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What in the world would cuase the bike not to get over 5K rpms. Unless the bike is in neutral I can barely get this thing over 5K
It almost seems that when I am on the throttle pretty hard or just climbing a hill, the bike will pull strong smooth and nicely til it maybe starts to use main jet. Then it boggs down and wont go? I am running 72 / 105 so nothing huge. I am at 3 turns out on a/f screw.
City driving with a passenger and or solo, the bike runs great. starts fine, idles fine, and rides around town fine. just when I try to get on it, does it bog.
Could something be stuck inside the carbs?
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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 Do I have these backwards? is main jet in primary and primary in main? Both jets fit the same screw hole
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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charging system good?
1981 SS with Kerker 4-1 exhaust and extremely attractive rider.
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Yep. Fires up everytime. Battery holds charge
Sent from my iPhone On Jul 7, 2013, at 3:55 PM, "Johnnylevi [via Honda CB750'S]" < [hidden email]> wrote:
charging system good?
1981 SS with Kerker 4-1 exhaust and extremely attractive rider.
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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Could it be the accelerator pump? What does it do?
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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Your jets are in the right spot:
http://youtu.be/Gy_Bj3Wyca8Accelerator pump squirts a little extra gas into the carbs when you quickly flick the throttle on. It only matters for the second that you hammer on the throttle. If it is clogged then when you hammer on the throttle your bike will bog because it just went super lean, but then the bike should recover as gas will get sucked in with all of the air now flowing.
If you can't get your revs past 5K even when you're slowly turning the throttle up then it's not your accelerator pump.
1981 CB750K with 900 cams
90K KM's, rebuilt head, rebuilt carbs, upgraded valve stem seals
My wife's recipe website that I'm trying to help promote: Strawberries for supper. Yes, I am a lucky man.
My cb750 video site
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Dumb question number one:
Is the ignition advancing properly? I don't recall when it should go to full advance, but a quick check with a timing light should help.
I'm sure you've had the carbs apart several times to clean and adjust. I can't think it's just dirt in the line. Sounds almost like there's a passage that's plugged or something.
Good luck.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.
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No dumb question at all. Hadnt checked timing, as I felt if the bike ran up to 5K fine what could be wrong with timing? (Shows my education level when it comes to that subject)
The carb clog would make sense. will try timing first
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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Are you using the factory air box with a paper filter? Pods can give CV carbs fits...
1979 CB750K
1978 CB750 Four SS (gone but not forgotten!)
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Yessir using standard breather box with fresh filter, but for as much as I have been fiddling with these carbs and jets, etc. I might as well of gotten pods.
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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Just out of curiosity, why did you increase the jet sizes? 100/68 is stock for the 80 cb750f...
1979 CB750K
1978 CB750 Four SS (gone but not forgotten!)
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Also, check your fuel cap vent hole for obstruction. If clogged, this can cause negative pressure in the tank that will reduce gravity-fed fuel flow. You can try running with the cap loose as a test.
1979 CB750K
1978 CB750 Four SS (gone but not forgotten!)
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where is fuel cap vent hole? I went up in jets due to 4 into 1 exhaust.
Just checked timing and it was a tick off. the advancer seems to be working, although hard to get throttle to stay at 6K and check at the same time. I pushed idle as far as I could and I could see the advancer coming on,but not constant. I am sure if I had another person holding throttle I could tell for sure
Odd thing is I am running a tank bag, that completely covers gas cap.
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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I am no carb guru, but I've always been told the CV carbs on these old Hondas do not require rejetting to use an aftermarket exhaust. I don't know that's your issue, though. Uncap the tank and run it in neutral, see how it revs. Easy thing to eliminate. There is a small hole on ths side of the metal portion of the cap. You should be able to blow air through it. If not, use compressed air.
1979 CB750K
1978 CB750 Four SS (gone but not forgotten!)
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Have you done a plug chop? Too rich of a jet can keep an engine from revving just like starving for fuel.
TOOLS
Life is not about the number of breaths, you take, but the moments that take your breath away.
I don't have an anger problem. I have an idiot problem. Hank Hill
Never confuse education for intelligence.
Happiness is a belt fed weapon.
I just can't imagine what could go wrong.
No fire? No explosions? So whats the point of your story?
Those who are too smart to engage in politics are punished by being governed by those who are dumber. ~Plato
It couldn't be done, but the darn fool didn't know it, and did it anyway.
We all got problems. Ksharp
I like vintage bikes because they take me away from the clutter of technology that I work with everyday and back to a simpler time of mechanical elegance and simplicity.. "ninadm"
Darkwing Duck: The worst part of public transportation is the Public.
"That is awesome shit there" Re-Run
"Fear nothing, attack everything" Eric Berry
" Oh, you read that on the internet? Clearly it IS a massive problem. Of course it CAN’t be normal operation."
1976 CB 750-A X 2
1977 CB 750-A X 4
1977 CB 750-K
1976 CB 750 F
1981 CB 750
1966 Kawasaki SG 250
1981 KZ 750 LTD
1973 CB 350
1979 CM 185 Twinstar
1982 Honda XL 80
South of Eden (Kansas City MO)
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Going to do a quick ride , and see what its like. With the tank bag off, and timing adjusted lets see what shes like.
Will do plug chop next, and then if that aint it, taking the carbs back off again, and going through them again.
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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NOPE. Still same thing. took tank bag off and even cracked gas cap. No difference. It just seems like it starving for fuel.
I will get some new plugs and do a plug chop.
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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How is your fuel filter?
1979 CB750K
1978 CB750 Four SS (gone but not forgotten!)
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I guess I could replace it, but its barely a year old. looks good though.
@FastCletus552 aka Jimmy C, buildin' rides out of Napa CA
Current Build 1980 CB 750 F
Finished Build 1975 CB 500T Cafe Racer - SOLD
2002 Ducati 998 Biposto
2005 Rossi #46 Scooter
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Not sure what bike you have. I take it the 105 is your main what is the 72 the year? Have any mods been done to the intake or exch.? Need a little more info. From what I can tell so far it is right where you start using the main circuit. Have you ever had the carbs out for a good cleaning? How does the air filter look?
Ken
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