Topic: cb750 carb problem

[efyou]

Go here for pictures of the bike taken the day I got and learned to ride it on the 30 miles trip home in the rain:  http://s678.photobucket.com/albums/vv150/efyou/  And yes, the other bike in the first picture is "a real bike".  I do not discriminate!

The Dynatek coils for the electronic ignition wouldn't fit in the original Amen coil/horn box bolted between the front downtubes.  The guy I bought the bike from had jury rigged it so the bike would run and kept the stock parts.  I didn't want to cut it up and found another Amen coil box on Ebay (who woulda thunk it!). I cut the back of it out with a Dremel, and remounted the coils and horn in the stock position. 

Since then I've done some other little stuff; added another mirror (couldn't get used to only one), replaced the tach drive seal,  and throttle cable, while trying to assess how much it's going to need for the mechanical resurrection.  The intent is to preserve, much like a survivor collectable car.  The alternative would be a complete restoration, which would not be possible without a winning lottery ticket

[efyou]

I forgot to add (and forgive me if I'm violating some forum protocol) in the last post with the pictures, If anyone can identify the girder front end, I'd sure appreciate whatever information you're willing to share.

Thanks

[Johnny5]

Nice springer front end. Im not much of a chopper guy, but that bike is pretty cool. Clean too.

[kvallelunga]

No comment on the name issue, but on needle clip position. I thought raising the needle out of the slide(putting the clip in a lower groove) would make the mixture richer by pulling the needle out of the main jet sooner in the throttle movement thereby allowing more fuel to enter the airstream? Correct me if I'm wrong.

[Johnny5]

No comment on the name issue, but on needle clip position. I thought raising the needle out of the slide(putting the clip in a lower groove) would make the mixture richer by pulling the needle out of the main jet sooner in the throttle movement thereby allowing more fuel to enter the airstream? Correct me if I'm wrong.

Yep, that's correct.

[mystic_1]

No comment on the name issue, but on needle clip position. I thought raising the needle out of the slide(putting the clip in a lower groove) would make the mixture richer by pulling the needle out of the main jet sooner in the throttle movement thereby allowing more fuel to enter the airstream? Correct me if I'm wrong.

Correct, at certain throttle settings.  Specifically, between about 1/4 and 3/4 throttle.




TwoTired posted this specific chart but I think I've seen it in a couple of places.  It really should be in the Carb FAQ.


Efyou, have you read the Carb FAQ?  If not, check it out:

http://forums.sohc4.net/index.php?topic=5410.0;all

Don't neglect the Technical Library on the main website, either.  Great info!


mystic_1

[mystic_1]

BTW, great looking bike.  It's got a nice overall presentation, and as others have said it looks very clean.  I love the air filters.

However, I was looking at your rear brake linkage and I see what I think is a problem.  The pivot arm that passes the linkage from the outside of the frame to the inside of the frame, behind the motor, looks to be angled too far back.  In this position, the arm needs to rotate many degrees (40 or so) before it actually begins to pull forward on the rear brake rod.  I think you'll get better brake action if you realign this part, but I don't know if it can be done with your setup.  Depends on how the stops are set up.

Anyway, here's a pic of what I mean.  The red line is what you have now, the blue line is where I think it should be.  I may be completely wrong, however.

mystic_1

[manther]

........................................

I think your mains are plugged right up, clean them..

good luck..

.......................................

From the way I understand things if his main's were clogged he'd be having more trouble in the first 1/4 of the throttle. With the way he's describing the problem sounds more like lean needle clip position.

[manther]

whoops looks like mystic just made this same point.

[754]

Fork, girder for sure.,

Could be maybe, Fury, Durfee, Smith Bros & Fetrow, or one of the many others.

 Handling tip. When assembled the side links should be parallel, and the same length between hole centers.. for optimal handling.

Sure looks a lot like 1080s brothers 650 amen (from the neck back) cept the motor.

[Gordon]

Gordon- Almost as creative as mine. The fact that "prick" is proudly emblazoned on yr every post pretty much negates any gripe you've got.

"Honest Prick", is obviously (to the common observer) aimed at myself.  "efyou", is obviously (to the common observer) aimed at every single person who reads it.  It's a subtle difference, I know, but I'd be happy to explain it in further detail to you if you so desire. 

[754]

I got a crazy idea,, I am pretty sure someone will go to great lengths to inform me of the lack of validity of my idea..but here goes..

 Lets try to get the OP's bike problems sorted out.. coff..coff..mains..cof..coff.

[Gordon]

I got a crazy idea,, I am pretty sure someone will go to great lengths to inform me of the lack of validity of my idea..but here goes..

 Lets try to get the OP's bike problems sorted out.. coff..coff..mains..cof..coff.

I see no evidence of anybody stopping anybody else from helping him with his bike problem.  Do you?

[cherry bomb]

so the size of the stock mains are 105...I know for sure they haven't been changed out. I'm looking for a jet kit on the internet...I should go up in size to increase fuel which will in-turn enrich the fuel-air mixture, end result the bike will return to idle like its supposed to...right?

[cherry bomb]

also what size would be a good one to start out at keep in mind there are hi-flow air filters and straight pipes on it...maybe 115?

