Topic: Mo the 80 CB650 Custom: "As the Spanner Turns..."

[Frankenkit]

sometimes being a dirty damn hippie comes in handy.

[Hush]

Submerge the front end of the bike up to the handlebars in your neighbours pool (don't worry he will understand) start your bike and look for bubbles.

[manjisann]

HAHA, Kit that's a great idea, only real drag is the wind around here. Well I'll figure something out.

Brandon

[manjisann]

I went for a ride today, first long one on this bike (long is a relative term) and it was AWESOME!!

I wanted to put clean plugs in just to see what the deposits would be. I don't know that I'll be able to do a proper plug chop any time soon, I'm just not sure where to go that I can get away with it. Unfortunately this was not to be as my plug cleaner appears to have run out of cleaning grit, guess I'll be paying Harbor Freight a visit this week! Actually, does anyone know if I could get away with using fine sandblasting grit in a pneumatic plug cleaner?? Anyhow, fired her up (I only have to have the choke on for a short instant and then off again, I wonder what that means exactly, oh well  ) I went for a 20 mile ride and put her through her paces, as well as I could on the rodes, fastest I was able to hit was 50mph, the bike would go tons faster, but the local constabulary wouldn't be so understanding I'm sure. Before heading out I put a piece of tape on the throttle and marked the different positions, 1/8, 1/4, 1/2, 3/4 WOT so I could see how she was acting at the different positions and also monitor how much throttle I had to give in different situations.

I found that she revs and pulls like a demon, I don't know if she'd do a wheelie or not, but I'm not dissapointed in the power by any means. I never felt any bogging at any point, there was a little burbling, but no backfiring and nothing but a slight hesitation when suddenly opening the throttle. I find it interseting that when I go to stop sometimes the rpms want to drop a little low, not 100% sure what's causing that.

I stopped off at a friends on the way back to show him the bike, we talked for about 20 minutes then I suited back up, kissed the starter button and she roared back to life and I rode home.

I let her cool for a bit and then pulled the plugs, just to see what they showed. 1 and 4 still look a little lean and 2-3 were dark, but as I hadn't been able to clean them I really don't know what it means. I'm going to pick up some grit to clean the plugs and then ride around again. I don't know that an official plug chop is really necissary as I found that I really didn't exceed 1/8 to 1/4 throttle except to excellerate. I'm going to try the duck tape trick again and see if that helps with the outer plugs and try and determine the optimal covering. Once I've got that figured out I'll weld up some nice covers and then really start trying to get the carbs sorted, though I'm not too worried about getting them exact. I'd accept a little rich, I just don't want her running lean, but I'm not super concerned about getting it exact and tan on every throttle position.

Thanks again to everyone who followed this thread and has given advice, wisdom, and encouragement. I can honestly say that I wouldn't have gotten here without all of my awesome friends on this board!

Now I just have to sort the few minor bugs left, add a few bits and bobs, and enjoy riding her as much as possible!!

Thanks,

Brandon

[754]

 You should not have to clean the plugs very often.. color change can occur in a minute or less..

[Hush]

Too much Brandon, that is way cool mate.
I only use my choke to fire the motor, once she fires I close it and just add some more idle using the adjuster down by the carbs.
You sound like you need a really good carb sync now, it would explain the different carbon deposits.

[manjisann]

You should not have to clean the plugs very often.. color change can occur in a minute or less..

Ok, that is good to know thanks. In that case I think I'm in the ball park, maybe a wee bit rich. I'm pretty sure I'm rich on the inner two, it's the outer two that I'm not totally sure on.

Too much Brandon, that is way cool mate.
I only use my choke to fire the motor, once she fires I close it and just add some more idle using the adjuster down by the carbs.
You sound like you need a really good carb sync now, it would explain the different carbon deposits.

Good to know about the choke Hush, thanks  It ssems to me that on my 500 I'd have the choke out for a few minutes before I could put it back in, otherwise she didn't stay running. Either way, she is super easy to start, so on complaints there. As for the different deposits, I did do a carb sync a week or two ago and the carbs were really off then. I haven't done anything since then that should have affected them though..... although I guess the buggered pulsers could have affected the running even before she started bogging. I guess before I go chasing nonexisting gremlins I'll do a carb sync again and see what I get, at least then we'll know for sure what's what. I may still make the covers I was thinking of just to see what happens, they'd help keep the rain out if nothing else.

