Maximum revs?

[EddieStone]

This may be a bit embarrassing, but one thing I don't understand about Lambrettas (or even two strokes in general) is what limits the revs.

I understand the mechanics of two strokes and Lambrettas, but what is the limiting factor for maximum revs. Is it the port timing, exhaust, carb?

For instance, what would I have to change to get my 175 kit to rev faster? A TS1 will rev to 10k, so why does mine only rev to 6k, or so?

(Also, if anyone has a non intrusive way of actually measuring revs (phone app maybe) then I'd be grateful!)

Sorry if I'm being a bit of a numpty - I understand what limits 4 strokes, but not 2 strokes.

[paulnobodyimportant]

Someone will come along with the correct answer for you, but it is a combination of all 3, with some having a greater effect than others, such as exhaust and porting.

But in respect of measuring revs, I bought this simple rev counter that just has a wire that you wrap around your spark plug lead. I've used it as a temporary thing in the past to help in timing, jetting or seeing if my revs on the road match or feel like my dyno curve predicts. Looks like MB are out of stock, but I'm sure you will be able to source from other suppliers

http://lambrettaspares.com/spares/speci ... u0819.html

[coaster]

As Paul says, a cheap inductive rev counter will do the trick, I have had one of these installed on my Jet for a few years now and still going strong on the original battery http://www.ebay.co.uk/itm/XCSOURCE-Digi ... Swh2xX-zhL

As mentioned, port timings play a factor in max revs but the exhaust system will need to be able to extract the gasses at high revs and promote power delivery at those revs too. Box type pipes don't usually produce much if any power above 6.5k RPM (There are some exceptions) and the JL3 expansion isn't much better. It therefore goes without saying that the carb and inlet needs to be able to draw enough fuel in and the ignition system has to be capable of delivering a spark at high revs too.

What exactly is your current setup?

[Minority]

Interesting subject, especially Coaster's comments regarding the JL3. I had one on my Lambretta and had read the commonly held view that it was an effective rev limiting device, and so it was, having made it's best by 6.5K and not wanting to rev past 7k at all. That is until my quest for speed led me to give the exhaust timing a few more degrees, bang, power to at least 7k and revving on to 7.5-8k.
So, as said already definitely a combination of factors!

[Eibar]

http://www.henryarmer.com/sendec_2_new_.htm

best by far of low budget rpm meters 9 abillion farmers cant be wrong ! run these on both my scoots - brilliant get 25hr one