Thoughts , jetting/exhaust

[Mike-bristol]

RT195 , 30mm Delorto AS266 ,X7 3rd clip , 50 pilot , 125 main , 40 slide. Static timing at 17.

Started running in with a PM pipe and all was fine when keeping the revs low and being gentle.
Got to about 250 miles and wanted to start opening it out and wasn't sure about the jetting so had a quick dyno run came out with 17bhp but topped out at 54mph. Results showed a little lean low down and slightly rich at the top end. Tried it on the road and flat out 52mph and wouldn't accelerate hard. Felt like it did when it was way too rich.
Spoke to the guy who dyno'd it and he said the exhaust could cause similar problems.
Next took the PM off and put a Clubman on, 64mph but won't rev much over 6,500 revs.
Richend up the lower end and it struggled so this is where I am now.
It runs well enough , rides nicely if you accelerate gently but still holds back if you try and give it everything..... which I tend to do.
I will bee trying to borrow an expansion chamber exhaust to see what happens then. I did wonder if the PM was blocked , it shouldn't be carbon'd up as there is probably less than a couple of thousand miles on it.
Any ideas ? Should it rev higher ? A mate has a similar set up that is good for 70 , where mine seems to struggle up to 64.

[corrado]

Have you tried a smaller main jet? Go smaller but do plug checks. Check that choke is opening and closing properly. Most people ditch the factory fitted AS266 for an AV266.

[stonerosesmod]

My 200 mugello must be similar jetting wise but im using a 26phbh and Ancillotti

Pilot 53
Atomiser AV266
Needle X7 2nd clip from top
Main 110
Slide 45

Runs really well like this and good plug colours at 1/4, 1/2 and over 3/4 throttle so far.

[berniek]

I would think that your initial problem might have been a mismatch of pipe , port timings and gearing. PM pipe is revvy, as far as I am aware the RT kits are pretty low port timings to provide a low - mid range grunt. Basically I wonder whether you were ever getting into an area of exhaust use that makes power. You do not say what gearing you run but at 64 mph at 6500 rpm you do not appear to be asking too much if exhaust and cylinder are something like matched, roughly 10 mph to 1000 revs is not tall.

This seems to be backed up by the fact you put a clubman on and you were able to use the available power to reach 6500 rpm and some 10 mph or so quicker. Basically the clubman let you use the power . On face value it seems to be a better match of port timing and exhaust. I think I would leave the clubman on, get it right with that and then worry about attempting to "improve" by putting an expansion on. First thing I would do is run at 3/4 and flat out and flip choke on at each setting, if you bog down when choking you possibly are on the rich side and safe to test by weakening off. If this is case then alter jetting at top end, weakening slightly and testing, you obviously have a rev counter so you can judge improvement easily, as Corrado says watch the plug. You will need to judge throttle opening against actual rpm to weigh up whether you are changing main jet or possibly altering needle.

I a bit surprised your dyno operator could not identify potential probs on the dyno if in fact it is a mismatch of gearing, pipe and port timing. Not being rude but was it someone who understands two strokes and lambrettas?

Good luck

[Adam_Winstone]

^... ditto

[Mike-bristol]

First off the gearing , standard Li 150 box with 15t front sprocket.

I have decided to get a few more miles on the barrel before playing with it too much.
Had a ride over to Tintern and it is fine , accelerates nicely and up to 50 is enjoyable. Coming back across the Severn bridge doing 50 I tried to open it out a bit more and it almost died so I think the main jet does need dropping down.
What would be the options for exhaust?

The guy that did the dyno run knows little or nothing about scooters and the run was for me to see if I was near enough on jetting to start opening it out a bit more.

Now I've started wondering if it's worth getting some porting done but if I go down that road I guess I should put in a 60mm crank. I may just ride it as it is though as I've got a Series 2 in bits that really needs to get moving.