MZ/MuZ Riders

Hi, does anyone have any ideas why my Skorpion sport is such a pig to start after a short lay off? She has fuel (I only use super unleaded, and drain the carb before the lay up) and a spark but she just turns over and over but will not fire! She does it every time she's not used for a few weeks (and before someone says it, yes I realise the way to stop it happening is to ride it all the time!) I usually have to resort to easi start or a carb strip before she'll fire up.
Any help or advice much appreciated. Tony

fresh gas in carbs and tank
remove tank so you can see under it
on top of the rubber piece that mounts the left Carb to the engine
at the top there is a tube that has been plugged
i have know idea what it was originally used fore
it is a direct input to the intake and has been plugged
on my bike and a spare carb set i have
it can be used to prime engine
1 gas tank
do remove the bracket from where it is fastened to frame
DO NOT UNBOLT U shaped bracket FROM PLASTIC TANK
too much risk of making a hole in the tank
these tanks are getting hard to find

attach a hose to the intake and place it so you can access it from the front
make sure it is not kinked and add the lawn mower fuel shut off on the end
use it to add a bit of fuel to the system when it will not start
the pictures should help
dave


here is TUBE into engine location

Thank you Dave, that all looks simple enough. Just one question, do you leave the pipe permanently attached? Many thanks, Tony

leave the shut off closed and secured where it is easy to get to without taking off the tank
it needs to be so the added fuel can flow down hill
then add a few cc of fresh gas when needed then shut tap and crank bike
when it fires do not roll the throttle on so the vacuum will draw fresh fuel into carb
may have to do it a few times to get it to go when it has been standing for a few weeks
BE CARFUL too much fuel can get you flooded or make motor over speed

mine has been standing for 2 years and you ask your question just as i was starting to clean it up and get it running
the black crap on the frame is mold and crud from a wet back porch shop area that needs a new roof
i am off to the shop to clean that tank and get is ready for a new coat of forest green
Dave

David. Are you trolling this guy or did you really do that to fix your starting problems? LOL If you jet the carb correctly, the bike starts just fine in all temps and running conditions. Factory jetting is too lean on the bottom and too rich on the top. Keihin 135 and 155 for the mains and a Mikuni TM28/486 #40 or #38 on the pilot will make it start great and respond very well to throttle inputs. My stock bike with those jets, a Pro Circuit silencer and K&N filter mod with no snorkle made just shy at the wheel what the motor is rated for at the crank and started great with a little choke in the morning and nothing the rest of the day. I'd try some different jets before adding extra fuel taps and valves, or at least try your pilot screw at the nearly falling out setting first. Screw it in all the way but don't over tighten when fully closed. Count number of turns until screw falls out. Probably around 8 and a half to 9. Then reinstall screw to fully closed again and unscrew to about 7 turns or no less than 1 and a half from where it fell out. This will be the richest setting you can achieve with the current pilot jet and might be enough to help the bike start without pulling the bowl, but is not the correct way to jet the bike. Pilot circuit should be jetted to have the correct mixture at around two and a half to three turns out if memory serves correctly.

i did it because mine sets a lot anymore and where i live this thing is impossible to find any carb parts...
once its started
it runs OK just do not let it set for a week

the rt125 is the same deal set for more than a week and no start

i have copied your post and will try it but doubt i can find the parts in my area

Those Mikuni pilot jets are very common and will be in stock in most Japanese dirt bike dealerships or shops and the Keihins can be found here. https://www.jetsrus.com/a_jets_by_carbu ... ection.htm

Just take your factory Teikei jets out(nearly impossible to find Teikei alternate sizes by my experience), measure them, then match them to the appropriate Keihin jet on the page in the link provided. Dimensions are listed after you click on the jet you want to look at and I think the first two listed under "mains" are the ones you need for the 660. The jet sizes I settled on should be in the safe range since my bike was still on the rich side at the last dyno run.

this bike is low miles and part of the reason for low miles...is
its never been correct for any one that owned it because of the jetting

thanks Dave

When I had my Skorpion Traveller I found exactly the same problem, hard to start after leaving for a few days.

The cure for my bike was to turn off the fuel and run the carb dry before putting the bike away, then when I came to use the bike I just turned on the petrol before getting my kit on and it would start quite easily.

No more problem starting for 12 years.

This only works if you have no fuel pump fitted, petrol tap piped directly to the carb's.

I would think draining the carb before mothballing would dry out rubbers inside carb,,i never drain the carb, i just flush it through before starting,something soaked in petrol all its life would not like drying out ,

Keihin 135 and 155 for the mains

which carb does the small one go in





660carb

Smaller jet goes in the carb with the bowl that feeds a single intake valve. (first pic) The larger goes in the CV carb, the one with the diaphragm, and feeds the other two intake valves. (second pic) There's a small crossover port in the head but only a small fraction of the fuel/air mix can crossover, and only from the smaller carb to the larger port behind the other carb. Here's a pic of the crossover if you are curious. I had started to clean up the ports before sending it to a professional for some major work.

Hell you may be able to get away with just swapping the jet on the CV carb if you weren't pulling the bowl off the other already to put in a proper pilot jet. The CV carb jet is STUPID EASY to swap out. I can do it in about 2 min if the fuel is drained already. It's just beneath that big ass brass nut on the bottom.

den wrote:I would think draining the carb before mothballing would dry out rubbers inside carb,,i never drain the carb, i just flush it through before starting,something soaked in petrol all its life would not like drying out ,

The problem would be not so much the carb rubbers drying out but the ethanol in the fuel degrading them.

Have you noticed your fuel tank distorting, sides rippling, getting harder to fit as the years go by, ETHANOL.

Hi, Quick update. before I tried Dave's idea of extra fuel pipe I had a quick play with the pilot screw as edfmaniac suggested. Screw out 7 turns and she then started on the button straight away! Looks like i need to spend sometime on the carburetion to get it set up properly. It also might explain the strange 'altitude sickness' the bike suffer this summer while negotiating the Stelvio and Grossglockner passes, as I climb higher and higher the bike would just splutter and refuse to pull cleanly from tick over, it would eventually clean up if revved through the fluffiness. And as soon as we descended down the problem cleared and it ran perfectly again. Thought it might have been a blocked air filter, looks like i may have been on the right track after all.

Thanks for all the advice everyone

PS I did actually drain the carb before laying it up as now paranoid about gumming my carbs up, after all the horror stories you read. I also try and stick to branded Super unleaded as most do not contain ethanol, or so i am lead to believe.

Tony101 wrote:Hi, Quick update. before I tried Dave's idea of extra fuel pipe I had a quick play with the pilot screw as edfmaniac suggested. Screw out 7 turns and she then started on the button straight away! Looks like i need to spend sometime on the carburetion to get it set up properly. It also might explain the strange 'altitude sickness' the bike suffer this summer while negotiating the Stelvio and Grossglockner passes, as I climb higher and higher the bike would just splutter and refuse to pull cleanly from tick over, it would eventually clean up if revved through the fluffiness. And as soon as we descended down the problem cleared and it ran perfectly again. Thought it might have been a blocked air filter, looks like i may have been on the right track after all.

Thanks for all the advice everyone

PS I did actually drain the carb before laying it up as now paranoid about gumming my carbs up, after all the horror stories you read. I also try and stick to branded Super unleaded as most do not contain ethanol, or so i am lead to believe.

Please come back & let us know how you get on.

My pilot screw was set at 5 turns out.