Scooterotica

I changed expansion and cylinder head on my standard ts1 I then had it dynoed to check carburation. That is fine, very slightly rich across the range but within acceptable parameters. The scoot runs very well but has an annoying flat spot at around 4200 revs. I am thinking of trying to advance the timing by 1 degree to see if this will help. Think it is set at static 17 but I shall have to check that. Am I on the right track?

Just to explain my thought process here.

I am aware of the dangers of advancing the timing on a two stroke engine but I was thinking of trying this as this will give more time for the fuel to fully burn.

Other than this, given that the carb settings have been confirmed as OK by the dyno, I'm at a bit of a loss to know how the get rid of this flat spot. There is scope to increase the front sprocket (at the moment it's Li150 46/16, but gut feel tells me it will now pull a 17 front sprocket). But, this will just move the position of the flatspot, and not get rid of it.

All thoughts gratefully received

PS, the dyno graph is in this post:

http://scooterotica.org/forum/viewtopic.php?f=7&t=25033

An Augusto or Mtech advance retard device would allow you to advance the ignition to around 21 degres or so with it retarding back to a safe 16 at higher revs I know it's something else to go wrong but sometimes technology is unavoidable.

That did occur to me, Col. For this year, I'll put that on the back burner though.

wot reeds r ya usin?

Standard TS from AF. Had them on for 2 years and about 6000 miles, I think. I had the engine out a couple of months ago, and the reeds had no splits or feathering.

i think its more to do with the characteristics of your pipe,ie out of the power band
is it really that noticable on the road?
i wouldnt go up a tooth,4.8 is what lot of us us with your set up

Try it with a 50 slide Paul. You may need to up the pilot slightly.

Yeah, it is noticeable out on the road. Don't get me wrong, I have no regrets about getting the supertourer. It's a marked improvement. I'm probably just too fussy but if there's a tweak that'll just smooth it over, I'll give it a go .

Al, I've just ordered a 56 and 57 pilot and the 50 slide. I'll report back. Cheers

Diablo wrote:Try it with a 50 slide Paul. You may need to up the pilot slightly.

Al, you were spot on. 50 slide and a 56 pilot = absolutely no flat spot

Quick plug colour and choke test seems to indicate (only been out for last 40 minutes or so) that it's "just" the right side of lean at around that throttle setting. So, I'll do a bit more testing and maybe even try a 45 slide

Thanks again for your help