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Old 04-02-2013, 09:20 AM   #1
pjm204 OP
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Aprilia Pegaso Issue(s) - F650GS guys welcome to help.

I'm helping a friend work on her newly purchased 2000 Aprilia Pegaso Cube. It was purchased in excellent condition however it had not been ridden in years so it was running albeit poorly.

Here is a description of the symptoms:
1. Consistently stalls out below 1500 RPM
2. Has stalled out will riding at highway speed
3. Will idle at ~1100rpm only with a little choke applied


Here is what we have done so far:
1. Took carb bowls off, cleaned jets, replaced a few bad o-rings
2. Tested battery, ~12.5 voltes sitting there, over 14 while running
3. Checked plug, it is a nice golden brown color
4. Changed oil
5. made sure connection between airbox/carb was good

It starts up instantly but just does not want to run well with the choke off. This to me sounds like a fueling issue, it is not getting enough at low RPM. However, the fact it cuts out so quickly seems strange to me. It does need exhaust gaskets between the header and muffler but I doubt that would cause this issue.
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Old 04-02-2013, 01:32 PM   #2
pjm204 OP
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Current bikes:2006 DL650, 2008 WR250R
Past bikes: XT225, TTR125, '04 CRF50 '74 DT125,'70 TS250,'85 v45, '89 zx600c, '78 GS400x, '99 GS500E, '01 GS500E '05 Z750s, '77 GS400e, '82 GS1100ez, '97 GSX600, '07 VFR800, '03 KLR650, '03 FJR1300, '06 DL1000, '00 KLR650, '99 WR360, '08 DL650, '05 DR650, '08 EX650r, '96 CR500, '82 GS450T, '06 Ural
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Old 04-05-2013, 07:56 PM   #3
'74Stratos
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US specification Pegaso carbs suffer from compromised stock jetting which, among other things, causes the header pipes to glow red and excessive "popping" from the exhausts at certain throttle positions. Then, when you add to that gummed up carb innards from prolonged non-use and you have what you are experiencing. My guess is your friend's carbs have to come out again for a complete cleaning (blow out and poke through every jet). If her bike is stock, the air mixture screw will need to be readjusted and the floats may be out of adjustment from soaking in nasty degraded gasoline.

Again, if it is equipped with stock jetting and exhaust I have two more recommendations:

1) Look up the carb settings I posted on the "Blue Peg Rebuild" thread here and on the AF1 Racing Pegaso Forum <---that thread is more complete with additional updates;

2) PM my brother, Andysrage on this forum. He lives just over the river from you in Trenton and is a master at setting up Pegasos. He has rebuilt several from tip to tail.

Don't worry, she will run and run well. They just like a little (lot) of extra attention.
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Old 04-07-2013, 08:39 AM   #4
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pjm204,
These are classic Pegaso Cube symptoms. These bikes were set up excessively lean, especially for the US market, so even if you rebuilt the carbs to spec, it would barely stay running off-choke (it is actually an enricher circuit in Mikuni BST). This hack jetting is due to the addition of catalytic converters in the mufflers and the need for excess air for them to work properly. Its BMW F650 sibling uses richer jetting yet gets around this problem with an Exhaust Air Injection system connecting the header to the airbox (BMW was likely thinking ahead to meet future emissions requirements). Aprilia did not have these provisions built-in so they just leaned out the US bikes until they past emissions.

These carbs are very reliable once cleaned and set up right. They only appear sensitive due to the fact the factory jetting is on the fringe of working. Assuming the bike still has the tiny 37.5 Pilot jets, set the idle mixture screws to 4.5 turns out (good luck getting your hand in there to do this!). This will give you a less cold-blooded bike that runs without choke and won't stall at idle. Next (even though it is an absolute pain in the rear), I would pull the carbs again and clean out every orifice thoroughly. I use little bits of wire like from twist ties or plucked from a wire brush to chase each passage. While the carbs are out again, you might as well drop in larger pilot jets. I have a bunch of new jets so let me know.

