb-from-greece?highlight=T50+carb

Might be worth contacting the Greek seller argyr-maria to see if he has any left. Or contact All Spares in Wolverhampton (bike breakers) http://www.allbikesallspares.co.uk/contact They had one on eBay recently & may still have it or others. Worth a phone call to find out.

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Re: Yamaha t80 t50 carb difference ?

Post  Duckrider on Wed 6 Jul - 23:01

Hello, again

As i own a T50 and recently change the cylinder with a T80 one but i kept the rest parts of the engine the same i am looking this time for a mikuni vm16sh carb.
Here in Greece i can find used carbs from 20 euro but as you can understand it is hard to know if they work right.
For example this one http://www.car.gr/parts/view/5810319/
I can also find new carbs made in China from 45-65 euros but i don't know if i can trust these items.

From parts list you can see that ,,,,
for T80
14....22f-14142-12 pilot
9....22k-14141-14 nozzle, main
19... 18A-14143-17 main
23 ...22f-1490j-00 needle set


for T50
13 ...22f-14142-12 pilot
8.....46j-14141-11 nozzle, main
20.... 18A-143-66 main
24....22f-1490j-00 needle set

.... pilot jet and needle set are the same, the difference is at main nozzle and the main jet , from 77.5 to 85 , so i am thinking if i will not find a good used carb to change only the main jet , even if i will do this for a few time.

My problem is that at Haynes i read that pilot jet is 12.5 for T50 and 15 for T80, i don't know which is the right value.

Another option is to change the whole carb with a new one so i will be able to find spares more easy.
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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Thu 7 Jul - 4:13

As you have fitted a T80 cylinder onto a T50 which has a shorter stroke than T80, the capacity will be 71cc as against 79cc for T80. So even if you fit a T80 carb you may have to adjust the jets accordingly. I would think the difference of 8cc will not make that much difference though. The used carb in the ad looks OK except for small round plastic cover over choke operating lever & spring is missing.

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Re: Yamaha t80 t50 carb difference ?

Post  Sheldon cooper on Thu 7 Jul - 18:50

Duckrider where did you find these new Chinese carbs. Do you have a link? Me and another forum member are trying to find shaft seals so you know where we can find these? Thanks

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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Thu 7 Jul - 19:32

I think these are the Chinese carbs http://www.ebay.co.uk/itm/Brand-New-Yamaha-PW80-Carb-Carburetor-PW-80-PIWI-Y-Zinger-PY80-1983-2006-/151649513423?hash=item234f03efcf:g:B4EAAOSwk5FUsEQN
but they are for a PW80 which has a 2 stroke engine so they may not be suitable for a 4 stroke. Also they are clip fitting so would need to have an adaptor made to fit a townmate manifold. Would also probably need an adaptor for air filter hose.
I would think a carb off a Honda C70 or C90 would do the job but these have built in fuel tap & choke lever so you would need to make suitable cut out in leg shield moulding.

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Re: Yamaha t80 t50 carb difference ?

Post  Sheldon cooper on Thu 7 Jul - 20:14

Yeah I don't want to go down 2 stroke carbs or modifying carbs to fit it's not worth the trouble, the carb I have is off a bike with 1100 miles on it so is like new! Just need to find some dam shaft seals.

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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Thu 7 Jul - 21:10

I am not convinced that the seals are an issue, as long as the bearings are ok. The shaft is outside of the actual 'carburation' part of the carb. I assume the seals were there to top any ingress of dirt, rather than seal it.
Problem is that it will be critical unobtainable new parts like the carb & frame that will see off the Townmate

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Re: Yamaha t80 t50 carb difference ?

