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Discussion in 'Yamaha 250cc In-Line 4's' started by Yetiburger, Oct 7, 2017.
Inox Plus, MX5 penetrate's and contain's Teflon to help keep thing's smooth
For really rusty bits I use a wurth product called 'Rostoff'.
So I bought some new carbs. they are 3ln1 carbs. I checked the needles and they looked good so I slapped em on and started it up. seemed to run ok but the exup valve may need a look at as it was making a bit of noise. I already have the kits so I'll just rebuild the carbs anyway. they are pretty filthy. does anyone have a good technique to clean them up then i'll soak them in WD40 for a week before i pull them apart.
I have a video of it running but it says the file is too large to upload.
Upload it to youtube then 'share' it (with the youtube share link) using the 'media' button in the 'post reply' box on here
Try and find some Threebond Super Engine Conditioner (petrol engine) for the carby's
Upload the video to Youtube and then link it back here
if the carbs are good then leave them alone, no point in changing things for the sake of it. from what ive read about the keystar kits is that they are inferior to the genuine yamaha stuff so if your needles, jets float needles etc are good then leave them be. just my opinion, someone may come along and differ.
ok so here is the video
Also the bike seemed to have quite a bit of trouble starting and going back to idle. just thought a thorough clean out and revamp would make them perform smoother. Is that three bond engine conditioner for cleaning my67xr?
Ok so finally got around to pulling my new 3ln1 carbs apart. Wow what a difference got the tubes out with only my thumb.I have put all the carbs in a mix of petrol and degreaser to soak for a few days. I can't seem to find anybody who will put them in their ultrasonic cleaner so I think I will have to buy my own.
They look much better inside,
Look's like the jet housing rubber's were shrunk a little, you can see a black witness mark where they were leaking on the carby base.
And those round alloy plug's in each carby just above each mixture screw, inside the bowl, need to come out too
There's 3 tiny fuel port's for the pilot jet's underneath that cap that can easily block up giving you a hesitation off idle
Gently pry them out with a flat head screwdriver, work your way around evenly on the outer lip so it come's out almost square to the carby
That mark may have been a smudge from my fat fingers but i've got a kit from litetek to replace them. Cheers for that I got the alloy plug out fairly easily. Is there any other bits that trip people up? I took the brass jet out from the front but there seems to be another bit in the other recess and a couple of bits in the jet housing do I need to take these out? Also I got them a lot cleaner than they were with the petrol and degreaser but there is still some grim on them. Will that threebond cleaner do a better job? and dose anybody know where to get it in NZ?
Also there was a lot of black marking around the butterfly on the inside of the carb throat. what would this be from? and can I just polish it out with some polish and a rag? I tried to get a photo but might have to wait till tomorrow.
When rebuilding make sure theres an o ring here
Repco NZ should sell the Threebond, look's like there are a few in your area.
They usually keep it behind the counter so you may need to ask for it.
Don't soak any rubber part's in it, it will make them expand
The black after the butterfly is from the idle being set too high, usually trying to compensate for running too rich (worn emulsion tube's and needle's) Threebond on a rag will help get it off
The pressed in air jet in the intake side can stay there, no need to remove it, same with the other brass restriction's in the jet block.
When you refit the float's make sure you use some silicon oil/grease on the o'ring's to help them seat properly.
Float height's should be checked and set at 16mm for the 3LN1 carby's, this will give you a fuel level of 9.2mm above the line on the outside of the fuel bowl.
There's a picture of how to make a float height tool with an old playing card or some plastic icecream container etc
To check the fuel level use a piece of clear hose from the fuel bowl drain and run it up past the top of the fuel bowl, then turn the ignition on and prime the system (can take a few goes on/off to fill the bowl's, when the bowl's are full the pump wont prime or will just tick once or twice when the ignition is turned on)
Now loosen the drain screw and fuel will flow up the hose and you can compare the height with the line on the bowl (should be 9.2mm above the line)
While they are apart check the hole in the emulsion tube for any oval-ing and check the needle for any wear
ohk awesome. yeah the needles looked good but I've got the keyster kits so will replace them and put the old parts in storage. Dose anybody have a rough idea of how long a new set of needles and tubes will last in these carbs? How do you actually adjust the float height if it is incorrect?
also does anybody know where to source the rubber boots from the carbs to the airbox? mine must of done some serious shrinking.