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Author Topic: AUXILIADORA 1981 HONDA CB750K BUILD  (Read 2620 times)

Offline CB MIKE

  • Posts: 91
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #20 on: Aug 29, 2017, 19:05:36 »
Thanks a bunch guys!!

Wow that would be awesome ! Thanks!
So it looks like just about 8in from the top to the heel

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81 CB750C

Offline PRIMEWORKS

  • Posts: 18
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #21 on: Aug 29, 2017, 20:20:25 »
So it looks like just about 8in from the top to the heel

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sadly that kick stand is the same as mine :( thanks anyways. Looks like I'll need a kick stand thats about 5 or so inches in length

Offline CB MIKE

  • Posts: 91
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #22 on: Aug 29, 2017, 21:03:52 »
sadly that kick stand is the same as mine :( thanks anyways. Looks like I'll need a kick stand thats about 5 or so inches in length
Damn sorry man, I guess your bike is low good luck

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81 CB750C

Offline PRIMEWORKS

  • Posts: 18
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #23 on: Aug 31, 2017, 14:42:16 »
So I ended up cutting my kickstand from the bottom of the hook where the spring attaches and just above the foot of the kickstand (roughly between 1 - 2 inches cut off) and it works perfectly. Just need to ensure I get a good weld done and I'm golden.

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Offline PRIMEWORKS

  • Posts: 18
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #24 on: Sep 01, 2017, 15:15:38 »
Alright so this isn't an update but more me needing input from people and just some help brainstorming.

My problem with the stock carbs and them pissing out fuel.

My main goal with this bike was for it to be reliable and with the carbs pissing out fuel it's neither reliable or safe. I mentioned this before and how I thought that the floats might be sticking but got comments saying to clean needles but the thing is, is that I rebuilt these carbs and they have all new hardware in them which leads me to believe it's something else. Something to note is that these carbs come with a vacuum valve as shown below



I've read around and have found that many ppl say this vacuum valve causes a ton of problems so I just went about bypassing the vacuum valve and doing this (petcock attached to top of tube allowing direct fuel to the carbs)



My thoughts are that there is to much fuel going into the carbs over flowing the bowls and therefore causing them to piss out fuel. If this is the case then I'm not sure if there is a way of regulating the flow of fuel or if I should just deal with the headache of reinstalling the vacuum valve and troubleshoot it. My other thought was what if I just got different carbs? If I keep the stock carbs it's obviously going to be way cheaper (which is great for me because I'm a university student) but the headaches that come with dealing with these carbs might kill me and I'd have to run a stock air box because these carbs run like shit with pods and I'm not willing to deal with re jetting just for pods. However If I got a different set of carbs maybe I wouldnt have this fuel pissing out problem and I could run pods which would make the bike look a lot better. However It would obviously cost more.

What are your thoughts?






Offline CrabsAndCylinders

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #25 on: Sep 01, 2017, 16:24:36 »
You could check to make sure the floats float.  If they do then recheck the float heights.  Is it only one carb or all that leak fuel?
Lighter, Quicker, Faster.
ZX-14, 900F x 2, 1100F, R100, CBR600, SR500, GT500, RZ350, KZ1000 x 2, Moto Guzzi Lemans lll, CBX550, RD 350, 750 SOHC police special, RG250, TL1000R, GT750, KTM Super Duke 1290 R, Harris/Z-1, Norton 750 Commando, Green 77 KZ650

Offline PRIMEWORKS

  • Posts: 18
Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #26 on: Sep 01, 2017, 17:17:29 »
You could check to make sure the floats float.  If they do then recheck the float heights.  Is it only one carb or all that leak fuel?

2 out of the 4 carbs were leaking fuel heavily. I'll likely clean them again and attempt to troubleshoot if I have to honestly. Right now I need to focus on wiring and that alone is a whole other beast to tackle.

Offline CrabsAndCylinders

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #27 on: Sep 01, 2017, 17:52:29 »
Dumb question but are they leaking from the overflow or could it be very bad gaskets, cracked bowls or if they have drains, from leaking drains?
Lighter, Quicker, Faster.
ZX-14, 900F x 2, 1100F, R100, CBR600, SR500, GT500, RZ350, KZ1000 x 2, Moto Guzzi Lemans lll, CBX550, RD 350, 750 SOHC police special, RG250, TL1000R, GT750, KTM Super Duke 1290 R, Harris/Z-1, Norton 750 Commando, Green 77 KZ650

Offline jpmobius

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #28 on: Sep 01, 2017, 18:24:12 »
So, do you have a stock airbox? If so then your simplest plan will be to keep it.  If not, getting it to run well with pods may not be too dreadful (some bikes are evidently).  Replacing the carbs altogether will be dreadfully expensive unless you get used, and whether stock replacements or from an alternative bike, you either are where you are now (you already have stock used carbs) or will likely see plenty of jetting work to get it to run properly - of course you could get very lucky - but it's not usually how it goes.  The vacuum valve itself is not a bad thing.  If it works, it's fine.  If it has issues (this is not your carb leaking problem) then fix it.  Just because others say it has problems does not mean it is terminal.  Of course you can simply eliminate it as long as the petcock works properly manually so you can turn off the fuel when you are parked.  If you bought aftermarket rebuild kits it is very possible that this is an issue.  If you kept your old parts put them back in.  The assembled height of the needle/seat assembly is CRITICAL, and aftermarket assemblies often are not correct.  You can "fix" that problem by adjusting the tang that sets the float height, but you trade one problem with another, which is screwing up the kinematics of the float mechanism by having the tang not meet the needle's tensioning pin at 90o when the fuel level is correct.  While you're thinking about this, make sure you have the correct washers under the seats as this will hugely affect the resulting assembled height of the parts.  Another reason to have the OEM factory gasket, seat and needle.  For the record, these parts almost NEVER need to be replaced unless mechanically damaged by corrosion or stupidity.  I've seen some wear on 2-stroke race motors, but otherwise consider them to be lifetime reliable only needing cleaning and polishing to be good as new.  As previously mentioned, it would be good to know EXACTLY where the leaks are.  I reckon everyone is presuming it is from the bowl overflows.  Assuming that to be the case, you should take off the bowls and fill them up with gas on the bench almost to the top of the overflow tube.  If no leaks, you can go back to troubleshooting the floats, mechanism and need/seat assembly.
Mobius


On a long enough timeline, the survival rate for everyone drops to zero.

1973 RD350 Yamaha build  http://www.dotheton.com/forum/index.php?topic=66498.0

Offline The Jimbonaut

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Re: AUXILIADORA 1981 HONDA CB750K BUILD
« Reply #29 on: Sep 01, 2017, 21:15:39 »
Dude I'm totally enjoying reading through your build - anyone working on '81 CB750K is cool as f*** as far as I'm concerned.  Might be a bit biased, but hey.

If you're still having issues with your carbs, there's a dude called Mike Nixon (he has his own website, you can google the guy) - he knows a ton about Honda carbs.  I got a ton of help here on the forum with mine, and spoke to Mike a load as well. Got mine running like champions, yours will too mate. 

Keep on keepin' on, high fives from Montreal
"I'm telling you Donnie, nuthin' but nuthin' but right"