79' Grande Bogs/Stalls. HELP

Nathan Edwards /

Okay...

So I bought a new SHA 13/13 carb (had a stock 12/12) for my Grande and put it in earlier today... Started up fine, started to run but bogged down and was about 1/2 the speed of having a 12/12.

I said okay lets do some testing. I pulled off the airbox and when I put it full throttle it stalled completely in a matter of seconds.

Pulled off the stock exhaust and it stalled at full throttle. Put a promo circuit exhaust on & airbox and it would run at full throttle but was 1/2 speed.

If I put on a 13/13 shouldnt it be okay to run right out of the gate? Am I too rich? If so, wouldnt pulling the airbox give it enough/more air and not make it worse?

Its too nice out to keep doing this without expertise. I admit Im an amateur and would like the help of experts.

Thanks so much in advance.

Nato

** Also, I bought the SHA carb from www.50cc.nl (photo attached) and it doesnt have the throttle cable guard (the upside down 'L' shaped thing) and so I put the 'L' shaped thing on from my 12/12. Without it, I have too much throttle cable... could this be a problem? I tested the slide/ throttle mechanism and it seems to work like a charm but if anyone else has done connected it properly w/o the 12/12 upside down 'L' thing let me know.. Thanks!

Re: 79' Grande Bogs/Stalls. HELP

Nathan Edwards /
nato OP

heres the SHA carb from 50cc.nl

1120368738_21163.jpg

Re: 79' Grande Bogs/Stalls. HELP

you've got to do plug chops to find out where to start from. find out what jet you have in the original carb and the new carb and do plug chops with what equipment you want on your bike.anything else will endanger the engine your just guessing.jim

Re: 79' Grande Bogs/Stalls. HELP

Nathan Edwards /
nato OP

I know it is recommended that a plug chop be done with 1/2 mile full throttle but I cant do 1/2 mile full throttle (im in the city). Can I do 5-6 blocks?

Re: 79' Grande Bogs/Stalls. HELP

Nathan Edwards /
nato OP

In this case, do the symptoms tell me I need smaller or larger jets.

Re: 79' Grande Bogs/Stalls. HELP

I think you got the wrong carb. See the attached pic of the 12988 13/13. It has the correct choke lever and elbow connector pipe.

1120373013_dellorto_12988_13_13_carb.jpg

Re: 79' Grande Bogs/Stalls. HELP

Nathan Edwards /
nato OP

I emailed them and they said it would work.... but, they also said the proma circuit would fit right on... yeah right! I'll drop them a line and see what they say.

Re: 79' Grande Bogs/Stalls. HELP

The carb you have will work but you have to use the adjuster on top of the carb to lengthen the cable sheath and make sure there is no air leak where the throttle cable goes into the top of the carb.

Was there a rubber boot sleeve for the throttle cable that came with the carb?

Leave your stock air filter on.

Do you know the number of the jet in the carb? It should be stamped on the jet.

Re: 79' Grande Bogs/Stalls. HELP

Nathan Edwards /
nato OP

ok. I will try adjusting the top of the carb.. I tried to adjust it but it wouldnt budge. So I put the elbow connector from my 12/12. I will put the one on that came with the carb and fiddle with it.

I didnt recieve a rubber boot sleeve for the throttle cable... should I have?

I will try and get the jet # when adjust the carb tomorrow.

Thanks.

Re: 79' Grande Bogs/Stalls. HELP

Does your stock throttle cable fit snug into that brass fitting in the top of the carb? I think the problem is with the cable length and maybe an air leak on top of the carb where the throttle cable goes in.

Try this, take off your stock throttle cable and measure the cable sheath and the actual inside cable. The sheath should be about 41" long and the inside cable about 43".

Now measure that elbow pipe from your old carb including the screw adjuster that screws into the elbow pipe. I think it equals about 2" in length

Subtract the length of the elbow pipe and adjuster from both the cable sheath length and the actual inner cable.

Example:

Stock sheath 41" - 2" (length of elbow pipe and adjuster) = 39" New cable sheath length.

Inside cable 43" - 2" = 41" New insdie cable length.

Measure the inside diameter of that fitting on top of the NEW carb.

Now take your stock cable with you and go to a local bicycle shop and have them make you a new throttle cable with the new shorter lengths. (39" and 41") Try to find a cable sheath with a wide enough diameter that will fit snug into the brass fitting on top of the new carb.

You will have the file the button on the end of the new cable down to match the button on the end of your stock cable so the new cable button will fit properly into the carb throttle slide. The button is easy to file down, so file a bit and then compare it to the stock cable button and also try it in the throttle slide to see if it will fit.

