Beta Techno Carb Woes

[cello]

I'm having a mare of a time trying to get the carb to stop *issing out petrol that ultimately causes blk oil to leak out of the exhausat header when kicking the bike over!

 

 

Let me explain the bike was running ok until I switched over to reserve one day , after a few minutes of running it cut out and has not run properly ever since, I thought there was crap in the carb so refuled the bike and clesaned the carb out , a thousand kicks later still no good so cleaned the carb again and then a while later drained some fuel and even with tha fuel filter there was debris in the sample. 

I traced this back to a damaged fuel filter so replaced it and clenaed carb again abut still no luck , the bike feels like its binding a bit when i kick it over but still get blak crap out of the header. 

I cleaned the carb and set the float height and also had the choke to pieces but still it does not fire up , cleaned and checked the plug and still nothing.

Weeks later I'm wondering if the floatr height is the issue as looking on the net there seems to be conflicting advice on float height , some say 15mm some say 20mm , some say level tangs with float tangs , I'm confused now and wonder if someone with a working techno on a mikuni carb with plastic floats that slide up and down on pins can give me some advice on how to best set the float height please.

I like the techno but now this bike is like the Tardis and i'm losing time not getting anywhere.

The carb is now off the bike and I can add photos to check the float setting when I've adjusted it correctly just to confirm.

TIA 

[lemur]

Does it make any difference if you raise or lower the front wheel considerably?  That is a tell if the float height is off.  for example: it bogs out every time the front wheel is down in a hole, float height is likely off.

Inspect the reed valves might also be advised, if there is fuel leak down past the reed valves they must not be sealing very well.

[cello]

Thks Lemur, bike wont start atm so cant tell what effect the front wheel height has. Also the reeds are there to prevent back pressure from the cylinder side not the carb side tbmk so doubt they would have any effect on the problem, I did take a look tonight and they looked fine.

 

I'm wondering if the fuel mixture I put in now is too oily and or if the spark plug has seen better days, replacing it anyway and will bung some neat fuel down the airbox to see if this works.

I also cleaned the carb , set the float height to 15mm where the tangs are not level with the casting, slightly downhill looking at it from the side. I hooked the fuel line up switched it on and no leak  fitted it to the bike and with the bike on its sidestand switched the fuel on and...........it *issed fuel out again  LOL FFIN LOUD, FFIN THING

[lemur]

2 hours ago, cello said:

...

I'm wondering if the fuel mixture I put in now

 

I run 50% premium pump fuel mixed 50% with 100 octane race fuel, oil is 1% amsoil sabre.  Makes the bikes run good and very little smoke or exhaust residue.

Ideal float level is when the fuel level is half way up the emulsion tube, because that's when the emulsion tube can function best, if fuel pours out the float bowl vent the seal on the float needle and seat must be failing to regulate the fuel height.  ... or a vent pipe is incorrectly routed, that could do it.

[Tr1AL]

@cello have you checked that the floats actually float in a bowl of fuel , over a period of time they  can become porous and fuel gets inside stopping them from being sufficiently bouyant.

[Tr1AL]

https://www.trialsport.com.au/beta/Manuals/mikuni       Forget the REV 3 bit  a Techno and REV3  are virtually the same with a different Frame.

Edited 21 hours ago by Tr1AL

[lemur]

I must be the only one in the world that checks a float needle and seat by removing the float bowl and lifting the float with my finger to see if it shuts off the fuel flow at the right height or not at all 🤔

[lineaway]

Have you pulled the header pipe off the bike. Sounds like it is full of fuel. The crank could be full as well.

[cello]

Checked the floats , they appear to be intact no cracks etc and float in petrol fine. 

I turned the fuel on with the carb off the bike no leaks but then fitted it to the bike and it *issed out on the stand, hold the bike vertical and it stopped but still wont start , not even a hint at catching. 

New plug on the way and will do a compression check while I wait, thks for your suggestions.

[Tr1AL]

2 hours ago, cello said:

Checked the floats , they appear to be intact no cracks etc and float in petrol fine. 

I turned the fuel on with the carb off the bike no leaks but then fitted it to the bike and it *issed out on the stand, hold the bike vertical and it stopped but still wont start , not even a hint at catching. 

New plug on the way and will do a compression check while I wait, thks for your suggestions.

From what you are saying it seems that you have a problem with an incorrect float height or the float arm is sticking open  for whatever reason when you tilt the bike. If it were me I would bend the float arm central tang (that touches the fuel inlet shut off valve) upward slightly  so the fuel shuts off with less fuel in the bowl. The reason your bike will not start is that the crank case is flooded out. When this happens take the plug out and clean and dry it off put it back in then try holding the throttle wide open while kicking it over  , if it is mildly flooded it will start but not if it is seriously flooded. 

Edited 1 hour ago by Tr1AL