Guys

firstly i'd like to thank the people who helped me about 2 months ago with my post about the RC valve removal (posted under a mates login). got them out fairly easily once i figured out what i was doing! the hammer claw worked a charm

now, after much waiting, the time has come to rebuild my baby after the rear cylinder shat itself at the track, apparently due to detonation. I'm thinking about going to premix, and i just want to ask about the jetting. I've had a look around on the forum, and whilst the info is helpful my question is a little more specific

two questions:

Is it worth it? the bike is a 50/50 road-track bike. i've got a 600 to get around on, the NSR will only see street action when i feel like annoying the local residents and my 4 stroke owning mates . So i'm not worried about having to carry some oil to mix every time i fill up.

and secondly, what i really want some help with. I'm planning to go 30:1 fuel ratio which seems to be the standard, is there a rough guide i can go by to increase my jet sizes to keep a good air/fuel ratio? Or is it a play it by ear thing? Am i better to wait until i can afford take it to a mechaninc and get it dyno'd and just run is standard for now?

I don't know much about it's history or setup, i bought it from a dealer, but it's running no airbox (pod filters), rear head on the front, and seems to have been jetted to suit.

thanks in advance!

Personally I don't see why you'd bother with pre-mix, it's a lot of hassle for little (or no) reward.

Make sure it's jetted properly first before you worry about anything else, just the fact that it runs only means it's quite near, it doesn't mean it's not a couple of sizes too lean and going to seize someday soon anyway.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

Because it add to that "whats he doing" look at the petrol station,

First you pull up on something with no lights, sounds like a bag of nails and smells. Then for some reason measure some sort of liquid and put it in the petrol tank!? Followed by shaking the bike... after which you have to run with it to start the thing... then pulling away the same bag of nails clatting around with large amounts of revs and smoke, leaving the bloke whos filling the 4x4 up wondering wtf just happened there!
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If I have to take the carbs off once more...

StephenRC45 wrote:Because it add to that "whats he doing" look at the petrol station,

First you pull up on something with no lights, sounds like a bag of nails and smells. Then for some reason measure some sort of liquid and put it in the petrol tank!? Followed by shaking the bike... after which you have to run with it to start the thing... then pulling away the same bag of nails clatting around with large amounts of revs and smoke, leaving the bloke whos filling the 4x4 up wondering wtf just happened there!

TART !
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Harley Davidson is the worlds most efficient way to turn petrol into noise without the harmful side effect of horsepower.

For the street? Stick with oil injector. Check your pump often and maks sure the feeder tubes havent backed their way off the nipples below the intake manifold.

For track? rip it off and go pre-mix. One less mechanical thing to **** up on you, as well as a slight weight savings. Oh and you can have a better selection of oils to use since the good ones shouldn't be used for injector systems.


As for jetting and stuff when using pre-mix, check out the other thread going at this very moment titled "PRE-MIX".
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Charles Gallant

Thanks guys for the assistance, been reading the pre-mix thread too

Whilst i'm getting advice, another Q:

the engine died on the track. took the cylinders off and the rear piston had kinda melted, the rings were compressed and sitting flush with the wall of the piston. Had to file away at it so i could get the piston pin out. The damage is i believe due to detonation, extreemly similar to this: http://pg.photos.yahoo.com/ph/rothmansmc18/album?.dir=f9ce. Only happened to the rear cylinder, the front was fine by comparison.

So, my question, what are the likely causes of detonation? It had BR8ECM spark plugs that are probably a bit hot for Sydney conditions, i bought it from a country town where there winters are much colder. cold days here are 15 C, there it can be lucky to get over 10 in winter. I was using a low octane fuel (91 RON), and rode it to work the day before it died in shocking traffic (10km trip=30 minutes), so it got more than a little hot.

Would using cooler plugs and higher rated fuel be likly to help solve the problem? i thinking about getting BR10ECM plugs, and using 95 octane fuel.

StephenRC45 wrote:Because it add to that "whats he doing" look at the petrol station,

First you pull up on something with no lights, sounds like a bag of nails and smells. Then for some reason measure some sort of liquid and put it in the petrol tank!? Followed by shaking the bike... after which you have to run with it to start the thing... then pulling away the same bag of nails clatting around with large amounts of revs and smoke, leaving the bloke whos filling the 4x4 up wondering wtf just happened there!

hahaha i wish, NSRs and strokers in general are as scarce as hens teeth around here. I got it at a very good price (AUS $3000, about £1200), with a full years rego and insurance, but it's a MC21R, so no bag of nails . The dealer even delivered it 400kms to my house, as he was heading to sydney anyway! I didn't buy it as a street bike, i've got a hornet600 for that, but i do take it out every now and then, just to keep the engine cycling

Once again guys thanks for the help, this whole DIY mechanic thing is still kinda new to me! Carburettors was about the extent of it before this!

I would always use 95+ ron fuel and BR9ECM plugs (or 10's)
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If I have to take the carbs off once more...

For any given setup colder plugs and/or higher octane fuel will ward off detonation.
The bike just needs setting up to suit the fuel it's running and plugs that won't melt but there's going to be a max you can push it to (ignition/compression wise) for a given octane.
Hence you just can't get a '28 on an 010 card or a '21 on a race fuel cdi to stay alive on anything other than Avgas or proper race fuel.
I wouldn't have thought a normal full power NSR is ever going to be that happy on 91ron and BR8ECM's, road or track.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread

StephenRC45 wrote:Because it add to that "whats he doing" look at the petrol station,

First you pull up on something with no lights, sounds like a bag of nails and smells. Then for some reason measure some sort of liquid and put it in the petrol tank!? Followed by shaking the bike... after which you have to run with it to start the thing... then pulling away the same bag of nails clatting around with large amounts of revs and smoke, leaving the bloke whos filling the 4x4 up wondering wtf just happened there!

i have to see this for myself sometime...
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do i need an NSR to be a member ???

StephenRC45 doing his silly wiggly dance at the pumps really is something to be seen!

Re: the original topic, I have to agree with Fontyyy, 91 octane and BR8ECM plugs is not only a combination I wouldn't ever consider running - I personally wouldn't use either full-stop! I had to use 95 in my 21 the other day, and even that made me think twice about what I was doing with the throttle and the load on the motor!!
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Andy.
NSR-WORLD.COM

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It had BR8ECM spark plugs that are probably a bit hot for Sydney conditions, i bought it from a country town where there winters are much colder. cold days here are 15 C, there it can be lucky to get over 10 in winter.

The air temperature has nothing to do with what temperature range the spark plug should be, its determined by the internal temp. in the cylinder.

The ambient temp. for a cylinder is around 50-60 degrees C and is determined by the cooling system, which keeps the cylinder at a constant temp. at air temp. between 0-35 C.

Internal temp. in the cylinder is aroung 7-800 C and is determined by: way of use, octane rating of the gas and degree of tune.

The normal NSR should use BR9ECM and at least octane 95, a tuned might use BR10ECM, so the BR8 and the 91octane could be the reason for the seizure.

Air temp. does however influence the mixture ratio, but thats another story.
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Poul
"If Life Gets Boring, Risk It!"
MC21SE, KISS box
MC21SP, HRC box, racing loom

thanks guys for the help! Going to give the BR9ECM's a go, and 95 octane fuel and see how she runs next track day at the beginning of december

Will to have a word with my mechanic, whos a good mate, and see if i can borrow their dyno for a while i think. going to leave it with injected oil till then.

and pbekkerh, thanks for the info, i was mislead by someone whom i'm now thinking knows less than they seem to believe

I'll let you all know how i get along! Once again thanks for the help!