Lean carburation?

Hello,
After six months of sleep my SR has starting to roar again on this morning ...
... but... something doesn't seem OK.
Here's the problem: although the engine is hot, is runs only with choke middle opened. If I release the choke, it slows down and then stops.

I've tried to check with Colortune, here's what it says:
- choke on, flame is orange-ish (obviously, rich mixture);
- choke off, flame is blue-ish. It should indicate right mixture, but as I wrote before the engine slows down and after a little it stops. It keeps on running only if I twist the grip a little bit but, doing that, the engine backfires.

(Engine is as factory fitted, standard air filter and muffler.)

Could it be something connect to lean carburation? I remember that something like this happened also during last times I started the bike, but in a very minor way.

Can anybody help me?

Greetings!

Hello,
Thanks for the answer. I've checked the rubber joints: while the one between air filter and carb looks OK, the Ansaugstutzen between carb and engine head is full of little cracks. I don't know if they reach the inner side of the rubber... Also noticed that, although the circular metal retainer around the Ansaugstutzen is very tight, the carb moves slightly if twisted a little bit.

I'll try the spray-test and the high voltage check. I'll let you know ASAP.

Thanks!

Zitat

Original von sven

That's the way the Stutzen normally looks.

Normally, they don't.

Why don't you just try and adjust a little higher idle speed?

Regards
Sven

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Hmm. I don't think it's something related to low idle speed: it's true that if I twist the grip a little (= set the idle speed a bit higher) the engine doesn't stop, but it it starts backfiring.

Greetings

Simone

Zitat

Original von sven
Ignition setup o.k.?

It looked OK, but I didn't check thoroughly. I'll take a closer look.

Zitat

Original von Hudriwudri
hello simone

come stai?? spero bene

secondo me try the trick with the break cleaner since "IF" you have a vacuum leak then the speed will increase substantially.
And if the gomme di farfallati is as old as i think it is than time to change it anyways.
Otherwise or anyways listen to svens tips.

ciao

christian

PS: And if worse comes to worse im in may in firenze

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Hallo Christian!

Alles gut, danke. What about you?

Yes, the intake rubber manifold is very old. I fear it's the same they installed in Yamaha in 1981 ...

Kustomweekend! I'll try to get there, but I'm not promising anything: my girlfriend and her family are moving to a new house, so it's very likely I'll have to stay and help them.

Greetings!

Simone

News
I've tried the "spray-on-Ansaugstutzen" trick in the afternoon: speed didn't increase very much, but the engine began staying on at idle without any problem.

Anyway, it keeps on misfiring when I turn the grip

I've then dismantled the Ansaugstutzen to check its effective conditions: it's really bad... I've already ordered a new one, obviously with new gasket. I've also took off the carb to check if it's allright inside.

I'll keep you updated.

Greetings

Muffler

(P.S. Since I like to torment my brain, I'm preparing a self-made circuit to install an alternator warning light on my SR. I'll let you know about this trifle, too...)

No news about the carburation unfortunately , but I've tested my circuit to make the alternator warning light working: everything seems fine, obviously I've had to check it with an AC-DC power supply because of the dismantled carb.

Greetings

I've disassembled the carb: pilot jet was almost completely obstructed ... Maybe it was the problem's cause.

Greetings

Simone

Zitat

Original von Muffler82
I've disassembled the carb: pilot jet was almost completely obstructed ... Maybe it was the problem's cause.

Greetings

Simone

I've reassembled and reinstalled the carb, after a good rinse in solvent, a KEDO Vergaser-Reparatur-Set, a new Ansaugstutzen, and so on. Result: engine now keeps on running very well, and revs up with no hesitation.

Here's what Colortune says: everything is fine at idle (blue flame, correct mixture), ...
... but...
when I twist the grip, mixture gets richer and richer (orange flame) although engine runs normally (no backfiring, etc).

Will moving jet needle's clip up solve the problem?

Greetings

Simone

Zitat

Original von Hudriwudri
no stai tranquillo perche tu usi un pompa di acceleratione io credo/certo?
altrimenti: Never change a (adesso) running system
siamo in firenze al fino di prossima settimana!

ciao e tanti saluti da me e rosa

Chri+ro

PS: sistema della colortune non e molto accurato e con risultato molto ordine o preciso

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Hallo Christian und Rosa!
So you are in Florence now! Do you like being in Tuscany? I hope you're having a good time! Me and my girlfriend will try to get there to meet you, most likely on Saturday because of work. I'll let you know.

Unfortunately my Mikuni VM34SS hasn't got the accelerator pump any more: it's been token off (broken?) by previous owner.
Although this, I notice a quite high fuel consumption all the same, also without considering what Colortune says: to start the bike I connected a funnel to the carb with a short plastic tube (not to bother with Benzintank), I then filled with fuel until half a glass of it could be viewable remaining in the funnel. Engine started with no choke, a couple of minutes to warm up twisting grip a little bit, and the fuel that was previuosly viewable in the funnel... was viewable no more. It was already out!

Maybe the best way to see real mixture situation is really to get on the road, "in gear", and then check Zuendkerze's colour, instead of controlling with bike stopped on central stand. I'll try as soon as possible: Sitzbank is at upholsterer's the moment and I should drive sat on relays

Greetings!

Simone