Why does my ST 70 engine stall ?

I introduce myself, I am bertrand age 47 french living in La Baule France, happy owner since a couple of month of a Honda DAX ST70 1972, (9000 km), pretty good and completely original condition.
I look forward to share my interest in that bike with all of you in the limit of my capabilities in english !

I have a problem of settings with my ST 70 of 1972 : the engine starts well and keeps its idle rev normaly, (either when engine is cold or hot), every thing is fine but… engine often stalls when I have to stop to a redlight for instance, (it seems to happen when I use the selector and when I have to slow down until a complete stop going back to second or first gear : it’s when I relief the clutch by letting the foot selector go to its normal position that engine stalls)

Carburator’s settings seem fine, I have adjusted the clutch following the proceedure described in owner’s manual, and clutch works quite smoothly, but when I stall I feel it comes from the fact that clutch might not completely function normaly, like if springs were tired, but I could be wrong, I would like to have your idea on that before going towards wrong directions…

I thank you in advance for your help & suggestions,

Cheers,

Bertrand

Hello Bertrand,
You seem to have identified the two main areas I would suggest as being responsible for the problem you describe.
A very common cause for stalling as you describe is slight fuel starvation.Check fuel tap filter,needle valve for fuel inlet,fuel level(float height) and pilot(slow running)jet for restrictions.An excess of fuel could also give the same symptoms though.
Clutch dragging(not releasing correctly) could be the problem.
A way to check if its a clutch problem would perhaps be to take it up to its maximum speed in second gear and then select neutral and stop,if it still stalls its not a clutch issue,if it deosn't ......................
The clutch adjuster screw only adjusts the mechanism that dissengages the clutch when you change gear as the clutch is an automatic centrifugal unit.
Solution would be to strip,clean,examine and rebuild/replace the clutch as neccesary.(very thick poor oil can cause drag also).

David

...and replace the clutch springs!
In a semi clutch, these springs release the clutch! (manual clutch = the spring are there to prevent slipping of the plates)

And, as Chief said, check, clean, lubricate all clutch-related parts.
Did you try to increase the idle with half a turn? And check the spark plug colour as well to make sure it isn't a mixture issue.

Waynus and Chief,

Many thanks you for your prompt and "to the point" replies, they will help me to organize my checkings on both carburator and clutch. I will neglect neither of them, but I have the feeling that it is the clutch that doesn't dragg well, (it seems to stay engaged instead of being completely released as it should do), as the carburation of petrol, (at idle rev, medium or "high" rev), is always fine..

But thank you anyway. as being a a newcomer in ST70 community it's reassuring to get your support and I didn't find any serious french site about the ST !

Have a nice day, I will come back to you with results and with other issues, (my right handle dealing with the accelarator cable) disengaged sometimes, it's not nice as it takes some minutes to get it back, and I havent understood yet why it happens sometimes, (when that happens, the all handle can split out towards the exterior of the bar and of course as the cable is loose the accelation is unprecise...

Thank you for help and support,

Cheers Bertrand

Salut La Baule... ici le Médoc.... t'a des photos de ton dax?

Svp continuer en Anglais.
C'est plus agréable pour tout le monde si on peut comprendre tous les messages.
Dans "general chat" vous pouvez parler dans le langue de votre choix. (Ou utilise "PM" pour contact direct)
Il y a plusiers bulletins en ligne ou on parle le français (attention ils ne sont pas si sympa comme st70.net )
Merci de votre comprehension!

In other words, please keep it all in english so that we may all enjoy the subject matter.

Many thanks Simon