Once you have the throttle button filed down the proper size, then install this new cable and sheath from the carb top up the frame to the throttle handle. Leave the top off the carb with the cable slide and spring connected. (this is so you can visually test it out of the carb for tension when you get the throttle handle end of the cable installed)

Slide the plain end of the cable into the throttle slide that is under the throttle handle grip and snug up the cable sheath end to meet the metal of the throttle handle perch. Push the inner cable through the hole in the throttle slide and pull the excess through and leave it sticking out by the throttle grip. Screw in the little securing screw in the throttle slide to secure the cable

Now twist the throttle grip and observe the CARB throttle slide and spring to judge if it looks like you have the correct tension.

When you think you have it right, install the carb throttle slide into the carb and tighten the carb top down.

Push down on the choke lever and twist the throttle all the way to see if the choke lever pops up properly. (later You can switch the choke throttle lever from your old 12/12 carb onto the new carb if you want)

Now fire up the Grande and test the throttle with the engine running and the bike on the center stand. Let it warm up a bit and adjust your idle screw on the side of the carb. If the engine is idling too fast or turning too many rpms, loosen the securing screw up on the throttle grip end and pull a little cable back for slack and then retighten the securing screw. Once everything seems OK, then take it for a test drive.

You may have to adjust the tension on the carb throttle slide by loosening the screw up on the throttle grip slide and pulling a little more cable through one way or the other. Pull it through to increase the tension and rpms OR pull some cable back through to lessen the tension and reduce rpms.

Good luck.

Zip

Re: 79' Grande Bogs/Stalls. HELP

Nathan Edwards /
nato OP

Thanks Zippy.

I will give that a try today.

Nato

Re: 79' Grande Bogs/Stalls. HELP

Nathan Edwards /
nato OP

Okay. The bike shop wasnt open so I couldnt work on the throttle cable. But, I checked out the carbs... The 12/12 has a #49 jet and the 13/13 has a #43 jet. Isnt that way too low of a jet? Shouldnt it be in the sixties? I am currently swapping the jets and testing that first to see if there is any difference and to make sure the problem doesnt lie there.

After that, I will get a new cable (I know it will work that way but want to try the easy stuff first :)) Thanks again for all the help.

Nate

Re: 79' Grande Bogs/Stalls. HELP

That may help.

This is what I think happened. Grandes were called "CBA" in Europe and are no longer made. The Grande/CBA has a different engine than a Ciao/Bravo. Grandes in this country came equipped with a 12/12 carb with a #49 jet. The Bravo's in this country have a 12/10 carb with a #43 jet.

So I think what you got from 50cc was a modern version of the Bravo carb 13/13 thus the #43 carb,

It should run better with the bigger jet. See how it does and then decide if you neeed that shorter cable.

Re: 79' Grande Bogs/Stalls. HELP

Nathan Edwards /
nato OP

zippy, do you think I should start somewhere in the sixties? I know each bike has there own jet, but I am wondering what range... upper 50's - 60's? I dont want to go broke on jets :) Do you have jets for sale?

Thanks,

Nate

Re: 79' Grande Bogs/Stalls. HELP

Go with the #49. That with the proper length throttle cable you should see improvement and get the Grande back to running normal maybe with a little more top end speed. (1-3 mph)

I am ordering an assortments of jets from Italy but they are not yet in stock. hopefully by the end of this month.

Another thing I thought of about the #43 jet. If the carb you ordered was for a Bravo, the Bravo's here in the states have a different air box than your Grande. The Bravo air box doesn't allow as much air to flow into the carb as the Grande box, so with less air the #43 runs OK. on a Bravo setup.

When you put that 13/13 carb with the #43 jet on your Grande with the Grande airbox, more air was allowed through by the Grande box so it made you run Lean with the #43 jet. Once you swap the #49 jet you will have more gas flow and it should balance out with the Grande style air box.

The rule of thumb is to upjet 4 number sizes when you add a performance muffler. But the Vespa's seem a little different, Here is what I found about the Vespa Crabs and jets.

The 12/7 has a #39. These Carbs are usually the stock Ciao carb.

12/10 has a #43, these are usually stock on a Bravo

12/12 has a #49, stock on a Grande.

so a 13/13 on a Grande with a performnace muffler, maybe in the 53 to 55 range for the jet. A #54 would seem to strike a happy medium.

The Ciao and Bravo have the same engines but different carbs as you can see. Most Ciaos are also single speed (there are some Variable speed Ciaos) and all Bravos are variable speed.

The Grande has a different engine than the Ciao/Bravo and also all Grandes are variable speed.

Some Bravos (20 mph models have the 12/7 carb) I upgraded on of these to a 12/12, #49 for a cutomer and went from a top end of 20mph to 27mph (tracked with my GPS).

Let me know how you do with the #49 and a proper length cable

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