Topic: Well, it wasn't the pods...

[DammitDan]

Every time I start cruising on the interstate for more than 5 minutes, averaging 70-80mph (>6k RPM), the engine starts running rough and the exhaust gets very loud, the throttle becomes jumpy and sluggish/unresponsive (if I open the throttle all the way, it will only JUMP forward randomly... if I keep the throttle in one place, it will slowly lose speed), and if I stop on the side of the highway after these symptoms, the engine will die at idle unless I keep the throttle on.  I've also noticd that if I stop and hold the throttle on the side of the road, then after about 30 seconds to a minute it will begin idling normally and the engine will sound OK again.

I initially thought it was because I was running with pods, which was making the mixture rich at high speed.  But I switched back to the airbox today, and while it DID run a LITTLE better on the interstate, it was still acting up and running rough.  What could this be?  I don't have any other symptoms of this anywhere else... the throttle is right on everywhere else until I run it in 5th above 6k RPM for an extended period.

[Dennis]

Every time I start cruising on the interstate for more than 5 minutes, averaging 70-80mph (>6k RPM), the engine starts running rough and ......

if I stop and hold the throttle on the side of the road, then after about 30 seconds to a minute it will begin idling normally and the engine will sound OK again.

What could this be?

... the throttle is right on everywhere else until I run it in 5th above 6k RPM for an extended period.

Sure seems like a fuel flow condition, not enough flow to keep the carb bowls filled under a high demand running condition. I would check everything in the fuel supply starting at the vent and working my way down to tank, petcock, screens, lines, filters and last carbs.

What kind of bike?
Do you know where the OEM screens are installed?

[MetalHead550]

Agreed,  sounds like mabey the floats are set to high and not allowing enough fuel flow, starving it in the upper throttle range.  But yeah start with the simple stuff.

[Buffo]

It could be that it is starving for fuel but it could also be running very lean...and that means HOT... maybe VERY, VERY HOT.

 You are also discribing what happens when your bike is moments away from seizing up...if you put pods on your bike and did not re-jet you are most likly running lean...especially at higher rpm...when running very lean the bike runs hot...you slow down...the bike runs a little richer and it cools off a bit and starts to run a bit better...or...it might be starving for fuel

DO A PLUG CHOP!!!

[MetalHead550]

Ow! My ears.  Good point B to the M.  You definitly dont want that sucker seizing up doing 70mph down interstate...youd be in a very bad way.

[Terry in Australia]

The symptoms you describe are of a lean mixture, evidenced by the slight improvement when you returned to the OEM airbox, as it doesn't flow air as much as pods, thus slightly richening the mixture by providing a "choke" effect.

If it's not something as simple as a partially blocked fuel filter or petcock screen, then I'd suggest that your float levels are incorrect, not a biggie to adjust, just a pain because you need to remove your carbs, or do as I do, and set each float on a spare carb on your bench. Cheers, Terry.

[DammitDan]

It's a 1982 CB650.

Boy I don't even want to think about it siezing up on me on the interstate.  It's done that once before with my old engine when the cam sprocket came loose and lodged itself in the head wall.  Thank goodness I was only doing 20 mph when happened.

I've been avoiding even touching the carbs for a very very long time now.  I guess it's time to have a looksee in there this weekend.  And avoid anything above 50 until then.

The PO put on the pods... and I have a feeling he didn't know crap about what he was doing, either.  I may as well rebuild the carbs, since I already have 4 kits on the ready in my toolbox.  Hey, I told you I've been procrastinating on this for a LONG while!

Oh, and what the hell is a PLUG CHOP?

[Buffo]

dont touch the carbs yet!

a plug chop is taking your plugs out (several times) at various throttle possitions.

first your remove and clean your plugs...reinstall and start your bike...let it warm up and run your bike at 1/4 throttle for about 1/2 mile...pull in the clutch and kill your engine with the kill switch at the same time...stop the bike and pull out the pulgs...all of them... compare to the pics in the manual...some one may have posted plug pics in this forum...clean, re-install and do the same for 1/2 throttle, 3/4 throttle and full throttle...the plugs must be cleaned each time...

you want to do this with the air filtering system that you want to run on your bike INSTALLED or the readings will be off.

make your adjustments after you have PROPERLY dianosed your problem.

...I dont know much about the 650's

Buffo The Magnificent

[HackNslashCustoms]

I'm having similar problems. Maybe some of the suggestions in my post can help. I'm finally off to mess with mine right now.

No more hurricanes! I'll sit this round out thank you verry much!

