2006 rs 125 , 34 mm carb, Running problems

[archyrcv]

Hi iam new on here but not new to bikes.
i have rebuild a 2006 rs125 that was sold to me in boxes. the engine has been rebuilt by others but works absolutely fine.
so she starts first time every time. choke works perfect
she idles very nicely too
she revs right up through to about 8/9k
the power valve works fine and is free and clean
the cdi black box has had the bridge removed ( which made a big difference
the 34mm carb was a puzzle at first and this is what iam working with now
main jet 155 with atomizer 266
needle k57 on the top notch ( was on the middle notch before but i moved to the top before i de-restricted the cdi module)
float needle and seating 300
choke 60
idles / pilot 36
it has new fuel line
new plug BR10
the carb is clean
mixture screw is 1 & 3/4 out from shut
the cdi box for the powervalve seems to be working as the blade movement is good too
so to clarify she pulls well right up to about 7k and only has a top speed of 50mph
the carb filter was broken so i removed it , it has a filter on the vacum tap on the fuel tank so not worried about the fuel.
i have removed the air box nose rubber too

can anyone help with this , my fireblade has 4 carbs and ive set them up in 30 mins this rs is doing me nut in.
she looks amazing and is complete now i just need to sweak her a bit
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darren jones

[P.]

What compression does the engine have currently?

Do you have an aftermarket exhaust? Thats hell of a load of changes without changing the horrifically restrictive stock exhaust. This means you need to account for other changes too...

[redeem ouzzer]

Too many changes, too little dyno time.
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Be a REAL MAN!

[archyrcv]

Hi
The exhaust system is a arrow tail pipe
The expansion from the header has had the baffles cut out and then welded back up .
Today I put the k57 needle notch back to middle but it was worse so I placed it back to the top.
Tested the power valve again and it works well and is very responsive .
Not sure if the signal it receives whilst driving is good but I guess it is as it comes on throught the lower to mid range but not after 7k revs and just splutters
It's going for an mot today now I might ask the old boy in the bike shop to cast his old eye on it.
Compression test not done as yet

I read on an article that a guy in America was using a 185 main jet
I thought that was a bit excessive though especially as I've got a 155 in mine.
I think if anything it's over fuelling
Any thoughts guys
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darren jones

[Easy-X]

Fine until high revs, then splutters. Needle adjustment hint at rich mixture over lean

I'd say there's either a problem with the carb at wide open throttle or some restriction in the air/exhaust flow.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[-]

[archyrcv]

So I just came back from having the mot
The old boy told me to use super unleaded first as all of his motax122 two strokes were run on it
The jetting seems normal
I will take off the snorkel again and put the needle down to bottom as I tried the middle earlier today
Get back to you all
Thanks guys
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darren jones

[P.]

[archyrcv]

so today i emptied as much of the old new fuel and filled up with super unleaded ,
went for a spin , done about 50 miles ...... still the same . the bike now revs up to 7k in ist then 6-7k in 2nd then a flat 5-6 for the rest of the gears. max speed 50 mph
very disappointing.
think i will start from the beginning and replace all the jets. maybe i will reduce the main jet for a 140 from the 155 as one of you helpful guys suggested.

Can i ask , is it possible the the power valve would work correctly whilst in neutral but under load whilst driving it could fail ?? i dont think so myself but has anyone heard anything like that.

So what about the airbox , i have taken the snorkel off as it feels better and seems to want to run better too.
the filter is a black & red one think its a piaggio one as it has a P on the red side . Any suggestions on this airbox.

like i said ive never know such a fucking twitchy setup , very sensitive eh

oh and can i ask has anyone got a setup i can copy that is proven for what i have

think i will check the plug tomorrow see if i have been over fueling
and maybe buy a comp test kit any suggestions on a reasonable priced one please

regards
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darren jones

[archyrcv]

forgot to ask , anyone know where i can get the jets from , for the 34mm delorto

cheers
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darren jones

[redeem ouzzer]

You could stick it on a dyno instead of guessing....,
____________________
Be a REAL MAN!

