Lighter throttle spring on RD400

[Holeshot]

Has anyone been successful on lightening the throttle springs on RDs?
The cable, throttle and oil pump are properly cleaned and lubed but the force needed to twist is still pretty heavy.
Any suggestions?

[m in sc]

on stock vm28s?

[Holeshot]

Yes

[m in sc]

fit vm 24 or 26 springs

[Holeshot]

Are these springs smaller diameter or shorter length?
Or smaller gauge?

[m in sc]

smaller diameter wire typically and thinner gauge.  the s series kawi triples used 24's for sure .02

i have ot say, ive owned a lot of stock rds, ive never found the pull that bad. what year is your bike? it it possible somebody jammed high top springs in some short top carb bodies?

[Holeshot]

It's a '76 400c and everything seems very stock OEM.
I'm in the "easier to twist for less fatigue" camp...
Do you know any Mikuni part# or link for those smaller springs?
Cheers!

[m in sc]

this says for vm22-28 but?

https://www.ebay.com/itm/Genuine-Mikuni-VM22-Flange-VM24-VM28-Throttle-Slide-Return-Spring-VM24-195-/161874398824?_trksid=p2385738.m4383.l4275.c10


ive always had spare stuff laying around to do this, like ive used vm38 springs for vm34s.

[Dvsrd]

smaller diameter wire typically and thinner gauge.  the s series kawi triples used 24's for sure .02

i have ot say, ive owned a lot of stock rds, ive never found the pull that bad. what year is your bike? it it possible somebody jammed high top springs in some short top carb bodies?

On that note, I believe that the Hi Top carbs should have lighter pull at larger throttle openings,  IF the spring force at fullt close is the same. Standard short vs long spring behaviour.

[m in sc]

im not sure if the coil diameter is the same TBH, may not be. thats an interesting point though. however, a high top spring in a short top carb = way stiffer.  but since we are dealing with a 400, all short top stuff.

[Kawtriplefreak]

Niche Cycle in FL is who I use for low effort throttle springs. I bought a set for the 34s on my H2 750 triple and they were still too hard. On the advice of M in SC I put a set of VM 28 springs for an RD and a new throttle cable well lubed with dri slide cable lube and it is now a one finger and thumb pull. I just bought a set for the VM30s on my RZ which I have yet to install. They are cheap and fit right. My wrists are not what they once were and it makes a huge difference for any long duration flogging.

http://www.nichecycle.com/ncs/mikuni/parts-by-category/throttle-springs.html

[SUPERTUNE]

Always check the throttle tube, if broken or grip rubbing the bars will always hinder drag.
I use Tri flow for a lube.
Chuck

[Holeshot]

Thank you all for your insight on the subject...I'm taking M in SC & Kawtriplefreak's advice and order up some VM22 springs.
Also, I'll make sure I'm thoroughly lubed and friction free!
Cheers!

[rd400canuck]

This exact reason is why I run premix. The pump spring seems to exert twice the force in the cable as the two carbs combined. I unhooked the pump for some reason a few months back and ran premix and I was astonished how much it changed the way the throttle felt. The bikes feels easier to ride because of it.

After that tank i put the pump back on and went for ride. I disconnected it as soon as I got home and never connected it again. A stiff throttle makes me feel like I'm struggling to get going... going through the gears felt like a chore. For me it's work having to premix to not have to deal with an arduous feeling throttle.

[Kawtriplefreak]

I ran the 1st iteration of the Phoenix Projecton pre mix on the advice of the late Ron Reichert of Purple Haze Racing and I swore never again. M in SC plumbed up a ball valve and a hose hooked to the factory oil tank so I could tote oil with me and I had a small oil bottle with ounces marked on it so I could calculate the right mix at the gas pump and it was still a pain in the ass. That being said to each his own, just my 
A new throttle cable and some light springs properly lubed and setup as stated before and I can open three VM34s with my thumb and index finger.