Skorpion Tour sputter/spits/backfire randomly

[J-Ball]

Hey guys, I just got a "new to me" 2000 Skorpion Tour from a friend of mine. He bought it new and has never really had problems other than the carb got gunked up from sitting for a while. The carb supposedly has been recently cleaned and should be good to go. After that the bike sat a month or two. I was able to get it going with a little starting fluid and running it a bit.

The issues;
At idle it sputters a bit but runs and idles decently now. Now that I've run it a bit with carb cleaner in the gas (Seafoam) it runs pretty well around town, plenty of power etc. The problem is when I get on the highway it will run great for 5-10 minutes of 70mph riding then starts to loose power, back fires etc. Usually resulting in having to pull over. If I immediatly try to start it, it wont start. If I wait for a 1 minute it'll start right up and the whole process repeats it's self. It doesn't seem to be running out of gas, the little in-line fuel filter (pre-carb) shows to have gas when it's sputtering and spitting. The air cleaner is clean, fresh oil and coolant etc.

Also, I have noticed a few intermitent electrical issues. The high beam indicator will randomly flash at times as will the neutral light (only when in netural). Also, sometimes when I put the side stand down it will kill the engine (as it should) other times it won't. Could this be the heart of the sputtering/spitting/backfireing?

Any help at all is appreciated and thank you in advance.

J-Ball

[Bill Jurgenson]

most probably, the problem is the side stand switch. On left side near the CDI there is 2-pole connector. Pull this apart and join the two pins to simulate the side stand being up all the time. If that cures the problem, then it is the switch. What you do is your own choice. I always throw the damn thing out right from the start. It is a headache in all bikes I know with a big single Yamaha engine.
If you relace the bolt/axle of the side stand with a something quite a bit longer, the spring will catch on that and make the stand snap up by itself. You don't need the switch then (legally).

Your other problem sounds to me like a clogged filter screen. The needle valve has its own small screen; check that.
Remove the petcock entirely and check that the screen on it inside the tank is free. Then the petcock is notoriously too small to begin with. Drill it out carefully or get one fro a Baggi which is bigger. Or take it off entirely. I use a quick release connector with a 6mm hose.

quick release.jpg (67.41 KiB) Viewed 4166 times

You can't possibly be more "turned off" than completely disconnected and it makes removing the tank a hell of a lot easier. Not so much having take of the hose each time as fumbling,forcing the big petcock past the harness in and out. This is not good for the harness at all.
Whatever the cause, it sounds like the engine is overheating due to starvation/too lean mixture, so you 'll have to find out what is wrong fast.

[droy]

Bill,

Question on the picture.

Is that quick connect ( male side) just epoxyed into the tank? In the past you mentioned using a Aprilia part that would replace the stock peacock, do you have a picture or part number? I recently installed a universal Arebac (sic?) peacock that was a little smaller in profile and diden't drag on the wiring harness as much but it's still not perfect.

Thanks

Doug

[Bill Jurgenson]

Hi,
that is the Aprilia part. It has 3/8" (??) pipe threading which I tapped into the tank, not quite all the way so that the thread cinches up.
I do not have a part number for that tho I can try to find out. My friend and Aprilia dealer has them on stock so there was no need to order.
I fitted thre or four tanks with this one and two with a home-made hose fitting of brass soldered from an 7mm tube and a flange to use the existing bolt holes. The flange has a recess for the O-ring. These two use in-hose quick releases.
In all cases I adapted the filter screen from the original petcock onto/into the new fitting. Obviously, there is no reserve.

[J-Ball]

Bill, Thanks for all the great advice. I'll lose the side stand switch pronto and see if that helps. That still wouldn't explain the high beam indicator flashing on and off randomly. I think there is another electrical issue somewhere though I couldn't find any loose or rubbed wires anywhere. I still think my main problem is a starvation issue. I'll check the petcock, lose the in-line filter (for now anyways) and dig into the carb if need be. I've had a strong dose of Seafoam in the gas sitting in the carb for a week now, hopefully that will help.

Questions;
If I do have to go into the carb, how do I access the needle valve that you speak of to clean it? Best way to clean it? This is the pin like vavle that works with the float correct? Any other things to check while the carb is off?

Also,
You mentioned that it could be overheating because it's running too lean and to fix it fast. Do you say fix it fast because it can be damaging to the engine? If that's the case can someone explain how too lean can damage an engine and how to "richen" it up? (fyi this is a stock carb with no mods)

Thanks guys, I'm pretty green and wrenching on a bike.

