44mm conversion

Taffy · Sep 7, 2018

I carried out this work two years ago and was let down for testing continuously by people that promised to run the carb conversion with my jetting kit on it - but didn't.

This Spring and Summer a Dutch customer ran my carb and loves it! he loves the 4" stack on it even more but even with my little blue belmouth he says its a big improvement on his std FS650 with 41mm carb. The intake also changes tone and becomes deeper. he sorted the jetting his way, not the way i would have gone but he got there and so it ran really well and he reports keeping up with the new Husky 701s.

the carb has to be bored front and back and a new 'ring' bolted into the centre for the slide to drop over.

I have just two rings left for sale at 40gbp plus vat (if in the EU)
the boring of the carb is quite simple.

will probably do a video of it on my FB page soon

Taffy

tinwelp · Sep 10, 2018

IS this an over-bored FCR Taffy? 41mm out to 44mm?

If yes, can you post some details please? I may have another application for your solution if it's a reliable modification.

Cheers... Paul

Taffy · Sep 10, 2018

https://www.facebook.com/taffmeisters/videos/274312909845934/

I hope this video convinces you! all you need is the ring in the middle and find an engineer for the rest.

here is a link to a video with someone else getting an overbore done; https://www.youtube.com/watch?v=kvLsQ2tDVQU

after that the next thing is the bellmouth and the air filter. this is what i am presently working on.

regards

Taffy

tinwelp · Sep 11, 2018

Thanks for the information Taffy. I've yet to see if this can be done on the downdraft version of the FCR, which I think Keihin call the "slant-body". The MX seems easy enough, so it should be possible as they're structurally very similar, but I've not been brave enough to pull one apart yet... and particularly so as the mid-body gaskets are reported to be different to that of the MX.

Once apart, boring the main body and choke plate seems simple enough, and reassembly with epoxy isn't rocket science.

I'll continue to research the gasket issues and maybe get back to you.

For your bellmouth/intake trumpet/velocity stack... Frank! MX probably make something close already, and will make specials to order if needed. Normally they bolt directly to the inlet flange so you can avoid the inevitable step you create by just stacking them up.

Thanks again.

Cheers... Paul

Taffy · Sep 11, 2018

the Frank MX is for a 43mm conversion and hardly worth getting out of bed for. but do you have a link to their velocity stack?

years ago some a yank advertised a new part to go on the back of the carb. it had a screw facing out to the left and one to the right. they were ac Pilot Air Screw and a Main Air Screw.

they said it developmental and was anyone interested in testing it. I wrote and said i wansn't just interested but excited by it if I could please, please, P-L-E-A-S-E have one but I think they were worried that I knew more than them? they'd done it as an engineering exercize but didn't know the consequences of what the tuning might be.

By then I was changing the PAJ and MAJ and it was a very long time consuming job. this piece would have taken seconds to adjust!

the possibility still exists to create that adaptability with a 4" (100mm) bellmouth and AFA but we no longer really need to test. I've done it all. I did the original PAJ to PJ ratios AND the PAS to PAJ ratios 15 years ago.

however, with todays CNC machines, the opportunity is there. borrowing a pointed screw is easy enough.

fitting it all on the bike is the difficult bit.

cheers

taffy

tinwelp · Sep 11, 2018

All their stock velocity stacks can be seen on their website, and if you want something special, write to them with a sketch or drawing. They'll make most things FCR related if you ask nicely.

As for the externally adjustable air jets, yes I remember the device you mention... and I think nothing came of it. Probably because most users either don't adjust the air jets, or maybe don't even know they are there!

I cannot speak for an FCR on a Husaberg as I still use a Dellorto (on an FE400). It's OK. Not brilliant, but acceptable. I use FCRs on V-twin KTMs, and they're a very different kettle of fish. However, despite hundreds of jetting changes in my case, I think I've only adjusted the air jets a handful of times to add polish to the response, and then they're left untouched. Having external adjustability just isn't needed. Is it different with the Husaberg applications? As a tuning tool, they'd be brilliant.

Developing something to do what you describe isn't at all difficult, but if nobody wants to buy it, it's just an academic exercise or an engineering challenge, depending on your point of view. Not to mention the audience is forever diminishing...

A 4" stack is not going to be easy to package on a carbed Husaberg, particularly if you want a decent taper angle. The current stacks I have on my KTM are about 80mm long (so not hugely dissimilar to yours) and the outside diameter is over 100mm at the entry to the stack to keep the boundary-layer under control. Would that fit?

Cheers... Paul

Taffy · Sep 11, 2018

I have to agree with all you've said. I needed that adjustability to set the bike up but had to slave for hours learning. now I know the ratios.

I drilled out the front face of my dell ortos and threaded the holes to put in PJs as AJs!!!! my image host appears to have gone AWOL at Imageshack otherwise I'd put up a photo.

I then turned down about 8 PFs from 6.6mm to 5.9mm and it left the numbers just visible and meant the jets fitted inside the bellmouth O ring on the carb.

It made all the difference..... it's for people like me to find the answers and then others just have to fit it. its the adjustability.

cheers

Taffy

Search

Search

44mm conversion

Taffy

tinwelp

Taffy

tinwelp

Taffy

tinwelp

Taffy

Similar threads

Register CTA

Recent Discussions