Mukuni carbs Pre 75

[Freakshow]

Ok so i get that  you cant use Vm or flat sides carbs on Pre 75 and they need to be round TM slides and bodies but does it matter about the Choke set ups, the plumbing and the like ?

seems like its would be ok to me but thought id ask before someone has an issue and cuts off cheap carb suplies because the doo hicky is in the wrong spot or there is somthing else technical like im missing and makes it seeming ly illegal even if disconnected.

For example
http://cgi.ebay.com/ebaymotors/NEW-Mikuni-Carburetor-38mm-Yamaha_W0QQitemZ200394441875QQcmdZViewItemQQptZSnowmobile_Parts_Accessories?hash=item2ea8708493

What the gravity fed line on the float overflow back to the throat do  ?  is that some kind of anti freeze thing on the skidoo's or is that some other kinda idea i should be aware of or need to disconnect for pre 75 ? i cant see any technical advantage other than it just refeeds overflow fuel and isnt actively pumped or driven, and thus Vintage OK

 

[LWC82PE]

VM = roundslide
TM = flatslide

What the gravity fed line on the float overflow back to the throat do  ?

This sounds similar to the accessory add on power jet set up but they normally go to the inlet/engine side and the nozzle is a lot bigger.

[Mick D]

Hi Freakshow,
                      forgett the flatslides on a pre75. Below are the MA rules for 2010. Flat slides for pre75 are prohibited.
18.6.0.4 Carburettors:
a) Any round-slide carburettor of a type
available pre-1975 may be used
except the Pre-1960 class where
a Mk1 Amal Concentric or period
carburettor may be used.
b) Flat-slide carburettors are prohibited,
c) No reed-valves permitted on
machines up to and including Pre-
1970 class.

http://www.ma.org.au/AM/Template.cfm?Section=General_competition_rules&Template=/CM/ContentDisplay.cfm&ContentFileID=41129

Personally I think the cheap new VM round slide Mikunis are great bang for anyones buck. Cheap readily available parts and jets. Dead easy to dial in the jetting to a snappy throttle response.
Cheers, Mick.

[Freakshow]

Woops sorry have my TM/ Vm Round the wrong way, but you get what i mean.   Does the plumbing matter as per picture ?

just those Sled types are cheap as shit and i see them all the time come up for nix, but i dont want the grief if some peanut goes on about misting, pumping, dribling, choking, multi lines etc etc. cause someone can weave it into the rules and not Kosha

[Freakshow]

VM = roundslide
TM = flatslide

What the gravity fed line on the float overflow back to the throat do  ?

This sounds similar to the accessory add on power jet set up but they normally go to the inlet/engine side and the nozzle is a lot bigger.

So does that matter pre 75 ? as its not an active but passive feed unlike the pumper jets


i just think these are cheap options...

[Mick D]

Hi Freakshow,
                      I say with 100% comfidence that all Mikuni VM roundslide carbies are pre75 legal, regardless even if it was only manufactured yesterday. I read it some where and saved it. When I find it, I will share it. See you at Griffith in September.
Cheers, Mick.

[Freakshow]

ummm.... just  cause somone wrote it dont neccasarily means its ok. 

There are Some vairiation in VM's from what i can see with misters, pumpers and a host of hoses, chokes etc such as those on the snow mobiles does that mean they are all legal if its a VM roundslide body ?

[LWC82PE]

I don’t think power jets on roundslides for pre 75 will be legal.

One thing you will need to look at on any snowmobile carb is the needle valve. It will probably be a 1.5 and you will need something like a 3.3 for a dirt bike.

[Mick D]

I don’t think power jets on roundslides for pre 75 will be legal.

One thing you will need to look at on any snowmobile carb is the needle valve. It will probably be a 1.5 and you will need something like a 3.3 for a dirt bike.

OK I see what you mean now freakshow
http://cgi.ebay.com/ebaymotors/NEW-Mikuni-Carburetor-38mm-Yamaha_W0QQitemZ200394441875QQcmdZViewItemQQptZSnowmobile_Parts_Accessories?hash=item2ea8708493
I should have clicked on that link first and had a look before I commentted. That's one awfully modified VM.

[Tim754]

Freaky it is cheapish....but.... the very fact that your obviously very concerned about its pre75 legality, is telling you it is trouble. My personal system that all can follow if you want is " If it don't look right in a picture it wont look right in the flesh".

[Freakshow]

YEs but is looks the Basis for LEgality and functionality ? its not really a major component after all, rule just says round slide.

[Freakshow]

I don’t think power jets on roundslides for pre 75 will be legal.

One thing you will need to look at on any snowmobile carb is the needle valve. It will probably be a 1.5 and you will need something like a 3.3 for a dirt bike.

why its gravity feed not powper based so its a latent system.    Where can i see that in the rules to check.

[Ji Gantor]

I like many here have rebuilt carburettors.
You get them cheap and then have to jet them to suit your bike.
The slide, main, pilot, float bowl jet, needle and needle jet.
The slide costs $180,
main jet $10,
Pilot $10,
Float bowl jet $35,
Needle $12 and
Needle jet $35
Total cost for jetting $282.
If we forget the slide and use a file to create the correct cutaway it still ends up $102 plus the cost of the carb.

Then we have the problem of matching up the intake manifold and the boot to the airbox.
And last we have to get a cable to fit.

What looks cheap in the begining can turn expensive pretty fast.

Just my 2 cents worth.

The question is it legal may be outwayed by the cost and fitment problems.

Ji

[Freakshow]

THEy fit.
A new Muk is only $100 out the states anyway, but i wanna see how it goes in a dry run before i go down the path.

[Ji Gantor]

So they fit to the airbox and cylinder and the cable is the same?
So how about their jets surely they cannot match exactly?
Any way if it is all good apart from their legality then they are cheap.

Good luck mate

Ji