View Full Version : Rejetting and Rebuilding carbs . help
It's gotten to the stage where i badly need to rejet my stock set up carbs.
Currently on my 01 i have a K and N air filter, and a CCC can, the results of which are a huge flat spot at 4K rpm in second gear, and general lumpiness down low, and between gears.
What i aim to do is, Remove the carbs and clean them, following this thread http://forum.svrider.com/showthread.php?t=85513
Once thats completed, i'll fit Tank spacers and remove the foam from under the tank, and rejet.
I have been half thinking about fitting a BMC RS filter also, but cash is a bit tight and will have to wait :(
My main questions would be as follows.
Based on the set up described, ( CCC can, K and N filter, tank spacers and removed foam ) who wants to guess the jet sizes i should aim for ? cash is a bit low, remember we are in a recession over here also in Ireland.
What about cleaning my carbs, would ethinol be usefull in this process or would i be better off take then some where and get them blashted ( not the technical term of course)
Dappa D
22-01-09, 11:02 AM
wouldnt wanna guess as im pretty useless..hower i will say with my viper end can, standard system, bmc rs race filter, defoamed and raised i was using 155 mikunis and it was spot on...it may have been better with slightly larger or smaller ones but i started at 155 and was happy enough not to go through all that again lol
wouldnt wanna guess as im pretty useless..hower i will say with my viper end can, standard system, bmc rs race filter, defoamed and raised i was using 155 mikunis and it was spot on...it may have been better with slightly larger or smaller ones but i started at 155 and was happy enough not to go through all that again lol
Had a good read over your thread DD, it was pretty good help in getting ready to do this, it's just a bit of a pain in choosing the right sizes.
Lets see what the pro's have to say ....
DarrenSV650S
22-01-09, 11:09 AM
Isn't there a proper way to work out what size you need? I think my tzr needs new jets, its pouring fuel out the exhausts
I think my tzr needs new jets, its pouring fuel out the exhausts
You know im no expert, but that really cant be good right ..
DarrenSV650S
22-01-09, 11:31 AM
Nope. It's because it has race jets. I don't think it will get through emissions in the mot
Dappa D
22-01-09, 11:32 AM
i know of a way of testing them based on throttle position/speed/revs etc...however this is a long process....rejet...test...rejet...test....rejet... .test....
well....
when i say i know of a way...what i mean is i have the testing information in a file somewhere im sure......would it help if i can find it and mail it to you?
i know of a way of testing them based on throttle position/speed/revs etc...however this is a long process....rejet...test...rejet...test....rejet... .test....
well....
when i say i know of a way...what i mean is i have the testing information in a file somewhere im sure......would it help if i can find it and mail it to you?
Already have that PDF matey, think you actually mailed it to me, get her in 4th gear at 6.5K rpm and see if she pulls and then let the trottle back to 7/8 position ...all that stuff
Cant be terribly hard to test, just need a general idea of sizes to order i guess
yorkie_chris
22-01-09, 05:14 PM
Flat spot at 4k, try raise the needles a clip setting before forking out £6 for jets. Mains kick in more like 6k though there is some cross-over.
Do not use ethanol except where you are certain no rubber or plastic parts remain. Degunk the float bowls with carb cleaner if you wish, however the safe bet is to use petrol and compressed air.
Quick test, whack it wide open at 6krpm and see if it stumbles.
Nope. It's because it has race jets. I don't think it will get through emissions in the mot
No such thing. And what is a race jet when it's away?
Dangerous Dave
22-01-09, 05:16 PM
Flat spot at 4k, try raise the needles a clip setting before forking out £6 for jets.
+ 1
As Dappa said, 155's maybe the ones to go for.
yorkie_chris
22-01-09, 05:18 PM
Yah with RS, that will be sloppy as feck with K+N.
All carbs are a little different, some engines will run good with different jets to others.
Dangerous Dave
22-01-09, 05:28 PM
Yah with RS, that will be sloppy as feck with K+N.
Ahh yes with a BMC, the K&N doesn't flow much better than stock.
DarrenSV650S
22-01-09, 05:39 PM
No such thing. And what is a race jet when it's away?
