'82 XS400R Number of Idle Adjustment Screws?

robindean

robindean

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I recently bought a rebuilt '76 Honda CB500T, which has two idle adjustment screws (one for each carbarator).

I was freaked out when I discovered this, thinking that perhaps I needed to do the same for my '82 XS400R.

Does my '82 Yamaha XS400R have two idle adjustment screws or just the one on the right?
 
Are you sure those are idle adjustment screws? My friends cb360 had two different mixture screws on each carb, but there is only one idle rpm screw.

Try finding a manual for that bike to be certain what they do. Hondatwins.net was a good site.

"Idle screw" is a vague term. Did you mean idle mixture or idle rpm?

Edit:

I did the leg work for you. Here you go: http://www.hondatwins.net/forum/viewtopic.php?f=50&t=10846
 
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Damnit, BC ... you need to be closer so I can buy you a beer!

So then, our bikes (the '82 XS400R / J) only have the ONE idle rpm adjuster, correct? The one that's on the right of the engine by the throttle switch (where the cable ends), right?

Assuming that's correct, cue my sigh of relief.

I'll dig into that manual but it would seem that there are in fact two for my Honda twin. Both reside immediately next to each separate throttle connection.

Time to do some reading.
 
One idle rpm screw, two mixture screws is correct unless the later models are wildly different :)
 
bcware said:
One idle rpm screw, two mixture screws is correct unless the later models are wildly different :)
Click to expand...

That's exactly right, but I think that, as stock, the idle mixture screwed are covered. There is also one screw to adjust the balance between the carbs.

I'm a big believer that more adjustment is usually better, but I would think individual idle speed adjustments would have you chasing your tail a lot.
 
Well then (and I realize we're not talking Yamaha here so ... hope we don't get into any trouble) ... I think you both might be mildly entertained by these photos LOL.

I believe I'm correct in that there are TWO idle screws for this particular bike. Now, don't hold me to it because I've not checked the manual yet but, I will say that adjusting these does change the idle as well as the compression.

Photo one = one side of the bike
Photo two = the other side

Mind each screw you see (THAT'S WHAT SHE SAID!)

idle_a.jpg


idle_b.jpg


Now, what do you both see? A pain in the arse? Me too! LOL.
 
Actually (and I'll check this the next time I uncover the bike) ... I only see a set of gold screws pictured on one side of the bike! It might be the camera angle but ... are the vertical, silver screws by the throttle the idle or that mix you were mentioning? I was under the assumption that the silver, vert/diagonal screws are idle related.

Learning a lot!
 
Oh hell.

HAHAHA!

Time to break out the manual.

I'm selling this beast for $1200. Let me know if anyone you know might know someone who knows they'd like to have it ;)
 
So, then ... I've probably been using my throttle stop to idle my XS400R. Ugh.

BC, you up for taking a picture of where I'm supposed to adjust the idle at on my Yamaha?
 
You adjust the idle speed from the throttle stop,however that doesn't mean that the fuel mixture and/or air mixture screws won't also have an effect on the idle speed.To properly adjust the idle,you turn the air/fuel mix screw to achieve the fastest idle,then adjust the throttle to the specified speed. Repeat until satisfied. lha
 
So, if I decide I want to perfect the idle, do I crank the throttle stop all the way loose, crank it wide open, or set it to the middle point before adjusting the fuel/air?

I'm guessing middle?

Also, (and yes, I do have the pdf manual but wanted to ask for the sake of conversation) where do I adjust the fuel/air on my XS400R?
 
those screws will affect the balancing of the carbs. I'm assuming here that both carbs are operating separately and have two cables from the throttle.

lots of room for error there and as an added bonus, they must affect the idle too.
 
Set the mixture screws about 1-1/2 turns out from GENTLY closed[if you don't gently close the screws,the rest won't make any difference,as the screw tips will break off], start the motor and set the to idle at 1000-1200 rpms. Then,adjust the screws out until the motor runs it's best,then adjust the throttle stop to 1000-1200 rpms.Repeat this action until the motor runs well,and can not be improved.During this adjustment,adjust the screws on both carbs the same amount. This is assuming that you have Bs34 carbs linked together as in a stock setup. I guess that the pictures that you are referring to is of the Honda,but your question is about the xs400,right? lha
 
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robindean said:
Thanks for the lesson! :)

By the way ... what does lha stand for?
Click to expand...

You're welcome and lha is my initials.Good luck on your bike,hope you get'er running well.I'm fixing up some Kz900 carbs for my '82 seca,as they work on slides with levers on top,with adjustment for synchronization on the top like tappets,making it a bulletproof design,and they're mikuni,and work on a single cable.I just have to make a manifold for them. lha
 
I set my mixture screws @ 2 and half turns and went from there.You have the idel stop screw on the bottom and another screw in the middle of the carb on top that balance out the carbs.A good idle speed while warm would be between 13k to 15k.You should make all adjustments to the carbs while warm.When cold your choke fully opened will probaly increase the idle to 2-23k
 

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