dellorto Q's for the dudes out there

***Kim Jong illest*** /

so uh, when my carb is hooked up but not on the motor, and i pull the throttle, gas should come out right? i mean, it doesnt need the vacuum of the motor to "suck" it out does it? i cleaned the shit out of my carb, took every piece apart and sprayed it down really good.

does the nipple where the gas line attaches come apart? is there a way to take it off to clean it? i dont see any kind of thing to put a wrench to.

bikes got awesome spark and the timing is on my marks, but when i try to start it it makes a PUFT sound instead of starting, like its igniting something but not enough, and once it backfired.

dont make sense to me. should be pouring out a little gas right? the bowl fills up, gas oves through the line, but when the throttle is open nothing comes out.

help?

Re: dellorto Q's for the dudes out there

gas doesnt really spill out.

How is your compression dude?

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

i dont have a tester but it semms good, nice and hard.

Re: dellorto Q's for the dudes out there

actually im pretty sure the vaccume of the motor is the only thing that draws the gas out, you can do the starting fluid test to see if its fuel or spark(timing) a small squirt should get a quick firing of the engine if all is well electrically

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

well the back story is...

i put the motor back together, timed it to perfecto, whole nine. then i went out riding. after the last stop i noticed that when starting it, it didnt really want to go, so i had to keep the throttle on wide open, and then slowly the engine caught up ya know, after that is was all good, normal throttle response and what not. ran great till i stopped for lunch.

came out and nothing. i pushed the fucker while tryng to start it for blocks. BLOCKS! nothing. got home, checked my spark, all good in the hood, so i thought it must be fuel. it KINDA sounds like it wants to start but it doesnt.

Re: dellorto Q's for the dudes out there

r u using the choke to start it???? u might have either a massive air leak or a head leak

also there is no "pump" or forced fuel injection, it works purely off the low pressure created in the intake by the piston moving up and down to draw fuel out of the jets

carbs are venturi systems... come on josh i thought u where a car mechanic thats carbs 101

Re: dellorto Q's for the dudes out there

If you want to test it off the bike, put some gas in the bowl and your mouth over the spigot and suck. If it tastes like gas, you are doing it right.

Re: dellorto Q's for the dudes out there

Test for spark and compression. Put your thumb over the sparkplug hole and have someone crank it over. if your thumb is pushed off, you have decent compression. With that said and done, pour a little gas into the spark plug hole, turn it over like you're gonna start it w/o the spark plug a couple times, then put the plug in and turn it over. It should fire up. If not, I would check the timing. If both those tests pass, then clean the carb again.

And to answer your question, no there shouldn't be gas coming out unless the engine sucks it out.

Re: dellorto Q's for the dudes out there

I usualy just take a little squirt bottle full of mixed gas and squirt it in the carb. I don't like thw whole starting fluid bit with two strokes. It should start for a few seconds and die. If it doesn't start then you have problems elsewhere. Do you have a fuel filter on it?

Re: dellorto Q's for the dudes out there

Tyler Jacobson /

i dont understand how the dellorto choke works. can someone explain?

Re: dellorto Q's for the dudes out there

I second the air leak. Last time I took the head of my puch I stripped out a stud putting it back on. It did the exact same thing; needed full throttle to run, with a degenerating condition to non-running.

Re: dellorto Q's for the dudes out there

clogged pipe.

bad timing

two things that usually cause back firing.

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

HAHA! YES ELLIOT! but, with a cars fuel system, the fuel line is pressurized. so for example, any carbuerated car, you can pull the throttle and deliver gas without any force from the motor. but of course this is a limited effect due to the pressure in the line.

thats why i asked about the "sucktion" or air displacement needed to pull the gas through. i wasnt about to start huffing on my carb until i got a second opinion though. i had a slight suspicion about the head leak as a few times my nuts had come slightly loose. ill check it out today.

HAHAHA! YES ELLIOT but 2 stroke still have funny quirks from regular motors that puzzle me from time to time. thats why i never was able to get my msd coil to work right on the "gimp" moby i experiment on.