Thanks again!
J-Ball

[Bill Jurgenson]

HI beam indicator flashing randomly? When the lights are on or always?

re carb: Stuff like seafoam can degunk passages but it won't remove actual crude caught behind a filter screen. The petcock itself has a filterscreen screwed onto the bottom. Have you looked at that?
Have you removed the petcock from the tank? It has a sizable filter screen inside the tank that could be partially clogged.
Have you checked that the tank vent is working? It is that back rubber hose going down from the right side of the tank next to the carb. Open the gas tank and blow into it. The screw-in fitting on the underside of the tank to which the hose is connected is notorious for electrolytic disintegration.
The rubber carb mounts could be cracked, allowing air to be sucked in, leaning off the mixture.
This is all stuff that happens. Not just freaks.

You can get at the needle valve when the float bowl has been reen removed. It is of th usual type lifted by the float against its seat.

If it actually is running too lean, much too lean, you can et into trouble very fast, ending up with a siezed piston at at best.
There is no need to richen the mixture if the everything is OK. The carb is jetted on the rich side, but if it is not getting sufficient gas, jet size doesn't matter.

[J-Ball]

Hey great news, the MZ is alive and running well! Thanks to Bill for the all the input. I've put about 125 windblown, sore butt, grin from ear to ear miles on it so far! I believe the potent dose of Seafoam sitting in the carb for a week did wonders for it. I was able to start riding it bit by bit then with the occasional flutter. Once I cleaned the screen in the petcock it really opened up and now runs smooth. I have re-installed an inline (car sized) fuel filter and so far so good. I noticed that it stays mostly empty but the bike seems to run fine. Shouldn't the gravity flow from the tank fill up the in-line filter and it stay full? Does this bike like an inline filter or is it not needed? I'll keep mucking with it.

I think a new spark plug is next in line, any good recomendations? Anyone know the gapping for this bike's plug?

Also, I'd like to add some extra lights, it has a light switch on the right side that seems to do nothing. Is this for additional lights? If so where can the "switched" wire end be found?

One last thing, anyone know of a fairing/windshield that could work on this bike. I don't need much, but it shure would be nice to have bit of protection from the elements.

Thanks again Bill, I appreciate your help. Have a great day all.......

J-Ball

[Bill Jurgenson]

If the Filter is THAT big, it will only fill up when the engine is not running. The petcock is too small; just barely able the manage the thurst of the carb. The petcock of the Baggi etc is larger. But I already wrote this. You can drill out the the OEM petcok about 1/2mm; the Cup racers do this, since they must use the stock part.

Plug: NGK and nothing else (well Denso, if you want to pay that much).
The stock plug is a DPR8EA 9
here is the key to NGK's coding:
D= 12mm thread (C=10mm; B=14mm)
P= projecting middle electrode
R= resistor, Spark arrested, (better for the radio - do you have a radio on the bike?)
8= heat range. running from 2 = very hot to 11= very cold
E= 3/4"=19mm thread reach, H= 1/2" reach
A= "special design"(=normal); S= standard type = pretty much the same thing. IX= iridium , VX = platinum

9= 0,9mm gap - a number here gives the gap in 1/10mm

I use a D8EA: 12mm thread 19mm long without resisitor and with the most normal type electrode imaginable.
cheapest thing available and more that good enough. I used them even for racing.

here is a very good page on plugs in general, read it:
http://www.ngksparkplugs.com/tech_support/spark_plugs/index.asp?mode=nml
more specific
http://www.ngksparkplugs.com/products/spark_plugs/standard.asp?mode=nml
and FAQs
http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/index.asp?mode=nml


re additional lighting
keep the output of the generator in mind. If you go overboard, the lighting will run off the battery. Obviously it can do this only a limited length of time and then the battery is empty. Since the OEM battery is too small to begin with, this is not just theory. And a larger generator is not easily possible.

Adding additional lighting will also add weight/mass to the head set and influence handling negatively.
Admittedly,the headlight is not the very best, but, seriously, what do you want the additional lighting for?

[J-Ball]

Bill, thanks again for the info. I will look into drilling out the petcock as soon as the tank gets low on fuel. (I guess I'll have to go ride more) I'm not sure what it'll look like when I pull it out. Where do you drill the 1/2mm hole? Are we just making an existing smaller hole larger i presume? Sounds easy enough.

Thanks for the tips on the plug. Much appreciated.

As far as lighting, I was just trying to make the bike more visible to day dreaming motorist--both day and night. Safety reasons. I was eyeing a pair of 3.5" round 55 watt lights that could mount off of the upper forks. I was planning on aiming them out into the bar ditch a bit to also help in spotting deer eyes at night. I live in whats called "The Deer Capitol of Texas". Oh boy! The lights very well may not happen in the end.