Topic: Im perplexed, what's next

[redschwa]

Well since I bought my bike I've had problems in the top end of speed.  The accleration is good and it warms up pretty quickly. The problem is when i get into high RPM's (5000 or more) the bike hits a brick wall. It happens in any gear and limits the top speed to around 65MPH. I'm usually hitting 5000 around 3/4 throttle and if I add more throttle it sounds like its choking on too much gas. I just recently finished cleaning my carbs to fix the problem. I found several missing parts and replaced them. I bench synced the carbs.

[scunny]

try a little choke and see if this helps, this will show it's running lean. if that doesn't work remove your airbox cover and see if this helps.

[fmctm1sw]

As noted above, my air filter was clogged.  And it did exactly what your bike is doing...

[redschwa]

I just cleaned my airbox and the airfilter only has twenty or so miles on it. I'm going to try the choke thing. Any other ideas?

[fmctm1sw]

Try the choke.  I guess you have to assume it's fuel starved or flooded...  one of the two.

[redschwa]

Well i got out thier tonight and tried the choke. I got the bike up to the speed where it stops going anymore and when i applied the choke the engine sputtered and the speed dropped immediately. So with the choke on the bike runs even worse. Unfortunately while I was out my bike completely died and wouldn't start unless i gave it a ton of gas and then it would only run around 4000rpm or more. I did this for about a mile then It would run at all without choke and the RPM aroun 4k but it only ran for a few seconds like this. I adjusted the carbs for a richer mixture and this didn't work I tried upping the idle and lowering, nothing. I also tried the inverse or that. I'm not sure what's wrong but I think I'm caving and just going to the shop. I'm missing too much good summer riding.

[d_soles]

Oh, don't cave and get fleeced by a shop!!  What's the fun of having one of these old bikes if you can't even learn how to tune the air/fuel mixture correctly?  Some people give up way too easily, and think a problem will go away when you start throwing money at it, instead of elbow grease.  Sounds like you're running way too rich.  Assume float height is off, or you were in a hurry and took a wire to clean out your jets (bad things happen that way).  Take your filter out, see how she runs (choke off, as well).

This is simple stuff, don't be intimitaded. 

Doug

[bryanj]

WHAT BIKE!!!!

[Johnie]

WHAT BIKE!!!!

I was assuming it was the '82 CB650SC listed.

[mlinder]

Sounds rich or very very out of synch carbs. You sure you're running on all 4? Check for that, please.

[CBGhia]

after you run it for a second, spit on all 4 exhaust headers.  If they all sizzle, good.  But it doesn't sound like you are running on all 4.

[MJL]

A lot of 650 guys have this problem, so try taking the cover off the airbox and going for a short spin.  Seems to solve it easily.

[redschwa]

Allright I won't give up. Im going to try all those ideas tonight. It's like 100 degress out now. I decided to pull my plugs just to see what i'm working with and I took pictures. They are all covered in soot. But I can't figure out how to upload pics.

[d_soles]

That soot could be left from when it was running fine, in order to do a good plug chop, install brand new (I mean it!) spark plugs into the bike, find a nice spot where you can run the bike wide open throttle for a mile or so.  Start it up, hit it, and don't let up.  Then, after that mile has passed, while you're still gunning the engine, hit the kill switch on the engine, and coast to a stop.  Then, DO NOT RUN THE BIKE until you have removed those spark plugs.  You want those spark plugs with only the running at WOT, and nothing else, not even a ride back home.

It helps to bring another set with you, and a spark plug wrench.  Watch out, they're gonna be hot spark plugs.  If you ride the bike back to your house, you'll ruin the plug chop.  Pushing the bike back home works, too, but a mile is tough to push a 500lb bike. 

Then, take some pictures of the plugs, and label what cylinder each came out of.  That'll help us out. 

Doug

[redschwa]

I tried to take my air filter out but the damn screws are just spinnin. so that's a no go. Al four cylinders are firing.  I did a half ass plug chop on the first cylinder. I can't really run it WOT. at about 3/4 she starts to choke out and die. So i ran it as hard as I could then pulled the first spark. My camera isn't working so I'll have to wait until tomorrow for a full chop with all four and pictures. How do I upload pics? But my quick chop had the brand new plug covered in soot.

[d_soles]

I'd still say you're running rich, that's what it sounds like from the symptoms.  At least you know you're not burning a hole in your pistons (although all of that extra gas in the cylinder will "wash" away the film of oil, hard on the cylinder wall and the piston rings.  That's assuming that I'm right and it's running rich.  Either way, it's starting to look like you're going to need to take those carbs off at some point or another.  If the air filter is clogged, that could be choking the bike, making it run too rich as well.  You could do what I had to do with my stator cover, and take a 1/4" drill and then proceed to, slowly and carefully, drill the heads off of the screws.  Then you can usually take the cover off, and proceed to get the old screws out after that.  Bad news is that you need to source some new screws.

Doug