THANK YOU EVERYBODY!

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

YUP! loose head nuts. time for some lock nuts.

RIIIIIIING-ING-ING-ING-ING-ING-ING

Re: dellorto Q's for the dudes out there

The choke on the sha simply blocks off a good portion of your air flow creating a rich mixture. The phbg on the other hand actually has an enrichment valve which uses a third jet to add an extra portion of fuel to the incoming air charge for a richer mixture for starting.

Re: dellorto Q's for the dudes out there

OK.... cnay let this go any farther...lol

First... A car has fuel pressure to the carb and the float/needle and seat allow the gas into the float bowl. There is no fuel pressure after the needle and seat in the carb! All automobile carbs have a "accelerator pump" that pumps a small amount of gas when you open the throttle.

Second fuel is not really sucked into the engine by engine vacuume. If that was the case how does a turboed engine with a "blow through carb work? Thats were the boost is pushed through the carb and into the engine... so there is no engine vacuume during boost... yet is still runs? Yes this was a popular way to turbo engine in the past but not seen much anymore.

Fuel actually enters the air stream because of the "Venturi effect" in the carb. The venturi is just a necked down area of the carb either cast in or made by the slide. As air moves through the carb it has to speed up to get through the smaller area causeing the molecules to spread out (less moecules in a area= less pressure or a vacume) the fuel nozzel is placed in the venturi and the atmospheric pressure actually pushes the fuel into the low pressure area.

Another way is to have your discharge nozzel stick into the bore with the engine side of the nozzel cut away... as the air goes over and around the nozzel a low pressure area is created behind the nozzel and again fuel enter the low pressure area.

Thus a pressured carb (turbo) has the float bowl pressurized and the ventury makes a lower pressure area than the foat bowl and the fuel enters the carb.

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

yeah so uh, it was workin great. i went for a ride through the park, came to a stop then death. i knew i should have made new bottom gaskets again, it just takes so long, and its a pain in the ass. oh well. as im taking my walk of shame some ass hole speed suit cyclist slows down and says, DITCH THE MOTOR, YOU NEED PEDAL POWER, LOOKS LIKE IT WOULD DO YOU SOME GOOD ANYWAY. so i threw my helmet at the guy. he screams at me FUCKING MANIAC! and pedals off. as this happens two unknown mopeders on puchs ride by and rubberneck a little. they circle back a few minutes later but dont come over as i wave them in. i guess they were worried i WAS a fucking maniac. its too nice a day for this. im taking the other running moby out. yay, 25mph.

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

i havent seen that kind of turbo since the old volvos and such. as for the accelerator pump, that wasnt something that came around until the early 70s, and is totally standard on any after market carb now, ie holly edelbrock. older style like from the sixties still relied on fuel pressure, if you lost it you had to crank the motor a little.

how old are you ottoman? i like your knowledge of vintage fuel systems, as thats been my real passion for a decade. you wrench classics too?

Re: dellorto Q's for the dudes out there

dude don't throw ur fucking helmet at cyclist cuz they run their mouth.... WTF! that could kill someone.

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

nah...

Re: dellorto Q's for the dudes out there

dang it takes me like ten minutes to get my helmet off.

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

mine was already off, and its not like i beaned it at him or aimed for a head shot or anything, just a "get the fuck out of here" kind a lob. i aint tryin to hurt nobody, but dude did pick the wrong time to kick me when im down.

it doesnt matter, this is a carb thread.

Re: dellorto Q's for the dudes out there

I am old very old... Accelerator pumps in carbs have been around longer then me... I have seen them in carbs from the 1940's and I think it goes back before that

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

my car carb experience only goes as far back as mid sixties models and all domestic. and at college the main focus was on current technology, ie fuel injection. carbs were covered in my power and performance classes.

Re: dellorto Q's for the dudes out there

Did you figure out the problem?

Re: dellorto Q's for the dudes out there

***Kim Jong illest*** /

for a minute i did. now im cutting new gaskets. we'll see tomorrow

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