Morris Minor Owners Club

Hi guys, heres the storey so far.
I bought an RGV 125 Gamma as a bargin to get to work on. Thing is that it was in bits, so the plan was to throw it together and ride it to work and back. The problem is that the carb hates me

The carb is like an A series carb in the way it operates evept that there is no fuel pipe underneath, the fuel simply sits in the float chamber and get sucked straight to the needle. The carb is a plunger in the body opening an aditional channel.
There is a fuel pipe (big) feeding the float chamber (inlet i assume).
There is a small pipe from the top of the float chamber
There is a small pipe into the bottom of the chamber like the overflow on a toilet cistern.

Where to these pipes go? I presume the third is an overflow and should simply away from anything hot. Where does the other pipe need to go?
I have had the bike running (roughly but rideable) with both of them going to atmosphere but then it would go unless I blew and sucked on these pipes to pull fuel into the carb (I have a clear fuel filter on there) Nothing came out of either small pipe.

Could the rough running be a symptom of the choke plunger not seating correctly?

Please help cos im fast loosing faith in this heap!

Is this the carb?http://www.andersonvintageparts.com/auc ... 43d30a.jpg
Useless picture as it doesn't show where 2 of the pipes go to.
A lot of Japanese bikes have vacuum operated fuel taps so I would see of there is anywhere in that area for a pipe to go.
Otherwise have a look on the inlet manifold for a connector.
That would do the sucking for you

that looks very similar, ill try and grab a pic later on.
The thing I cant figure out is; if one of them is a vac line ()i.e. the top one) then wouldnt it just suck air in through the other pipe as they both end in the same chamber?
besides that I cant see any holes lol. The other option could be like on a radio controlled car where the tank is pressureised from the exhaust, but again theres no take off on the exaust, and also It would just bubble exhaust gas through the tank.

Haven't been on this site for a while and just saw this...

Does the small pipe feed into the inlet stream somehow - if so it may be the feed pipe from the 2 stroke oil pump. In which case, don't start the engine with it disconnected!

I've got a Yamaha stroker of the same vintage, so I'll take a look at the carb tomorrow and see if it's got similar connections.

thereis no where to tap into the inlet. The oil is on a seperate pump under a small silver cover, under the main engine casing on the left hand side. when the carb is off you can see that on the way into bottom end there is a piect of 3mm brass tube coming un vertically. This pipe is fed by the oil pump.
I have stripped the carb again in the last couple of weeks after it guzzeled half a gallon of petrol while off (tried to start and luckily it all got coughed out of the exhaust.

I have had her running now (still need to sort out fuel pipes though). Im just stuffing a funnel into the inlet pipe for the float chamber. When she was running I tried blipping her up the revs. She will climb quickly then just after 5k she coughs and sits at 5k.
Its almost like there is a limiter but the revs get to it too quickly so it just passes it and then sits on it.

The choke system is "working" as when moved there is a difference in running.

Im not far off either putting the fuel on the outside (and drying it with a match) or just slapping it on E bay.

AAAARGGGGHHH why did I stray from the next morris!

Why not wander into your local bike store (a Fowlups would be ideal), and see if they've got one kicking around. If they have, have a nose at it and see where the pipes go

theres no where like that round here, they are all new dealers stacking the bikes high. plus the gammas are apparently quite scarce and different to the more common FuN version.
I might have found a new carb to play with just in case the one thats on is playing up.

Oh by the way, any tips on getting proper fuel flow from the tank? its a gravity feed but I dont think there is enough "head" of fuel to push it through a fuel tap and filter.

polo2k wrote: Oh by the way, any tips on getting proper fuel flow from the tank? its a gravity feed but I dont think there is enough "head" of fuel to push it through a fuel tap and filter.

In that case you must have some sort of blockage - normally fuel will flow quite readily from a bike tank. Worth taking the tap and filter aparts and thoroughly cleaning and clearing. Also check that the tank cap is breathing, or that any other breathing arrangement for the tank is working - if not, a bike tank will soon build up enough vacuum to stop the fuel coming through.

Hope this helps!

ill have to try it without the carb I guess because it pours out perfectly when the outlet pipe slips.

polo2k wrote:ill have to try it without the carb I guess because it pours out perfectly when the outlet pipe slips.

Exactly - take feed pipe of carb, turn tap on, if you get lots of petrol pouring out, then at least you have eliminated the fuel feed issue! *

BTW - I have lots of experience with bike engines, but haven't commented yet because it's difficult to be sure when I can't see the thing.

You have 3 pipes? My guess would be:

1) - fuel feed - self explanatory
2) - possibly a vacuum feed to a vacuum fuel tap *
3) - not sure about the 3rd one - possibly just an overflow pipe going to fresh air.

Personally I'd be taking the carb apart ond testing/blowing down the pipes to see where they went and what they did. If in doubt, blank the pipe off, otherwise it will probably introduce too much air into the intake, upsetting the mixture.

* Many (or possibly all!) modern bikes have a vacuum tap. A conventional tap requires the rider to turn it on and off before and after each trip. The problem with forgetting to turn it off, is that any leakage past the float needle (and there will probably be some, especially on a bike parked on a side-stand, and therefore left leaning at an angle) will quite often dribble down into the cylinder. At best this will flood the engine, in the case of a 2-stroke, at worst it will dilute the oil and cause all sorts of problems, in the case of a 4-stroke.

To avoid this, manufaturers fit a vacuum tap. This is held open by manifold vacuum, but as soon as the engine stops, the vacuum collapses and the tap closes. Of course you need to create some vacuum in the first place to open the tap to atart the engine, and usually turning the engine on the starter is enough to do this. However, on a multi-carb bike that has been left standing, the float chambers will have evapourated dry, and it can take a lot of cranking to make the tap open long enough for them to fill and start the bike. For this reason, many bikes have an additional feature on the tap which is "prime" - it bypasses the vacuum mechanism to enable the carbs to prime manually.

If your bike has a vacuum tap, or if the carb was intended for a bike with one, then one of the pipes is likely to be the vac feed to the tap.

Note also that if it IS a vacuum tap, you won't get any fuel out of it unless you present the feed with a vacuum - you should be able to see the vacuum feed pipe inlet on the tap - suck on this and the fuel should flow. However, I suspect that you may well have a "normal" tap, and the vac feed pipe coming from the carb is redundant.

Hope that helps (and hope it doesn't sound too patronising if you knew all that stuff!)

Cheers

dont worry, im still learning
If the carb is off a bike with a vac tap then would this be the pipe from the top of the float chamber or the one with the "toilet overflow" type arrangement?