"Help... dies at 60 mph...http://www.sohc4.us/forums/index.php?topic=4996.0

[DammitDan]

Well, I didn't do a plug chop, but I can pretty much assume it's running VERY lean.  All plugs were very light tan, and #2 was almost white.  So, I know it's running lean, but especially at high speeds.  Now what?

I adjusted the tappets today and installed a new in-line filter (the old one was, well, REALLY old) but it still exhibits the same running conditions.  I haven't done anything to adjust the carbs except balance them with a manometer about 2 months ago.  Should I go ahead and make this a weekend project and disassemble/rebuild my carbs?

What should I be looking/watching out for?  This is the job I've been dreading for so long...

[Terry in Australia]

G'Day Mate, either raise your slide needles a notch (the clip is normally set in the factory on the middle notch of five notches, so remove the clip and place it on the notch below the one that it is currently on, that "raises" the needle and richens your mixture, or you can just fit a larger main jet in each carb, which will have the same effect. Cheers, Terry.

[Sam Green Racing]

I would take a guess and say it would be easier to change the jets as you only need to drop the float bowls off.

Good luck  Sam.

[Terry in Australia]

You're right Sam, but you need a handfull of jet sizes to get it right, whereas needle adjustment will give you a more precise adjustment, "pain in the butt" that it is. Cheers, Terry.

[pmpski_1]

then I'd suggest that your float levels are incorrect, not a biggie to adjust, just a pain because you need to remove your carbs, or do as I do, and set each float on a spare carb on your bench. Cheers, Terry.

Terry you are a genius. That trick needs to be added to the FAQ.

[DammitDan]

Well, when I started taking #1 apart, I noticed that all the pilot screws were set to different settings (I think that's what they're called... they're the little screws with a flange on them on the bottom of the carb bowl).  Would this make a difference at 70 mph, or do those only affect the engine at idle?

[Terry in Australia]

Well they're CV carbs mate, so the pilot screws will have an effect right across the rev range, as opposed to regular slide carbs. A word of warning though, don't mess with these screws unless you have the original set-up info, which the factory didn't like making public, most workshop manuals will tell you that these screws were set in the factory and shouldn't be altered from those settings.

Anyways, it won't make that much of a difference at 70 Mph, as your mixture is determined mostly by your slide needle position, and if it's running that lean, you'll need to do the adjustments that I previously suggested. Cheers, Terry.

[Terry in Australia]

then I'd suggest that your float levels are incorrect, not a biggie to adjust, just a pain because you need to remove your carbs, or do as I do, and set each float on a spare carb on your bench. Cheers, Terry.

Terry you are a genius. That trick needs to be added to the FAQ.

Thanks for the compliment mate, I like to think I am too, ha ha! Cheers, Terry.

[Sam Green Racing]

Terry is a three ball genius

[DammitDan]

Ok, now I'm REALLY confused.

There's absolutely nothing in the manual about changing the needle clip...  And it says that because the floats are plastic, they cannot be adjusted.  While I was taking them apart the only needle I noticed was the main jet needle, and that just sits down inside the carb body from the top end.  I didn't see anything to keep it from moving farther up or down.

[Sam Green Racing]

It's in the piston/slide, you get at it from the top of the carbs.

[DammitDan]

My needles don't have a clip!  I can only assume this is the clip you're talking about... This is from a CB750.



Here's what the needles look like on '82 CV carbs...



I don't think i saw any way to modify the actual slide's position...  So, I can't modify the float, I can't set the needle height, and I don't want to change my main jet to anything but stock.  What now?

[Sam Green Racing]

Oh heck

[Terry in Australia]

I don't think i saw any way to modify the actual slide's position...  So, I can't modify the float, I can't set the needle height, and I don't want to change my main jet to anything but stock.  What now?

Well, you might have to. I've got a set of US Honda CB650 (?) CV carbs in a box somewhere, I'll pull one apart and see if that's right. Cheers, Terry.

[Sam Green Racing]

Terry,

Had you not been in work all day (Mon) he could have had it fixed (Sunday night).

I have never seen a fixed needle before. 

Sam.

[Terry in Australia]

G'Day Sam, I think there were fixed needles in some carbs due to stringent EPA laws in the US, also metal plugs over mixture screws as well. I didn't go to work today, took a "sickie" and took my Great-Grand Daddy's old (1870) Black Powder shotgun for a shoot, hot windy day, so I'm covered in soot, but was great fun, ha ha! cheers, Terry.