as the title says my bike is cutting out around half throttle n further. im guessin its my carbs? i think i need new diaphragms b/c it doesnt have top speed like it should n has cut out around 7k in all gears. other than the top end cutting out it has usually ran fine, cept today its been actin all crazy. some help would be awesome
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xs cutting in and out at half throttle and beyond!
- Thread starter smk2mch
- Start date
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- Tags
- carburetors
littlebill31
Smells of Raw Fuel
That would most likely be the jet needle, 1/8 to 3/4. From 3/4 to full is the main jet. Read http://www.amckayltd.com/carbguide.pdf
http://www.iwt.com.au/mikunicarb.htm
It'll help ya.
To check the diaphrams you will want to, from the air filter side, lift the slide valve up, cover the top port, (picture 7 in the carbs guide)and release the slide. It should fall slowly. If it falls fast it probably has a leak. A good cleaning does a lot as well. make sure you always adjust the cam chain tensioner, valve lash, timing, then carbs in that order. Notice the carbs are 4th in line.
http://www.iwt.com.au/mikunicarb.htm
It'll help ya.
To check the diaphrams you will want to, from the air filter side, lift the slide valve up, cover the top port, (picture 7 in the carbs guide)and release the slide. It should fall slowly. If it falls fast it probably has a leak. A good cleaning does a lot as well. make sure you always adjust the cam chain tensioner, valve lash, timing, then carbs in that order. Notice the carbs are 4th in line.
littlebill31
Smells of Raw Fuel
You said it was running fine and always had the upper end lag? Then today there was more than just the lag? Sometimes not fixing a problem, such as lag at the top end, for a period of time can cause additional problems.
Couple questions: What year bike? Mods? Last time you ran it? Did it sit for a month or more then started up again? Last time the carbs were cleaned, and I mean stripped and cleaned?
The smallest piece of junk or varnish from old gas can cause a bunch of problems.
Couple questions: What year bike? Mods? Last time you ran it? Did it sit for a month or more then started up again? Last time the carbs were cleaned, and I mean stripped and cleaned?
The smallest piece of junk or varnish from old gas can cause a bunch of problems.
yea it was extra laggy..its a 79 special with pipes cut under the mid controls, with cone filters jets drilled last year when it was cleaned. i didnt run it from september of last yr until a few weeks ago, ran fine then last week i fouled the plugs out and replaced them. yesterday and first thing this mornin it ran good. 2nd time i started it 2day is when i had the probs.
littlebill31
Smells of Raw Fuel
I suggest giving the carbs a good cleaning per the carb guide. http://www.amckayltd.com/carbguide.pdf
It never hurts, only helps. The old gas will varnish the insides. After a bid of running these pieces break up and find their way into the little ports, clogging them.
If you left gas in the tank, clean that out as well. Ya, you might waste 10 bucks with new gas, but it's worth it.
Always listen to your plugs. Do they read lean? Rich? Were they gapped correctly? What happened when the plugs fouled? Did you change anything? What is the mix screw set at? Are the carbs synched? Idle screw setting? Lots of stuff to check. One adjustment missed can cause a problem.
With cut pipes and cone or pod filters, the jets, as you probably know, need to be changed. Were the jets that were drilled stock then drilled? I would just buy new jets. I really got tired of screwing around and bought several new jets, read the carb guide front to back then sideways, and did a little "trial and error" testing. Runs great now.
If it sat since Sept I really suggest a good clean and adjust. Oil changed, cam tensioner, valves, timing, carb cleaning. Even if it was only run a few miles last season, change and adjust.
These are some suggestions that need NOT be over looked. The XS will complain if it is not maintained.
Also, put some info about your bike in you "signature". It helps others help you. Read the carb guide, believe me, eveyone will tell you this.
It never hurts, only helps. The old gas will varnish the insides. After a bid of running these pieces break up and find their way into the little ports, clogging them.
If you left gas in the tank, clean that out as well. Ya, you might waste 10 bucks with new gas, but it's worth it.
Always listen to your plugs. Do they read lean? Rich? Were they gapped correctly? What happened when the plugs fouled? Did you change anything? What is the mix screw set at? Are the carbs synched? Idle screw setting? Lots of stuff to check. One adjustment missed can cause a problem.
With cut pipes and cone or pod filters, the jets, as you probably know, need to be changed. Were the jets that were drilled stock then drilled? I would just buy new jets. I really got tired of screwing around and bought several new jets, read the carb guide front to back then sideways, and did a little "trial and error" testing. Runs great now.
If it sat since Sept I really suggest a good clean and adjust. Oil changed, cam tensioner, valves, timing, carb cleaning. Even if it was only run a few miles last season, change and adjust.
These are some suggestions that need NOT be over looked. The XS will complain if it is not maintained.
Also, put some info about your bike in you "signature". It helps others help you. Read the carb guide, believe me, eveyone will tell you this.
pamcopete
Ride.Enjoy.Life is Simple
smk2mch,
Could also be that your spark advance is not advancing, which would start to show around 3,000 RPM and above. Check your timing for full advance at 3,000 RPM.
Could also be that your spark advance is not advancing, which would start to show around 3,000 RPM and above. Check your timing for full advance at 3,000 RPM.
Right, Pete--ignition first. And how many times does it have to be said? Never, ever touch a carburetor before inspecting the ignition, and that means checking cam chain tension first. If you have points, inspect for corrosion, pitting, and contamination, polish and clean with solvent if necessary, and check timing and function with a strobe.Then check valve lash and compression. After you've eliminated those items as sources of grief, forget that throttle-range stuff; you're dealing with jetting that was working for you. In addition to diaphragms, you could be looking at jets that have loosened up, leaking floats, dropped needle clips, and so on--look for the obvious first.
littlebill31
Smells of Raw Fuel
Check the "tech" section under General Maintenance.
Get a manual and stop expecting people to hold your hand--oh, yeah, lol.
You can get a manual lots of places. There are even free down loads. biker.net is one. I like a Yamaha Factory Manual. In the original book version, not on a cd. You can find them on Ebay. Money well spent.