PM me if you need help. I'm only 30 minutes from Philly.
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Old 05-02-2013, 09:43 AM   #5
pjm204 OP
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So we got the bike running well. I rode it 10 or 15 miles, took it on the highway, had no issues. My friend then took it for a ride last night and it cut out on her on the highway. Obviously this left her frustrated with the bike. We had turned the air fuel out to 4 turns, it idles normally.

Any idea what this cutting out issue? It almost seems electrical to me, like maybe the R/r is heating up and cutting out or a coil?
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Old 05-03-2013, 05:28 PM   #6
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It sounds like the tank air vent is blocked.Try riding with the tank cap open and see if that helps.If so then clean out the tank vent.
Try these guys too.They were great when I had my Peg.
http://www.apriliaforum.com/forums/f...50-Cube-and-IE

Cheers
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Old 05-08-2013, 07:47 PM   #7
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Fresh fuel?
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Old 01-15-2015, 01:05 PM   #8
moizu
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My pegaso 650 cube is stalling too - cannot ride

pjm204,
Did you ever solve the problem?

I also just bought a 2000 650 Cube and it stalls out at low rpm. My last ride was super sketchy, when it cut out as I was heading into an intersection and the back tire skidded.

Last night I pulled the carbs, cleaned everything, and put in bigger jets. I set the mixture screws about 2.5 turns out. I started it this morning and it still doesn't want to run below 3k rpm. It makes an awful "clink" sound and sometimes recovers and sometimes stops.

So, after looking at a few more forums I've ordered a new coil, but I do not know if this will fix my problem. I put main jets as 112.5 and I can up them to 117.5 (I think I'm remembering these #s right), and I can open the mixture screws a bit more. Spark plug is brand new.

Any help would be greatly appreciated. Once this is solved, I can move on to fixing the water pump. I hope this bike will be worth all this trouble - I haven't yet had a clean ride.
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Old 01-15-2015, 03:18 PM   #9
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Quote:
Originally Posted by moizu View Post
pjm204,
Did you ever solve the problem?

I also just bought a 2000 650 Cube and it stalls out at low rpm. My last ride was super sketchy, when it cut out as I was heading into an intersection and the back tire skidded.

Last night I pulled the carbs, cleaned everything, and put in bigger jets. I set the mixture screws about 2.5 turns out. I started it this morning and it still doesn't want to run below 3k rpm. It makes an awful "clink" sound and sometimes recovers and sometimes stops.

So, after looking at a few more forums I've ordered a new coil, but I do not know if this will fix my problem. I put main jets as 112.5 and I can up them to 117.5 (I think I'm remembering these #s right), and I can open the mixture screws a bit more. Spark plug is brand new.

Any help would be greatly appreciated. Once this is solved, I can move on to fixing the water pump. I hope this bike will be worth all this trouble - I haven't yet had a clean ride.
I had the same problem. I ended up taking out the carburetors and taking them to my mechanic who soaked them in fresh fluid and cleaned them well. The problem has been fixed without replacing the jets, but he did have to re-bore them.
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Old 01-15-2015, 08:35 PM   #10
Andysrage
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Quote:
Originally Posted by moizu View Post
pjm204,
Did you ever solve the problem?

I also just bought a 2000 650 Cube and it stalls out at low rpm. My last ride was super sketchy, when it cut out as I was heading into an intersection and the back tire skidded.

Last night I pulled the carbs, cleaned everything, and put in bigger jets. I set the mixture screws about 2.5 turns out. I started it this morning and it still doesn't want to run below 3k rpm. It makes an awful "clink" sound and sometimes recovers and sometimes stops.

So, after looking at a few more forums I've ordered a new coil, but I do not know if this will fix my problem. I put main jets as 112.5 and I can up them to 117.5 (I think I'm remembering these #s right), and I can open the mixture screws a bit more. Spark plug is brand new.

