Dellorto SHA 14.12 rejetting

New to the moped world, so bear with me:

Needing to rejet mt Dellorto SHA 14.12 for my Tomos Bullet a3. Currently running a 51 main jet and pretty sure I need a larger one.

It wasnt running when I got it but after cleaning points, setting timing, finall getting a spark, ect, I got it to run. But only for about 20 to 30 seconds before it dies.

Does anyone have any suggestions on what I should rejet it to? Id also like to rejet the idle jet. Not sure what size it is. Any suggestions, or anyone running the same carb that has rejetted?

Thanks yall.

Re: Dellorto SHA 14.12 rejetting

Unless you've made some modifications or upgrades, such as a new exhaust, you shouldn't need to change the original jetting. (I don't know what that is for your bike.) Upjetting is not a repair option.

Also, 14.12 Dellortos don't have an idle jet that I'm aware of. They have a jet that feeds directly into an emulsion tube (its that tube in the middle of your venturi) that has four holes. One of those four holes (at the bottom) feeds the engine at idle. To make it richer, you'd have to drill out the hole, a risky and permanent experiment. Generally, though, the 14.12, when properly jetted for WOT on a bike, is a bit rich at idle. To combat this condition, some people modify the slide to allow more air at idle, thus leaning the mix.

I'd venture a guess that your difficulty is probably not related to jetting.

Here's a place to start learning about your carb. There is other information all over the wiki, too.

Re: Dellorto SHA 14.12 rejetting

Dirt in the carb.or lines going to it, or air leaks likely. No upjetting needed, like Ike said. don-ohio (:^)

Re: Dellorto SHA 14.12 rejetting

idle hole, make sure it's clear

dell_orto_carb_idle_jet_hole.jpg

(edited)

Re: Dellorto SHA 14.12 rejetting

Rusty Shackleford /

Yup, I'd check the idle hole as well. Should idle fine with a 51 if the carb is healthy. My sha came with a #1 throttle slide and the idle was rich even with the stock 53 jet. Got a number 2 slide (leaner) and up jetted to 60 and it's pretty happy everywhere.

Super low compression makes it tough to get a reliable idle as well, I'd check compression since it wasn't running when you got it. and I'd double check your timing as well. My a35 has points and it never runs as nice as it could after the first setting of timing. Granted I don't have a super scientific way to set my timing, your system may be more reliable than mine.

Re: Dellorto SHA 14.12 rejetting

Rusty Shackleford /

And what don said, make sure your float and valve are working correctly, check the screen filter behind the fuel inlet banjo, make sure your petcock is flowing, clean tank etc etc.

My stock reeds were pretty trashed and contributed to a crappy idle as well.

Could be a combination of more minor issues if it's been sitting a long time.

Re: Dellorto SHA 14.12 rejetting

Going to make sure the idle hole is thoroughly cleaned, that was a spot I missed when I cleaned it originally. Timing seems to be on point. Think yall are right with the air leak. Possibly at the intake. Also going to check compression again. Thanks yall. Hopefully this will get her running.

Re: Dellorto SHA 14.12 rejetting

Yeah,keep at it, Evelyn! You'll get it! don-ohio (:^)

Re: Dellorto SHA 14.12 rejetting

If it runs but spools down then it is likely a fuel supply issue.

Try blow some air up the fuel line with a hand pump in case the filter, petcock or screen in the tank is partially blocked. Check the banjo filter on the carb inlet is clean. If the vent on the fuel tank is blocked that will stall you out. Also check the vent on the fuel bowl of the carb.

Re: Dellorto SHA 14.12 rejetting

Also the carb has been backfiring when I've been trying to get it to run. Would that also indicate an air leak?

Thanks again for the help y'all.

Re: Dellorto SHA 14.12 rejetting

Got her running! Turns out I just needed to swap out my 51 main jet for a 59 and now shes purring like a kitten!

Re: Dellorto SHA 14.12 rejetting

You must have an air inleakage. That jet is big for a stock 50cc dellorto carb. Check your spark plug. If it's whitish,find your air leak(should be tanor a little darker). don-ohio

Re: Dellorto SHA 14.12 rejetting

ephraim zimbalist jr /

larger jet is compensating for your air leak...for now

Re: Dellorto SHA 14.12 rejetting

Thanks guys! Checking for the leak now.

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