Post  Sheldon cooper on Thu 7 Jul - 21:43

Well it says in the hayns manual to replace them to avoid air leaks, my bike will run if bump start it and keep going but will not kick start or idle, the only thing wrong I can see is the shaft seals

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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Thu 7 Jul - 21:48

Sheldon cooper wrote:Well it says in the hayns manual to replace them to avoid air leaks, my bike will run if bump start it and keep going but will not kick start or idle, the only thing wrong I can see is the shaft seals

Dont think it has anything to do with the seals or for that matter the carb. Have you checked tappet clearances, if they are tight (particularly the inlet valve) it will cause the bike to stall on tick over.

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Re: Yamaha t80 t50 carb difference ?

Post  Sheldon cooper on Thu 7 Jul - 21:59

It could be that, but before I dismantled and clean the carb the bike would run, not 100% ( reason I cleaned it) but after in reassemble the carb it will not kick over like I said,

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Re: Yamaha t80 t50 carb difference ?

Post  Sheldon cooper on Thu 7 Jul - 22:00

It could be that I have not put it back together correctly, it needs further investigation

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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Thu 7 Jul - 22:07

Best bet is to buy another carb when one comes up on eBay next, & try that, if same problem then its not the carb, Unlikely that two carbs (even used ones) would be duff, Townmate carbs do not usually give problems, anyway as carbs are getting thin on the ground a spare one is no ill store, & you could always sell it on again.

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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Thu 7 Jul - 22:08

Deleted duplicate posting


Last edited by JohnW on Fri 8 Jul - 2:58; edited 1 time in total (Reason for editing : duplicate posting)

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Re: Yamaha t80 t50 carb difference ?

Post  Sheldon cooper on Fri 8 Jul - 0:02

Yeah one step ahead I have a spear one, but I bought it with out seeing it and it's worse than the one I have lol, i will try it soon and see what happens. I would still like to find the shaft seals, we need someone to make a adaptor kit so we can run Chinese c90 carbs they are every where and cheep!

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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Fri 8 Jul - 3:00

Yes but C90 carbs have built in fuel tap & lever choke on carb so will need hole cutting in legshields to access!!!!

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Re: Yamaha t80 t50 carb difference ?

Post  Sheldon cooper on Fri 8 Jul - 3:13

My c90 car doesn't have a built in tap, even if you did have to cut the leg sheild better than the bike siting not running

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Re: Yamaha t80 t50 carb difference ?

Post  Duckrider on Sat 9 Jul - 2:26

JohnW wrote:As you have fitted a T80 cylinder onto a T50 which has a shorter stroke than T80, the capacity will be 71cc as against 79cc for T80. So even if you fit a T80 carb you may have to adjust the jets accordingly. I would think the difference of 8cc will not make that much difference though. The used carb in the ad looks OK except for small round plastic cover over choke operating lever & spring is missing.

scratch I have to say that i did not know that. This is because the diameter of the crank is smaller at T50?
No problem, i have now a T71 Very Happy , with three speeds, and because i keep the same cylinder head i have more compression ratio than the T80, and i believe because of the lower transmission ratio at the gearbox and the bevel gearbox i will have a fast bike , at least for the first kms ....Embarassed
Is there a way to adjust the jets or the needle? Or i have to do this practically?
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Re: Yamaha t80 t50 carb difference ?

Post  Duckrider on Sat 9 Jul - 2:41

Sheldon cooper wrote:Duckrider where did you find these new Chinese carbs. Do you have a link? Me and another forum member are trying to find shaft seals so you know where we can find these? Thanks

I don't know if it matters but i found theme in Greece,

http://www.car.gr/parts/view/2174403/

http://www.car.gr/parts/view/5843382/

http://www.car.gr/parts/view/7684833/

http://www.car.gr/parts/view/3215577/

http://www.car.gr/parts/view/841595/

http://www.car.gr/parts/view/6451416/

you can contact seller via email and ask any questions you may have.
And maybe i will be able to help you.
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Re: Yamaha t80 t50 carb difference ?