Well when I say race jets, I just mean bigger that standard:p
I'm gonna find out what the standard jet sizes are and get them. Does it have the jet size written on the jet? Or is there a way to measure them?
I don't understand why my bike has bigger jets when it only has a standard air filter. Although it does have race exhausts. Is there another variable that would require bigger jets?
Flat spot at 4k, try raise the needles a clip setting before forking out £6 for jets. Mains kick in more like 6k though there is some cross-over.
Do not use ethanol except where you are certain no rubber or plastic parts remain. Degunk the float bowls with carb cleaner if you wish, however the safe bet is to use petrol and compressed air.
Quick test, whack it wide open at 6krpm and see if it stumbles.
No such thing. And what is a race jet when it's away?
I'll take her out on the road, i assume it's in 4th gear, 6K rpm and snap open the trottle and see if she stutters and then goes.
I'll get some carb cleaner and attack them with that, and perhaps go with 150 and 155 jets, just in case, they are cheap enough i guess.
Altho i'd love a bmc filter.
For the moment i'll move the needle and see how we get on, it's horrifically lumpy even in 2nd around 1500 and 3000 rpm
d.
northwind
23-01-09, 12:42 AM
Currently on my 01 i have a K and N air filter, and a CCC can, the results of which are a huge flat spot at 4K rpm in second gear, and general lumpiness down low, and between gears.
SNIP
I have been half thinking about fitting a BMC RS filter also, but cash is a bit tight and will have to wait :(
My advice, don't **** with it. You can go to a lot of hassle here to rejet, fit a better filter etc but with just a slipon the benefit will be minor, so really what you're doing is dialing out the running issues which you've added with the K&N. They're just little red bundles of fail, they flow well enough to give you running issues but not well enough to be really worth rejetting for.
If I was in your shoes, I'd sell the K&N and fit a stock filter, your running issues should be cured with the spinning of 10 bolts. A slipon alone very rarely causes any issues.
But, if you do want to go further- yes, Race RS is the one to get, or desnorkel a different filter (could desnork the K&N if you want). But even with a really good system the gains are not massive but it's a pain in the bum to do (or, expensive). Yes, you can get good results with the butt dyno, but it's time consuming and generally a pain.
Obviously I'm the last person who should be advising people to leave things well alone :mrgreen: But the performance benefits of a filter/rejet with a quality system barely justify the investment of time or money, doing it without the system gives not much benefit at all for the exact same investment of time.
Of course, you might enjoy it. I kind of did, but I got righteously fed up of taking the damn carbs off. As a result, I have a very finely honed butt dyno, but on the other hand I never want to change a jet again :mrgreen:
Northy with some very sensible advice i have to say, and i've heard for a long time that the K&N filters are pretty kack.
The only thing that comes to mind is, as it's just so darn lumpy at low revs/speeds, perhaps it's the fuel float height that really needs cleaning / adjusting.
And i wont have my answer for that until i remove the carbs and take a look
Dappa D
23-01-09, 02:59 PM
totally agree with northwind.......
i would say tho....after my bike got wrote off (and i sold the bmc filter..stupid boy!)..and i bought my bike back....so had to refit stock filter and rejet back to standard :-( ...that now it does feel different...only way to describe it is that it feels a bit choked......BUT like nw says i certainly wont be going out my way to get a good filter and rejet ect again..as its not a great difference...although untill u actually do these things and see for yourself you wil always have that nagging feeling that you wanna do it...so i dont blame ya!
northwind
23-01-09, 07:18 PM
The only thing that comes to mind is, as it's just so darn lumpy at low revs/speeds, perhaps it's the fuel float height that really needs cleaning / adjusting.
And i wont have my answer for that until i remove the carbs and take a look
Bike'll be getting on a bit, even if it's never sat about unused it's likely to be a bit gunked up so it can't hurt. Unless you completely destroy the carbs :mrgreen: Using carb cleaner is very good for the soul, watch what you thought was evil unshiftable grime on the casings just fall off.
The carbs were actually a set i got off on of the guys here, and they were taken in to a garage, and " cleaned" or so i was told, only one way to find out, i'll have to sit down and open em up.
Just a follow on bit of advice, good carb cleaner ? anybody want to recommend some here, I was out at the weekend, but didn't find any :(
I'll have to ebay some I'd say.
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