Any help would be greatly appreciated. Once this is solved, I can move on to fixing the water pump. I hope this bike will be worth all this trouble - I haven't yet had a clean ride.
Let me try this again….wrote a huge response only to have laptop battery die and lost everything so you're getting an abridged version.

To start with, we need to know where you are located as the tuning spec varies around the world. From your language/writing style, I'd assume the USA which is good as that is the spec I have my background. Considering their age, any Pegaso Cube that has not be extensively gone through will have the "classic" problems that are more a result of time than anything else. These include the carbs, tank vents, head gasket, and voltage rectifier. After sorting these, the bike will be a dream.

Good news first. You can return the coil and apply the money to other fixes! Why? Because the bike starts. Stalling and the subsequent high idle are all fueling issues. The metallic "clank" when stalling is simply the sprag clutch (one-way freewheeling clutch between starter and flywheel) suddenly grabbing when the engine kicks backwards as it's dying. As long as the starter keeps engage and disengaging, the sprag clutch is OK though too much of this kickback will damage it eventually. As for your new spark plug, save it for after sorting the carbs ( why foul a perfectly good plug).

Now onto the fueling fixes but bad news is that the carbs are coming out again.
First, clean the carbs again super thoroughly. Focus especially on the passages between the pilot jets, mixture screw and throttle bore (three tiny holes) as well as the vents in the intake bell mouth for the emulsion tube and bowl reference vent. Lastly, make sure the emulsion tubes (the perforated needle jet that live above the main jets) are clean. Check all the rubber orings and replace that are cracked or non-pliable; find these easily from a Suzuki GS500e 1989-2000.

Second, you mentioned changing jet; which ones? If you are running a stock exhaust, leave the 110 main jets. The stalling issue is a lean condition at idle and bottom end, not at full throttle. Going with bigger mains will only result in a worse throttle curve with a hefty flatspot as you transition from the pilot to the needle (1/3 throttle…right where most riding is done). Add to that, the cats in the stock exhaust will not appreciate the excess fuel, your consumption goes up and your new plug goes to pot. I run 112.5 mains at sea level in conjunction with FMF dual exhaust and K&N air filter and it sure doesn't run lean. I experimented unsuccessfully with 115 and 117.5 and found them far, far too rich.

Third, has you vapor canister (lives on skid plate) and lines been removed? If so, make sure the two ports on the right carb are capped. If so, check the caps for cracks or loose fit and replace caps as needed. I found that some rubber caps degrade in as little as a year, resulting in a sweet vacuum leak. I've plugged mine permanently.

Fourth, the idle/stalling/starting fueling issue will ultimately be resolved by focusing on the idle mixture & pilot jet combo. There are several combos that work. While less than ideal, when using the stock 37.5 pilot, set the mixture screw to 4-4.5 turns out. The excessive mixture setting indicates the pilot is a bit too small. The combo I recommend for a mostly stock Pegaso is the Austria/Swiss spec 40.0 pilot and 3.5 turns out on the mixture. Lastly is a 42.5 pilot and 3 turns out which is what I run along with the aforementioned intake and exhaust mods.

Fifth, Check your float level. Probably wouldn't impact the stalling issue but will further up in the revs. You've got the carbs open anyways!

Sixth, check your carb boots for cracks.

Seventh, clean your fuel tank's vent port. You've got the tank off at this stage anyways. When the aluminum nipple on the tank bottom corrodes, it blocks the vent and the tank will not drain properly and fill the carbs. Usually the bike starts and runs fine only to die 20-30 minutes later as vacuum builds up in tank, cutting fuel flow.

