Hi folks,
In a few recent threads there has been discussion around watching slides rise/fall while bike is running.
I'd just like to get some feedback from folks who have actually done this. The reason I ask is that when I did this, the slides oscillate a surprising amount during normal operation, which makes it hard to know exactly how they are responding. A few other posts on this forum have indicated a similar finding, and I've found this supported on another forum. It would be great to get a larger sample.
So, are you a slide peeper, and if so what did you see?
Cheers
HnN
It actually did help a lot in tuning my engine for the first time after I got it, when I rebuilt the carbs and upsized the jets.
On first startup, the bike ran really rough and though the slides oscillated a bit, they really didn't rise when I hit the throttle.
I had put some grease on the slides, thinking that it would help them move with less friction. Turned out the grease was actually causing them to bind. Washed it off, and now with throttle the slides slid up, and the engine was much happier.
So I vote for checking them out in action.
Hi endopotential. Thanks for the input. How did the slides behave (regarding oscilation) after you had cleaned off the grease?
If you have it running with the air box off, it's hard to not look at them as they do their dance. When mine was running super rich I could actually see a little puff of vapor cloud coming out the left carb, then get sucked back in. Above idle they don't jump around as much but they do go like crazy at low RPM.
Intake vacuum lifts them up, then at the end of the intake interval, there's no more vacuum so they drop back down under spring pressure. Since intake is only 25% of the cycle and things are happening relatively slowly at idle, there's more time for the slide to come down before the next intake pulse. This is happening about 10 times every second at idle. At higher RPMs there's less movement and it becomes too fast to see.
The slides should be clean and dry. If you stick a finger in there (with the bike NOT running, of course) and lift the slide up manually, when you let it go, it should glide down smoothly and slowly. If it pops down, you may have a bad diaphragm or vacuum leak.
Quote from: herennow on September 05, 2018, 08:01:59 PM
...the slides oscillate a surprising amount during normal operation...
Yes they do, and it's perfectly normal. The time to worry is when they're not doing that.
The slides operated pretty much as kilted1 described. At idle, they vibrated slightly at the lowest position. Then with throttle they both jumped up to a higher position, still vibrating a bit at that higher level.
Getting rid of the stock airbox and going with the K&N lunchbox makes the entire back side of the carbs easier to work on and inspect.