$50 flatslide carbs for triples

F

Frank from Quebec

Full member
Location
St-Ours Quebec Canada
Hi guys,
In another thread I asked about the tuning of flatslides whitout the acceleration pump and the answers were that it can be made to work good so I went ahead and bought a set of Mikuni 33 flatslide from a Yamaha 700 triple snowmobile on us ebay for $50.00 It was a good price but there are plenty available for less than $100.

In this thread I will detail my experiment with them on my 1200 Mirage.

Here is how they look beside the Delorto:

003-1.jpg


They are quite clean inside and the synchronisation mechanism looks very easy to operate:

007-1.jpg


They really are smooth inside and being 33mm should be enough to replace the 32mm roundslide :

005-1.jpg


They do not fit in a straight line with the manifolds so I intend to use angled manifolds rubber sleeve like you see on some snowmobile to position them kind of like that :

004-1.jpg


The jetting is anybody's guess but  I want to first start it with whatever is in them and take it from there.
The cable holding bracket will also need to be modified as it interfere with the fuel tank as it is but no big deal.

To be continued...

 
Frank

I've got a set of Mikuni TM33 with accelerator pumps on my RGS. It's taken me a while to get the jetting right but I've been using a LM1 to sort it out.  Runs pretty well now. Biggest problem you will have without the accelerator pumps is getting the mixture rich enough just off idle.

If its any use, tuning wise what I've ended up with is:

Slide 1.5
Needle Jet type 499 P8
Jet needle 6DP2 #3
Main 105
Idle jet #17.5
Main air jet 0.5
Idle air jet 0.7
Idle mixture 0.5 turns out

Cheers

Phil



 
I've just sent you an email Frank with details of my own 2 RS carbs and some photos of how they looked out of the box from Tophams.
 
Frank from Quebec said:
They do not fit in a straight line with the manifolds so I intend to use angled manifolds rubber sleeve like you see on some snowmobile to position them kind of like that
Click to expand...

Frank, if you're planning on using filter pods instead of the original airbox, the wide spacing will mean you won't be able to put the sidecovers back on unless you do pretty radical surgery on the sidecovers. As it is the RS36s require some sort of modification for the right sidecover, either moving the front attachment point out about 10mm, or bending the pod filter. You'd have to do the same on both sides.
I'd think seriously about spacing the carbs same as the Dells, will eliminate a lot of hassles.

Ken
 
Even then if it's oval pods they will still foul the sidepanels.
I ended up repositioning the sidepanel mounts on the frame as far back as they would go. Only had to shave a few mm off the sidepanels, and turn the oval pods sideways.
 
mcnicol said:
Frank from Quebec said:
They do not fit in a straight line with the manifolds so I intend to use angled manifolds rubber sleeve like you see on some snowmobile to position them kind of like that
Click to expand...

Frank, if you're planning on using filter pods instead of the original airbox, the wide spacing will mean you won't be able to put the sidecovers back on unless you do pretty radical surgery on the sidecovers. As it is the RS36s require some sort of modification for the right sidecover, either moving the front attachment point out about 10mm, or bending the pod filter. You'd have to do the same on both sides.
I'd think seriously about spacing the carbs same as the Dells, will eliminate a lot of hassles.
Ken
Click to expand...

Ken
What you smoking man ? One of us is misreading what the man wrote ! I read that he's thinking to change the angle of fitment downwards, kind of like what Reds angled manifolds do.
Are you thinking he going to have 2 outer carbs pointing outward or sitting wide of the inlet stubs  ?  :D
 
Frank ,
I'm assuming these carbs were originally destined for a two stroke motor. If so you might have to look at changing the emulsion tubes for a four stroke specific item. Quite often carbs are two or four stroke specific and won't be happy being used in the wrong application. I don't think it will be a big deal but bear it in mind when you start trying set them up.
 
Thanks for the interest you have for my experiment  :D

@ Phil, Thanks for the info, I did not know others had tm33 on their triples.

@ Rob, Received, thanks for the info.

@ Ken, I will of course respace the carbs but I also need angle them more horizontal.

@ Grant, I'm thinking of installing velocity stacks.

@ bob, I know about the emulsion tube difference but I also know that all the VM carb kits for Norton, Triumph etc use the 2 stroke type. I have myself successfully installed dual VM34 from a snowmobile on a MG Midget using again the 2 stroke tubes so I'm not so sure they need to be changed.

I have a Wideband LM2 system and will obviously use it.

Off to the shed now...
 
I  guess I am not really clear on the concept here. What is the advantage of the swap? If someone wanted to eliminate the pumps, why not just turn them off? The Delortro carb is an excellant carb.
 
mar said:
I  guess I am not really clear on the concept here. What is the advantage of the swap? If someone wanted to eliminate the pumps, why not just turn them off? The Delortro carb is an excellant carb.
Click to expand...

It was... once upon a time.

Fact is, most of them are fairly worn by now and it just isn't financially feasable to restore them properly.  By that I do not mean a bath in the ultra-sonic and new jets, but a complete and thorough overhaul.  This sets you back by ?500 easy.  But the worn bodies remain, meaning the next overhaul is closer than you realise.  If the bodies are to be reclaimed, you'd probably need to add another 2 or 3 biggies.  Compared to such an outlay, new Mikunis are dirt cheap, and offer a load of advantages over the stone-age Dellortos.

piet

 
I received my test angled manifold and it does not look good  :(

The carburetors do not fit under the tank.

The fact they they have the throttle shaft in front vs the back for the RS prevent me from mounting them closer to the cylinder head as this is already close to the timing chain boss on the head.

So I'm back to my first idea and shopping for suitable CV's.
 
Don't give up yet...was your angled manifold simply a moulded rubber curve which went onto the OE stub manifold ?

What I'd be doing is making up a curved set which start curving from the head joint then have straight rubbers.
Even making up a rough set using exhaust tube bends welded up should give you proof of concept.
Looking at your pic with them held up against the tank it's apparent there's room if the manifolds curve from the head.
 
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