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Discussion Starter · #1 ·
I posted this earlier, but I figure Id make a build thread to keep track of the progress.

1996 cbr f3, new welded tail, leaky lowered front forks, supertrapp short exhaust, maybe sorocket?



Waiting for a 96 yoshi rs3 exhaust in the mail, i might have fucked up the addrress tho, shit

ek or rk 520 chain kit with 15/45 sprockets, i forget, but steel sprockets and 9000lbs tensile seems fine

need to look at carbs and jets. Also have to take the fucking battery off the block!!

No good.


I also dont know what kind of shock that is. Purple spring, looks like twist to adjust dampening?


I tried to rig a simple battery holder with some l brackets i got at a hardware store..



I havent put the new battery in yet, but to mock up. I have two brackets, one holding the battery on the bottom, and one holding it wedged on the metal undertail so it wont slide forward.. seems snug. I Hope its far enough away from the shock, and I hope those brackets will hold under heavy wear.

I have to take the carbs off basically to take the battery off the block, and I Dont have a garage right now. Dreading doing it on the street, goin to try and use my buddies garage when I can.

Going to clean it up a bit too, could use a wash I guess. And an oil change, though the kid before said he changed it, with or err uh added synthetic.


Its definitely a fun bike, it really needs to be wide open to run good. In traffic, at a stop, it bogs hard. You Have to baby and drop the throttle, or snap it quick to get it moving, then once its going and getting fresh cool air it loves the high rpms... But theres a shit ton of vibration, and the radiator feels like its the one humming around..

Also it popped out of 2nd after a high rev quick shift, i might have just fucked up though.. I do want to figure out how to tune the transmission though, keep it feeling tight.


Alright enough for the day, hopefully I get some real progress soon
 

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Good start!

For the battery I made a plate to cover the rear of the engine then made a box to bolt to that for the battery it sits about an inch above the engine block where you had yours originally !
if you want cheack out my thread for ideas the link is in my sig.
 

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Discussion Starter · #4 ·
Alright, finally got some garage time all night last night, poor friends garage wreaks of gas now..

I went through, removed the carbs, moved the battery off the block and onto the subframe, and replaced the shit 3" gravity feed fuel lines. Now the fuel lines are about a foot and serpentine to the carb inlet, little crease in the line at the carb pick up too.


Anyways, after logging in hours cleaning the jets, trying to figure what jet setting is best for "whatever" jet kit I may have, and trying to figure out what clip needle setting is best, I ended up with these carb results:

I have no idea what jet sizes I have

Jet needle setting clips rest on the 2nd setting from top and they sit on a washer as a shim in the vaccum chamber.

I set all jets to 1.6ish turns out from stop.


So with those settings and a fresh fuel line, it started right up. On the freeway it screamed at like 8k-13k, like hit it and the power just shot up in 2nd or 3rd and I thought my wheel was just spinning?

But then it would not idle, and die. Or if I was on the throttle, after a full throttle run, it would die sputter out. Then I'd have to kick the starer over and over and hope it would fire. I suspect the carbs get starved out at high rpm from the gravity feed, and then the engine chokes with no gas because it already runs leaner up top.

I am under the impression f2 gravity feeds = rich at idle low speed and city traffic / lean at high rpms and on the throttle for long time ..


After riding it around all over today, trying to get the idle to hold, trying to figure out what the hell is going on, I finally got home a little beat down..... ONLY to find! My yoshimura rs-3 exhaust :).. which is basically what I set the carbs for, I've yet to ride it on the street, but the rs-3 is on.

ONLY problem with the rs-3, is tthat I can't freaking mount it properly to the stock subframe because there is none! Damn. Going to try and figure something out tomm, not having a garage reallly fucking blows.



I'll post some pictures up when I load them.
 

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Discussion Starter · #5 ·
Here are some pictures.. any help on what jet needles and settings I have would be really appreciated. I think it might just be the stock set up? but I have no clue..

Clip setting with Shim



Here's my problem with the rs-3 exhaust, no where to mount it! ahh, I just want to ride so bad too.. some sort of mount to be made tomm..




