Project Vento has begun: help wanted.

[graeme]

These days, new doesn’t always mean it’s good quality.
I’ve had new needle and seats stick shut and others not shut off after a few weeks.
You’re on the right track re the needle and seat.
I’ve also seen floats stick down due to the tight gaps between the alloy bits that the float axle pushes through. Pinching the float when the engine is hot. (expansion)
Had to file the float ends to give side clearance.
Not the two floats but the bit that joins them.
But that was PHM 40, not 32’s, but same thing.

Graeme

[cooperplace]

Well, we have compression and spark. Timing OK so I believe. Fuel? maybe? The tap is on, and if I crack open the float-bowl nut it leaks out. All the fuel leaks seem to have been fixed. So I kicked it, and kicked it, and kicked it. About 20 times. No start. I'd use full choke and crack the throttle a bit. I'm perhaps a little hesitant to keep kicking after the 250 kicked back like a mule a few years ago and my heel hurt for a year. But I am giving it as big a kick as I can.

What do people think about spraying some Start ya bastard in there?

I also tried it with no throttle and v little choke. Same result.

[ducwiz]

I don't know much about the Vento's ignition system. But if it has a battery/points ignition, the AAU might be in the wrong angular position. Rotate it by 180°, so the spark will occur in the correct T.D.P.

cheers Hans

[Duccout]

Sometimes these problems are due to something very trivial, but the engine should start easily - sometimes I have had engines start first kick after a rebuild. I would check everything over carefully, particularly the ignition timing and fuel delivery. Is the spark plug getting wet? That is a big clue, if it is then you know that fuel is getting through. Is the spark plug new?

Keep us informed!

Colin

[ranton_rambler]

I don't know much about the Vento's ignition system. But if it has a battery/points ignition, the AAU might be in the wrong angular position. Rotate it by 180°, so the spark will occur in the correct T.D.P.

cheers Hans

Yes, I did that when I first put my 175 together.

Ian

[cooperplace]

The carby had a blocked idle jet. Great, I thought, cleared it, reassembled, still won't start. I'll have a look at it again tomorrow.

I still think there's no petrol coming out of this carb. No petrol smell that I can pick up coming out of the plug hole. The float bowl fills tho'.

[cooperplace]

After getting sick of kicking it, I got out the roller starter, and it started and ran. Seems very rich off idle, judging by the black exhaust. When it warmed up it settled down to about a 1200 rpm idle. I can't ride it on the road yet because it's not registered, and I need to get it inspected before it can be registered: it was an import from NZ.

[Duccout]

Great, at least it is running.

[Ventodue]

... it started and ran. Seems very rich off idle, judging by the black exhaust.

1. You SURE that the choke piston is sealing correctly?

Easy to check. Take the float bowl off, get yerself a thin piece of tube, stick it over the pick-up for the choke (see below) and try blowing up it. You shouldn't be able to, nat' ...

Choke jet.jpg

2. Otherwise, good chance it's the air intake at the front of the carb that is blocked. But more on that once you've confirmed that the choke is sealing right ...

P.s What size idle jet do you have? I don't know what Jon uses, but mine is a 58.

[cooperplace]

Hi Ventodue,

Thank you. I can report:

1. I can blow thru the choke pick-up whether the choke is in or out, if you see what I mean. With it pulled out, it's slightly easier to blow but not much. I replaced the o-ring on the choke support casting but it made no difference. Do I need a new choke piston?
2. Idle jet is a 55.
3. I'm not sure if I correctly set the float height. I followed the (for me) vague instructions provided by Bevel Heaven, in which I had the carb sitting on its venturi mouth and the float on top. But from the instructions in John Savage's "The Dellorto Tuning Manual", it seems I should have the floats at the side of the carb while checking their height. This makes a huge difference to their setting. If anyone can clarify, that would be great.

Thanks

Peter.