Mikuni RS 36 Flatslides Carbs

[wildfire]

Its a long shot but does anyone have experience with Mikuni RS 36 Flatsides carbs. It does not have to be on a FJ. I am trying to find out what the factory setting is for the fuel accelerator screw is.

[Pat Conlon]

Hey Tom, I have not had experience with the RS, but I know several forum members have...
Most recently Mike (Skymasters) had a set on his FJ.

Hang tight, I'm sure knowledgeable folks will chime in...

[wildfire]

I made the stupid mistake of adjusting it without first noting what the original setting was.

[JMR]

The 'original" setting is pretty meaningless.....it really isn't tuned to or for anything. I'd set the onset at about 1/8 throttle and keep the duration moderate. The problem with the pump is you can put a lot of raw fuel in the engine....less is often best.  On the dyno to much pump duration gives the "RS" deadspot at about 5,000 to 5,500 RPM. Eventually the engine clears it throat and goes but you can feel it.
I have used 36's, 38's and 40's on my FJ. I have FCR 39's now. I use RS 34's on my CB750 (1000cc). The RS's can work very well and don't let anybody tell you they can't idle etc as well as stock....that is bullshit spread by ignorant people who can't tune them.

[wildfire]

The 'original" setting is pretty meaningless.....it really isn't tuned to or for anything. I'd set the onset at about 1/8 throttle and keep the duration moderate. The problem with the pump is you can put a lot of raw fuel in the engine....less is often best.  On the dyno to much pump duration gives the "RS" deadspot at about 5,000 to 5,500 RPM. Eventually the engine clears it throat and goes but you can feel it.
I have used 36's, 38's and 40's on my FJ. I have FCR 39's now. I use RS 34's on my CB750 (1000cc). The RS's can work very well and don't let anybody tell you they can't idle etc as well as stock....that is bullshit spread by ignorant people who can't tune them.

Thanks

This is my first experience with RS's and I agree  that they do idle  well. Mine has smooth idle and I actually find them quicker to sync. Let me ask you this, in your experience could the pump coming in too early cause a hanging idle ?

Also how would I "set the onset at about 1/8 throttle and keep the duration moderate."?

[JMR]

 A hanging idle is generally caused by a lean mixture (or horribly rich). If you have no vacuum leaks try turning out the pilot screws a quarter turn or so. I have the pump set up on my CB with the onset screw at .400 out and the duration threaded adjuster  at a height of .280 above the carb cover. I had a problem with the duration adjuster threading itself in secondary to vibration (the oring under the carb cover wasn't holding). I placed a rubber o ring over the adjuster and rolled it down having it seated against the carb cover.
An A/F meter comes in real handy when tuning. I use a Wego unit and it has saved a lot of time.
Good luck.

[wildfire]

Yeah I know what you mean by a vacuum leak giving a hanging idle.The return to idle was fine until I adjusted the pump screw and I was thinking maybe it nowhere near its  original setting and the extra fuel is been pumped in as soon as I open the throttle even the slightest amount.

I have a single white headed screw . Is that what you are refering to as the onset screw? if yes where would I find the duration threaded adjuster.?

[Pat Conlon]

Hey Mike (JMR) can you recommend any online tutorial on the RS carbs?
...or anything published? There is a lot of BS misinformation out on the web.

[JMR]

Yeah I know what you mean by a vacuum leak giving a hanging idle.The return to idle was fine until I adjusted the pump screw and I was thinking maybe it nowhere near its  original setting and the extra fuel is been pumped in as soon as I open the throttle even the slightest amount.

I have a single white headed screw . Is that what you are refering to as the onset screw? if yes where would I find the duration threaded adjuster.?

Yes. Make sure the pump lever is not touching the accelerator pump rod at idle. It shouldn't touch until about 1/8 throttle. The small threaded black rod sticking through the #2 carb cap...that controls the duration of the shot. You need a very small allen head wrench for that one. You may have to set onset of the pump a little later than 1/8 throttle (ie closer to 1/4 throttle). Experiment a bit. Be sure not to back the onset/activation screw out to much as the spring will not apply enough pressure and it will fall out.

[JMR]

Hey Mike (JMR) can you recommend any online tutorial on the RS carbs?
...or anything published? There is a lot of BS misinformation out on the web.

Pat....Roadracing World had a pretty good article on the tuning of CV, smoothbore and flatslide carbs in May 1991. I have the article (a bit worn and tattered). I'll see if it can be scanned. The contributors included Marc Salvisberg from Factory Pro, Sudco and Yoshimura.

[wildfire]

Thanks for the help Mike. Much appreciated.

Tom

[wildfire]

Problem solved . Thanks TMR

[FJ1100mjk]

JMR = de facto FJowners.com Mikuni Flatside carbs guru 

[wildfire]

JMR = de facto FJowners.com Mikuni Flatside carbs guru 

He knows his stuff alright. I wonder why it is so hard to find any info on flatsides online. Are they that rare?.