Hi all, Ive just bought an Across around 3 weeks ago which is unregistered and needs some work. Ive fixed some major issues with this thing to get it back on the road. Im currently trying to sort out the carb tuning, and just to get it to idle, and rev is an issue. What ive done so far: take off the carbs, and clean them thoroughly. Ive removed all jets, needles and sliders, and float bowls, and cleaned everything out as best as possible. All jets have been cleaned so theyre able to be seen through. All needles are set at the stock setting, ie number 3 from top. (ive read somewhere that if the white clips in the sliders have play then they could give a leaner setting as they drop the sliders lower than normal) They have a small amoutn of play, nothing too bad, maybe a 1mm. Put back together and made sure the air box is on properly, and all vac hoses are put back. At one point i had it idling and reving quite nicely (by spraying wd40 to start it) and by adjusting the 4 screws ontop, near each balance vac hose. Then the next day it wouldnt start, properly, and only idle on full choke setting. Oddly if i spray wd40, it will start to respond to the throttle and rev properly. Seems like its not getting enough fuel. It dies everytime I open the throttle, even if at 1mm open throttle. Is there any other setting apart from the 4 air bleed screws next to each balance vac hose? I cant see any other fuel mixture setting sscrews. Not sure if Im making sense, but hope this helps paint the pitcture. If anyone has any advise in getting this going, itll be appreciated. Cheers
this might help http://www.scribd.com/collections/3674639/Suzuki-GSX250F-Across-Carburettor-Carby-assorted-info-Mikuni-BSW27
Great thanks for that. Looking at the diagrams there are only the four carb fuel mixture screws for balancing, and obviously the idle throttle adjustment. Another question, the far right screw doesn't come out for cleaning. The other three do. It seems to just stop as its unscrewing. I managed to get the other three off and blasted them with carb cleaner. Anyway thanks for the help
The 4 screws only adjust the idle mixture. The manual setting is 2 turns out i think? but mine are 1 1/2 turns out from seated. They dont affect the balance at all, the only one that does is the single screw between the two banks of carbs On that topic I'd suggest using it to balance the carbs cause that very well could be the bulk of the issue. If its the sliders it should still run and idle okay, it'll just have no power and sound like its running on 3 cylinders or so if one drops out. Odd the last screw doesn't come out, cause it should. Perhaps the thread at the bottom of the brass needle has stripped or something.
Sounds like fuel starvation to me. Is the breather on the tank clear? Any rust or junk inside the tank? .... is the fuel "new" ? Fuel petcock working correctly?....any internal filters in the tank clogged up? Fuel filter been changed lately? All the fuel lines in good order and not kinked? Fuel pump doing its job? Pull off the main line to the carbs and see if fuel is flowing freely. ;D
these two lines just made the penny drop. For some reason I hadnt picked up on the fact that is how you balance the carbs. Pouring through the scanned workshop manual and other online sources just didnt make me realise that this is how to do it. For that i thank you! Also i'll definately be checking all of what greyimport has stated. Also thank you to ozbiker for links!! all good stuff ill keep you posted.
just to answer your questions - Im not sure where the breather on the tank is. Would it be the fuel cap? - I had a general look in the tank, doesnt seem to have any signs of rust. - The fuel petcock seems to work, albeit has a micro leak around the seal of the tap. (not dripping however) I wasnt aware there was any fuel filters in the tank. I will investigate. - Fuel lines seems to be in ok order, and the fuel pump ticks over a clicks when the carbs need fuel. I accidentally turned the key on while i had the fuel line off and it pissed fuel all over the shop, so i guess the fuel pump works The guy before me used vac hose for the fuel line, so I might change that over to proper fuel line. I also had to change the stator as the guy before left a bolt in the flywheel and chewed it to pieces. (Well theres ya charging problem!) Working on LED light replacement. Ive bought a Narva LED flasher, which doesnt seem to flash with the incadescent or LED lights (another work in progress). The Stock ones were smashed to pieces. anyhoo.. cheers again!
Dont own an across but the breather would be somewhere in the cap and surrounds.....a way to test is to open the cap after running the bike (or trying to start it) and see if theres a vacuum in the tank..... Previous owners do some wonderful things.....new fuel lines sure wont do any harm! Fuel gushing out is a good sign but it could be just whats in the lines etc from sitting and when u throttle up it cant get enough. This may sound silly but are the lines connected correctly? The Fizzer has 2 lines from tank to petcock.....and heres what it looks like inside to show the buildup of crap (there was a heap that fell out of the hole as well) ,the internal filters (long one has the mesh at the top ,thats not in the pic) and the setup that gives u reserve and normal on your petcock. As said I dont know the Across setup but it gives u some idea what to look for. If u remove it be careful as theres probably an "o ring" type seal there.