[Spanner 1]

I know I'm a 'dumb foreigner' , but all you folks who posted were given the finger by the OP ages ago. But y'all go ahead oblivious ! Why are you all so enthralled ? Oh, but he's got some 1970 chopper forks....re-read his insulting posts....it's NOT in the spirit of this forum...
Damage is done , efyou, your lack of upbringing is apparent, and uncouth..enjoy your life !!

[scondon]

   Spanner, I love ya man, but I'm more insulted by your behavior than I am by the OP's name. You've been abusive and name calling right out of the gate, and show no sign of stopping until your view is satisfied. I get it, you're very,very,very,very,very,very offended.

Thanks so far for the replies.  Please don't take my username as some personal affront. (now i unnerstand if yer a little miffed that you din't think of it 1st!) It's merely my username!

[Brantley]

"Honest Prick", is obviously (to the common observer) aimed at myself.  "efyou", is obviously (to the common observer) aimed at every single person who reads it.  It's a subtle difference, I know, but I'd be happy to explain it in further detail to you if you so desire.

I don't consider myself common. I don't really consider anyone that chooses to have to go to great lengths to ride a 30 plus year old motorcycle common (which means everyone here who only have in common that desire). Common is also used as an insult for the higher-minded sorts toward the 'lower classes' and 'less learned'. 'Sh!t kicker' can be used in place of 'commoner', for example. What you have in common with efyou is a self effacing, light hearted view (there's that drama word again) of yrself as far (at least) as this forum is concerned. That was my only point. Please don't think me so common as to not catch the 'subtle difference'; I have: efyou's friends call him that, you call yourself 'honest prick'.

[moham]

Why are you all so enthralled ?

That's exactly what I am asking every time I read one of your posts on this thread. Give it a rest already...

[cherry bomb]

anybody got any suggestions on the main jet question?? maybe i should change my name to get some attention! Ha Ha!

[mystic_1]

so the size of the stock mains are 105...I know for sure they haven't been changed out. I'm looking for a jet kit on the internet...I should go up in size to increase fuel which will in-turn enrich the fuel-air mixture

Yes.

end result the bike will return to idle like its supposed to...right?

No.  Main jets do not affect idle mixture.  Well, much anyway.  See chart posted earlier.


mystic_1

[cherry bomb]

well i understand they wont affect the idle mixture but doesnt it mean that if a bike will not return to idle rpm that it is running lean? and by changing the main jets to get more fuel in there it will enrichen the fuel mixture and make the bike return to idle like its supposed to...i probably worded it wrong last time...hopefully it makes sense now. i mean is my line of thinking right?
Ive been looking at the charts and anything else i can find on the FAQ, tech files other threads and ive pretty much determined that if when a bike is given throttle and it will not return to idle a lean condition exists...fix = main jet adjustment...right? if this is the case I need to go up in size to create a richer mix...maybe a 115?

[Gordon]

well i understand they wont affect the idle mixture but doesnt it mean that if a bike will not return to idle rpm that it is running lean? and by changing the main jets to get more fuel in there it will enrichen the fuel mixture and make the bike return to idle like its supposed to...i probably worded it wrong last time...hopefully it makes sense now. i mean is my line of thinking right?
Ive been looking at the charts and anything else i can find on the FAQ, tech files other threads and ive pretty much determined that if when a bike is given throttle and it will not return to idle a lean condition exists...fix = main jet adjustment...right? if this is the case I need to go up in size to create a richer mix...maybe a 115?

Have you looked at your plugs to see if you're actually running lean, or are you just assuming?  There are many issues that could cause the throttle to be slow on returning to idle, and an overly lean mixture would probably not be one of my first suspects.  Air leaks at the intake boots, badly unsynchronized carbs, sticking throttle cable, or a sticking advance mechanism are some possibilities. 

[mrbreeze]

This is some funny sh!t here. You have a double post going on with an attack going to the first poster.
If people have a problem with this guy's handle.....don't post here. His handle may be offensive to some but he isn't saying FU Gordon(or Lloyd or Spanner).Let it go .He seems to be OK other than having an odd username. You don't have to communicate with him. There are plenty of people here that I get along with great as there are many that I wouldn't miss at all if they left.
And Cherrybomb......you should probably start a new post because you landed in the middle of a bad one.

[scondon]

well i understand they wont affect the idle mixture but doesnt it mean that if a bike will not return to idle rpm that it is running lean? and by changing the main jets to get more fuel in there it will enrichen the fuel mixture and make the bike return to idle like its supposed to...i probably worded it wrong last time...hopefully it makes sense now. i mean is my line of thinking right?
Ive been looking at the charts and anything else i can find on the FAQ, tech files other threads and ive pretty much determined that if when a bike is given throttle and it will not return to idle a lean condition exists...fix = main jet adjustment...right? if this is the case I need to go up in size to create a richer mix...maybe a 115?

Have you looked at your plugs to see if you're actually running lean, or are you just assuming?  There are many issues that could cause the throttle to be slow on returning to idle, and an overly lean mixture would probably not be one of my first suspects.  Air leaks at the intake boots, badly unsynchronized carbs, sticking throttle cable, or a sticking advance mechanism are some possibilities. 

   Thanks for tapping that one out, Gordon. My thoughts as well