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RS36 tuning update - some questions...

  • Thread starter Thread starter JimmyR
  • Start date Start date
J

JimmyR

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Thanks to all who are helping me tune my Mikuni RS36 carbs on my '82 GS1100G with stock-ish pipes. They came with 130 mains and 17.5 pilots - I had assumed from reading the Mikuni manual that the pilots would have been 20 as stock but I replaced them today and discovered that they were 17.5.

So I had been intending to go to 15s on the pilots because the adjusting the pilot screws did nothing to affect idle. So I went to 12.5 on the pilots and now if I turn the pilot screws to around 1 1/2 turns out I get a faster idle.

I had also previously gone to 120 mains and although the bike ran it was a little sluggish. So now I have 122.5 mains and the bike seems a bit more responsive.

I also tightened the exhaust flanges a little and now I get very little in the way of exhaust backfire. The little I do get is at the top of a blip on the throttle. But it is much reduced. I do seem to get the odd hiccup-y pop in the carb side of the engine, like it's missed something. Not sure what to call that. It occurs on idle.

I guess my next step is to synch, but that will have to wait until tomorrow. Is it ok to test ride it a short distance to see how it goes under load? I have found that it seems that is the only way to really judge as I am such a novice at this.

Am I going in the right direction? FWIW the bike started first go with choke on, and choke was needed for about a minute.

Thanks guys!
 
Ok I took it for a short ride this afternoon to gauge where I am at. Better than before but still a fair bit of a kind of sputter coming from the carbs under gentle acceleration or steady speed. It just seems a bit uncertain and a bit lacking. Not smooth!

I need to get the right second throttle cable as only the opening cable works at the moment - the closing cable is too long. So it takes a while for the revs to come down after acceleration.

So tomorrow I will try synching the carbs. But I suspect it will take a bit more than that to fix them.
 
Well I just synched (sunk?) the carbs. I couldn't get them exactly the same but they are all within a line of each other on my Carb-tune. So they're pretty darn close! Yes the engine definitely does seem more willing now, but I am still getting a few spits from the carbs now and then. Got a pop from the right pipe on acceleration too. Haven't been able to ride yet because it's just started tipping down with rain.

One oddity - the first 3 pipes have all now started blueing. They were starting to discolour but since I did the synching 3 are quite blue but the 4th isn't. It was the hardest to synch and I couldn't get it to go below the level of #3 only above. It's close to even now though. Does this mean I need to check the valves again? I had a local bike mechanic adjust the valves for me only a month or so ago.

More to follow after a test ride - don't know when that will be.

Thanks!
 
Well I went for a very quick ride up and down my back laneway - the rain let up a little but I still got wet! Wow - huge improvement after synching. Still not quite there yet though. I get popping in the exhaust on decel which I actually quite like (!) in a British burbling kind of way but I'm still getting this spitty pops in the carbs and the mysterious non-blue fourth pipe. The spitty pops reduce power.
 
I seem to be writing to myself here, but I'll keep it updated in the vain hope that it may be of use to someone!

I think I discovered why #4 exhaust isn't blue like the rest - it has clearance of less than .03 on the intake valve. My Suzuki gauges don't go lower than .03 so I don't really know what the gap is. From cylinders 1-4 I have .05, .04, .05 and <.03 on the intake valves and .11, .09, .11 and .12 on the exhaust valves.

So now all I have to do is wait for my tappet depressor to turn up, read the values of the shims in there and fix it. I don't think I'll be using that mechanic again.

Oh well... getting there...
 
Well it's all new ground for me! Still, I feel a bit more confident about all this stuff and won't pay for someone else to do a second rate job from now on. When I first started working on bikes I was working on my Harley and had some really good help from a guy called Bill who was from Colorado and had been trained at the Harley factory. He was a great guy who taught me a lot but unfortunately he had to return to the States.

Now Suzukis are quite a lot different and I haven't found a mobile mechanic to compare. But with the amazing help I get here I feel quite confident I can sort out this engine. Harley forums aren't in the same league as this place.
 
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