Sputtering certain throttle spots.

My bike runs pretty well right now. but when im hitting the highway or just full throttling it there are spots where it starts sputtering (sounds differnt). this happens alot when im on the highway at about 5.5k rpm and i open the throttle hard. and i sort of lose acceleration at that sputtering point.

the thing is i can blow past it by just opening the throttle more. then it zooms on just like normal. being pretty knew im just going to guess that at a certain throttle open spot its giving it too much air in the mix. or something similar to that or a carb issue (or is that pretty much the same thing) well i thought id ask here before i take it in to the shop (where they quoted me 100 dollars a carb!!!!!) any advice would be appreciated.

 

How do the rubber boots that attach the carbs to the engine block (carb holders). Cracked?

Other than that, it does sound like a dirty carb. Gummed up main jet, float valve cranky, dried out float bowl gasket.

 

ill go check the rubber boots. ive been using seafoam to hopefully clear it up and it actually has gotten better. but its still there so im hoping to figure a way to do it myself without having to fork out a ton of money

 

You have to tune that puppy. Carb screws might be to open or to closed. Ask Rick, but that sounds like bike is running to rich. Don't clean the carbs just yet...

 

They might be good and the shop won't mind charging you a lot of money for doing NOTHING. First make sure that's the issue

 

Have a look at your spark plugs to give an idea where the problem might lie.

If the bike did not come right after that rrev range I would say plugs/coils, but since it does and seafoam helps...

Have a look at Rick's carb cleaning guide in the suggested FAQ section, it sounds like the carbs are dirty and would suggest that the emulsion tubes might be blocked or maybe a float is not set right. You can do the work yourself with a few basic tools. Main thing to remember is every thing must be "white room" clean.

Bench sync the carbs before you replace them on the bike.

Make sure there are no air leaks.

 

I get the same thing when my bike gets wet. Like when I ride in the rain or if I just washed it. I washed my bike yesterday and had a hell of a time starting her. After about 10 minutes of cranking, i just let her site for an hour or so and when I came back, she finally fired up but coughed and sputtered when I gave her gas. After a few turns around the block it was better and would idle so I went for a longer ride and had the same thing you described. After a few miles on the expressway she was good and hot and running ok, but still had trouble when I gave her that gas.

I was nervous this morning when I left for work, but she fired right up and had no problems on the daily commute.

The point I'm making is that this could be a spark problem, maybe with the coils (I've read the stock coils are weak) or maybe the plugs or the wires. Check all the plug boots and make sure they are well seated to the plugs.

 

Since you don't mention anything about stalling-out or Backfiring ... it's a "Thumb Rule Guess" that you are running ~~> Just a Tiny Bit RICH!

Plug Read will show you a Deep Dark Brown almost approaching sootiness.

Turn IN the Pilot Mixture Screws.

About the with of a DIME.
Road Test.
See what the adjustment did.
Gone? Done.
Better? Add another Dime width IN.
Test.

Remember how much you Tweak ... It could get worse ... and then, you have to go Back 20-cents and add a Dime the other way!

 

I've had a bad coil, the thing is it did NOT come right after the 5K rpm and the problem was always there (dry or wet). A bad plug (had one of them too!) gives similar symptoms but most likely the bike will only run on 3 at all rev ranges.

When you wet the coils and then the symptoms appear that points to electrical (crack in coil body, tracking from bad lead, plug cap). This can be fixed by coating the coils with Liquid Insulation Tape (very handy stuff) and/or surgery on the coils to replace the wires as net time you get caught in the rain the bike is going to start missing again.
Check this fix out:
Coil Problems in the wet

Always a good idea to check the plugs!

 

i think maybe i did forget to mention that when im revved high. (like downshifted to begin to stop at a stop sign) that i hear popping sounds sometimes. not loud but just little pops. do you think this is linked to my sputtering when i open the throttle about halfway?

im really new to all this so alot of things people give as advice seems way over my head.

what does plug read mean? take out the spark plugs and look at them?

running a tiny bit rich? this means im getting too much air in the mixture right?

i dont even know where the pilot mixtrue screws are. i think i need to order that haynes manual now.

 

You absolutely need to invest in the Manual.

Given your explanation ... it's not a stretch to think you might have some Tight Valves.

If that's the case. THAT is what you need to get on top of ... first!
The Manual walks you through the process of measuring your valve clearances with a nice straight-forward explanation and photos and illustrations.

Read the section on Checking Valve Clearances and see if you think you can do that!

 

Yes it can be hard to understand these things. Most of us who tinker have been doing so for years (decades in some cases). We try to help but sometimes can only guess. Alot of the time it helps to have a known good test part as it is the best way to rule out a problem (coils, ignition, computer). There are posts in the forums that can give you an idea of what can be wrong (serch forums link on left) and also Google to look up terms and examples (wikipedia is great for this).

A manual is also a very good investment to get a understanding of how things work and the settings they need and test procedures.

There are also books on how to work on motorcycles and other engines, Amazon.com bookstores are worth a visit.

Popping like that = Lean backfire can be caused by lean mix OR bad ignition. With other symtoms = ignition. You have the same symtoms I had, mine was bad coil wire, yours could be that or bad coil or plug (or other electrical, but these are easy to check). Yes take spark plugs out and look at them. Have a look here which number are your plugs?

Rich is too little air.

Manual will not tell you about pilot adjustment, only not to.

You need a colortune or CO analyser to adjust mixture. You also need a manometer (home made check suggested faq $5 sync) and a YICS tool.

 

Another get product for waterproofing, is a "paint on liquid" used on hockey skates to save the toe-cap from excessive wear. It's black, applies with a brush and makes a great waterproof seal. You can probably get it at a sporting good store .... I know, for those of you living south ... "whats hockey".