Mikuni 38's for a 750

D

Dale

Senior member
Location
Malta
I have read on earlier treads the consensus of the group is that conversion to Mikuni's should provide more power and economy.
So...I now have a nice pair of second had Mikuni 38mm's (from a Ducatti) being sent to my home.
I haven't seen them yet, but will be home again in two weeks.

Consequently I am after anyone who has made this conversion to let me know their experiences with fitting these to a 750 SF2.

What brackets/flanges will I need to get?  (I am not particularly handy with fabrication, so will need to either buy or have made for me).
Will the jeting need to be changed?  (SF2 with 2:1 exhaust. Not racing, just regular road use).
Will the cables fit or will I need to get new ones?
I had intended to remove the air box and replace with a pair of cone filters onto the Del-orto's when I go home this time (am becoming fanatical about weight), is that still a good idea with the new carbs?

Any info will be apreciated.

Thanks
Dale
 
You will need to be more specific to get advice.
Are they rubber flange or alloy flange type?
Do they have any linkage type system be able to build onto to connect them?
Are they RS, flatslide, roundslide, CV, ....?
I fitted 39mm Keihin FCR flatslides to my SF2 and it is a revelation over the Dells, which felt reasonable before I swapped them.
There was some machining to fit them to the original stubs (not rubber mount type), and sort out a linkage (from an old set of twin-carbs from a wrecker) to use with one cable and able to be synchronised. The original airbox rubbers fitted them and I have a cutdown original airbox with 2 huge foam filters into the rubbers.
I have a good deal of experience with jetting and it took some time to get right.
If you aren?t handy with the tools it could be pretty expensive to pay a shop for help.
Have a look at the steel dimension of your SF frame.
 
Dale,
We have 3 x 880cc Laverda twin engines in our workshop that we are working on at the moment.
One of them is going on the street, other two are heading to the track so will run Dells.
Street engine will be running 40mm RS Mikuni Flatslide carbs.
We have already made the inlet manifolds for the 40mm Mikuni carbs but I have not done the conversion yet.
If you wish we can make you a conversion kit to turn your 38mm carbs into a twin set, that is if you have the RS Flatslide bank.
We don't bother stuffing with CV carbs so you need to have the RS set if you want us to help out.
Am a few weeks away from getting into the carbs, am still working on the cranks though have done the 880cc conversion, oil cooler conversion and the head/barrel dowel arrangement.
1st Crank is going in to get the balance factor worked out this week, have machined 5.2kgs off the crank weight.
If interested, drop us a pm.

Good luck
Red
 
Tippie, Red:
Thanks for the info.
I was hoping that there might be some off the shelf items to adapt, but it seems that I will have to start from scratch.
A picture is attached.
As you can see, they are already bracketed together with a single throttle cam, but, as they were from a Ducatti, I would be suprised if they fit straight onto the inlet stubs of the Lav.


Tippie:
When I get to it, I would apreciate any info that you can pass on about your jetting results.
It will give me a good starting point.

Red:
I don't need to increase the capacity of my cyllinders, but I really want to!
If the engine ever wears out, that is the path I will take.
Obviously more power, but what does it do the the responsiveness/'reviness' of it?
(I remember my Triumph Sprint 900.  More power than I needed, but I still envied the 1200 owners)
(un)Fortunately the Lav seems still good at 35 000km, and suposedly will last for ever.

Dale
 

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Dale
hard to see from such a small photo but what I can tell you is that they are not RS Flatslides
can see a butterfly arrangement inside so that rules out the RS series
also, your twin is 150mm bore centers which is a lot wider then the carbs in the photo so will not bolt on

Phil,
what I didn't mention is that we started with an early GTL crank so 5.2 kgs was easy
we have a brand new untouched never used bare SFC crank here that we probed and entered into the CNC program
due to the weight of the 880cc pistons that Andy Wagner sells, which are a set of Accarlite's (should be called Accarheavies) we left extra weight on the counterweights until we see where the balance factor is right now
weighing the bare SFC crank and the crank in the photo, can tell you we have a lot of metal in reserve
am still considering getting new pistons custom made from Ross Racing Pistons which I estimate will be at least 60 grams lighter then these slugs, have 4 engines to do in total, 3 at the moment so is worth while
need to send you an e-mail shortly as KN sold us this twin head that you ported to the maximum and for the life of me I cannot work out what you had in mind for pistons, we have machined up custom inlet manifolds to actually seal on what was left of the inlet stub mount, but the size of the combustion chamber  :o , is causing me some issues

Nearcompletecrank1.jpg


Nearcompletecrank2.jpg


 
Hi red - I did a head for my 880cc SF that I spent ages on - the ports were beautifully tapered and a great shape  - took me ages - that motor never made good power. We had done Steve elliot's 870cc SFC with the ports hogged out to the max (similar to that  head you got from KN)  - using 40mm dell's- it had gobs of power and went like s--t off a shovel. - not much meat left for stubs - i'd planned to weld them on. Can't remember what pistons I'd planned to use - knowing me - i may have going to be using different length rods, barrells or god knows what - the Accralites that AW uses are the type I got accralite to make about 20 years ago. Is that the original centre joining pin (25mm broach)? wouldn't like to trust that!- I see you've got one of my "Big pins" in the background - this stops any chance of doing a 180 conversion whilst riding down the road! - Keep up the good work - Regards - Phil
 
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