Engine struggles/sputters at high RPM

[RickBlaine]

I have a '95 Skorpion Tour. two weeks ago I started riding again after two months off, during which time the bike sat in my garage. Since I started riding again I have noticed that the engine starts to struggle when I go over 4 or 5k rpm, or when I open up the throttle. I'm not sure how to describe it except that it is as if at a certain point it can't get enough gas to accelerate the way I am asking it to. This is a big problem, obviously, as I need that torque for passing and for staying rubber-side-down in turns. I have put some Techron additive into the tank in the hopes that it will clear up any sludge that might have built up during the two months the bike sat, but I'm wondering if the fact that it is only in the higher RPMs suggests a more specific problem?

[phlat65]

if it is fuel starvation, you can usually reduce the throttle and the rpm will pick up. is it a smooth loss of power, or is it missfiring? I would replace the sparkplug if it is a miss, if it just has no power, it is possible the secondary carb is not comming on correctly. the diaphram is a known problem. if you open the carb drain screws (I am not sure if these carbs have them, but most do) do you get fuel from both carbs?

good luck!

[RickBlaine]

Thanks! I'm not sure how to answer your questions but I will try. If I reduce throttle, the RPMs dial back, and the engine runs smooth again. Same if I upshift. The problem only kicks in at higher RPMs (over 4k), but does seem to happen most often when the throttle is more open, such as when I accelerate to pass. Then, it is almost like a rev limiter -- no matter how much gas I give it, the engine is stuck putting out the same amount of power, in a pulsing sort of way that feels like when the bike starts to sputter out b/c I have to switch to reserve fuel. Sometimes it feels like it works through the problem and accelerates smoothly, other times I have to dial back the throttle or upshift.

I will check the plugs and the drain screws this weekend. Thanks for your suggestions.

[Wonky]

If sat for two months you need to strip and clean your carbs. Most common problem is the right hand carb has gunked up and no fuel cleaner will irradicate the problem. The main jet has crap in it and when you open the throttle the second carb opens up to allow more fuel to the main jet, because there is crud in there it's obstructing the flow of fuel and starving the engine. If it was a spark plug issue it would do it all the time and not at higher revs, when a plug breaks down it's usually an absolute nightmare to get the bike to fire, although putting a new one in wouldn't harm it. But 99% sure it's a dirty carb!

[m4panther]

Wonky, it there fuel filter in the tank of the panther ? I have the same problem only at wide open throttle or over 100mph the carbs just cant keep up with the demand for fuel. I really don't feel like pulling the carb off.

[Wonky]

Wonky, it there fuel filter in the tank of the panther ? I have the same problem only at wide open throttle or over 100mph the carbs just cant keep up with the demand for fuel. I really don't feel like pulling the carb off.

Have you fitted an aftermarket exhaust on your bike? It is possible that your carbs need setting up to match, not usually neccessary but if the bikes been ridden for many miles then had a pipe put on or even if it's standard it may just need a good overhaul. My MUZ was a bit like that and i kept brushing the limiter which made the bike cough a little. The tank dosen't have a filter inside as i am aware, maybe a gauze on the outlet and to be honest the tank you can take off in 10 minutes, easy peasy! Flush it out and drain it!

A good local Moto-X service centre would be able to sort your carbs out and balance them for you no probs! Standard the MUZ won't really do much more than 105mph anyway so expect a little reluctance from the engine at that speed...

[DAVID THOMPSON]

read link on spark plugs also

http://www.mzriders.com/mz/viewtopic.php?t=1090

change made a big difference in my saxon tour

[RickBlaine]

Thanks, all!

Sounds like it is definitely the carb thing, as the failure manifests as a rhythmic surging, consistent with your description of one jet working but the other not.

The muffler is standard, but I did notice the other day that there is some air coming out of the fitment between the wide part at the end and the pipe at the bottom of the bike (make sense?), and I wondered if that clamp there needs tightening or if that "escape" is normal. The bike has always backfired a little when I come back from WOT.

Is cleaning/adjusting the carbs something I should not attempt to do myself (very limited experience/expertise, but plenty of interest in doing my own work)?

What is a "Moto-X" service center? As in motocross as in dirt bikes?

[Wonky]

Yes Motor Cross service centre, or a reputable superbike mechanic could strip and clean them for you! It's always worth having a play yourself as the more you do it the more you will learn, if you take pictures on a digital camera before you take the carbs off you will always have a reference for putting them back together, they come off really easily. If your not very confident then definately take them to a mechanic.

[RickBlaine]

I'm going to try this today. Any special tools, devices, etc. I need before I start?

[jimc]

some hints if it's not too late
Before ripping everything apart, have a look at a carb. parts diagram.
also, try cleaning out the filter & bowl under the on/off reserve.

You can get to the main jets without pulling the carbs, especially the secondary.
Be careful no to go crazy with compressed air , you can collapse floats....

[Wonky]

No special tools, just take your time! Have fun and don't panic, it's just like learning to ride a bike....

[RickBlaine]

So, it was a less than successful weekend. Here's what happened:

1) I removed the tank and drained it. Everything looked clean inside.

2) I checked the filter in the fuel petcock. That was torn. I couldn't see a way to remove it -- do I need a whole new petcock assembly?

3) I started to remove some hoses in preparation for removal of the carbs, when I noticed that the large hose that runs over and across the carbs from the bottom left of the bike (ont he engine) to the middle right of the bike (attached to a hexagonal piece that seems to connect up to the carbs) was worn through in a number of places. I wrapped electrical tape around the entire hose to seal it back up.

4) I opened the tops of the primary and secondary carb assemblies, just to peek inside, and everything looked clean. I didn't go further, because I did not have confidence in my ability to keep everything straight, and because it appears that my owner's manual for the engine is missing the first page of the carb disassembly instructions.

5) I also noticed a few other hose issues while I had the tank off. One, there is a little nipple on the right side of the tank, presumably for air venting, that was disconnected from a tube that runs down to the bottom of the bike. I reconnected it. Two, there was a hose hanging right under the left-side carb assembly, which appeared as if it should be connected to the lowest of the three cylinders hanging from that assembly. i could not find a clear picture of this in my manual. I connected that hose as well.

6) In order to get at the large hose where it connects to the engine, I had to disconnect a hose running from the same area of the engine along the left side of the bike to the oil tank. When I started the bike back up, it started fine but then stalled. It was then I realized i had forgotten to reconnect the hose, and so I reconnected it.

7) The bike continued to start up, but die after a few seconds (or once I pushed the choke back up). This happened for a while, now it won't even start.

I spent my sunday afternoon walking the bike to the nearest motorcycle repair shop, where I will rejoin it when they open tomorrow morning.

[Chayanne]

Posibly the fuel tank acumulate water in the reserve..

Open the carburator drains until the gasoline change color from clear to yellow-orange.Disconect the fuel tank hose and drain with the same procedure. Probably the fuel tank isn't properly sealed in the top opening.

[Wonky]

What you should have done was attach each pipe individually, then start the bike, if it dies, disconnect the one you just connected and try the next pipe you found and connect that to where it seems to belong. This way you can illiminate each pipe one by one and not all at once leaving you unaware of which one was causing the problem. I know it can be daunting but really it's always the simple things and not as complicated as it seems. Good effort though, i've been there mate!!!