Topic: 81 cb650f bogs down while riding up any sort of incline...

[heffay]

hey guys... a buddy of ours is having trouble w/ his cb and we're gonna try to figure out the cause in the next couple of weeks sometime.

here's what he says:

Heffay, I am having minor difficulties with my 1981 CB650Four. She seems to be running alright until I go up any type of incline. She bogs down significantly. This occurs when I am on my way to work each day, just after the transition from I-25 to the Boulder turnpike just before Pecos. It's not a tremendous incline but just the same I feel a significant bog until the road levels out. Obviously this occurs in other places as well, I just wanted to give you an idea of the minimal type of incline that affects the bike.

anyone care to take a stab?

[mlinder]

Lean condition, wrong gear? What rpm is he at on the incline?
All 4 firing?

[clearcan]

are all the cylinders firing?

[heffay]

not my bike... never ridden it... not sure i've ever seen it.

can't answer any of these questions but i'm pretty sure the guy knows how to downshift 

i suppose not firing on all 4 could intensify the condition since it would be down on power but it doesn't seem like the answer as we're talking about an only uphill problem.

if he hadn't already lost a bunch of weight i'd ask the diet question.   

don't see how a lean condition would change going uphill 

[mlinder]

not my bike... never ridden it... not sure i've ever seen it.

can't answer any of these questions but i'm pretty sure the guy knows how to downshift 

i suppose not firing on all 4 could intensify the condition since it would be down on power but it doesn't seem like the answer as we're talking about an only uphill problem.

if he hadn't already lost a bunch of weight i'd ask the diet question.   

don't see how a lean condition would change going uphill 

Lean condition wouldnt change... but consider, a very lean condition will make you very down on power (or a very rich condition, for that matter) so while the power may be enough to keep you at 65mph on the flat, you will lose speed on any kind of incline. Same thing as, say, firing on 2 or cyls.

[Soos]

Almost sounds like it's on 3 cylinders, 1 of the spark plugs may have gone south...
I have ran with a dead spark plug, and MAX speed was like 75mph or so, started showing poor gas milage as well, 5MPG loss or so.  On a hill I would be lucky to do 55-60mph.

The carbs are dirty? When did he last check them?

When was the last time he looked at his airfilter?

Timing?

Valve clearances...

JETS.... but thats the last thing i would suggest to him... the simple things first.
But at the elevation he is riding at, possibly going to a leaner jet could help... 120's stock i believe.

Overall, a basic tuneup, and checking a few extra...


What tire pressure is he running? That can make quite a difference at times.


Good luck, long distance over the net to the person is one thing, through the net to you, then him.... this sounds almost funny..... 

Good luck helping him.

l8r

[swan]

Check the float level heights of the carbs?

[heffay]

yea... thanks guys... i'll be working on the bike this weekend.

gordon?  wanna come help too?

i would have to agree there are a lot of unanswered questions here 

[kghost]

Check the float level heights of the carbs?

Low float levels would be my guess.........

[Gordon]

yea... thanks guys... i'll be working on the bike this weekend.

gordon?  wanna come help too?

I might be able to stop by after work.

And tell Mad Dog to sign up on this website for himself, already!

[Gordon]

Oh, and tell him to downshift!

[76 cb550]

I'd guess it's the spark plugs.  a cylinder isn't firing for one reason or another
My girls pontiac was doing the exact same thing.  One of the plugs was broken in half.

[CBJoe]

Check the float level heights of the carbs?

Low float levels would be my guess.........

+ exaggerated by the fact that with an incline the gas is the bowls would angle toward the rear, close the float prematurely and not let enough gas in....Joe

 ???wait... i think I'm backwards with that thinking Too much fuel into the bowls?

[Gordon]

Check the float level heights of the carbs?

Low float levels would be my guess.........

+ exaggerated by the fact that with an incline the gas is the bowls would angle toward the rear, close the float prematurely and not let enough gas in....Joe

 ???wait... i think I'm backwards with that thinking Too much fuel into the bowls?

I don't think the floats in the '81 650C are adjustable.  At least the ones in my friend's aren't.  They're plastic, including the tang that is normally adjustable on older carbs. 

[cb650]

If its a stock 81 the floats are not adjusable.  I'd help but apparently I dont know #$%* about 650's or other things .
Gordon if you go let me know and I'll ride up with you.




                Terry

[Gordon]

I'd help but apparently I dont know #$%* about 650's or other things .

Admitting it is the first step to recovery!

[heffay]

i thought denial was the first step. 
                     

[Gordon]

i thought denial was the first step. 
                     

And knowing is half the battle......

[troppo]

i thought denial was the first step. 
                     

And knowing is half the battle......

but i thought de nile was a river in egypt

[Jerry Rxman Griffin aka MuthaF'er]

Pecos. The bike just doesn't want to be on Pecos.

My guess is the mains are 1 size too large. Check the air filter first and clean it then try smaller mains. My increase to 115s helps top end but it wants to bog around 3 to 4K in 5th with a load on it. Time to down shift and hammer it!! I try not to run it below 5K anyway, just sounds too good 

[cb650]

  JETS    I would say that to but I dont have 40 sets laying around and a dealer to tell me the ones to run. .
Anyway try it with out filter and or the side cover.  Seems the cover to the stock filter restricts it enough to cause problems. Sounds like I did mushrooms but several people on the 650 sites claim it works.  I've never had to do it but usually run pods. Also if someone stops to get me and I ride with you bring a rope to tow me.
I evidently have been loading my bike in the van wrong for the past 15 years.



                          Terry

[heffay]

what is all this evidently stuff... cb650?

are you making jabs here or about stuff people say on another forum?

[Gordon]

what is all this evidently stuff... cb650?

are you making jabs here or about stuff people say on another forum?

Kind of wondering the same thing myself.

[cb650]

Yes it seens after owning and riding a 650 as of 1984 with no dealer help I apparently have been doing it all wrong.



                    TERRY

[heffay]

says who, we were asking... it is apparent that someone is telling you things... evidently.   

just wondering who the schmuck is.