nsr, revs sticking at 8k

[paul]

Hi

I have an 02 nsr 125 and wanted to derestrict it so I took the exhaust off and could not see a restrictor so I went for the other restrictor in the intake manifold, It was a white block, I took this out and the bike was revving much higher as expected but spluttered at 8000 revs in 3rd and sort of froze at 8000 revs in 4th and didn't want to rev any more, my mate said it needed upjetting but was too much hassle at the time so i just put the restrictor back in. When i rode it again it wasn't right and still gets stuck at about 8000 revs, the revs are fine before and after this and i'm finding i have to take the revs up to about 10000 revs before changing gear in order to avoid the problem and when it stops at 8000 i have to drop a gear and rev the bollox out of it so when i change up again it doesn't stick. This never happened when it was restricted before so i don't know what is going on.

I read a post that was put up a couple of days ago with someone experiencing the same problem but said it was something to do with cables put round the wrong way on the r/c valve or something so i don't think i have the same problem as i didn't touch the cables.

So what should i do?
and where is the other restrictor?

I would really appreciate anyones help and thanks for your time on reading this

Cheers, Paul

[alains]

you probably have a restricted CDI . find an other one , and put a BR10 EIX sparkplug . also you are probably restricted on the RC valves . type this https://www.125ccsportsbikes.com/forums//index.php?s=46559d76d67360144976e5d96238ac20&showforum=10 you will look the topic i put on
if you are interessed mail me at asaniard@neuf.fr
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the worst day fishing is better than the best day working

[Zen Dog]

I didn't touch the RC valve control cables either. It was done by one of the previous owners.

Try to check the RC valve is functioning correctly (some suggestions were posted on the thread about my bike about how to do this), and I'll get Zaphod to post a thread detailing how you can check if your bike is the same as mine was i.e. control cables the wrong way around.

The test that we did to show that it was the RC valve that was the problem, was to disconnect the cables from the RC servo and tape them in the "closed" position. The bike then ran fine, but the powerband was missing (as expected). Then we taped it into the open position, and at 7k rpm, the problem occurred again. Then we knew it must be the exhaust valve.

There is a picture of the control cables taped, and a photo looking into the exhaust port with valve open (i think), on the other thread.
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Current - '94 VFR750FR, '00 VFR800FI Previous - '10 Street Triple R, '92 MZ ETZ301, '05 TTR250, NSR125R, KMX125, "Honda" Win (chinese copy of an old Honda design with a C90 engine)
My bike trip around S.E. Asia 2010/2011

[ProXimaCore]

[paul]

sorry I haven't replied, I have just got back off holiday

Ah rite Yes it was a white triangle shaped block but I thought that was the restrictor because it looks as if it restricts the air flow, but anyway I did put this back in and the bike still has the same problem just not as bad.

and I thought only the import RR bikes had a CDI restriction in them??

I did have some problems with my spark plug a while ago, it had some petrol or whatever on it, could it just be the sparkplug?

and zen dog it was ok before we took out the "restrictor", then seemed to run lean so put it back in and there was still a problem.

sorry bout this being so long winded but bear with me please

Cheers, Paul

[alains]

it could be the spakplug , but i will think about the valves , could you tell some more like mileage , which plug , which petrol & oil ?
are the rc valves on full opening at 7800 rpm (you will see that on your right) where the cables and pulley are .
i will give you some pictures later
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the worst day fishing is better than the best day working

[alains]

do not be confuse beetween reed Valve (intake) and RC valves (exhaust)
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the worst day fishing is better than the best day working

[alains]

here are the RC valves
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the worst day fishing is better than the best day working

[alains]

here is the adjustment of RC valves
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the worst day fishing is better than the best day working

[paul]

rite, its done 4200 miles, think the plug is a br8 but the man i bought the bike off also gave me a br9 but i dont know a lot about these. I use just normal unleaded petrol and fully synthetic oil. i did use some low smoke oil last month though because they had no fully synthetic left but i dont no if that is the problem because as soon as i put the block back in the intake manifold it started to mess around. I think it could be the rc valve as you said alains because I may of knocked it when taking the airbox out and putting it back in. would this of affected it? Im not really that good on the mechanics side of things but i will check the rc valve tommorow.

Appreciate the help and input from everyone

Cheers, Paul

[alains]

if you do not mind the price put on a BR 10 EIX , buy it from https://www.sparkplugs.co.uk/ , price £ 6.84 +VAT +shipping
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the worst day fishing is better than the best day working

[alains]

i said BR10EIX but it is BR 9 EIX . for myself i put the 9 nov to apr and then i put the 10
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the worst day fishing is better than the best day working

[paul]

alrite then I will try the br 9 eix then and will see what happens, thanks a lot for your help

Cheers, Paul

[theshmoo]

i had same fault you may have put the read valve in up side down or the gasket is letting in air.i have a 02 nsr that had no restrictions on it it tops out at 85/90 with the revs at 8000 but bike will rev 2 red line in all other gears but not in 6th.i got a cdi from a british bike on ebay £40 waste of money bike won't start with it in it.
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CBR 1100 blackbird.

[gsxrboy]

I am no expert but it sounds to me like you haven't tightened the carb down straightly and there is a slight air leak, this would explain the loss of power and the need to get it revving high enough to change gear to miss the problem. make sure you also haven't fouled the choke cable as this will also alter the fuel mixture and cause a power loss. best thing to do is do exactly what you did before when taking it apart but pay more attention to how it logically goes back together, it does sound like a fueling problem to me.

Regards,

Alex

[paul]

the air leak seems to be the most possible problem. Thanks a lot for the help theshmoo and gsxrboy this helps bigtime, I will see what happens.

Cheers, Paul