Throttle Response...or lack thereof!

[AstroPenguin]

Quick question for the masses - my throttle isn't quite responsive when I first roll onto it. It feels like a there's a slight dead zone before it actually opens up. It does snap back however. I'm guessing this is just a simple throttle cable adjustment...but I'm not quite certain how to "tighten it" so to speak. Any advice? I've never had to adjust a throttle cable before...

[alpo]

There are two places to adjust the throttle cables: Where the cables attach to the carbs and at the throttle itself.  Both have a threaded adjuster and a lock nut. The ones at the carbs need a 10mm wrench; the ones at the throttle adjust by hand.

I find it best to get most of the slack out of the cables by adjusting them at the carbs. Raise the gas tank. Loosen the lock nuts at the throttle and tighten the adjusters all the way towards the throttle. Loosen the lock nuts at the carb then turn the adjusters out until there is less slack in the cables. Don't go too far with the pull cable, or the carb butterflies will be open too much and you won't have any adjustment left at the throttle - just get the extra slack out of the cable. You will be able to feel it by turning the throttle as you go. Tighten the lock nuts. Then use the adjusters at the throttle for fine tuning to suit your preference. 

[Watcher]

I might add that you should adjust little by little and turn the bars full lock left and full lock right as you go to make sure you don't experience any automatic throttle application.

[mr72]

There are multiple things going on here.

Usually "throttle response" is not how you describe slack in the throttle. I believe the FSM specifies 5mm of slack in the throttle cable. That doesn't really affect throttle response, which is usually characterized as a delay between turning the throttle and response from the engine. This is really about throttle engagement. Once you take up all of the slack, then is there a delay between when you open the throttle and when the engine responds?

When talking throttle response usually we're talking about a delay which is actually inherent to some extent in a CV carburetor setup like this since opening the throttle doesn't directly allow more air into the carburetor, but it allows vacuum to be created which lifts the slide and it's the lifting of the slide that results in more air (and fuel) to the engine. This delay is caused by the time it takes for the slide to be lifted due to vacuum. If you have a vacuum leak or holes/tears in the diaphragm(s) then it can cause this delay to be much longer and make it feel like very poor throttle response. There are other causes as well, but if you really have bad throttle response and not just slack in the throttle cable, then look for a vacuum leak and inspect the diaphragms. There are many likely causes of a vacuum leak.

This isn't the only cause but IMHO the most probable.

[Kookas]

Usually "throttle response" is not how you describe slack in the throttle. I believe the FSM specifies 5mm of slack in the throttle cable. That doesn't really affect throttle response, which is usually characterized as a delay between turning the throttle and response from the engine. This is really about throttle engagement. Once you take up all of the slack, then is there a delay between when you open the throttle and when the engine responds?

I get where you're coming from but when you have play in the throttle cable and roll on the throttle from closed, the extra time taken to get over the deadzone adds to the throttle response time in that instance, so I think this is what was originally being referred to.

[mr72]

I get where you're coming from ... I think this is what was originally being referred to.

Probably so and I hope you're right because this is very easy to fix.

Just wanted to post up to be complete in case later someone searches and finds a thread about "throttle response" ...

carry on...