lurching at high speed

hello guys and gals.
i have a 86 700 which seems to run fine at 2k-5k 0-60 mph but after that it seems to lurch even cut off once at about 75mph.
i just recently cleaned the carbs and checked/reset valve clearance. however i did not use any rebuild kit on carbs just a cleaning.
i'm assuming as the bike goes faster there is more air flow over the carbs which makes some sort of air leak worse.
i'm going to go ahead and order at least a gasket set for carbs and try that first. will keep updated on results.
is ther any other problem or issue i should also check.
thanks for any help.

 

What is the history behind this bike? New to you or a new problem?

 

Is the problem based on engine speed or road speed? IOW, is it exactly the same symptoms in 4th gear as it is in 6th?

 

And in line with hawkrider's question, mine did the same thing, and it was excessive vacuum on the float bowl vent lines due to routing them to the airbox's clean side after arguing with the (broken) emissions equipment. As the engine revs picked up, the vacuum due to the loss through the air filter would cause fuel starvation as it changed the ratio of air in the bowls to the pressure of the air rushing under the sliders.

 

Surging/lurching is a lean condition. Check your manifold boots for tightness. If original they most likely need to be replaced. About $10 a piece.

 

thanks for replies. i did check manifold boots for tightness they were loose. i tighten them and that did seem to help but not elimanate problem.
history of the bike. i bought this bike a couple of years ago out of some guys junkyard. cleaned carbs then rode all summer pretty good.
then let sit up winter next summer cleaned carbs and noticed problem at about 100mph not sure engine speed.
i attributed poor handling to leaking fork oil and just kept bike under 100mp.
this year rebuilt forks with honda parts cleaned carbs again but just not doing great.
i don't believe problem is the same in 4th gear as it is in 5th or 6th gear which does concern me. however i'm sire i need to get carbs straight
before i check any other problems. i hope i am communicating this well but already this conversation is a little over my head. thanks again

 

The problem I was referring to would happen in every gear, so it sounds like that's not it. My bike was stumbling massively when the cams woke up at 6-7K rpm (in any gear) when I was having the issue I mentioned. Good luck, and double-check that the pilot jets are clean, that there aren't any vacuum leaks, and that they're well synced.

 

yup, definitely sounds like a vacuum problem. Double check all your lines and proper routing. Check float bowl levels to within spec. Cam timing or valve adjustment could possibly create that high speed surge, but you'd probably notice other symptoms as well. But start with the routing and check for leaks in the vacuum lines.

 

o.k. i ordered new manifold boots two have a tear in them. all four are $55.00 from local honda dealer.
here's the problem, a couple of the o-rings that go in between the carbs are also torn and the big ones on top just look worn out.
when i went into the local honda dealer to order the replacement kit i thought the kit for all four was $41.00. not $41.00 a carb.
the current economy has found myself to be minus one day a week of work for more tthan a year, that adds up after a year.
i just don't have the extra money so i ordered the manifold boots which have to come from honda and i am going to try and piece together the other.
does anybody have any experiance with that? i'll try to give an update this weekend maybe i'll have all the stuff by then.
also woody 77 i kind of didn't understand what you were saying because i think there is something missing from the airbox.
is that what that hole is on top of the airbox to route some sort of air line back to the carbs if so i'll have to come up with something.
thanks again and hope to be riding soon.

 

johnny, I don't think what I was referring to applies to your situation (mine stumbled in any gear)

 

Possible fuel filter?