aprilia rs50cc moped problem

[normspanners]

Just spoken with lloyd
It was - 2 this morn and he gave it full choke no throttle and it fired up straight away on the button after standing 24hrs left it to warm up and it rode up to work fine, maybe a little slow in first for awhile,
that was on the old f****d with plug so is fitting new plug after doing another comp test tonight so we can see the mixture a little more clearly.
But the job is looking better allround, than it ever was before.

 

[normspanners]

comp test results 80 hot as it was riden in-- 90wet both full throttle, on the starter button he didnt try it bumping though, from what I have found out 110 is normal for these but that is not definate.
The old plug still looks slightly weak,
hard to believe that I have gone over twice jet size from .95 to 1.4 and it is still weak!!!
was wondering about if needle size could be wrong, though I couldnt see any numbers on it.

 

[octo0072000]

Norm
you said the jets you bought was wrong size are we sure it,s even the right carb for it big bore kit here
shows no carb or jets so must use original on some it says up main jet and needle but not what to
plug gap from aprilla forum
The O3 Rs50 manual calls for .024-.028 in my USA model
http://www.apriliaforum.com/forums/showthread.php?16656-spark-plug-gap

http://www.bikepartsuk.com/?i=250300

 

[norlander]

comp test results 80 hot as it was riden in-- 90wet both full throttle, on the starter button he didnt try it bumping though, from what I have found out 110 is normal for these but that is not definate.
The old plug still looks slightly weak,
hard to believe that I have gone over twice jet size from .95 to 1.4 and it is still weak!!!
was wondering about if needle size could be wrong, though I couldnt see any numbers on it.

aint got a zorst gap sucking in air has it?? did not see that mentioned when I went over posts.

 

[normspanners]

Norm
you said the jets you bought was wrong size are we sure it,s even the right carb for it big bore kit here
shows no carb or jets so must use original on some it says up main jet and needle but not what to

I didnt buy the jets Lloyd did, I am trying to let him do a little off his own back without demoralising him he just got the wrong thread and sizes (but they were jets!!)
I need to check bore sizes etc Just thought he got a new crank I wonder if there is long and short stroke?
Ar, so you do need to alter the needle. The needle doesnt seem to actually go into the needle jet as deep as it does on some, so maybe it has the needle jet housing adjustable also? But doesnt seem to want to move in the carb.

 

[octo0072000]

have a look on apriia forum in my link think 49mm is piston size for 70cc kit

 

[normspanners]

aint got a zorst gap sucking in air has it?? did not see that mentioned when I went over posts.

There does'nt seem to be any leak have looked around the joints and seems fine.

 

[normspanners]

Just the latest on this bike original needle in bike was A12 set on highest needle /lowest groove ie richest and would not run well on any other setting, and needed choke to help it , so I ordered first class the next richer A32 arrived late as usual, last night, stuck it in and it did not like it at all, seemed way rich , any hint of choke would kill it dead, so dropped the needle down, each time better and better, till the clip was at the top still rich so I machined a sixth groove and the clip was at the actual top.
Now WAY weaker than the A12 would ever be, and the bike is now pulling low down but still sounds little rich---- WTF!!
Seems like everything is upside down Coz if it was pulling air,(leak) it would need to be richer at the bottom and weaker at the top.
Again for a fifty it is going well and was pulling me on the short ind estate 50mph before backing off.
Also now never fails to start off button.

needle chart http://www.dellorto.co.uk/images/parts/A-M Needle charts.pdf

 

[octo0072000]

Norm remember you drilled the main jet out so maybe it now wants a smaller main jet with the new needle

 

[normspanners]

Norm remember you drilled the main jet out so maybe it now wants a smaller main jet with the new needle

Cheers for that but the main should only comes into full operation 'on its own' when on full throttle the last quarter or 1/8 of slide movement when it is totally unrestricted by the needle, and my full throttle plug chops read a good mixture there.
so to go weaker on the main would mean a weaker top end.
------NORMALLY --------but this one seems to be rewriting the rule book!!
PS
Just thinking with your idea------ Maybe ---- the needle jet/ attomiser has been wrong all along maybe even from new and that is causing some weird occurrence HUM ???

 

[normspanners]

From the dellorto manual

3.6.1 Full-throttle system usually used on two-stroke engines
Figure 22 shows the full-throttle mechanism used on two-stroke
engines which features an extended nozzle (6) at the end of the
atomiser (7); this produces better performance during acceleration.
Air from the inlet (3) passes through channel (2) and flows into the
round extension (1) formed by the upper outer end of the atomiser
and by the inner part of the nozzle (6). It then mixes with fuel
metered through the main jet (4) and coming from the atomiser (7)
and then flows into the venturi (5).
A larger atomiser-needlejet size produces an in crease in fuel
delivery at all throttle positions and, conversely, a smaller size will
produce a decrease in fuel delivery at all throttle openings.
fig. 22
Usually the atomisers on Carburetor s intended for two-stroke engines are
manufactured in two types: with either long or short upper parts (figure 23).
The atomisers with longer upper parts cause a weakening of the mixture at
low speeds and du ring acceleration from low speed, on the other hand,
atomisers shorter upper parts produce extra enrichment. Carburattors for
racing motor cycles use atomisers with short upper parts.
fig. 23

Ya learn summat new every day,
even how to die,
then ya mind seems to slow down.

 

[octo0072000]

odd system get a old amal on it

 

[Robotstar5]

odd system get a old amal on it

Is there room for a 4 barrel Holley?

 

[AndyStobbs]

Norm its a single cylinder small capacity 2 stroke, you won't achieve perfect fuelling across the entire RPM/load scale. Struggling to properly remember my fifty troubles, but MJ will influence fuelling in the midrange more than you would expect.

 

[octo0072000]

Is there room for a 4 barrel Holley?

you mean a double pumper

 

[normspanners]

F-----LIP you could SUCK the piston clean through one barrel of a Hoolley

Norm its a single cylinder small capacity 2 stroke, you won't achieve perfect fuelling across the entire RPM/load scale. Struggling to properly remember my fifty troubles, but MJ will influence fuelling in the midrange more than you would expect.

Yeh I do realise I have set myself an 'interesting challenge' shall we say
but it was interesting quote from the dellorto manual that the atomiser neck effects the whole range, especially with the long or short top section.

 

[norlander]

e-mail Stan Stephens

 

[Robotstar5]

e-mail Stan Stephens

Stroker god

 

[Wallace]

I thought needle was 1/4 to 3/4 and main jet above 3/4?

 

[normspanners]

I thought needle was 1/4 to 3/4 and main jet above 3/4?

on early two strokes and 4ST yes,
but read post 91 a quote from http://danskkartingcenter.dk/dellorto_motorcycle_carburetor_tuning_guide.pdf or read pdf if you have time it is very informative.
About the mods they have done for 2ST.