Which slides - 3 or 3 1/2 ? Also thoughts on a change to single Mikuni

MichaelB

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2 ring needle goes with straight spray tube, usually 750's
4 ring needle goes with cutaway spray tube, usually 850's.
 

Fast Eddie

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Thanks, yes. I have had a read of the article too, and it’s bookmarked for a longer read.

But, should I be fitting no. 3 slides to fully make it a mk2.?

edit, I’ve just seen the last reply. It did have black filter and black cap,silencers. Now it’s a K&N and pea shooters.
You’re gonna have to read the article and follow the advice within to find out which is best.

In my experience, the difference between them is not great. I find it hard to believe, that if all else was equal, a bike that runs perfect on 3 1/2s would be rich enough to foul plugs using 3s.

Marking your twist grip so you can see exactly how open the throttle is, and understanding which carb circuits are in play, will go a long way to helping you ascertain what’s what.
 

Fast Eddie

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Landspeedracer, you said you think it’s weak cos of the plug colour… you’ll get a lot more useful feedback if you post some pics of them there plugs…
 

Fast Eddie

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Well with today’s funny petrol looks can be deceiving and I’ll be interested to hear what others think, but personally, I think they look bloody good!

What can of riding did that 100 miles consist of?
 

Onder

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To me there is quite a difference twixt the two sides. The lean one looks more like my 850 than the right. I would like them both to look like the RHS plug.
 

concours

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I have completely stripped and cleaned thoroughly (ultrasonic tank) my 2 x 932 Amals that were fitted to my 74 mk2a

the mods it’s had during my recommissioning include Pazon Surefire , new unbalanced exhausts and pea shooters, and a narrow K&N air filter. All in place of the balanced exhaust, black caps and plastic air filter

I‘ve now fitted 260 mains, 106 needle jets, new float needles, new 2 ring needles in the middle notch.

I have it up and running using the 3 slides, most of my running appears to be at barely more than a quarter throttle from what I can notice, apart from when I wind it on and get it to fly. It does appear to be running OK-ish but the plugs seem to show its a bit weak

Should I have also changed to the 3 1/2 slide as well? what difference would it make, and more importantly how would I recognise it’s different?

Part of me wants to scratch an itch and fit a single Mikuni 34 kit in place of twin carbs for ease of balancing ie none. I’d like your thoughts on this too m
Unleaded fuel does not color the plugs like race fuel/old time pump gas.
 
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It’s a shame I photographed them the wrong way round, left plug is right cylinder, the rh plug is the left cylinder.

so, the right hand cylinder appears to me to be a bit weak, also the right hand exhaust pipe is noticeably bluer than the left.

all of this running has been mainly light, 1/4 throttle 40/50mph, with a bit of 70/75 thrown in but even that is around half throttle - remind self, mark the twist grip before the next ride.
 

RoadScholar

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The slight difference in color, given the riding conditions that you mentioned, could be either or both of air screw settings or carb sync. I agree with FE that they look good as photographed.

Putting a piece of tape on the twist grip housing and also on the twist grip marking, after taking out any slack in the cable, from 0 to 1 then adding 1/4, 1/2 and 3/4 points, this will give you much better data.

Best.
 

maylar

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If you have no hesitation or spitting back on initial opening of the throttle then leave it be.
My MKII surges coming off idle. Kinda the opposite of hesitation, it's like a kick. Starts easily and idles perfectly, no fouled plugs even at low throttle (I spend a lot of time at 1/4 throttle). No popping when blipping the throttle, which is my criteria when adjusting idle air. Is this normal, or should I be looking to lean it out a bit?
 
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My MKII surges coming off idle. Kinda the opposite of hesitation, it's like a kick. Starts easily and idles perfectly, no fouled plugs even at low throttle (I spend a lot of time at 1/4 throttle). No popping when blipping the throttle, which is my criteria when adjusting idle air. Is this normal, or should I be looking to lean it out a bit?
Sounds like you've achieved nirvana..... Celebrate!!
 
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My MKII surges coming off idle.
Sounds like the tickover is lean and then the mixture richens on initial throttle opening. Suspect partially blocked pilot jets or just the pilot air screw is too far out. Tune for fastest idle with fully warm engine on the pilot air screws as a first step.
 
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I’m going to invest in a colourtune and see if I can adapt to it. I’ve been on YouTube and seen a few videos and they make it look easy. Yeah, right :)
 

Lineslinger

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Good thread . Lots of of solid/reliable guidance. Thank you.

I am curious what spark plugs are you running?

Just thinking out loud here but consider an infrared thermometer before purchasing a colortune.

I own and have used both.

Using an infrared reading and adjusting my carbs to the header pipe temps I was able to synchronize both 932's on my 74' 850 to within a final tweak of matching in mixture/plug color.

I got them close enough so that I could not detect a difference in performance...but of course I kept on screwing around with them until I was satisfied with the color match on the plugs vs. overall performance.
An infrared will run you around $18.
 
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RoadScholar

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Setting your idle mixture on the rich side aids the transition to the needle circuit.

Consider that when you take off from rest the transition from idle system to needle is rather quick. Given the inertial components of air and fuel the air flow will increase faster than the fuel. If you have a rich idle mixture the increased supply of air will drive the mixture toward a better stoichiometric ratio which in turn will sharpen acceleration and aid transition to needle metering.

A sports engine doesn't like idling.

Best.
 

baz

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I’m going to invest in a colourtune and see if I can adapt to it. I’ve been on YouTube and seen a few videos and they make it look easy. Yeah, right :)
A colour tune will help you set the pilot air adjusting screws
And that's about all I'm afraid
 
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I don't want to harp on this but the DENSO iridium IW22 plugs really will give you better response and over all running.
 
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My MKII surges coming off idle. Kinda the opposite of hesitation, it's like a kick. Starts easily and idles perfectly, no fouled plugs even at low throttle (I spend a lot of time at 1/4 throttle). No popping when blipping the throttle, which is my criteria when adjusting idle air. Is this normal, or should I be looking to lean it out a bit?
If it starts and idles perfectly, with no plug fouling, the only thing I would try to smooth the transition (if you think it merits attention) would be to lower the needle maybe?
 
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