Thanks,

Brandon

[Kurlon]

Not needing much choke when cold and revs dipping when shutting the throttle implies rich on the pilot adjustment.

[manjisann]

Not needing much choke when cold and revs dipping when shutting the throttle implies rich on the pilot adjustment.

Right again. I adjusted the airscrews and the whole dipping when shutting the throttle is largely gone.

I took the bike for a ride and she started smoking a bit out of the cam breather, so I think she's running way too lean. I had put the 107.5 mains back in today just to see what would happen now that the electrical issue is fixed (and because the plugs were fouling with the 125's in.) I only pulle the 1-4 plugs to see what they looked like and they were white, so uber lean. The engine was warmer than I really wanted to play with so I didn't pull the two inner plugs, I'll do that tomorrow when I get home from work (so much for riding in    oh well, better to wait than hole a piston.) I have the clips on the needles all the way to the bottom so the mains are as rich as it's going to get without upping the jets. Since I already have them I'll drop the 120's back in and see what happens, if it's too rich I can play with the clip positions and then start chasing jets from there. I also installed my pod covers, they look pretty decent, though I'm still playing with mounting ideas.

I've also got a pesky squeak with my front brake. I'm pretty sure it's not dragging since the tire spins just fine when it's on a jack. I think the pad is just leaning against the rotor and squeaking. Anyone got any thoughts on this?

Well, it feels as though I'm on the home stretch, and I'm really hoping that I can start saving some money up before something else dies.

Brandon

[scunny]

have faith in your bike, it's a Honda

[Hush]

Like Scunny said Brandon, Hell that bike has lasted 30 years, do you seriously think you can bugger it up so quickly?

[manjisann]

Like Scunny said Brandon, Hell that bike has lasted 30 years, do you seriously think you can bugger it up so quickly?

have faith in your bike, it's a Honda

AHHH come on guys, I was thinking that could be my super power (in an announcery kind of voice) ABLE TO BUGGER HONDAS WITH A SINGLE TURN OF THE SPANNER!!!

Nah, I don't think I've damaged anything beyond repair, just don't want to ignore the signs of a lean runner. In all honesty I think it's just a matter of dialing in the carbs. Since the next biggest size jets I have are the 120's they'll likely go in today and we'll see what happens. When I had the 125's in I rode around and got less than 30mpg on the one tank, and I don't think I was doing a lot of idling in my driveway. That plus the dark plugs tells me 125's are too rich.

Brandon

[Frankenkit]

...and now for today's episode of "As the Spanner Turns..."

[manjisann]

I've currently got the clips on the needles at the bottom and 107.5 mains. I'm going to go and toss in the 120s since they are the next biggest size I have. I'm guessing they are likely going to be too rich, but it's just a guess. So here is the question. Should I leave the clips at the bottom, making it as rich as possible, or should I move the clips, and if so, where?

That is the question of the day. I'm going to have the pull the carbs anyhow, so not moving the clip won't necissarily save me any real time.

Brandon

[Hush]

Have a dollar each way and fit them half way down/up.

[Kurlon]

If low/partial throttle is acting the way you want, leave the needles alone.

[manjisann]

If low/partial throttle is acting the way you want, leave the needles alone.

Hmmmm I already moved the clip all the way to the top. My figuring was that the 120's are likely going to be too rich and that moving the clip to the top would lean the whole thing out a bit, but from what you are saying my thinking may be flawed?

Thanks for the input guys 

Brandon

[Doctor_D]

+1 on not messing with the needle position.

The main jets don't affect much until you're above half throttle. Even then, you're just beginning to transition to the mains from the needle taper and needle jet.

FWIW, if your plugs are bleach-white with the clip in the bottom position -- you may want to find a thinner needle or one with a shorter taper, or you may want to go to a larger needle jet. Not sure that's an option on those carbs, as I generally deal with CR's or Amals.

