Split carbs on 900 SS

I used to have the Malossi 40mm Dellorto kit on both my 750 Sport and my '90 900SS so when I was trying to make my mind up about carbs for my current SS I made enquireys about the Dellorto route.

There's an outfit in Newport that specialises in Malossi stuff and came back with a rough idea of price which instantly made up my mind ...... FCRs it was! Still feel I made a mistake going for 39s, although the few running in miles I've achieved so far feel pretty encouraging.

I can trawl through my e-mails for the reply I had from said bloke in Newport if you like.

 

Please excuse my lack of knowledge, but what do you gain by splitting carbs?

 

If you split them you can mount them on much shorter inlet manifolds which give more top-end power at the expense of some bottom-end and mid-range. It also looks rather trick, with the vertical carb poking forward into the vee. You need pod filters so I suppose that as a side benefit one could extend the capacity of the fuel tank into the area previously filled with air-box.

I fitted the 40mm Delortos to my 750 & 900 because the Webber 44mm twin choke things fitted as standard were pretty awful in general use, although Baines reckon that with enough effort they would give more power than just about anything available at the time. No FCRs in them days!

 

Ahh I see. Thanks for explaining

 

Here's the last e-mail I had from TaffsSpeed, complete with phone number current at the time (2010)

For the 900SS a full set of PHM 42.5mm carb kit from Malossi is £1650.77

Individual VHSB 38mm or 39mm carbs are £235.00 each, but cannot find manifolds to suit at the moment; also they are not with accelerator pump jets!

Individual PHM 40mm carbs are £223.22 each & manifolds from Malossi @ £72.30 Front, £68.89 Rear, O rings & fittings extra.

As to cables etc for the VHSB or PHM carbs we may have to make something up.

Remember that next year the VAT changes to 20% adding further to the costs.

Let me know which carbs you wish to go for?

Best regards

Ian Frankland

<[email protected]>

Taffspeed

07971 818693

The PHM 40s are the ones I had on my early belt 900, and indeed on my old bevel. For what it's worth I think the current bike, which felt slower than the old one when it ( the current one) had stock carbs with stage 2 dynojet, now feels like its going to be considerably stronger, once it's run in, with the FCRs.

Cheers

Grunt

 

Are you sure? I talked to Allens about those and remember them being about 50% more than the FCRs. On the plus side they have chokes and are apparently beautifully built .... roller bearings instead of plastic bushings, for example.

I've just had a 100 mile lap on mine and the roll-on performance still really impresses, and that's with 39s. Vibrates a bit, though .... perhaps the pistons are lighter than stock? Mirrors very clear, mind you. I reckon a tuned SS motor in a 748 would be a very nice bike ..... eek, there goes my pension fund.

 

Imola

I have Dellorto 40's on my F1 rep...900SS engine, the manifolds are still available from Malossi, as are the pod filters. I have trumpets on mine...unfiltered with just a wire mesh 'filter' on the trumpets! I didnt buy the Malossi inlets, I used one from a Paso and then cut down and welded up a standard SS so it was the same length.

I have seen an 851 with a 900SS engine in it and Mikuni flatslides on it, the owner told me they were 38's bored to 40. You can get 40's and 41's pumper flatslides (for a...umm... Hardly diddly Davison!) you dont want to go larger than this apparently.

 

Hi Steve

dont know mate havent run the bike yet, havent been able to do any work over the winter whatsoever as it was down to -24 at times...and my garage isnt heated! and from sep till dec I had a slipped disc and couldnt even shuffle along on crutches properly let alone dart around a cold garage! 300 is a good price for new ones methinks and I am in the process of making my own cables. But I reckon I will ask the chaps at Venhill to make me up a set... not so good at soldering nipples me

whatever happened to your ST framed 888 rep mate?

George

 

Hi folks, finally made the migration from the Ducatisti forum.
I'm considering short manifolds and splitting my FCR's but haven't been able to work out the cable setup required yet. Anyone got some advice?
TBH sorting out the sprag clutch and booking some dyno time to set up Pablo's old 944 HC engine is more of a priority for now.
It's good to be back guys.

WW

 

Have a read of this Steve, especially the bit where they tried numerous valve sizes, porting, exhaust headers/cans etc, but just couldn't get any top end until they tried split carbs on short manifolds !
Reed's M944

Basically it's the manifold length and not so much the rest of the engine layout that holds the top end back.

I've split my FCR's and fitted them onto ST2 inlet manifolds with the rubber boots machined off! I had to make some cables and use an old style twin cable splitter, but the end result is, ...... you know the extra pull you get with a pair of FCR's over the standard mikunis, well that 'pull' carries on for an extra 2k rpm at the top end

Oh, and those worried about losing low/mid range .......... don't worry, it's still there!

 

I'll tell you what I think.............It's an effin sight easier setting up a pair of split Dellortos than it is an effin pair of linked OEM Mikunis......

.....to start off with, I never burned my arm setting up the Dellortos....

I would go for 'pumper' Dellortos any day of the week if I could afford to do it now.

AL

 

you've probably had a cast around the various Forums already Steve but if you are going to try really short manifolds, the limiting factor (more with the Dellorto's than the FCR's) is the front cylinder as the only good solution is a truly downdraught carb (which even the FCR 'downdraught' isn't). Several home-tuners have posted (from memory) describing the symptoms of 'going short' using split FCR's (one sidedraught/one 'downdraught') - one of them being stalling (partial flooding at a guess) on hard braking.

 

There'll never really be a perfect split carb setup on an L shaped engine. The need for a float bowl will always give some issues. ........ only real solution is to fit the Fi setup (and loom, sensors, ecu etc).

I've 'Taffy' modded my carb pumps (after trying without it all together) to minimise the effect, as the extra squirt of fuel at low intake velocities only helps to drop fuel out of suspension and kill power - the Factory Pro ideas on atomisation look to be along the right lines, but they don't do tubes for the FCR, only the Mikunis ( and were to say the least, cheeky little snots when I tried to speak to them about making some - even demanded money just to talk about it ).... and there are officially 0 (zero) Kwak ZX7R tubes left! It's not as straight forward as drilling the originals either as they are 'needle jet' config and not emulsion tube type .......

 

there's nothing wrong with it being an 'L' configuration AFAIC (MOO), it's just that front cylinder doesn't lend itself to an 'off the shelf' carb if using a short straight manifold. Ideal for an injector body though.

 

My mate had terrible trouble with his MHR for the whole time he owned it (one of the first 200 as well) because it was always doing what you suggest here, Chris.

They tried for ages to cure it, but never did.

AL