2005 stella fireball can't handle the throttle

double-o-soul · Post by **double-o-soul** » Thu Jul 09, 2015 11:38 pm

Hey folks,
any thoughts on what might be happening to my bike here?
https://youtu.be/_KfhjJInYEA

at :05 i give it a touch of throttle, at :12 a touch more, and then :17 a little more...
earlier in the day i was able to get some combination of screw settings to keep the bike alive all the way through a second or two of half throttle, but anything longer or more than that... same high revs and then engine cut :-/

spaco 20/20, 2.5 turns out on the mix, philadelphia summer...
drilled, de-blued, ggr hot reed,
if I remember correctly...
BE3, 102 main, and an idle jet just a tad richer than stock...

PLEEEASE halp!

ArgonV · Post by **ArgonV** » Fri Jul 10, 2015 1:21 pm

How's the gas flow?

Stators do go bad, but it's rare...

double-o-soul · Post by **double-o-soul** » Sun Jul 12, 2015 1:21 am

i'm going to take apart and clean the carb and gas tank per my friends suggestion, so you're def not the only one thinking that... i'm just curious why its revs high and dies no matter how high or low i am on the mix screw...

ArgonV · Post by **ArgonV** » Sun Jul 12, 2015 4:10 pm

Does your scooter have any of the evap stuff?

double-o-soul · Post by **double-o-soul** » Sun Jul 12, 2015 11:51 pm

i don't think so...
I put in a little of that winter time fuel additive stuff months ago if thats what you mean

PeteH · Post by **PeteH** » Mon Jul 13, 2015 3:09 am

I think ArgonV meant emissions hoses, canister, etc. An old Fireball 2T shouldn't.

az_slynch · Post by **az_slynch** » Mon Jul 13, 2015 7:20 am

Here are two mixture screw types: a coarse thread (usually found in P series Vespas with a DellOrto) and a fine thread (usually found in Spaco 20/20 Stella carbs). I'd guess you have a fine thread mixture screw, but I'd still recommend inspection. Usually, a good start setting for a coarse thread is 1.5 turns out of fully seated. I've used 3.5 turns out of fully seated for a fine threaded mix screw.

That said, I'd look at the linkage to the oil pump first and make sure nothing is impeding it's movement. A bent pump arm will bind on the housing and cause the throttle to stick. If that looks good, pupp the carburetor and check the action of the throttle slide.

I've seen distorted Spaco bodies where the slide could pinch. If the slide's binding, clean the slide and make sure it's smooth on the edges. Clean the slots that the slid moves in as best you can. If the slide still binds, lightly dress the slots with a fine hobby file, clean them again thoroughly and retry the slide. Once it moves easily without binding, reassemble the carb. When reinstalling, be sure to retorque the sleeve bolts evenly to prevent additiional distortion of the carb body.

double-o-soul · Post by **double-o-soul** » Mon Jul 27, 2015 5:51 am

whelp, I rebuilt the carb with all new gaskets from scooterworks, replaced the float and needle as well though there wasn't any visible damage.
I torqued everything proper and put it back in and voila! terrific response with my usual 2.5 turns on the mix...

then an interesting thing happened. I accidentally left the bike on the RESERVE tap setting and overnight a TON of fuel leaked out. it's particularly interesting because my bike never had a fuel leak when left on ON or RESERVE before.

Thinking back to the rebuild, I'm weary of the carb rebuild kit i got from scooterworks, even though their website says its compatible with my Stella. The base gasket between the carb and the airbox looked different, the washer that goes over the fuel overflow spout on the bottom of the carb was noticeably thicker than the washer i removed.

Furthermore, when i kicked it a bunch on OFF to empty out the flooded engine and replace the spark plug, it wouldn't start. I would hear a few pops and the lights would flicker, but I couldn't even get the idle I started with before the debacle/

OCStella · Post by **OCStella** » Wed Jul 29, 2015 11:32 pm

You might check the float, either it's getting stuck or it has a small hole. I've had this happen on older motorcycles. I'm not sure how it mounts in the carb, but check the tabs on the float, make sure the tabs are bent in the same way as the old ones.

"I rebuilt the carb with all new gaskets from scooterworks, replaced the float and needle as well though there wasn't any visible damage.
I torqued everything proper and put it back in and voila! terrific response with my usual 2.5 turns on the mix..."

az_slynch · Post by **az_slynch** » Thu Jul 30, 2015 12:59 am

double-o-soul wrote: then an interesting thing happened. I accidentally left the bike on the RESERVE tap setting and overnight a TON of fuel leaked out. it's particularly interesting because my bike never had a fuel leak when left on ON or RESERVE before.

Thinking back to the rebuild, I'm wary of the carb rebuild kit i got from scooterworks, even though their website says its compatible with my Stella. The base gasket between the carb and the airbox looked different, the washer that goes over the fuel overflow spout on the bottom of the carb was noticeably thicker than the washer i removed.

Furthermore, when i kicked it a bunch on OFF to empty out the flooded engine and replace the spark plug, it wouldn't start. I would hear a few pops and the lights would flicker, but I couldn't even get the idle I started with before the debacle/

The overflow washer likely isn't the culprit. It's just lacking about ten years of compression on it.

OC is hitting pretty close to the mark. Take the float out and check it carefully. Shake it and see if anything sloshes in it. If nothing, put it in a pot of warm water and submerge it. If you have a leak, you'll see bubbles. The warm water will help any holes expand and make the leak more visible.

If the float passes muster, and your kit came with a new needle, you may need to clean the needle seat. Dismantle the carb completely. Put some toothpaste on the end of a Q-Tip, stick it down into the needle seat and twist to polish the seat. Rinse with water and inspect. Work at it until the seat is clean and shiny.

If you have an old needle, inspect the rubber tip with a magnifying glass. If it has a ridge on the slopes of the needle tip, replace the needle.

double-o-soul · Post by **double-o-soul** » Sat Aug 01, 2015 5:34 am

thanks for the terrific suggestions all.
turns out I was using the wrong gasket between the carb and airbox... the right one has one less hole LOL

took her for a nice half hour ride with a lot of 4th gear WOT and she purred along fine. toward the end of the ride she started revving like crazy but I figure that's just cus I was taxing her so hard in really hot muggy humid philly air for a while. have to replace the idle screw spring and grommet because the engine vibrations are actually causing the idle screw to move little by little.

NEXT FUNNY THING:
this morning she wouldn't start after 4 or 5 kicks and i was in a rush so i turned the fuel tap off and left... 12 hours later on a hunch, i tried kickstarting WITHOUT pulling the choke and VOILA! 2 kicks and a healthy, regular idle. I take it for a spin, and great throttle response. Only issue i could detect was a bit of time getting back to idle after excessively gunning the throttle in 1st and 2nd like she was stolen.

TL;DR:
does anyone else not have to pull the choke on their stella 2t's in the summer? is this a bad thing?

double-o-soul · Post by **double-o-soul** » Sat Aug 01, 2015 5:36 am

i think I just answered my question in my own post lol
I didn't need to pull the choke this morning because it was already hot as balls out.
am i right?

az_slynch · Post by **az_slynch** » Sat Aug 01, 2015 5:09 pm

double-o-soul wrote:i think I just answered my question in my own post lol
I didn't need to pull the choke this morning because it was already hot as balls out.
am i right?

I'd say you're on the right track.

Air density decreases in relation to increases in temperature. On a hot day, lower air density would mean that less fuel would be needed to start things up.