Oh yea, also lost the fucking top tank screw, so I use a long hex that goes in... great way to fuck up the tank threads i suppose.



And this is how she sits, with a random dirt bike front guard as mock up, or whatever. I kind of like it though, maybe angled a little more up and hiding some guages ha.. and the red alpinestars through the mesh is on the ground.. it looks kinda rad

 

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Hack in a barn
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I can't say that I know any specific carb specs for F3's or know what jetting you should have, but...

Does it not even idle with the choke fully on? Probably too lean, adjust your idle mix screws to around 2.5 turns out.

You say you adjusted "screws" to 1.6 turns out. Are you talking about just the idle mix screws on each carb? Or are there more screws involved?

2nd clip from the top is pretty lean, the needle is more of a aid in the transition from all the jets and not specific for idle but if at 1/8-1/4 throttle if it's lean surging and lean popping on deceleration moving the clip down could help.

If you block off some of your air filter with some rags or plastic bags or what ever, and start the bike and it idles, you'll want to add more fuel on those idle mix screws.

The jets "SHOULD" have been marked with what they are... I dunno.. Best bet is to replace when in doubt, I mean jets are around $7 each, so for pilot in what ever size and main in what ever size for all the carbs it's about $50... Well spent imo...

Any ways. You'll REALLY want to make sure it's not a vacuum leak around the carb boots causing the lean conditions because you'll waste your time trying to jet for that. So if you can get it to idle you can spray carb cleaner, Wd-40, or if you have a small propane torch use that <open valve no flame though lol> and spray or let the propane go around the carb boots. If you hear a change in the idle, then there is a leak that needs to be fixed.

Then you'll want to get a carb sync lol... There is that :D
 

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Discussion Starter · #7 ·
also i dont have all the screws for the air box, only 2

i will adjust the carbs to 2.5 out, yea the fuel screw

as for the clips, ill leave them first to test the.fuel.screws,, then go from their

i need to do the carbs lean/leak test with wd or carb cleaner too
 

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goodonya fer workin so hard fer sure mate , gotta feelin ya wont stop till its rite on dialed:robssmilie:
 

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I don't know if it's allowed but there's a sticky on another forum specifically dealing with f2-f3 carb tuning. I'll find the link and share if ya like
 

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Discussion Starter · #10 ·
please post any link you can.. tough fimding a damned garage around here though!

Road it with the rs-3 yoshi and it sounds so much better.. still popping low down around 3k or lower when off the throttle

right now the bike starts up easy after sitting, ride around easyband it cruises mice when cold.

Heat it up, get high into the revs, and it dies after a while.. When you give it full throttle im the 7k to 8k range it wounds like it revs high and quick but it actually loses power, then basically dies if you cant recover the.idle..(edit, im pretty sure know this is because i was lean and.i didnt have nearly enough gas pumping in to keep up with the air flow)

I definitely suspect it is lean..

I did get a fuel pump, but its only 3psi at most, and ive read honda carbs like 4.5 or so.. should i return it??

Really want to figure out the carbs so i can work on the forks, pads, and front tires. I also wana get some better rearsets for it as wekk, woodcraft maybe?


sorry for the crap typing, phone keypad is way too small

also

"If the bike doesn't pull well at high rpm when cold and gets only slightly better when fully warmed up, the main jet is too small." from CV carb procedures

is why i suspect it in lean conditions right now, jet may not fully be too small for carbs may just be my screw adjustment since it seems aggressively lean...

which makes me wonder about the whole jet gas/air ratios for power.. itd be nice to blow past a ducati on the track with cheap and proper tuning :D
 

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So from the last post I would say the best place to start for you with these carbs is the float level. If they are off your bowls could be running out of fuel and that could explain the bike wanting to die after wide open runs.

If that pump is anything like in my R6, it is there to fill the bowls and will shut off when they are full and the float needle seats. I would suspect that if the demand is more than what the pump can supply then it could be a problem having only 3 psi instead of 4.5 or so.

But the most important place to start is the float level, and in reality replace the float valve and seat but definitely set them up right from the start, don't have this right and nothing will be right.