[archyrcv]

every time i speak to someone about the rs125 they run for the hills lol

i dont know anyone with a dyno around ross-on-wye area either.

all the reading ive done has got me going in circles to be fair.
thats why i said i will probably buy a couple of new main jets one larger / one smaller and go from there.

the airbox suggestion may need a look too !!
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darren jones

[stevo as b4]

Blue is right!
That sucker needs to go on a dyno to sort out, and optimise the set up for your engine and modifications.

Oh and thank you for this thread, as reading it makes me realise that although I know absolutely fuck all about two stroke engines, and also having a 125 with extensive modifications, the one thing I'll never to is come on here asking for advice on how to fix it or set it up.

I'd rather pay a good tuner and dyno operator to do that for me, than risk sounding like a totally clueless fool. To me that's worth several £££.

[archyrcv]

thanks for your input steve , but to be fair pal that isnt a way that i was brought up think. every day is a school day and if iam able to fix this issue then its a result even with help.
i dont like to be beaten

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darren jones

[mentalboy]

Presumably you had it working nicely before changing the carb set up or tinkering with the black box (as you say it made a heck of a difference)?
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Make mine a Corona.

[archyrcv]

hi
not i received the bike in pieces , i rebuild it up from a carcass all bar the new engine rebuild
it was running lovely in neutral from the word go. til i took it for a run .
i found it wouldnt reach 4k then possibly got to 5k
so did more research then did the cdi mod
this mad a nice difference . and now iam thinking down the road of over fueling a couple of guys have said this has happened to them so ive ordered a 140 main jet
the airflow has me a little stumped . unless the foam filter is an issue which i dont think so to be fair. she runs better with the snorkel gone but i think removing the foam from the airbox will give to much air
i wish i had a dyno close as it would benefit from it
have you had anything like this
____________________
darren jones

[-]

Compression test it before you waste any more time.
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TZR250 2MA road, TZR250 1KT road, TZR250 2MA race, TDR250, YZF-750R Boost colours.
Jaguar S Type 3.0 V6 Sport R, VW Transporter T5 GP LWB Shuttle 140ps DSG.

[mentalboy]

[archyrcv]

Hi
well i have a reading of 122psi on the comp test. its seems ok

i will wait for the new main jets and start from there i think.

i do document every little change and it seems like iam heading in the right direction as like i said this was a project bike that i bought so ive never known it running any other way than this.
i think i will start with the main jet now when i get them and document how it goes. and work from there

i am still intrigued about a guy on youtube converting his 2007 to full power and his jet setup was vast. i know the weather and atmospheric pressure comes into play but its a million miles off where the standard setup is
fingers crossed with the new jets anyway

regards
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darren jones

[-]

[archyrcv]

I have had the plug out today it looks slightly wet with a tiny bit of oil on it
I will drop a photo on here in a the morning
The slightly wet plug is why I think it's over fuelling
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darren jones

[stevo as b4]

Is the bike something that you just want to run and start each day and get you A-B or are you looking for the knife edge jetted on the ragged edge of lean/detonation with a crisp zing to 11'000rpm, and a happy left hand to cover the clutch lever all the time?

IMO you can't have both features in one two stroke engine? I've got doubts about my own 125, but once it's set up on the dyno I'm happy to accept 4-5000mile re-builds if I don't blow it up before. I'd have left it as a std bike and set it with slightly soggy rich jetting if it was going to carry my ass to work or earn its keep.

[mentalboy]

This has just occurred to me. As I don't know you from Adam, please don't take offence but are you familiar with the throttle vagaries between two and four strokes? If you accelerate a 2T the same way as you would a 4T it will be proper sluggish. Generally speaking, you have to make some zippy revs before changing up, in each and every gear.
Going back to your first post, was it pegging out at 7K in every gear or can you redline (ish) it in the lower gears with no grief?
____________________
Make mine a Corona.

[-]

[archyrcv]

hi all

so i am aware of the difference between the 2 and 4 stroke , iam not really looking for the bike to perform and not splutter. i dont mind if it gets to 100mph or 90 to be fair. The bike was for my son who has lost interest since he has car now. So i guess i will get the bike running well then sell it once ive completed the rebuild. Just waiting to fit the last couple of parts that ive ordered.

at the moment its un ride-able.

At 45-50mph in 5th or 6th gear it doesnt smoke but it lacks power.

it never reaches 8k maybe only in first just before i change up to 2nd.
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darren jones