1996 aprilia rs 125 extrema

[burnsy]

Hi guys iv posted in the new bikers section so please do say hi!

1996 aprilia rs 125 extrema (extrema meaning im the fastest bike on the road lol )

right it starts, runs, and rides ok. 28mm carby on there (rarrr!!) has some stainless end cane on it (birds love that ) other than that I think its in standard trim in being full power.

NOW! when riding all seems well, but full throttle giving it some bean on a B road around 50mph engine dies dead, let off the throttle and straight back on its ok again, or when I change gear its ok again...but only happens when I ask for the full beans? doesn't feel as fast as other have said it should be.

there was a oil leak when I got it a couple of months ago, on which has been booked in for repair (power valve gasket was wrong way round or something) £65 later and still have a leak just not as bad as before. main jet in carb is 120.

any ideas would be greatfull

[kerr]

When you say giving it beans are you snapping back the throttle all the way instantly? they don't respond well to that, needs a smooth opening of the throttle.
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aprilia 125 Af1 Futura >> Suzuki gsxr 600 srad >> J1 zx6r >> cbr 600rr >> Speed Triple

[evoboy]

Sounds like the main jet is too small/its running lean at full throttle.

Does it sound like its running out of fuel when you give it full?

Does it have the airbox on it or a paper pod filter?

Is it just the end can that has been changed or the whole system?
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Suzuki GT250 x7------- Fazer 600------CB250RS------Aprilia Rally 70----- Bandit 600

APT Motorcycles

[Kickstart]

Hi

Main jet size sounds about right for the 28mm carb (but possibly a touch on the small size), but I would expect an RS of that age to have the 34mm carb as standard (and a ~150 main jet to suit).

Does it have an air filter? And damage to the rubber block between the carb and the engine?

All the best

keith
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[burnsy]

no im not throttle snapping
airfilter is standard I believe, standard box with a orange filter with a thin layer of white filter ontop...the air box does move about abit as the isn't a great seal between box and rubber though.

yes just dies like there was a total fuel cut and stays that way until I re-throttle it or change gear, which in turn could be the revs dropping slighty, I don't know lol

engine was fully rebuilt 4k ago costing £1100 with genuine aprillia parts including barrel costing £475 alone...so engine should be pretty fresh really.
yes I have read a 34mm should of been standard on this model...but I think a 17 yr old sold this for pocket money in its past life lol

[Kickstart]

Hi

Check the needle position in the slide. Or just try moving the clip a notch towards the sharp end (richens things a touch on mid throttle), and just give it a try.

All the best

Keith
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[burnsy]

ok keith, ill give this ago tomorrow if I can and ill report back. In the middle of looking for a good 34mm to replace it, but didn't want any running problems with the 28mm in the mean time.

[nathan k]

Clogged main jet. Clean the carb.

[burnsy]

right guys I dropped the needle one to see how she would ride, I did so and I thought I would check fuel air screw (28mm) and the smaller screw nearest to the engine is missing....wooops. not sure if this was me or how I bought it.

I cant seem to find anything that's fits, once I do is it 3 1/2 turns out...and while I am at it what should the large screw be, turns out?

she is smoking quit abit this morning I must say, choke off.

regards burnsy

[nathan k]

[stirlinggaz]

hi,
the bigger screw is usually the idle screw, which actually controls throttle/slide height.
smaller screw nearest air filter end is air mixture adjust screw,
smaller screw nearer engine is fuel mixture adjust screw.
if any of them are missing, carb wont work correctly. could get away with throttle stop screw being missing, would just be difficult to get it to idle correctly.
if air/fuel mixture screw is missing, replace it with one from here https://www.dellorto.co.uk/merchandise/products.asp?CategoryID=2&PartsectionID=24
cheers,
GAZ

[Kickstart]

Hi

There are 2 screws. One controls the idle speed by providing a stop for the throttle slide. With this missing the idle speed will be low, and possibly it might be a touch lean (but probably not by much).

The other controls the idle mixture. If this is missing the mixture will be totally screwed at idle (probably less so at higher speeds / throttle positions). Don't just replace this with any random bolt as the shape of it will control the flow of air / fuel throw the idle circuit.

All the best

Keith
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[burnsy]

kickstart I think your right its idle is slightly different, ie from idle on a quick little rev its upset until it reaches around 2500rpm and seems fine from there.

but very smoking on idle without choke at all (I only use choke cold morning to start her anyway)

where would I get the screw from or should I leave her in the shed until the 34mm carb is orderd (im looking at a few on ebay now)

but she still is ticking over ok at 1500rpm, its only when I want a little free rev she goes to die but picks up as normal at 2500rpm.

burnsy

[Kickstart]

Hi

For Dellorto bits:-

https://www.dellorto.co.uk/

Note that with the power valve, it is open below 2500rpm (means it gets regularly operated around town to hopefully stop it sticking; might knacker the power below 2500rpm but they don't really expect anyone to try using those revs).

