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Hey all

I wikied and searched so here's what's happened and what I've done.

The scooter had been acting erratically lately, would fail to start except with full throttle and excessive running of the starter. Then, would hesitate while riding and shut off completely.

Thought it was the evap system - unplugged hose and some gas came out, thought I had fixed it. Left hose unplugged, rode home, scooter was running great and then same problems began.

This morning I went to take it out, and I heard a spring pop (not sure if that is relevant). Scooter cant get out of its own way and tops out at 20mph. Engine is operating at low RPMs.

Throttle cable makes full motion and cable moves that round spring thing all the way as normal. I do hear knocking, though. I got a new tank of fuel and poured in some octane booster, absolutely no change.

Checked that the spark plug cover was on and tight. Attempted to take off the top of the carb - one of the screws is completely stripped from a previous owner. Now I'm at a loss with both problems.

And of course, Herb Chambers Vespa can't see me for 3 weeks, not that I want to give them my money, anyway.

Thanks for any help in advance!
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If you mean the four phillips screws located on the bottom of the carb, someone has posted the replacement sizes. I'll see if I can locate that post.
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michael_h wrote:
If you mean the four phillips screws located on the bottom of the carb, someone has posted the replacement sizes. I'll see if I can locate that post.
I mis spoke - the screw isnt stripped, the head of the screw is ground down. I cannot remove it.
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Check out got mine's last post in this thread Becareful of the bowl screws

Also take a look at DougL's post in this thread Looking for LX150 carb screws

Hope that you get it sorted out!
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michael_h wrote:
Check out got mine's last post in this thread Becareful of the bowl screws

Also take a look at DougL's post in this thread Looking for LX150 carb screws

Hope that you get it sorted out!
alrite I'm going to attempt to pick up an extra thanks for the link.

anyone have any advice with the performance problems and removing a stripped screw in my OP
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Did you clean your air filter? If there's stuff in there it won't be getting enough air and could cause it to bog down. Might not be the problem but it's an easy one to do and rule out. Can't help you on the screws tho. They are crap and we had to dremel one to get a good screwdriver grip once. Wait could you do that? Is there enough of the head left to carefully dremel a bit out so you can get a screwdriver in there? Need to replace them with stainless steel ones. That's my next project. Good luck
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.

Mole-grips.

Fabio

.External inline image provided by member with no explanatory text
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judy wrote:
Did you clean your air filter? If there's stuff in there it won't be getting enough air and could cause it to bog down. Might not be the problem but it's an easy one to do and rule out. Can't help you on the screws tho. They are crap and we had to dremel one to get a good screwdriver grip once. Wait could you do that? Is there enough of the head left to carefully dremel a bit out so you can get a screwdriver in there? Need to replace them with stainless steel ones. That's my next project. Good luck
hey thanks for the idea with the dremel. What pattern did you dremel into the head? A phillips or just a split like for a flat head screw driver? The head of the screw is pretty much ground down to a hole, but I'd say I could drive two slits into either side to allow a thin flat head screw driver to go in there.
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judy wrote:
Did you clean your air filter? If there's stuff in there it won't be getting enough air and could cause it to bog down. Might not be the problem but it's an easy one to do and rule out. Can't help you on the screws tho. They are crap and we had to dremel one to get a good screwdriver grip once. Wait could you do that? Is there enough of the head left to carefully dremel a bit out so you can get a screwdriver in there? Need to replace them with stainless steel ones. That's my next project. Good luck
good idea, gonna do this tomorrow when the stores open back up so I can get some oil for the filter. I couldn't imagine that a dirty air filter could rob so much power so suddenly, but I hadn't considered how these vespa air filters get full of fuel / oil so easily
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Do the 2 slits. Whatever is easiest for you. Your welcome. Not a mechanic but sometimes i can try to help. The LX'S are pretty finicky when it comes to things. I had some severe carb probs and just spraying out the choke with some carb cleaner (junk you really couldn't see with the naked eye) solved the problem and the scooter purrs like a kitten now. Good luck and there is a light at the end of the tunnel.
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judy wrote:
Do the 2 slits. Whatever is easiest for you. Your welcome. Not a mechanic but sometimes i can try to help. The LX'S are pretty finicky when it comes to things. I had some severe carb probs and just spraying out the choke with some carb cleaner (junk you really couldn't see with the naked eye) solved the problem and the scooter purrs like a kitten now. Good luck and there is a light at the end of the tunnel.
Hey I just did some research in the wiki and it appears that we may be talking about 4 different screws. I am talking about the 4 screws that attach the black piece to the carb. As seen in this picture:

External inline image provided by member with no explanatory text

NOT these four:

External inline image provided by member with no explanatory text

Apparently I didn't even need to remove those to get to the jets. Oh well. I'm gonna pull out the carb tonight using the wiki advice and spray down the jets and what not. Any advice on plugging the fuel line as I have a full tank of gas right now, and would rather not have a small environmental disaster when I remove the fuel line from the carb going to the gas tank. THANKS AGAIN!!