[manjisann]

FWIW, if your plugs are bleach-white with the clip in the bottom position -- you may want to find a thinner needle or one with a shorter taper, or you may want to go to a larger needle jet. Not sure that's an option on those carbs, as I generally deal with CR's or Amals.

I moved the clips to the top position with the 120's and rode her. The idle jet feels like it set about where it should be, but mid throttle was pretty flat and a lot of burbling (I know, nice technical term Brandon  , but I really don't know how else to describe it, it's not a backfire.) If I went wide open the power picked back up. From this I'm concluding that my clip is too high and thus I'm running lean midrange. This seems to be confirmed by the beautifully white plugs    For the record I'm not able to do official plug chops, I'm just going by my butt dyno and kind of reading the plugs.  Anyhow, I'm going to drop the clips all the way down again and see how she behaves.

I've read and believe I understand, the clip position and needle characteristics (ie taper, length etc) control mid range throttle position, so I kind of understand how the clips position will affect the fuel that can be sucked up at a given throttle position. Here's my question/thinking, even though the main jet doesn't come fully into play until just about WOT, the main jet size will still effect how much fuel can be sucked up at a given throttle position over 1/4 throttle right?

Thanks,

Brandon

[Doctor_D]

I've read and believe I understand, the clip position and needle characteristics (ie taper, length etc) control mid range throttle position, so I kind of understand how the clips position will affect the fuel that can be sucked up at a given throttle position. Here's my question/thinking, even though the main jet doesn't come fully into play until just about WOT, the main jet size will still effect how much fuel can be sucked up at a given throttle position over 1/4 throttle right?

It might seem so, but not really.

The main has very little overlap with the lower throttle position circuits, as you can see in this chart:



As you can see in this cutaway carb, the needle and needle jet are the principle restriction for fuel until the throttle is opened enough to withdraw the needle from the jet.

[Zaipai]

Nice examples Doctor_D.. That makes it much easier to understand, at least for me..

Thanks.

.: Scott :.

[manjisann]

Doctor D, thanks for the info and the cutaway pic, very helpful.

For now I'm just gonna fiddle with jets and clip positions and see where I end up. My understanding is that you really only start changing needles if you are trying to super fine tune midrange throttle for racing and such. Thats a bit more than what I'm aiming for. However, in the unlikely event that I do determine I need a different needle, does anyone know how to tell which needle style I need for my carbs?

Thanks,

Brandon

[Doctor_D]

Happy to help. Unlike the Honda-specific questions on this board, I actually know enough to help with generic carb tuning questions.

The general rule is that if you must use the most extreme needle clip position, all the way at the top or all the way at the bottom, then you would do well to change your needle-jet.

In your case, with the larger main jets installed, you may find that second from the bottom clip position will now suit you.  If you still need to use the bottom clip groove, you may want to consider the next richer needle-jet.  This would allow you to lower the needle (raise the clip to the middle groove or higher), and would put the taper back into it's intended throttle position range.

Worry about grabbing a richer (thinner) needle, or one with a different taper only after you've readjusted the clip position and/or installed richer needle jets.

[manjisann]

Doctor D, thanks again, your info is much appreciated!  I did some searching and found this bit of info. I don't know that it pertains to my carbs specifically, but I think it is probably a pretty universal bit of info on how the needle dimensions affect the different throttle positions. I'd always wondered why the WOT was the first plug chop you were supposed to do, and between Dr D's explanations and this spiffy pdf I think I understand it better.

http://www.keihin-us.com/am/_media/pdf/slide_valve.pdf

Worry about grabbing a richer (thinner) needle, or one with a different taper only after you've readjusted the clip position and/or installed richer needle jets.

Will do, I was more wondering in case it got to that point. I'm still not totally convinced that the 120's are the size I need, I still think they may be a bit large, but I'll try the different clip positions first and see how the bike handles, the plugs look, and also what my mpg is. I'm hoping that even with pods I can still get 40 mpg, we'll see I guess.

Thanks guys!

Brandon

[Soos]

The MPG depends on your throttle use




l8r