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Post by prodigit on Jun 1, 2013 3:19:35 GMT -5
Hi,
I am experiencing what I believe is an extremely lean condition on my motorcycle.
Super impossible hard starts, does not run without choke halfway open, does not start in open air, does not start well with regular gasoline.
And so on...
So let's presume that it's running way too lean.
Is there something that I can do, like locating and changing the A/F screw; without re-jetting? (problem is, I think I see and can adjust the AF screw, but I can't take out the carburetor, because it will be too much work).
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Post by gitsum on Jun 1, 2013 11:02:10 GMT -5
check for a vacuum or air leak
change the air filter, fuel filter and spark plug.
thoroughly clean the carb and check the float level (this will require removal)
adjust the valve clearances
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Post by oldbikerider on Jun 1, 2013 12:25:20 GMT -5
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Post by prodigit on Jun 2, 2013 15:42:30 GMT -5
I'm basically asking how to adjust the AF ratio, when taking the carb out is impossible (or extremely difficult). Even reaching the air filter is difficult. As far as air leaks, there are none. The air filter is mounted straight on the carb, the hoses are all new, and well connected.
I'd also want to know if the jets are too small (running too lean), if I can compensate that with the A/F screw, or is it necessary to have bigger jets installed?
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Use the force, if it breaks,it nedded to be fixed anyway!
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Post by Tripper on Jun 2, 2013 16:31:54 GMT -5
If your jets are small, you can twist the A/F screw till your blue in the face, won't change the size of the jet.
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Post by buford1488 on Jun 2, 2013 16:35:19 GMT -5
lower the clip on your needle...........
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Post by oldbikerider on Jun 2, 2013 17:50:00 GMT -5
The carb may not even have a pilot jet installed,you need to pull it out of the bike and open it up or get another carb under warranty.
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Post by prodigit on Jun 2, 2013 22:24:46 GMT -5
It has a choke, I don't know if it has a pilot jet installed or not.
All I know is that at WOT the engine does not seem to suffer as much as at idle.
If the jets are too small (running lean), my hope is to adjust the AF so I can get a working fuel mixture, albeit lower in performance.
At this moment in time, I can't get the carb out. Not without a manual, or at least 10 hours of wrenching, which I don't have.
For that reason I need someone to verify where the AF screw is, and if it would make a difference to adjust it (if it would be possible to get a right mixture, despite running too small jets)?
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Post by carasdad on Jun 3, 2013 9:04:25 GMT -5
Which Mikuni model is it? My Suzuki RM250 has a Mikuni..and it seems bullet and fool proof. i.e. seems no matter how I adjust it...it will run...not always the greatest...but at least runs. Once dialed in..it never needs adjustment. Just a good cleaning occasionally as no matter how well the air or fuel filter filter..it still gets crud inside of it. If I had the money right now..my Chinese 2T scoot would have one now. They are more user friendly than these.. &^%$#@( China made TK carbs.. Btw..I live at sea level if that helps any...can go check my jet sizes...but it is a 250 and not sure what displacement your motorcycle is..
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Post by prodigit on Jun 3, 2013 16:43:17 GMT -5
I have a 125 (127cc actually).
Mine doesn't run at all, probably because they put another head on the engine (few cc's higher), and didn't re-jet. Probably set up well for the himalayas, but not sea level.
Mine is chinese I believe, not original Mikuni. Either original, or a clone; don't know. Mine is also 4 stroke, not 2 stroke.
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Post by alleyoop on Jun 3, 2013 16:52:32 GMT -5
You are going to have to bite the bullet and take the LEFT side cover by the side of the carb so you can get at it. It is not going to fix itself, if its to much work for you then take it to a shop and but be prepared to take a hit on hours of labor.
And yes it should have a Fuel Ratio Mixture on the carb and I am sure it is set really lean to pass emissions. So figure out how to take one of the side covers off to open some of it up by the carb area.
Alleyoop
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Post by prodigit on Jun 3, 2013 20:42:43 GMT -5
Taking one of the panels off is not an option.
I'd have to demount the front and top first, then the sides, and even if I do that, the frame would still be in the way.
There's a small hole in the panels for a screw driver to adjust the idle.
From that hole I might be able to drill out the rivet right next to it, which I believe is the AF screw, if I have a long drill. But I was kind of hoping someone had experience with the carburetor, and could tell me for sure if behind the rivet is the right screw or not.
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Post by prodigit on Jun 4, 2013 17:37:06 GMT -5
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Post by prodigit on Jun 6, 2013 3:55:52 GMT -5
Alright!
Through some magic plastic bending (to the limit), tiny wrenches <3" in length, one eye vision (and even that was cut off, so 80% I was working blind), and some ripping, I was able to remove and remount the carburetor.
The rivet was not a rivet, but a plate,
I drilled through it, and found the AF screw.
Adjusted it 1,5 turns open, and will get some gasoline tomorrow to test.
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Post by prodigit on Jun 6, 2013 16:14:18 GMT -5
Alright, my impressions where correct. Behind the silver cap, on the left of the idle screw is the AF screw. It needed 1 to 1,5 turn tight, for the bike to run. So far it's running great, because of rain I can't testdrive it though!  |
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..BAD TO THE BONE..