Push-Pull Throttle Cable

[mgy66]

Hello,

I have recently replaced the ignition breakpoint by an electronic ignition. The device is great and very simple to install and adjust.

I had issue with difficult start, specially in wet whether/morning. The idle is now much more stable.
Only drawback is that the idle is stuck at 2k even if the idle screw is completely down and not in contact with the carb lever (K1).

I have new throttle cables with a bit of slack as required from Haynes and return spring is strong. Carbs snap back if I let the throttle goes back free.

My question is really around this other return cable... I read the manual wrt 'adjusting link pin clearance' and suspect it may come from wrong set up. When I turn the throttle beyound the idle point, I have the required clearance(2-3mm with the excentric pin)  but noticed it does not affect the idle speed.

What the operation of throttle beyound idle point is supposed to do on the carbs? Could it be the root cause of a high idle rev?

Many thanks for your guidance...

[neat street]

Hi, it could be that the carbs are not set up right (balancing) the four adjusters (one on each carb may need to be re-set) they open the throttles on each carb, but need to be balanced so all four let the right amount of fuel through. if these rae set too high, then you are getting too much fuel through, and the throttle stop will not work.
I hope this helps?
John

[Bryanj]

Basically you may have the slides "hanging" on the adjusters so thatthey are still open a bit even with the tickover screw unadjusted all the way

[mgy66]

Thanks, that must be something like that but I missed the point on how to adjust / push down the slides 'hanging'.

I have the lever holding the 4 throttle screw on to of the carbs (not a 4 cable system) and have set the rod tips flushed with the stop double flat bolt. In the manuel it actually say to keep 1.8mm between to face of the stopper bolt and the tip of the throttle screws. So I wod think my sliders are already deeper inside the carbs.

Also this is a 850 big bore version with standard jets #40 #105.

Any thoughts on how to reset / push further down the sliders?
Thanks

[neat street]

hi, on top of each of the carbs you have a lock nut and an adjusting nut. if the slides are too high, you need to lower them by loosening the lock nuts and adjuster nuts (this is also what you would do to balance the carbs, but would need a balancing kit to get all four right). this will also affect the engine idle speed. if they are not balanced after you play with them the engine will run rough. I did read somewhere that if you put a 1/8 drill bit under the slides, the setting will be close to right, but will still need to be balanced to get the set-up perfect.
hope this helps?

John

[mgy66]

Thanks John, that really helps. I did try to loosen the lock nuts and turn the adjuster nuts so that the rods disappear inside the nuts. As per my previous post, the prob is that the tips of the rods just flush with the lock nuts surface. I feel when turning further that I have reached a hard point, maybe the needle with the main jets?

What I am thinking is the guy that put the carbs together may have attached the needle to the sliders at the botom of the rims.

From your experience, do you think I would need to take out all carbs and dismantle them to check what is the position of the needles wrt the sliders? If the assemblies (sliders + needles) are too short could that explains why despite having the rods and lock nuts flushed I still have a high rev.

What do you think?
Thanks,
Mark

[neat street]

Hi, I am not experienced in big bore kits. or jetting them, but the needle clip would normally be in the middle, and the jets you have are for a standard set-up. if the needle is lower, you would get more air to fuel ratio, if higher, then more fuel to air ratio, but could affect the speed as well? it maybe worth stripping the carbs to make sure all is clean and you have the correct jets for your set-up? (different makes of jet come up to different sizes) Ashimoto or one of the other more knowledgeable guys would be of better assistance here I think, but try that first, it wont hurt.
best wishes
John

[mgy66]

Thanks,

I take it that I would need to strip out the carbs from the engine to access the needle clips inside the carbs... That is not good news as I am too comfortable with the whole procedure of disconnecting and dismantling all the pipes, cables and supports.

I will go with your first suggestion to balance the carbs and play with the adjuster nuts. I have actually tested to screw the rods upwawrd instead of downward and it seems it have a better result. The idle screw seems to be slowing down the idle and when I turn the throttle handle beyound the idle point I can hear the rev slowing down almost to stalling.

There must be something with this throttle return cable acting on closing the sliders without acting on the needles. It is worth noticing that though there is a idle screw to adjust the position of the carb lever but there is no screw to adjust the return cable manifold.

As you pointed out pushing up the throttle assemblies increases the richness of the fuel to air ratio. It may be that the effect is actually to reduce the idle and/or to allow the idle screw to play on a larger range of idle rev.

I will test further offsets between the adjuster screws and the tips of the rods and will post the effect on the idle speed.
Best,
Mark