Last night I went home from work and tried a few things to get this pig to idle and rev from a cold start. I only have a 30 minute window of starting and revving the balls of it (or trying to) before I start pissing my neigbours off. I tried leaning out the slider pins to position 2. No change. Still does not and will not rev while the choke is on - even when its warmed up. Also tried slowly releasing choke, but this makes it die quickly. I tried richening up the pins, to position 4. No Chance. Will not rev. I then sprayed WD40 in the carbs while running on choke, and blipping the throttle.. this makes it come to life and i can then rev to redline when the engine is warm. It will then be able to idle while i adjust the idling richening screws and get it balanced by ear (for now) Its almost as if there is a vaccum problem, as in, when i spray wd40, its like it overcomes some sort of vac pressure, either from the tank or wherever, so that fuel can run up the main jets and be vaporised, carburettered properly. (this is my theory anyway) Tonight, ill try again by looking at the tank, fuel filters etc.. There is definately fuel going into the carbs, as i have a clear filter inline before the carbs. I can see fuel going through.. (there are a few bubbles every so often). Ive also, by accident left the petcock on the off position and tried running it. Can someone tell me if the hose at the bottom of the air box is crucial to proper running and performance, and where it goes? (i was to flustered to check). Also, if there is a blocked tank vent, or anything to do with a the tank, could that effect this thing to not idle or rev properly due to vaccum pressures in the tank? (Kind of like leaving the petcock to off so fuel cant flow but fuel is still present in the carb bowls?) I got it to the point that it was idling and revving ok and all the idling mixture screwes were out 2 turns from stop. Ill take a photo of the carb setup tonight and show you how its all connected.. It looks ok to me, but it may be wrong. Sorry for the long winded posts..
The factory setting for your mixture screws should be 1.5 turns out, see attached I had a really dodgy set of carbs that wouldnt rev until it was 2.5 turns out..... Might help to try 1/4 turn increments out from 1.5 and see if that helps. Chris
You didnt read my last post? :icon_scratch: You have a bike that sounds like its had a PO with dubious skills.....therefore u need to check the basics before u start the fine tuning. Its no use playing with the carb settings untill u know theres no problems with the fuel delivery...in other words ..the tank (breathing/vacuum,filters ,full of crap) ,lines,inline filter etc etc. Just because u see fuel running here and there means bugger all....it may slow down or stop after time for wateva reason (like when a vacuum forms in the tank) vacuum/breather test .... Run (or attempt to start ) as long as u can so its sucking fuel from the tank...then shut it off and open the fuel cap...if theres an air whooshing type sound then the breather is blocked...or alternatively start or run the bike with the cap open......if it goes like stink then the breather is blocked. :angel:
Greyimport.. yes I read what you said and I did the tests today after work. I checked for any sort of vaccuum in the tank and there was none. Took the cap off the tank once i had run it, and there was no suction noise from the tank cap. Also there is no breather hose or anything on that tank, only a tiny hole on the tank cap.. which i guess would equalise excess vaccum. Also checked out the petcock filters and they were ok.. some crap was there but nothing to worry about really. Cleaned it anyway. No kinks in the lines and everything seemed ok. I have come across outlets/ inlets on the carbs which i dont know what they do. I unplugged one of the m and the bike suddenly revved and idled! WTF are these ports on the side of the carb?? originally there is a vac hose connecting both carbs together. As soon as i unplugged it, the bike was able to idle, and rev ok. I can now start it from choke, rev it and decrease the choke without any drama. The service manual doesnt state what these are.. any ideas?
there is 2 vacume hoses that join the carbies together these hoses must be airtight from one side to the other, and about every 12 months or so you need to "ballance" them check this video by a member of this forum Balancing Carburettors with home made manometer
The balance ports are further foward on the carbs, and from the tubing in the pic they're all connected Those are the fuel bowl vent ports. It lets the pressure equalise in the fuel bowls otherwise there will be a vacuum in there preventing fuel from flowing into it, which would indeed give you the problems you've been having if they are blocked or connected together! Take a look on page 183 of the service manual or section 8-12 and it shows you how the pipes connect up. They run down to the bottom of the bike with a couple of other ones. Mine don't even have the tubing on there anymore Should probably hook them back up one day! For the record the tank does have a breather hose, its on the left hand side of the filler neck if you are standing at the back of the bike looking foward. It runs under the left side rear fairing. Good work anyway brah
Desmo. I stand corrected on the breather! cheers for that! Indeed they are fuel bowl vent holes! Weird that they were originally connected together. I guess all the info was there in the manual. Was my fault for not being diligent enough. Thanks again to this forum. Everyone is very patient and willing to help. Anyway im happy that its nearly done and ready for the pits. I should be riding it in no time.
yes that's what it was! it was staring at me in the face. I've just finished putting led replacement indicators on just then. I can confirm that the narva led 2 pin flasher t also works. It does require a resistor on at least one left and right indicator, otherwise all 4 flash at once. all I have now is the chain guard and fairings bolts to source, and to put on. then it's off to the pits!