After that and the bike is running to the point of just needing tuning, then is the time to fuck with jetting and needle jet height. I prefer to start with the mains, get those where they feel good and then work down the ladder from there going to pilot jet and needle for the cruising and mid range and then fuck with the idle mix screw to get the idle perfect... But that is just me. And it does help to start with a bike that is "close" :D

It's a matter of how many times do you really want to take these carbs off and do the proper steps? If you take them off once, thoroughly clean them, buy new jets and re-jet to what other f3 guys have for exhaust and anything else you have. Set the floats and replace o-rings with the ones from the rebuild kit you should buy :D. Get them back on the bike with out vac leaks and then when it's running again sync the carbs. You will pretty much not have to spend the rest of you summer weekends taking the carbs off again :D
 

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Sticky: Carburetor Cleaning & Tuning 101
280 05-20-2014 by JNSRacing

http://m.cbrforum.com/forum/showthread.php?t=96888

There's the link I mentioned earlier. As far as I recall the float level is not adjustable on f3s I know it's not on f2s. I also know the f3 will run without the fuel pump. It will cause issues in the upper rpms though. Definitely agree with checking everything like f'dup said. I have a slip on that an idiot welded on and a k&n on my f2 and I'm running stock jetting and don't have too many issues. Base pilot at 2.5, ended up at around 2.75 out from full stop for best performance. There is a thread on the cbrforum also that has members pipe, filter, mod, and jet settings. A lot of good info there. And the guys there are very knowledgeable and helpful too
 

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Sticky: Carburetor Cleaning & Tuning 101
280 05-20-2014 by JNSRacing

http://m.cbrforum.com/forum/showthread.php?t=96888

There's the link I mentioned earlier. As far as I recall the float level is not adjustable on f3s I know it's not on f2s. I also know the f3 will run without the fuel pump. It will cause issues in the upper rpms though. Definitely agree with checking everything like f'dup said. I have a slip on that an idiot welded on and a k&n on my f2 and I'm running stock jetting and don't have too many issues. Base pilot at 2.5, ended up at around 2.75 out from full stop for best performance. There is a thread on the cbrforum also that has members pipe, filter, mod, and jet settings. A lot of good info there. And the guys there are very knowledgeable and helpful too
There ya go... Repped.

And I should say never take my word on any thing I say as law. It's best to look at the F3 specific jetting and carb setups... I only point in directions with generalities, it's what i do mang...
 

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Discussion Starter · #17 ·
thanks guys, i think i will return the pump for a larger one. soon..

heres a pic of my carb boots from the other day,the 2 outside boots sit on the bottom ofnthe carbs carbs, the.center boots stay on the head.. hmmm may be cause for an air leak.. also i dont really remember specifically tightening all the boots because the carbs slipped off easy after loosening the drive side boot (far left), plus id been sippen beer



is there anyone near portland that has a full garage and doesnt mind late night working?? i dont think my friend was very happy about the real dirtiness of working on this bike, i warned him tho ha!


I also got my chain and sprockets with the chain breaker tool, i have 15/45 set up waiting to go on.. but
thats worthless until she runs primo.


Anyways, I really dont mind pulling the carbs, tuning, replacing, and running into problems though, so I figure this will resolve soon enough
 

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Discussion Starter · #18 ·
just turned the air fuel screws out to around 3. now the bike idoes fine, pullbhard upbaroumd 8k and it sounds starved..

BUT, the airbox doesnt seal the k&n filter properly because a.) the airbox is cracked and b.) it has no screws but 2, to seal the top box to the housing.

So, maybe new airbox. And maybe new jet kit to figure the carbs, or maybe just move the clips down 1 (or 2??) on the jet needles?

Right now runs good enough to drive though.
 

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Does the bike still die after WOT runs?

Good on you for having the patients to work it out, and yeah I'd sort out the air box it is pretty important for atleast a good running base line. I ended up ditching the k&N in the r6 in favor of a stock filter because with the stock jets it was too lean with that filter. Mains seemed ok but pilot was way off. Stock filter helped with that.
 
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