Here's a reference threads:
http://www.apriliaforum.com/forums/s...h-Pegaso-carbs

Good luck
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Old 01-15-2015, 08:55 PM   #11
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Wow, what a detailed thorough summary. Andysrage has nailed it all in one post here. Most of what he outlines describes what I did with my Pegaso when I bought it used (and assumed nothing, checked everything). It starts right up on choke, and within a minute choke is off and it idles and runs perfectly.

edit: these bikes DO NOT like to sit for some reason. Even with fuel stabilizer after about 3 weeks I can tell, it doesn't start so quickly and doesn't run well for a few minutes. If they are run regularly, not sitting more than a week or two at a time, everything is good. Must be the carburetor design, or something to do with them.
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Old 01-16-2015, 05:41 AM   #12
Andysrage
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….. my Pegaso when I bought it used (and assumed nothing, checked everything). It starts right up on choke, and within a minute choke is off and it idles and runs perfectly.
^
^
This is the best advice. We did that with my brother's Pegaso and detailed the rebuild here:
http://www.apriliaforum.com/forums/s...ue-Peg-rebuild

Here's a thread on cleaning the tank vents:
http://www.apriliaforum.com/forums/s...n-poor-running

Another thread with some more carb tuning (performance exhaust) and capping of the emissions ports:
http://www.apriliaforum.com/forums/s...=1#post3387036
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Old 01-17-2015, 06:10 PM   #13
moizu
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Wow, thanks for the quick response!

Yes, I'm in the USA - living in Oakland CA (sea level) these days - and bought the bike here off craigslist from a home-dealer who got it at auction and immediately posted it. I don't know any history of the bike, but appearances give me the impression that it may have sat for some time.

Here's a video of the stalling (I'll delete after it's seen)
https://plus.google.com/u/0/11113764...46294473891821

I can't believe the carbs are that fickle. I cleaned them throughout and felt pretty confident. The sound also throws me off (listen to video), but, I'll defer to your expertise and go through the carbs again.

I put 42.5 for the pilot jets and 112.5 for the main jets, from a kit that I bought on Amazon. The kit also came with nylon spacers and shims for the needles. Do you think adding those might help?

I can try and cancel the special order for the coil, if you're sure it's a waste. I'd be much happier getting back on the road tomorrow, even if I have to pull the carbs again.

I wondered about those tubes on the side of the carb. One is "capped" with a rubber cap that is split wide open and the other is uncapped.

I gotta run right now, but will go through your post and try all suggestions tomorrow.

Thanks again!!
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Old 01-17-2015, 09:23 PM   #14
Andysrage
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Originally Posted by moizu View Post
I wondered about those tubes on the side of the carb. One is "capped" with a rubber cap that is split wide open and the other is uncapped.
^
^
This is your problem right here, also confirmed from your video that you've got a huge vacuum leak. Get new caps for both of these ports and she'll run fine. The sharp "pop" is an ignition occurring in the header, typical of a vacuum leak/super lean condition after several revolutions where it doesn't properly fire. Once the engine catches, it lights the fuel built up in the header. If you forced it to run long enough, the header will glow (ask us how we know). If you open the choke (enricher), I bet it runs better, right? These carbs are on dozens of other bikes so it isn't that they are particularly finicky, more that they are 15 years old and the bike sat without use. Granted, Aprilia spec'ed some super lean idle/pilot setting to pass emissions and provide sufficient air to the cats with adding the Secondary Air Injection like was done on the F650 sibling (and hence why they have a richer 41.5 pilot).

As for the jet kit, install the 42.5 pilot and idle mixture screws set to 2.75-3 turns out. As for the main jet, stick with the 110 (only use the 112.5 if you have a performance/catless exhaust).

In regards to the needle, use the factory setting which is 2nd groove (out of 5) from the top. There is also a plastic spacer from the factory that goes below the clip. Depending on the thickness of the shims, you might be ok adding one under then needle clip to "create" an intermediate setting between 2nd and 3rd grooves. If you replace the air filter with a K&N drop-in filter, then go the the third (middle) groove and eliminate the shim you added.
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Old 01-18-2015, 07:29 AM   #15
'74Stratos
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+1

Post closeup pix of the carbs when you have them out.
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