Rt195 , stuttering 1/4 to 1/2 throttle

[swissdean]

I am really inpressed with this kit but cant get my carb set up right, rode 300 kms today and its great except from 1/4 throttle to around half its holding back/stuttering. I know its rich as plug is black and sooty even though i was sitting at 100kph on the autobahn for best part of 30 minutes ( its great from 1/2 throttle onwards, very crisp and clean). Given the top end running is fine i am not sure if this is main jetbchange or something else.

Clip is on top setting, not sure what needle it is

No tuners nearby so going to need to have a crack myself

Running a 28 dellorto open mouth, with mb surround filter which is leaving an oil slick on my footboards, bgm v3, varitronic and side panels on ( its bloody hot under the panels too, hotter than any other lambretta i had which also has me nervous, for eg Petrol tank too hot to touch after a good run!)

As always help and advice welcomed

Cheers

Ps looked on here and scooterotica and advice doesnt seem to align to my sumptoms

[MickYork]

Suggest you strip carb' and make a list of jets, needle, atomizer, slide, etc.

What is your Varitronic/timing set at ? has it been strobed ?

[Digger]

its bloody hot under the panels too, hotter than any other Lambretta I had which also has me nervous, for eg Petrol tank too hot to touch after a good run!

That's something I'd sort out PDQ.

[Meds]

Have a look at this
http://scooterotica.org/forum/viewtopic.php?f=9&t=36233
Might help.

[Donnie]

as said you really need to strip the carb and list all the jets and slide too!

The mb filter is not leaving your oil slick, you carb is, the purpose of the filter is not to keep your panel clean.

Additionally you need to tell us what timing you set the varitronic at.

Otherwise sounds like there will be reports of a fireball travelling down the autobahn!

[Feersum Injun]

Clip is on top setting, not sure what needle it is...

Top clip is the leanest setting of the needle... if it's running rich on this it may be a X2. It probably needs to be X7/X13 - AV264/66 combination. As others have said, without knowing the carb set up it's hard hard to advise. Pilot / needle / main / slide etc all have an effect...

Running a 28 dellorto open mouth, with mb surround filter which is leaving an oil slick on my footboards, bgm v3, varitronic and side panels on ( its bloody hot under the panels too, hotter than any other lambretta i had which also has me nervous, for eg Petrol tank too hot to touch after a good run!)

Running rich and carb 'spit back' will be soak the filter in petrol, lack of air flow under panel will make it difficult for this to evaporate. Add to this the hot air under the panel it will probably make it run even richer. It is often a good idea to set the carb up with no filter/panel in the first instance and take it from there. Maybe the heat under the panel is just doing a lot of miles on a very hot day?!?! A mate described this happening to him on the recent Euro... it got so hot the petrol was bubbling!!!

You can never follow others settings exactly but here's my current set-up to give you a 'ball park' idea...

RT195 - 60/110 crank
42mm AF Clubman
28mm delly
40 slide
X13 top clip
AV288
50 pilot
118 main
250 float needle valve
Indian stator 12v DC, 17deg static

It does run rich at 1/4 throttle so I'm considering either dropping to and X7 or dropping to an AV266 and raising the clip on the X13... the dark art of jetting a carb. Others on here have far more experience than me but hope this helps...

[Paul_from_Thornbury]

Feersum Injun, how does yours rev with the 42mm AF Clubman? I had my RT195 dynoed with the same exhaust but it never achieved full revs. After discussion with MB he suggested trying an expansion pipe, I had an old Sterling exhaust that I stuck on there, it transformed the engine allowing it to achieve peak revs. Hated the look of the pipe so put a BGM clubman on and it's still fantastic. Peaks at 8000rpm with a 24mm PWK carb.

I'm going to strip and get rebuilt with a Reed valve over the winter to get rid of the spitback. Running with a filter at the moment to stop the spitback but it's upsetting my jetting a little since the dyno run.

[Feersum Injun]

When I originally got the scoot it had this pipe on and I never got round to changing it after fitting the kit... too many other problems to sort out!I don't have a rev counter and it's never been on a dyno! I just ride and tinker. It does run well though and sits fine around 65, but open the throttle and there's not much more... no more than 68, which isn't bad.
You're right though, it feels like a new pipe will make a difference at the high end. Probably go for either the BGM or TSR Evo over the winter rebuild and see what happens.

[Paul_from_Thornbury]

sounds like the pipe. I dynoed mine only because I couldn't get jetting right.
After dyno the engine was smooth through the range, but appeared limited at top end, would do 55mph (on a GPS as my speedo is rubbish) at 1/2 throttle and the last 1/2 throttle would just produce more noise and nothing else.
I put on the Sterling and it transformed it. 65mph easily, never opened it up yet in 4th to see what it will do, cruises quite happily at about 60 at 1/2 throttle.

But as I said it max's out at about 60 in 3rd at 8000rpm, which is spot on according to the gearing calculators available online which says at 8000 rpm it should do 61mph in 3rd, which equates to 78mph in 4th at 8000rpm.. I'm sure it would be aero limited at lower than that though.

If you fancy investigating it then try one of these, its what I use, it takes the slow boat from China (about a month) but it gives you RPM, Engine On Time and a Programmable Service Interval in Engine Run Time.

http://www.ebay.co.uk/itm/400800493832? ... EBIDX%3AIT

[swissdean]

Finally got round to stripping carb and having a look/check and resetting timing. Realise i had mis read/set up TDC and now fixed and have varitronic set as far advanced as it will go and it is ticking over at 21 degs and retarding to around 17 at 1/3 throttle so hoping that will be fine now...and allow it to run cooler

Stripped carb and can see I have the following...wondering looking on the forums if dropping pilot from 55 to 50 will do the trick stopping the first 1/4 throttle stuttering/hesitation

will take it for a run tomorrow and see if it still gets hot under the panels. advice on carb settings welcome..i'll be fixing it myself as 100's miles away from the nearest dyno shop (scooter centre, Koln)

RT195
107/58
bgm clubman v3v
varitronic
LI150 box, 16 front sprocket
mb panel filter
28mm delly
125 main
AV264
55 Pilot
70 choke
X7 needle (top clip)
40 slide

Thanks

[bluebob]

keep a close eye on that plug colour mid range.i run a very similar set up .av264 /x7 top clip seems on lean side ,although no two engines run the same.i settled on av266 .I swapped as soon as I saw the plug colour after a short run with the av 264.

[Feersum Injun]

That seems very lean. Have you checked the choke cable is sat correctly at the carb and isn't engaged??

[swissdean]

good point on choke cable, i haven't, but will do..