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?? for the carb gurus

  • Thread starter Thread starter Clone
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C

Clone

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My :oops: Yamaha :oops: :
1. hard to start, the choke doesn't help worth a damn :x
2. will not idle until hot, then idles really fast 8O
3. if I turn down the idle it dies :?
4. if I don't turn off the gas it all ends up in my crankcase :evil:
5. if I do use the choke once it is started the bike doesn't run faster it dies cold or hot. :?
It is a single cylinder with a single Mikuni carb, unfortunately I can't find the model of the carb. :oops:
Anyone in the know have some info for me? :? :?
 
When was the last time the carb had been re-worked?? Sounds like it needs an overhaul 8)
 
To my knowledge never. :oops: I haven't been able to get the model number. Because of a language barrier, my Chinese sucks, and their English is non-existent. :? I only get offered a new carb evertime I go to the repair shop. 8O (expensive) 8O I want to know if on the body of the carb it says a model number (where?) and then what specifically is wrong with the carb so i can hunt down specific parts on the web. Thanks 8)
 
what about looking like at dennis kirk online. www.denniskirk.com you can put in the year and model and the rebuild kits that fit it will pop up. check it out and see. this is where i got mine
 
Sounds to me like since your petcock is leaking fuel into the crankcase when not shut-off, that maybe you are flooding the engine due to the floats being overrun with fuel? i would check there first. The other place, if that checks ok, would be the pilot Jet area, as that controls idle/low speed operation.
 
The petcock work fine. I have been thinking about the float having sunk, but now I have been directed to the problem most likely being the needle valve the float operates. If this is worn out by vibration is it possible to replace the seat and needle? I still can't find the model on the stinkin' carb. I looked on Dennis Kirk and Bike Bandit for my bike model but it is not listed. I want to see if I can score a float, needle valve, and gasket kit somewhere. Rather than 8O 8O buying a new one 8O 8O "How much did you say?" :roll:
Naw, I always turn off the gas at the petcock when i stop. except the odd time i forget, then I change the oil.
 
Clone said:
I still can't find the model on the stinkin' carb. .
Click to expand...

if you try on ggogle with mikuni and carb, you'll find a lot of sites with sheme of the mikuni carbs

V++
rackham
 
Pull your carb off and pull the bowl. Put the float in a liquid (water is ok), and see if it floats. Shake it and listen for liquid in the float. If it sinks, there's your problem. Check the rubber tip(may be steel too) on the float valve. If there is a ridge or groove in it, it's junk. Is this a vacuum operated petcock? Pull the vacuum line from the carb and suck on it. If you get a mouthful of gas(yuck), the diaphragm is junk. After cleaning all of the orifices and jets out with carb cleaner, put the carb back on and check the height of gas in the bowl. Should be just under the bowl to carb mating surface. What model Yamaha is this, SR250? Bob
 
the bike is a SR 150. The petcock is not vacuum operated. i will pull the float. if there is a ridge in the needle can i refresh it with some valve grinding compound? to remate the seat and the needle? if the float has some gas in it is there any way of getting it out, ex drill a tiny hole and then put a small screw in after?
 
If it has fuel in it you need to find where it's getting in. Usually they leak around a seam whether it's plastic or metal. Leave it sitting in the sun for a day or two should dry it out. Then dab a little epoxy or the like around the seam. VERY LITTLE! as this will weigh the float down and you don't want that. I've heard of guys lapping in seats but i don't know how they did it as the valve is so tiny. When contacting the seat, the valve is usually flush with the outside of the seat so you can't hold it with your fingers. From the sounds of things, I'd pull the jets and give them a good spraying of carb cleaner first, then try it. Just a little piece of junk in the passageways can have terrible consequences. You don't have to ask me (or anybody else) how I know, just look at the most questioned topic on any motorcycle forum on the WWW. Let us know how you make out.
What year is this SR150 and I'd be happy to call my local Yammi dealer for you to ask about a rebuild kit. Bob
P.S. Make sure the spring is working in the float valve while you're in there cleaning. Don't know if this is a straight slide or a CV carb but all Mikuni's are pretty much the same as to where their jets and needles are located, they just change the sizes of venturi and jets for different applications.
 
Pulled it apart. And there is no model number or serial number on the thing. Found 0r actually didn't find my air filter, it has disintegrated over the last little while. cleaned out the float bowl, it was full of red dust, kind of like the dye we used to use in farm feul. the float floats :lol: , so i reset the height, the needle is a neoprene affair and looked good on inspection. I blew out the overflow tube to make sure the bastard would drain. blew out all the passages, i could not get the small jet out beside the main jet on the bottom of the carb, it looked like it had been cross threaded and then the tabs stripped off when the person tried to remove it. the top diaphram had a small hole in it, so i fixed it. Now according to my carb diagram, on the exit side there is an adjustment screw on top, mixture (?), bypass (?), when i removed it there didn't seem to be the correct number of parts. I took out three, and my diagram shows five. The missing two look like spacers or washers, not sure. And there is a vacuum port that the hose doesn't connect to anything :?? What the hell is that? 8O I have never seen a vacuum hose that doesn't go to something. And i scoured the bike looking for a place to hook it up. Replaced the sediment bowl filter and started it up. Now it will start with the choke and it will idle but the idle is still weird :? , it sits low for a while then speeds up for a while then slows down again :?: So for the time being I am a happy camper.

When you guys replace the stock filter with a k&n pod, where do you connect the crankcase breather hose?
 
I don't have a diagram of the carb but usually you have the mixture screw, spring, flat steel washer, and o-ring. This screw is your idle mixture. If it's on the engine side of the carb, out richens, in leans. Is the vacuum hose plugged? A surging is usually a vacuum leak. Possibly around the intake boot, the bowl gasket or that vacuum hose. Shoot some WD-40 or carb cleaner around these areas and listen for changes in RPM. Did you set the float when you put it back in? How does it run through the RPM range and what color is your plug at idle? I've never put pods on anything but most that do use a small pod filter for the crank vent as well. Bob
 
Went there tried that, could not find what i needed. I was thinking to drill a hole in the pod and put the hose in there. No the vacuum hose is not plugged. I think i will have to see if i can put a filter on the end. It actually runs pretty good now. just have to get the mixture set to pass emissions.
 
If the hose off the carb is a vacuum hose (one that usually operates a petcock), it needs to be plugged. That may smooth your idle out. I wouldn't put that crank vent into the pod just because of the pain in the @ss to seal it. I suppose you could run a bead of silicone around it. I forgot about the setting float comment in your previous post, DUH!! I'm like that at times, Mind like a steel trap, nothing in, nothing out. :lol: Bob
 
Prevoiusly you mentioned that the air filter had disintergrated, have you replaced it?
without the filter element, it will run a little lean and this could explane the surge at idle.
 
yep. replaced it. I am really eyeballing that vacuum hose as the real problem here. i routed it to the airbox and it idled fine but then driving at mid rpms was incredibly shitty, backfires and missing, dammit, no power :D , so i pulled it out and just hung it there , ran ok, idles ok, still no power. So I am going to plug the b'tard and drive around a bit to see what happens.
 
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