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Ok I had a post on here before but I got mono and I'm over it now so I'm ready to get this bike running. It's a 1974 cb750 and let me tell you the story. I bought the bike about 2 months ago. it ran fine when I bought it other than it wouldn't go over about 4000 rpm. I know that it's the carbs on it. i need to rejet them because it has the pod filters and it mess with the fuel to ratio. but then one day took it out of the garage to take it f for a ride and it barley started and wouldn't hardly go. I so I decided insted of riding I would wash it. so I did everything went downhill from there. since then I can barely get it to start up about 10 min to cranking on it.and it will run very very bad and will not stay alive. It breaths in slot of air it sounds like. So what I have checked is this, new spark plugs, I am getting spark on every one so ,coils are prob good so what now? Any suggestions and if you need info on anything on it let me know thanks!
justin kiser
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You got the choke on?
American by birth. Cowboy by choice!
Vero Beach, FL
http://i373.photobucket.com/albums/oo172/grandpaslinger/HD%20Road%20Glide/IMAG0046.jpg
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Do you know for sure you are getting fuel?
Simple if some one else can, why can't I
Jamie
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Pull the petcock bowl and make sure it is not clogged and is flowing gas.
American by birth. Cowboy by choice!
Vero Beach, FL
http://i373.photobucket.com/albums/oo172/grandpaslinger/HD%20Road%20Glide/IMAG0046.jpg
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Thats what i am wondering now i just got the carb off today and i have a glass fuel filter i see black chuncks so kinda thinking ita cloged up. I am not sure hot to go about cleaning the carb anyone have info on that and i am going to replace fule lines and filter.
justin kiser
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Is therw a digram to look at to take apart? i am lost on carbs lol
justin kiser
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Howdy, The black flecks you are seeing is rust particles from the gas tank. You will need to remove the carb bowls. If pre 77 then there is a spring strap that holds the bowl on. Push it forward & the bowl can be removed. Then remove the pin for the float. Float & needle will fall out. Use 10mm socket & remove float valve seat & fibre washer. Use 8mm tool & remove main jet holder w / main jet. put some kind of container under carb (s) & let some gas flush the fuel passages out. Use air nozzle to blow out carb bottom. Clean main jet & holder you removed. Clean float valve seat & screen if equiped. Re-install seat & jet holder (don't over tighten - brass parts). Put float needle up in seat, hold with finger from rear, slide float in from front over needle & re-install pin. You may or may not need to re-jet. Make a note of what ones you have while carb is apart. If brass parts are very dirty you will need to get the 1 gallon parts cleaner kit from an auto parts store & soak the parts. ($30.00) Now that I said all that, if 77, 78 Carbs need to be removed from the bike & dis-assembled then cleaned. You may or may not need to sync carbs afterwards. Now you need to address the rust in the tank or problem WILL return. I like the Kreme kit or replace the tank. Hope this helps, PHILLIP
PHILLIP Chop what ya got! G.O.T.F.
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Thank you for the help! I will tear it apart tonight. The gas tank is new so i am gona be pissed if its it lol.
justin kiser
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I forgot to say if you have apart, look @ the slide needles inside the hole the jet holders came out of to see they are clean. If they are green then the whole carb bank needs to come off & apart.
PHILLIP Chop what ya got! G.O.T.F.
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Most of the time hands on is the best teacher.  Just lay things out the way you take them a part. That way you can use the same steps to put them back together. Pictures as you go can be a big help to.
Good luck. You tube can be very helpful to.
Simple if some one else can, why can't I
Jamie
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Well carb.was clean as can be besides one jet and its a pilot jet? Maybe the name anyways long skinny one and i couldnt get it cleaned but other than that it was clean. So idk how to clean that one out + i wouldnt think thats the problem why it wont run or start?
justin kiser
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Did you change your filter and make sure you have good fuel flow?
Simple if some one else can, why can't I
Jamie
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I have some 8" pieces of guitar strings (single strand) I use to clean out jets. Also the tip cleaner tool for welding works well. Push wire in through the up side of the jet, it's easier to find the hole & push plug out. in extreme cases there are jet drill sets that are use with your fingers to remove crap from jets. Use extreme care to not damage the brass jet. You still need to verify fuel flow. The cavity above the float needle seat fills up with debris & stops the gas from coming through. You also may see gas over flow the carbs when the petcock is on if system is not clean. FYI if this jet is stamped #40 then yes it is a pilot jet.
PHILLIP Chop what ya got! G.O.T.F.
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Administrator
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get back to the basics.
pull a plug, put it back into into the spark wire,
hold it against the head or fins, and crank it. see if you get spark.
if no spark, look at electrics.
if spark is present, put the plug back in, hook it up and crank it again,
pump the throttle, pull the choke out, crank it maybe 10 to 15 seconds.
pull the plug again. if it's dry, look at the fuel system.
if it sparks, and has fuel, check compression.
fuel, compression and spark, somethings gonna happen.
look for the missing link.
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Administrator
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^^^^^^ Thats good advice right there^^^^^
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motogrady wrote
get back to the basics.
check compression.
fuel, compression and spark, somethings gonna happen.
look for the missing link.
I agree.
Low compression will lead to a hard starting or no starting motor.
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I just bought 4 new pilot jets so they should be here Monday and I will replace them. If it is compression how do you fix that? Rebuild? Also does anyone know the standard size for a fuel line? 1/4? I went to advance auto zone and they said what was on there wasn't ment for gas. So I got 1/4 and I cleaned out my fuel filter.
justin kiser
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Administrator
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believe it or not, i picked up some killer
1/4 fuel line at Lowes, in the plumbing section.
real thick stuff. mine was sucking into itself when it got warm
from the hot motor if front of it. 'specially when running
highway, it would kinda starve, fall onto itself, then die.
also, check out the lawnmower gas filters
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kiser1991 wrote
If it is compression how do you fix that? Rebuild?
First do a compression test.If it is low or has uneven cylinder results,you can do a leakdown test to pin point the problem.
A lot of times it is the valve ajustment or burnt valves.
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