Starts, Idles, and revs but not high revs?

[barrycoish]

Last week took the bike out for a ride and it started causing a few problems. It starts no problem, it runs but I can't get it to rev up like it should it revs like it's at about half throttle and that is it. Thought the carb might have dirt in it but no luck. Took the carb off and checked it out but all looks good. It's one of my 84 200x's by the way incase anybody thinks that matters. Any help would be great.

[smokinp]

give us some more info...what does the spark plug look like?is it smoking or anything?does it have compression,fuel and spark?

[barrycoish]

Thanx John I will check that out when I get home. The plug looks fine, has spark, compression and fire the bike runs but not right. Like I said starts fine, idles fine, runs at low rpms but will not rev up properly.

[smokinp]

try removing the exhaust and see what it does..

[atckowalski]

If you have a fuel filter, it may be clogged.

[wilb67]

Make sure your air filter isn't clogged up with dirt. Coil could be bad. Check timing and your valve clearence.

[barrycoish]

checked fuel filter, no problems found. Took exhaust off still no good. I am going to check the timing and valves tonight, not sure what else to do?

[cliff2302]

I had the same problem with my tecate and after over a month, we finally checked the stator and it was shot. i guess when stators go, they don't usually go away all at once. hope this helps.

[fat batster]

I sure wish that someone would let us know how to fix this problem. I have the exact same problem with my 1986 Big Red 250es. The problem comes and goes. I have tried different carbs, cdi boxes, spark plugs, spark plug caps, rebuilt the engine complete with valve job, new muffler, new timing chain, new fuel tank and petcock and I STILL have this problem. I am lost. The only other thing that I can think of is the pick up coil that is down by the stator. Anyone have any ideas?

[oscarmayer]

tuning?
it sounds like the tune is way off! i bet your runnign lean at the big end. when you are in liek 3rd gear and are at wide open throttle you should have some(jsut a little) black/gray (not blue) smoke comming out the exhaust.

here's what you need to do. use the old plug to let it idle up to warm oeprating temps and when it's very warm, then shut it off and change to a new plug.
take it and rip on it a few times then shut it down and pull the plug. see what it looks like and smells like. if shoudl be a nice carmel color (not a lot but a little but) and smell of burnt fuel. if it's black it's too rich, if it's not colored at all or has a whitish/yellowish coloring it's too lean.

too rich or too lean means re-jetting.

[fat batster]

Thanks for the reply.

I know that it is not the jetting. If it were the jetting it would run bad all the time. The bike will run great for hours and then I might shut it off for a few minutes. Once I start it back up it may or may not run good, its a crap shoot. Sometimes it switches between running good and bad without me shutting it off at all. It is very hard to explain. When it is running poorly, it acts like it is running lean however there is absolutley zero popping or backfiring. If you have ever driven an older car that has a mechanical advance mechanism that is stuck then that is what it feels like. It revs out but it does so slower than normal and with little power. If I upshift to the next gear then it is fine in the low to mid rpm range but once I try to increase the revs it starts struggling again. I am about to pull my hair out.............

[oscarmayer]

hrrm could be an overheating cdi or coil? i knwo on the old carbed hotrods we had issues with heat and fuel vaporization before it hit the intake. we had to put heat hose aroudn the fuel lines to kepe them cool so the fuel woudl not vaprize before getting to the carb from heat. (heatsoaked) i also seen old coils overheat and have issues too.

[beets442]

Sounds like main jet clogged or floats are sticking.
Ran good before this though?

[fat batster]

It still does run fine sometimes and sometimes it doesn't. I agree that it sounds like a float issue and/or a clogged main jet. I keep coming back to that conclusion over and over again but I have cleaned and tested the carb multiple times and it is spotless. I have a new theory that I hope someone can talk me out of. I am wondering if it is a slightly bent or burned intake or exhaust valve. If the valves in these engines rotate during engine operation then it could stand to reason that at some points along the rotation, the valve doesn't seat fully. This would cause a poor vacuum signal through the carburetor which would act just like a lean condition which would cause low power. If this were the case then the valve would eventually rotate around and begin sealing properly again and my power would be restored. If this were the case you would think that I would hear some popping in the intake or exhaust though. Please, everyone rack your brains with this one.........

[PaTriker]

Sounds like a fuel problem.