Whay a push and a pull on the throttle cable?

I am just wondering, why do we need a return (push) cable on our throttles? It looks to me like we just need a pull??

Mike

Apparently the four strokes generate alot of vacuum and would need a really beefy return spring with just a pull cable.

Just to add to Mike’s post, apparently it is possible for the slide to “surf” on the intake flow at WFO and this vacuum effect could in some cases not be overcome by your standard strength return spring. And that would be scary. I discovered on my KX 500 on one occasion that the kill button isn’t very effective when the motor is at redline (I also learned that proper throttle cable routing is an important thing on a KX 500).

Therefore on the FCR the “push” cable actually pulls the slide down when you twist the throttle back to the off (idle) position.

If ya wanted to research it, you'd find that just about every fourstroke around over 350cc has a push/pull throttle and have for years. Save some of the old BSA's Triumps and those ilk. They used springs good enough to hold up the fork for a return though

The slide getting stuck due to air flow is interesting I never thought of that. I always thought that it was safety in case the cable got frayed causing a stuck slide or something similar. I have never looked on the 2-strokes, do they not have double cables on most 250+ cc 2-strokes?

Originally posted by sirthumpalot:

I have never looked on the 2-strokes, do they not have double cables on most 250+ cc 2-strokes?

I’ve never seen one. My KX 500 just has one cable, heck it may even be the same carb as some of the older, non-power jet 250s (39 mm PWK??).

I wish it did have a pull cable. I almost rode the thing WFO from the garage into my roommate’s bedroom when the throttle stuck on me. :)

A fairly common problem with the DRZ's is that the return cable frays and then breaks. Most everyone that has had that happen has run with just the pull cable. I only remember one person having a problem that may have been related to missing the return cable and that was in VERY cold weather. Don't remember the exact problem. Do a search on the DRZ forum to find it.

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