Running in woes, need help!

[Tim_Craig]

A friend of mine is running in my scooter while I am abroad, in preparation for the Euro Rally.
It's a newly built engine which has been dynode, but is now on the open road not running well, hence the help needed.

This is how my friend describes the running.

The engine runs lovely on the stand. When you set off in first gear it's ok through the gears on low revs, as soon as you try to accelerate over quarter throttle the engine half stalls and starts to four stroke. As soon as you back off the throttle the motor picks up again, it's even worse on any hills. That's why I suggested dropping the slide needle, I think it's too low down the slide setting to be the main jet, and the pilot jet seems fine. I suppose a slightly smaller atomiser may improve things.

Engine spec below:

RT245cc
Electrex 12v electrics
PHBH 30mm carb
Franspeed race

This is the only info I have at the moment. Any help would be greatly appreciated, am running out of time to get this running right.

Thanks for any feedback.

[Jim Rose]

It sounds like it may be electrical especially as it's been on a dyno. CDI? Stator?

[MickYork]

Agree with the electrics, but wouldn't rule out the carb'. Without the carb' settings it's hard to comment, but it sounds like it could be too rich, possibly pilot, needle, slide or as you suggested, the atomizer. Is there an air filter on the carb'?

[Tim_Craig]

Thanks for the suggestions so far Gents, much appreciated. We are starting off with the simple things and on to the more serious.
It had not been run since it was on the dyno, no issues there I might add.

My friend did say it was running rich, this is how it was setup as advised. It is an open carb with trumpet bell mouth.

Thanks Tim.

[johnnyXS]

if the engine pulls cleanly through the rev range from idle to WOT when you open the throttle slowly but 4 strokes when you open the thottle quickly then it sounds like your pilot mixture could be too rich or there is a lack of sufficient air ie idle circuit blockage or badly adjusted air screw.

First of all I'd check that the choke is seating properly and shutting off the choke fuel completely. Your friend could check and adjust the choke adjustment so that there is plenty of slack in the cable. If the choke valve is not seating completely that might be the problem right there.

Open mouth carbs can be tricky to get jetted right especially at low revs because you have little control in achieving a consistant air flow . Your friend could try revving the scoot on the stand whilst partially closing off the air intake with the palm of his hand. If the engine revs up cleanly with a restricted air intake then you have too much air .

Its a common fallacy that initial pickup is controlled by the needle and main jet....it isn't.
Your throttle pick up at least to half throttle is governed by the pilot jet , slide profile and idle air or fuel mixture screw. I don't know if your carb has a idle air mixture screw or a idle fuel mixture screw but whichever it is it sounds like you need to adjust that to get your idle mixture correct first

if your scoot was dyno'd I can't understand why it is now not running right unless you have changed something?

[Rich Oswald]

Tim, my TS was like that after Dyno. Does it clear at full throttle? I dropped a needle clip and still did it so changed dyno operators X13 needle back to X7 which I set it up with originally and it was then fine.

Rich'

[Eden]

Make sure your mate has assembled the needle, slide, plate in the correct order, he may have the plate under the needle clip not above it?

[Rich Oswald]

Make sure your mate has assembled the needle, slide, plate in the correct order, he may have the plate under the needle clip not above it?

That's a good point but it doesn't say his mate has done anything other than ride it. This would surely have been noticed as rich at dyno. IMO I think most dyno operators leave the carbs purposely rich, some VERY rich, to cover themselves against comeback as we have all heard of scoots blowing up just after being ridden after dynoing,

Rich'

[Mel K]

Is the choke sticking on ?

[Tim_Craig]

Thanks for the input Gents, much appreciated.

Rich is correct in that Fred has not touched anything, just fired it up. It was setup, dyno'd & purposely left rich.
I have Fred & Martin at Chiselspeed working on it but time is running out. I have a TS1 but that has just undergone a major overhaul & dyno so that's an unknown quantity at the moment. Hopefully it will get sorted, not the kind of news I was wanting while I am abroad and really can't do anything myself.

Thank Tim.

[johnnyXS]

Tim why not stick a vertical ramair foam filter on it and rejet.
Its hardly good for any engine to have unfiltered grit and dust being sucked in off the road .
You should find it easier to tune with some stability and regulation of the air flow so that passing vehicles and crosswinds etc do not vary the air flow all the time
What oil and fuel oil mix are you using ? you can adjust the richness of the mixture to some extent with your oil/fuel ratio.

[Tim_Craig]

Tim why not stick a vertical ramair foam filter on it and rejet.
Its hardly good for any engine to have unfiltered grit and dust being sucked in off the road .
You should find it easier to tune with some stability and regulation of the air flow so that passing vehicles and crosswinds etc do not vary the air flow all the time
What oil and fuel oil mix are you using ? you can adjust the richness of the mixture to some extent with your oil/fuel ratio.

Thanks JohnnyXS that's good advice & something I am going to consider after Germany, no time to start messing now.

Good news is that it is now sorted. Turned out to be a fouled plug of all things.

Thanks for all the advice & input, much appreciated. Germany here I come!!

Tim.

[johnnyXS]

brilliant thats great news.
have a great trip Tim I'm very envious