Losing Accelleration at WOT

[wkreps]

I rarely go WOT but I did the other day going to work and every minute or so it would just lose power until I released the throttle. Then it would run fine for a minute and then lose power again. I'm thinking beings I have 4300 miles on my Super8 and never changed the air filter that it needs changed. Is this losing power at WOT a symptom of not enough air?

[tortoise]

Perhaps a fuel tank venting issue . . try a test run with the gas cap loose.

[wkreps]

Perhaps a fuel tank venting issue . . try a test run with the gas cap loose.

You know it could have been cause I had just filled it before going to work the day it did it. I'll loosen the cap and take her out for a run.

(after a run)
Nope. Still doing it. Started after about 3-4 miles of WOT.

[tortoise]

Might try testing the CDI by placing a cold pack against it  . . outboard example.

[Stig / Major Tom]

Wayne,
How does it run at 80-90% throttle?
Are you hitting a rev limiter, by any chance or the effects of an overfilling leading to a wetted one-way vent valve?

Your final drive oil leak into the airfilter (related to the WOT stalling?)........correct gear oil & not foaming at speed is it? Did you happen to collect & measure the orig. gear oil amount at first service? Not over filled? Incorrect manual? Some scoots have the correct amount cast into the metal near the drain & fill bolts?

A seal letting go ? Loose gear box fasteners?
These guys are kicking this around....http://scootdawg.proboards.com/thread/27192/oil-air-filter-box-pics
And here,,, http://www.topix.com/forum/motorcycles/scooters/T5ROM13MA7V7Q0DQS
Please keep us posted...sorry about your troubles!
Stig

[DMblues01]

Wayne, my Supe has done this a few times. Always after filling up. If it is slightly over filled, you could gas a little fuel escaping through the vent, into the emission cannister. That  then vents back to the carb, and can create an effect similar to flooding out when you apply throttle.
When it happens to me, I undo the gas cap, start it up, and let it run a minute or so with occasional revving, and then close the cap back up. It just lets it suck some air through the vent line.
Usually OK then. It will be a bit tempermental for a little afterwards until the emission cannister dries out.

I try not to squeeze that extra $0.50 in the tank now. Haven't had it happen for a while.

-Duke

[wkreps]

Might try testing the CDI by placing a cold pack against it  . . outboard example.

I don't think this is it because I can start it up and take off at full throttle and it is fine for a few miles. Then it starts acting up. I will keep it in my back pocket through in case other ideas fail.

[wkreps]

Wayne,
How does it run at 80-90% throttle?
Are you hitting a rev limiter, by any chance or the effects of an overfilling leading to a wetted one-way vent valve?

Your final drive oil leak into the airfilter (related to the WOT stalling?)........correct gear oil & not foaming at speed is it? Did you happen to collect & measure the orig. gear oil amount at first service? Not over filled? Incorrect manual? Some scoots have the correct amount cast into the metal near the drain & fill bolts?

A seal letting go ? Loose gear box fasteners?
These guys are kicking this around....http://scootdawg.proboards.com/thread/27192/oil-air-filter-box-pics
And here,,, http://www.topix.com/forum/motorcycles/scooters/T5ROM13MA7V7Q0DQS
Please keep us posted...sorry about your troubles!
Stig

Stig,
Great minds think alike. The 80-90% throttle was the next thing I was going to try. WOT it runs 55-60 on the speedo. I was thinking of running at 50mph and see how it does. Normally I'm running 30-40mph on the speedo unless I have cars coming up on my tail. Then I speed up to decrease the closing speed.

I don't think I'm hitting the rev limiter cause it was doing it going against the wind when the RPM's read 8700-8800. I turned around and ran with the wind and it took another mile longer before it acted up but with the wind, I was running 9000-9100 RPM's.

The drive oil in the air filter box may have something to do with it but it definitely isn't foaming cause when I changed it last as noted above I used the same gear oil I've been using from the start. Changed it yesterday for the 3rd time since I've owned it using from the same bottle of CASTROL 80W-90 Gear Oil. The correct amount is stamped into the CVT cover, .18L which equals the 180ml I've been putting in.

