hi all so ive recently fitted a rebuilt motor to my mc21 it has standard pipes and modified air box it has wire splice but i returned it to standard to run it in also its been wet all week here so thought i wont need any extra power.
while it was apart i set about fixing all the little things that were bodged over the years of previous owners including the missing tee piece and air correction plumbing not been conected
so i start it and runs fine but soon as i go for a rev it wont and just splutters at about 7000 obviously running rich so i take the air correction hoses off and it runs fine.
so to my understanding some one must have rejetted the carb's right!! or it would be way lean with this disconnected ? would'nt it so my main question is
is there some trick were the carbs are rejetted without these hoses connected.
or do you think it has been done to save finding the right tee piece
in the end i just want to know witch way i should go leave it as is cause it runs fine or spend the time to revert it back to how it should be.
any and all advice would be much apreciated ahhh "MATT" "stevenrc45" some one who has spent time testing both setups HELP
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"Batmans a scientist"

Hi Mate
Are your solinoids working ?
I would start by going back to standard . And then go from there . Running without the solinoids connected will mess up the mixture at differend revs .

hi buddy yeh im going to double check them tonight i did have a quick look at them but didn't have a vacuum pump handy.
has anyone got an idea when or under what condition they are ment to open or close.i just spoke to the last owner he said its been like that since he brought it also he said that he has some old piston from previous rebuilds when i took a look at them it seemed like may be a bit lean up top..
also he said when he brought it it had NSR.92 number plates please tell me some one here knows this bike cause it would be great to find out exactly what shes been through over the years

http://cid-091891bbbe80dea7.photos.live.com/self.aspx/nsr%20stuff%20s/Photo0506.jpg
thought id add a pic of the mc21 with my mc19
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"Batmans a scientist"

so what jets are in your carbs right now? you also got the little boost bottle thingos too?

considering i just spent 2 days building the engine and fully rebuilding the bike im not real keen to pull the carbs off again but i know i have to soon so im leaving it till tomorrow night so i dont know what size jets.
and yes it still has the boost bottles also uses standard oil pump once its all sorted ill go pre mix

Hitler wont let you talk about jet sizes here.

You are bound to have the most success putting it back to the way Honda designed. Including air box lid jets etc.
Standard jet sizes can be found in the workshop section here

yeh one of the resons i posted before checking jet size
ZIG HIELLE
but i dont have any problems tunning it no matter what config i run tunnings the easy part for me as i spent 6 years tunning after market efi systems
on cars "wolf3d and motec ect" a two cylinder two stroke is a walk in the park
just wanted to no if any advantage running without air correction system or if you can make the bike run just as good without it to save me doing all the work to return it to standard.
all the sign's point to me chasing up the right parts and returning to stock i guess.
_________________
"Batmans a scientist"

I`ll take tunning a EFI over a 2stroke anyday efi easy all computor ,2stroke on the other hand a lot of take of change jets put on then again and again and again an so on . I know i had mine on and of at least 10 times to get it where i wanted it . (go big and work down)
I have converted a few carb cars to EFI including a turbo 351 using haltec soooo much easier then anything with carbs

when you put it that way i agree its more hands on work to tune a carbbie compared to efi but efi has many more map points over the 4 or five circuits a carbie has i was sort of just saying that im more than confidant when it comes to choosing jet sizes or tuning it would be twice as easy as when i did my cbr250.
turbo 351 sounds sweet i mostly did turbo 4 and 6s rb's n 2jz's

so i got a new tee piece but when i fitted it makes the bike run rich again
pulled the carbs off and found the jets have been changed at some point
it has 148 mains and 55 slow jets fitted it runs well like this with no air correction but seems a little rich down low and feels like it leans out in top gears.
so now with all the air correction plumbed up and 128 mains and 38slows it idles smoother feels better in top gears only thing is it has a flat midrange untill warmed up.
witch is how a 2 stroke should be i guess.
so some one spent a lot of time and tuning to try and jet these carb's with no air correction fitted maybe cause it would never run right after they broke or lost the cross tee in the end no amount of tuning would solve the problem.
i will know a little better how the bike performs after a decent ride but im happy the air correction system is functional again as it should be.
and it goes to show some times factory systems are built better and out perform bodge tuners that think all carbies are the same.
honda spends well over 5 million a year in research and development yet there will always be those out there who think they know or can do better most of the time having done no research.

finally got some tuning time last night got the nsr running sweet with the following settings "jet settings are not open to discussion these settings are not final... and i dont need help with jet sizing.. they are close to my results so far.
xx
xx
xxx
although these would be good base settings for most standard mc21's i do not recomend them as all bikes and conditions varry.
as some of the jets were to big i used an old trick i learnt and filled them with solder then drilled to the right size.
as always i started at standard and slowly worked up from there.

Admin: No more jet sizes in free area. No more warnings.


Last edited by elmo on Wed Jul 13, 2011 8:52 am; edited 2 times in total

Hi elmo
I would edit out your jet sizes as that post may go missing .
Good to here you got it running good . not many nsr`s running the same jets in both carbs as the rear is less eficiant and needs to be setup to compansate it .
The solder would work temp but i wouldn`t trust it . I have a full selection of jets if you need any let me know .

yep the solder is a temp just to get it right so i know what size to order
cheers if you have a set of xx slows and xxx and a xxx main ill take em
i hope my post dos'nt offend andy im not discussing jets or sizes just posting my results
i know im right on the border playing with fire hope i didnt cross the line

Admin Topic locked. Please respect the few rules we have, or you will find your account suspended. This post could easily have been a PM.

You won't believe how stupid people can be, and someone with similar symptoms could easily read this thread and try following those sizes.