For anything not related to Speeduino, but still about car/bike/boat/engines etc
By roger.rrgt
#53901
Its only one of it, from a virago 250. The bike was working fine and then suddenly coughed a bit and couldnt rev anymore, only idles with choke. First thought was a clogged jet so i took it apart and cleaned, the carb cleaner can spray trough the little pilot holes near the pilot screw fine and its the same for the main jet. Emulsion tube and needle are new and the diaphragm doesnt have any holes in it. The float needle and seats are new too and the fuel level is only ok, its a bit rich but is fine doing 30 km/liter :D . Second, if i cover the intake behind the filter, it revs! So, why im running lean with no clogs and good fuel level? I will become bald if this continues, this is my daily!!
By LAV1000
#53903
Check fuel supply route.
Does it have vacuum operated fuel tap ?
Breather to fuel tank ?
Vacuum hose disconnected ?
Breather float unit ?
By roger.rrgt
#53910
LAV1000 wrote: Wed Nov 10, 2021 5:47 am Check fuel supply route.
Does it have vacuum operated fuel tap ?
Breather to fuel tank ?
Vacuum hose disconnected ?
Breather float unit ?
It has a vacuum tap and pump, they work fine and dont leak. What is this breather float?
LPG2CV wrote:Are you getting false air from somewhere?
This was my first try, the intake boot have some cracks in it (thats the chinesium rubber), sprayed carb cleaner and oil, no difference. I will take a closer look inside of it.
By LAV1000
#53913
Breather, float unit.
I meant whether the aeration of the float chamber is working.
Also check aeration hose/tube for kinks or melted part.
When pump and fuelvalve are vacuum operated, check those vacuum hoses for leaks.
They are connected somehow to the inlet manifold.

To test if fuel pump is toast.
Get a small tank or even a funnel, connect it to carburator.
In such a way that fuel is gravity fed into carburator.
By roger.rrgt
#53921
LAV1000 wrote: Wed Nov 10, 2021 4:45 pm Breather, float unit.
I meant whether the aeration of the float chamber is working.
Also check aeration hose/tube for kinks or melted part.
When pump and fuelvalve are vacuum operated, check those vacuum hoses for leaks.
They are connected somehow to the inlet manifold.

To test if fuel pump is toast.
Get a small tank or even a funnel, connect it to carburator.
In such a way that fuel is gravity fed into carburator.
I tried feeding directly from a bottle, only to find out that somehow water found its way inside the fuel tank and separated the alcohol, thats why it was running lean. Fresh gas in and solved all the problems :oops:.

Now is time to step up the game. Im rebuilding a TDM 850 4tx4. When the time for its carburetor came, i just couldnt make it work. The bike turns on with a lot of effort and dont rev too. The biggest trouble i found is setting the fuel level, bending the float tab very slightly makes the level from very low to leak from the needle. I would love to replace its float, but thats not possible as theres no replacement parts for it. Any tips for the bdsr 38?
By LAV1000
#53929
Float hight, it should be mentioned in a decent manual.

For new float and needle, there might be more bikes/ engines using the same type carburetor.
Might be a bit smaller or bigger on the diameter but using the same float set up.
By roger.rrgt
#53932
Only found this specific carburetor model from the yamaha R1 and it just says to bend the float tab to reach the fuel level, this is harder than looks and boring too. The needle and seat are new, easy to find. Bending that float tab is like a on/off switch, empty or leaking.
This is the most troublesome carb i put my hands into and will be the reason for my premature baldness.
User avatar
By PSIG
#53935
roger.rrgt wrote: Thu Nov 11, 2021 7:32 pm… Bending that float tab is like a on/off switch, empty or leaking.
See how it goes, but float level is not on/off, it is an analog level control and either right or wrong. The float controls the fuel supply flow, and should only be at the rate of fuel consumption, varying the fuel supply flow and correct float level at all times. Float level is often used to tune certain operation in racing, as it can provide a small or large increase or decrease of fuel under specific conditions. Float level is not controlled by the needle and seat. The needle and seat are almost never closed (off) when running, but instead constantly open to some degree and regulating supply flow.

As it is a very common cause of incorrect running, the float condition and level check is considered mandatory during carb rebuild or refreshing by most tuners. This is a long description to say that it's probably OK, but it needs to be checked in order to verify that it is. :lol: Whether it is OK or not, the check and any adjustment is not a waste of time IMO, and there is usually a way to verify operational fuel level without disassembling the carb. It's yours, so do your thing. ;)

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