I plan on contacting B&L for a parts order and will get a new air filter. I will try the 80-90% throttle test and do the running on the stand with the gas cap off. I do always try and fill to the top. It may have just bit me this time but Monday will be a full week since I filled it last. Knowing that DMblues has had the issues and it goes away is good news as I really need WOT for the camping trip I want to take in 2 weeks that is 140 miles away. I'll keep you posted but rain is coming this week so hopefully I can get out to test between raindrops.

[klaviator]

I doubt this is an air filter problem.  If it was clogged it would run poorly all the time, not just after 3-4 mins of WOT.  I change my air filter every 5-7K miles but it may be dustier where you live.  BTW, I spend most of my time running near or at WOT, usually 55-60 on the speedo.  After 19K miles it still runs strong. 

The carburation is slightly off on my S-8 since it often runs stronger if the throttle isn't twisted all the way to the stop. 

[wkreps]

So today I ran several runs at 6 miles a pop. Both with the wind and against the wind. Fresh tank of gas. If I run with the throttle all the way twisted until it stops, it will lose power after 2-4 miles. If I back off the throttle a little (300-400RPM) it seems to run fine. I did 7 different runs today and noticed that the last 15% I twist on the throttle seems to change the tone of the engine to a more throaty sound (as best I can describe it). It only gives me about 1-2 MPH at best if it even affects it at all. The engine is clearly running harder but it is not giving me any more MPH. When I backed off just this little bit, the loss of acceleration issue went away. To me this is good news but my personality begs to know the answer. It is also easier just to open the throttle wide open on long rides (of which I have one coming).

Do you think there is any sort of throttle cable adjustment that could be made it alleviate the issue or is it something that should be fixed and not masked by changing the throttle cable?

[klaviator]

I can't really answer your question but on my super 8 it seems like what happens on that last bit of throttle varies depending on conditions.  Sometimes I can be cruising at 60 (indicated) and there is still quite a bit of throttle left.  If I twist it all the way sometimes I'll get 1 or 2 more MPH, sometimes 5 or 6.  I think that the carb is very sensitive to temperature and possibly pressure.  Also, little wind can really affect top speed.

I guess what I'm saying is that on mine, that last bit of throttle is not consistent.  I wouldn't even begin to know how to fix that.  Probably just the nature of the carb.  I'd guess that FI might be more consistent, but my Sport City which has FI sometimes has more or less performance depending on conditions.

[chaz35]

I think you are starving for gas for some reason, could be clogged fuel filter.  At WOT, if carb is drawing down gas in bowl faster than is being replenished, eventually will run out of gas, then will loose power and rpms will drop and allow gas in carb bowl to fill up again.  That's my guess, good luck finding problem.

Which way the wind is blowing is huge for an under powered scooter.  I don't know the math, but it takes a lot of power to push a head wind, so if your maxed out anyway, it will slow you down a lot.

[wkreps]

chaz,
Hadn't thought of the fuel filter. That will be next on the list. I'm going to wait to do anything drastic until after the weather warms up. If it still does it, then I may just take it into the dealer. BTW, it does it both with and against the wind on these very breezy springs days in Illinois.

klav,
I'm not at all concerned about the slower top speed against the wind versus with the wind. When it loses power if I keep on the throttle it just keeps slowing down and sputtering. When I release the throttle to idle for a second or two and then throttle back up it is OK (until it does it again). Once it starts, you can't keep it full throttle or it will just keep doing it in quicker and quicker sucession. To me this sounds like a gas flooding issue as backing off the throttle allows it to "catch up" on burning the fuel. Does this make sense? So if this is the case then it would be an issue of not enough air right?

[BettinANDlosing]

One thing you might want to consider checking is the flow of fuel out the petcock. Reading though your symptoms it really seems like your petcock is acting up. Either not flowing enough fuel when open, or dumping fuel into the vacuum line (I've seen this many a time). If you get the seat off, you can just suck on the vacuum line with the gas line into a pop bottle or drain pan and make sure it's flowing a decent amount of gas, it should be enough to fill up a shot glass in 10 or so seconds. To me this sounds 100% like fuel supply, but not definitively flooding, possibly fuel starvation.

[klaviator]

My guess would be a fuel flow problem which could be either the petcock or the fuel filter.  It's pretty easy to bypass the fuel filter.  Bypass it and take it out and do a WOT run and see what happens.  If the filter isn't the problem then bypass the petcock and do another run.  You will either find the problem or eliminate those two as a possibility.