1971 T120R

[villa3]

Mate of mine purchased a 71 Bonny from a dealer who imported from the states, he was told it starts and has had the head removed and all is good. we have tried to start it with no luck, head hasnt been removed and the points didnt look to flash. i purchased and fitted a Pazon Surefire electonic ignition for him thinking this would do the trick. No luck so removed and cleaned out carbies ( both pilot jets blocked and set up float levels ) and fitted all new gaskets and springs and cables. Still no joy, plugs are dry so i am still thinking fuel problem. Any one got any ideas, the spark from the Pazon doesnt seem that strong but i am not sure if that is normal. Bike is positive earth and has been wired as per the instructions.

[L.A.B.]

i purchased and fitted a Pazon Surefire electonic ignition for him thinking this would do the trick.

the spark from the Pazon doesnt seem that strong but i am not sure if that is normal.

Did you also replace the two 12V coils with 6V ones?
If not, then you won't be getting the best out of the Pazon if you have two 12V coils wired in series (as they must be for the Pazon). The Pazon instructions say that two 12V coils will work with a low compression engine but that they "strongly recommend" using two 6V coils (or a 3-4.5 ohm dual ouput coil).
However it's unlikely that weaker sparks from two 12V coils is the actual reason the bike won't start but it probably won't be helping.

[villa3]

thanks for the advice, fitted a pazon to my 71Tiger since and i have the same problem. It ran and started no problem with the Boyer but i changed as i heard good things about the pazon and by buying two i got them at an excellent price. I have checked all the settings on my tiger and everything appears to be spot on, both mine and my mates bike run 12V coils and yes they are wired up in series. I will order the pazon coils and fit them to mine and see if that solves the problem.

[L.A.B.]

The two 6V coils should provide better sparks under compression. But the plugs wouldn't normally be dry-so something appears to be wrong there?

Did you check/clean the two small bleed holes (in the green/yellow area in the Bushman's link) in the carbs? 

http://www.jba.bc.ca/Bushmans%20Carb%20Tuning.html

How old is the petrol?

Is there plenty of compression on each cylinder?     

[villa3]

Yes i stripped both carbs and both pilot jets were blocked, i will remove the bowls and lap them as they are both leaking but i cleaned out both carbs with compressed air. I have ordered two 6V coils from Pazon which i will fit to my Tiger and see if that resolves my problem then i will tackle the bonny. I have just rebuilt my Tiger engine so that has plenty of compression, the bonny had about 140PSI on each cylinder but has been sitting around for quite a few years.

[L.A.B.]

Yes i stripped both carbs and both pilot jets were blocked

The pilot jets/bushes were not the ones I was referring to.

I meant the two bleed holes that can be seen in the green area of the Bushmans sectioned photo (or in the yellow area [pilot mixing chamber] of the sectioned drawing).

[villa3]

Are these two bleed holes visible when the bowl is removed as i didnt notice them

[L.A.B.]

Are these two bleed holes visible when the bowl is removed as i didnt notice them

No, the chamber is blanked off on the underside.

You can see the holes if you look into the bore of the carb, one hole is just under the slide and the other is on the engine side of the slide (see diagram).



 http://www.oldbritts.com/amal_tun.html

Be extremely careful not to enlarge the holes (by poking wire etc. into them) if they are blocked.

[villa3]

Thanks LAB i will remove my carb first and check, just checked timing again on the TR6 with degree wheel all spot on, check resistance of 12V coils all good, checked wiring all good but no smoke or noise just short of breath. I will let you know how i go with the carb, if all ok i will wait for the new 6V coils.

[villa3]

Checked carb on TR6 again all good, rechecked timing with degree wheel all good. Advanced timing by ten degrees and it fire first kick. gradually moved static timing back to 38 degrees fully advanced and it runs great. Just need to sort out dragging clutch and then i can road test it. Next i will try the bonneville the same way by messing around with the static timing.