edit: the screw is stripped on the vacuum chamber cover as per the workshop manual
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Mine didn't leak gas and i don't think the guys did anything special to it. If your worried just place the tube up on something. Fluid usually can't flow up. Please spray the choke with some carb cleaner while your in there. I don't know if people do it when they clean the carb but by doing mine it runs 1000 times better. We've had the carb off before and didn't do the choke. John just cleaned his carb (didn't do the choke) so he pulled it out again, yesterday and cleaned it, now his LX runs much better. Still wasn't running 100% after just the carb clean without the choke being done. Amazing how much of a difference it makes. Good luck and glad you got it off.
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Got carb out, got stripped screws off! Honestly the carb was clean as a whistle but I overnight soaked the jets and blasted out the rest of it. HOWEVER!, when I removed the vacuum chamber cover, the black membrane was discolored and mishapen. It appears to have white pieces all over it, and it was not seated symmetrically.

Could this be the source of the power loss? And would you guys recommend replacing or some how repairing this piece?

Thanks!!

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replace that diaphragm .
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old as dirt wrote:
replace that diaphragm .
Ordered.
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OAD has you covered but if that diaphragm isn't on perfect it will have the exact symptom you described. Ask me how i know I might get a back up one as well. Mines getting old. Hope you get it up and running soon.
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oh boy...

First; with the fuel line removed from the carb, and when it is held all the way down, should fuel be coming out at all? No fuel comes out when the hose is disconnected. Not sure if there is a vacuum of sorts.

Local vespa dealer had a used carb I got for parts, so I took out the diaphragm and slapped it into my now clean carb. Evap hose removed, air filters both cleaned and oiled. A good amount of oil came out when I removed the air filter.

With all this, I'm still having the original symptoms of severe loss of power. The scoot idles fine. Any more ideas?
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Make sure that diaghpragm is on perfect. If it's a millimeter off it will idle fine but go above 20 mph. Refit it and see what happens. Did you clean the choke? If not clean that. Sounds like something isn't tight. Good luck
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the "new" diaphragm appears to be warped. can someone tell me if this is how its supposed to look right after removing the cover?

THANKS again
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It does look funny and i can't help you since the guys did mine and i didn't see it. Sorry. Pesky little beasts aren't they? Still playing around with my carb. Round 2 will be coming up shortly. Good luck
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It looks OK to me, but it's hard to see whether it is seated well in the groove.

The critical things are that the diaphragm itself has no cracks, leaks, or holes and that it is seated and sealed around the perimeter in the groove in the carb casting. Some silicon grease around the perimeter helps to ensure that it is sealed there.
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All is finally good. Got the diaphragm aligned correctly and scooter has returned to normal power output. Just going to clean up the choke and that'll be that.

Thanks again for everyones' help!
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Awesome. Clown emoticon Clown emoticon
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uh oh! The original problem is back...it is stalling again at speed after warming up. The issue with the diaphragm is resolved, though, as I can accelerate normally with full power. after the scooter warms up, the engine will sputter and then die leaving me to coast to a stop.
today on the way home from work could not restart....walked to vespa, bought a spark plug and replaced it roadside. after cooling, scooter got me home and then problem remerged when I got close to home.
Carb was recently well cleaned, new diaphragm, air filters cleaned, spark plug brand new, new tank of gas. I did notice that when I first removed the fuel line it was dry as a bone, and then after the scooter sat and cooled...a few more turns of the engine and gas leaked out ...
would it be worth it replacing the fuel tap?
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flyingpertyhigh wrote:
would it be worth it replacing the fuel tap?
Yes, though that still may not be your issue. I don't recall reading whether your EVAP system is disconnected - is it? If not, that's priority #1 this weekend.
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Make sure the blue vacuum line from the intake manifold to the tap is not cracked or broken. It opens the tap under vacuum.
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Masala wrote:
flyingpertyhigh wrote:
would it be worth it replacing the fuel tap?
Yes, though that still may not be your issue. I don't recall reading whether your EVAP system is disconnected - is it? If not, that's priority #1 this weekend.
Yes, evap system hose is disconnected from the carb....gonna pick up a tap today when they open at 10, drain and clean out the gas tank / hose
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scootermarc69 wrote:
Make sure the blue vacuum line from the intake manifold to the tap is not cracked or broken. It opens the tap under vacuum.
blue line looked fine - theres only 3500 miles on this scooter so im rather perturbed that anything would fail yet.
I replaced the fuel tap (sigh, $40 with tax), checked all the hoses and lines. Replenished tank with fresh 93 octane fuel. Then went out on a fairly long two-up ride mostly WOT - did not experience any problems. I'm keeping my fingers crossed that the issue was the fuel tap. Herb chambers boston tried to convince me it was the battery, which makes no sense. Anyway, thanks again
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FLYING mine has almost 13k but the scoots are 5yrs old. I agree they should last longer. Mine is going to be changed out as well, soon. Fingers crossed this is the fix.
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