All the best

Keith
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[burnsy]

right its in the bin!! it wasn't the right carb for my bike anyway so its in the right place lol

34mm flatside carb has been ordered with manifold and racing reeds (might aswell while im in doing things)

bought items from a guys breaking his rs125 racebike which carb ect was all set-up. Hopefully this will get the aprilia running right, then exhaust to finish things off. Should be around the 30bhp mark or there abouts.

does anyone know if the 96 extrema's have restricted CDI units in place as I defo have a massive flat spot between 5-6k, but thinking this could be down to the dodgy carb also.

kickstart! you have a sensible aprilia rs 125 anything I can do for the bike to improve reliability and maybe slightly bit more power. when I had the powervalve serviced last week guys said there was two small scores on the valve itself but didn't think this would make any difference to performance (should I replace it anyway?)

regards Burnsy

[Kickstart]

Hi

They have no separate cdi on the older style Rotax 123 engined bikes. The ignition is contained in the stator and the coil (with just a wire to earth out the ignition to stop the engine). There is no restriction in the ignition (that came with the 122 engined bikes).

However you can adjust the ignition timing, and entirely possible someone has done that already, and made a mess of it. Note they were originally set up for high octane petrol.

There shouldn't really be a flat spot between 5k and 6k, although as with many performance 2 strokes a bit of a flat spot just before the power band isn't uncommon.

The power valve should be fine (just make sure it is the right way up, people commonly put them in upside down).

Not really anything simple to increase power. You could try a different exhaust (but the stock one is pretty good), or get someone like Mick Abbey to play around with the barrel and head. But both will probably give more set up problems and neither will improve reliability. Most important thing is to not thrash the engine from cold.

All the best

Keith
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[burnsy]

Ok back from holiday....34mm carb manifold and boy's reeds have arrived.

fitted all today (very clean) engine starts fine but idles at 6rpm and is very slowly creeping up, seems to rev past 6k fine but I only did this the once as it wasn't warmed up.

spoke to the guys iv bought this kit off and says its running a 162 main jet. any idea what settings I should have for the 162 to run ok...im going to check needle clip now and put it on the top if it already isn't.

burnsy

[stirlinggaz]

hi,
pretty sure i ran 34mm carb with 162 main jet.
when you changed the carb over, did you replace the manifold?
there are 2 different sizes, 1 for 28mm, other for 34mm.
does the manifold look cracked? it may well have a small split.
are the jubilee clips tight?
check it with a can of wd40 or similar.
spray it onto the manifold whilst bike is idling, & if revs climb, then you need a new manifold, although i have repaired a few, with sealant (granville black gasket stuff. which dries to a rubbery solid, just like mastic).
cheers,
GAZ

[Kickstart]

Hi

Sounds a bit large for a 34mm carb, although within reason. Think they are normally around a 155, although it does vary a bit with the exact model.

Check for air leaks in the intake as above (note that worn main bearing seals can also cause a high idle, but 6000rpm idle would likely require a very knackered seal), but also check that the idle speed screw is set OK.

All the best

Keith
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[burnsy]

think main bearing seals are fine as all was fine before carb change.

right played with the cable ontop of carb which has fixed the idle! wasn't closing properly, the choke cable was abit sticky (now all free)

but when I was changing reeds (on the block) the new ones had a very small gap one side which I thought was odd. anyway started bike and I think I can hear the reed plastic flickering, and when I took it for a quick run, I came off the throttle and it was kangrooing slightly.

which I think is the reed not closing fully....could it do this? im going to adjust the reed tomorrow (think its the wrong way round one side)

whats your views on this query regards reed plastics problems?

[Kickstart]

Hi

Reeds not sealing tend to make it difficult to start at first, assuming they are just not returning to seal against the reed block (if they just don't cover the holes in the reed block then all bets are off). Bit of revs and the reed valve are less important to keeping the mixture in, plus more likely to push the reeds closed.

All the best

Keith
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[burnsy]

thanks keith!

the only problem now is its idle slightly lumpy and every now and again it will stall once throttle is open, but past 2k it rev's lovely and a lot more freely than before.

could this be that reed not closing fully, as you say hard starting normally. 1500rpm to 2k bogs down sometime dies. but past 2k revs nice.

black oil leak now too onto exhaust chamber. this bike loves to give me things to do lol must be exhaust manifold as powervalve has just been serviced

burnsy

[Kickstart]

Hi

You can clean up the oil where the exhaust joins to the barrel. Think it is meant to be sealed with high temp silicone sealant (is where the exhaust goes over the ball shape stub).

Suspect the reed valve leaking could cause the stalling. Look carefully at the reed and check it hasn't moved slightly (ie, with age the reed can leave an indentation in the rubber of the reed block, then if the reed is moved slightly it no longer fits in the indentation).

All the best

Keith
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Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

[burnsy]

thanks keith!

will check all tomorrow and report back...(quick blip around the block) seems all hesitation has gone now, no lack of power between 5-6k, no flat spots ect. overall happy just a few more hours cleaning up ect then should be a good little bike (hopefully) lol

burnsy

[burnsy]

ok guys, 34mm carb all set ok now (finally!) I cant see the GP boy's back in the days messing around with this airbox, what a pig of a design that is lol

now iv taken the exhaust off to replace the manifold gasket and I didnt know the bolts are star shapes (which I don't have!) dam it!! So ill have to sort that out when I pick a set up.

Didn't use the boy's reeds as I think they are past there best and giving more problems an good...So standard ones back in and all is well there...might pick a set of carbon ones up at a later date.

anyone have a video or link to adjust clutch via clutch casing, I see today im on the edge of the clutch lever. I did take the centre bolt off a see a little screw inside for a flat end screwdriver, but this seems very stiff to undo. Am I one the right track for this?

burnsy