Scorpion popping during deceleration and dies when very cold

[maxgain]

Hi there all

I have been having awful problems keeping my Scorpion running when idling or decelerating. We are currently having a very cold spell in the UK at the moment, somewhere in the region of -2c to -5c. I had the same problem last year when the weather was extremely cold. At the time I thought it maybe damp getting in the coil, so I replaced the coil, lead and cap. It will start first time no matter how cold outside, but just starts making very slight popping noises on deceleration and dies when it reaches idle speed. It normally starts again OK. The bike is used every day as my main commuter and runs fine during warmer weather. One thing to add, sometimes when the starter button is pushed in (and held in) initially from cold it hesitates to turn for a couple of seconds then fires over and always starts.

Anyone here ever had similar problems, or able to point me in the right direction.

Regards - Stu

[basser23]

Stu,
Does it do the idle stall and popping when it is fully warmed or just when cold?
It maybe your idle mixture screw set incorrectly for the cold weather,it will most
likely need to be a bit richer.
I of course could be wrong here...
Chip

[maxgain]

Hi Chip

thanks for your response. It appears to do it when the bikes much warmer. I took it out Monday and rode it until warm and it still did it. Does this sound like it needs the mixture adjusting slightly ?

Regards - Stu

[basser23]

So,
When cold,it'll idle at say 1300rpm,run and no popping or stall on decel? Then when
fully warm it quits? Popping can be a symptom of an air leak in the exhaust,some
have adjusted the mixture screw out 5-7 turns. this again MAY be an issue.
You do say that it only happens when the weather is cold?
Hmm,I for one wont ride when below 40f...I get cold!!
Hopefully someone else with more knowledge in this area will respond...
Chip

[phlat65]

I would also inspect the boots between the carbs and the head, a small vacuum leak will cause these issues. if you turn the choke on slightly does the problem go away?

[maxgain]

I went to work yesterday with the choke still on a little and it appeared to be much more stable. I also checked the joint between the exhaust pipe and down pipe coming off the engine. There appears to be a little black powder around the joint. So I guess there is a slight leak around that. Is there supposed to be a gasket between these two pipes?

If the problem goes away with a little choke does this indicate an issue with the boots ?

Thanks for your input guys. Please excuse my ignorance, I am trying to learn how to maintain my own machines.

Regards - Stu

[phlat65]

by applying the choke, you are richening the mixture. I would first set the idle mixture screw to spec, or at least see how far out it is. count how many turns it takes to seat it, then put it back. I think stock is 2.5-3.0 out? also look for cracks in the boots, they have been known to fail.

A small exhaust leak can cause some popping on decel, there is no gasket there, I would replace the 2 screws on the clamps, and run the clamps as close to the end of the pipe as possible. the screws tend to corrode and become hard to tighten.

[Rod]

I have just bought a Scorpion Travellor with exactly the symptoms described!

The clamped union of exhaust pipe and silencer seemed loose and I have tried to tighten it, but I think there is still some leakage. It's not a good set up to have only 2 attaching points on such an exhaust silencer sytem especially on a big single. An additioal attaching point to the frame on the exhaust pipe near its union with the silencer is desireable but that is just comment in this case.

I've tried letting out out the adjusting screw on the carb a few turns. There was a small improvement but the problem was not overcome. I had a ride on another Traveller the day before so I know what they are like when running properly.

I'd really like to know what the outcome was with your bike/problem/fault/solution.

[maxgain]

Hi Rod

Sorry for the time taken to reply, I have been on holiday the last two weeks.

Really tightening the exhaust clamp has appeared to stop the popping.

I have adjusted the idle and mixture setting to no avail. The problem still persists when the weather goes well below zero. I need to check the rubber boots as recommended in previous posts and look to maybe overhaul the carb. Ideally I would like to do this during my next week off work. It’s a shame because the bike runs like a dream during wilder weather.

If you fix the problem in the mean time please let me know and I shall keep you informed.

Regards - Stu

[Exmoor beast]

hi there you will find that in very cold conditions the xtz motors will play up this is caused by carbs freezing which you can not fix . if the bike will run fine in warmer conditions you do not have a fault so don't play you don't need to i did 30 miles each way to work for three years it did it every time it froze to check wether you have a air leak spray wd40 or easy start between carbs and head if the revs get higher you may have a air leak proberly between inlet rubber and head this is commen trust me good lcuk

[hb7]

MZ Exhaust joint is best fixed using a piece of an Alu soda pop can as a shim/gasket.
The factory used a paste...