Post  Duckrider on Sat 9 Jul - 3:00

Sheldon cooper wrote:Well it says in the hayns manual to replace them to avoid air leaks, my bike will run if bump start it and keep going but will not kick start or idle, the only thing wrong I can see is the shaft seals

I found these special seals in a SKF store but these are not plastic around, i mean the outside material is metal, a gold in color and they need pressure to put in place .

As i have at the moment my engine and carb in pieces i removed for first time very carefully the main nozzle, i used to clean the carb but i have never give a look at the main nozzle. i found it in very bad condition, ih has around about 18 holes and the 7 was blocked with something like salt.
Now i will buy a special tool for cleaning these spares and try to clean the nozzle.
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Re: Yamaha t80 t50 carb difference ?

Post  3hundredspartans on Sat 9 Jul - 19:18

Duckrider wrote:scratch  I have to say that i did not know that. This is because the diameter of the crank is smaller at T50?
No problem, i have now a T71 Very Happy  , with three speeds, and because i keep the same cylinder head i have more compression ratio than the T80, and i believe because of the lower transmission ratio at the gearbox and the bevel gearbox i will have a fast bike , at least for the first kms ....Embarassed
Is there a way to adjust the jets or the needle? Or i have to do this practically?


Be aware that it is highly likely you will get detonation with too much compression. This can blow head gaskets, spark plugs and the engine will ping, causing it to run poorly. Engine won't last long as a result. Embarassed

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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Sat 9 Jul - 20:24

3hundredspartans wrote:
Duckrider wrote:scratch  I have to say that i did not know that. This is because the diameter of the crank is smaller at T50?
No problem, i have now a T71 Very Happy  , with three speeds, and because i keep the same cylinder head i have more compression ratio than the T80, and i believe because of the lower transmission ratio at the gearbox and the bevel gearbox i will have a fast bike , at least for the first kms ....Embarassed
Is there a way to adjust the jets or the needle? Or i have to do this practically?


Be aware that it is highly likely you will get detonation with too much compression. This can blow head gaskets, spark plugs and the engine will ping, causing it to run poorly. Engine won't last long as a result. Embarassed

I fully agree with 3hundredspartans the extra compression (14.9 to 1 by my calculation) will put heavy loading on the engine & will cause pre ignition (pinking). Far too high for petrol.
A far better solution would have been to fit a complete T80 engine which would also have the advantage of the 4 speed gearbox. In my opinion the T50 engine was rubbish, why Yamaha fitted the 3 speed gearbox is a mystery. Maybe to comply with legislation in some countries. In the UK the T50 was restricted to 30 mph to comply as a moped. this was achieved by fitting a restricted exhaust on the T50, I found this out myself when I fitted a T50 exhaust on my T80, it struggled to get to 40mph. When I cut open the silencer I found that the inlet end had been restricted. I removed this, welded up the outer casing & the performance improved. With the pattern silencers being the same for T50 & T80 this problem is no longer a problem. But even with a derestricted silencer the T50 is a sluggish beast.

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Re: Yamaha t80 t50 carb difference ?

Post  3hundredspartans on Sat 9 Jul - 20:43

I agree John re T50. I remember renting them in Greece 20 years ago and they were gutless. A 50cc is too small to start with and on top of that being a 4 stroke makes it even worse. Worth more for the parts let alone for the performance or lack there of. Yamaha would have been smarter to produce the Townmate in 100cc and 125cc versions. Very Happy

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Re: Yamaha t80 t50 carb difference ?

Post  JohnW on Sat 9 Jul - 22:39

There must be lots of those T50's lying around in Greece & with no rust to the frames, pity it would cost too much to import them to UK where they could be used to re frame the numerous T80's that have rusted out frames over here.

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Re: Yamaha t80 t50 carb difference ?

Post  Sheldon cooper on Sat 9 Jul - 22:55

Duck rider, I have had had look at your links and this could be what I am looking for, there is a difference in €10-€60 are they new or used? I have email the shop for help but may not get a reply

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