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Alright, its been awhile since i posted anything, so here's kind of an update. 1982 CB750F SS; since last time i have fixed both my charging issue (replaced both the battery and the RR) and my idle issue (swapped stock air box for individual K&N filters) and made adjustments.
was...
http://i42.tinypic.com/2145rn8.jpgis...
http://i40.tinypic.com/ily3bn.jpg
New problem, i can now ride this thing around, which is sweet, however i cannot yet take it home. This is because when i switch in gear, my RPM's are so low that i have trouble getting it to 20mph... sadness.
When in neutral i pull the throttle back and it screams, i could easily red line it. But as soon as it is put in first its a whole different (less powerful) beast.
Basically i am not getting damn near any torque when riding, any suggestions?
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Administrator
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Well without knowing or seeing you ride, it is hard to say what the issue is. I do not know what you have ridden before but these bikes require rpms to get moving. They do not run like a vtwin.
Rev up to 4K and then ease off the clutch and keep the Rs up.
The ride IS the adventure. The destination is just to get gas!
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sounds a little like lack of compression. runs good not under load but once uder load not enough compression to keep the pistons moving. have you done a compression test??
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Ive gotten take off down, and yes it takes plenty of RPM's at start out. It's after i'm in first and getting to second and third that is the problem. First to second isn't too terribly bad, but when switched into second it immediately dips down again and looses out all power, second to third is nearly impossible to get to but when i do it does the same thing. Runs more like a scooter than a 750 right now.
I have not yet done a compression test, that sounds like a good place to start. what would i need to do one?
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you can probably rent one from a parts store a compression tester
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i had the same problem , check spark and wires if they are not loose
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I've got a friend from work who has one and is going to help me out. As much as i'd like to find the problem, i'd hate for it to be compression, ive never rebuilt an engine...
Any other ideas what it could be in case its not compression?
Thanks for the help
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Sounds like you're down a cyl or something...
[quote]Rev up to 4K and then ease off the clutch and keep the Rs up[/quote] Geez, that's a bit much. Clutching is all about the TIMING and load. I can take off, on a hill, with a passenger, and have the tach sit at 1-1.2k until the clutch is fully engaged, and not ride the crap out of it doing it. 'Course you cant hurt anything...You just wearing out your clutch.
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Administrator
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It is the proper way to ride a 4 cylinder though. Anyone can burn a clutch 
The ride IS the adventure. The destination is just to get gas!
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Administrator
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Buy a cheap one and get it over with. You will probably spend more renting one.
Another thing besides compression is timing. If timing is poor, you will have poor power. It could be too advanced or too retarded.
The ride IS the adventure. The destination is just to get gas!
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Yeah, even in the condition mine is in it doesn't take 4k, but i know each bike varies.
My clutch catches around 2-2.5k.
I use to have a GMC Jimmy 4x4 that had a cylinder that would drop out every now and then and this feels pretty similar. So your probably onto something; i won't be able to check the compression until late this weekend so I'm going to keep playing with the adjustments and see where that takes me in the mean time.
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Also keep in mind that ignition-wise these bikes (most I-4's) are 2cyls. You could be down two, and bike will still amazingly idle OK. Start and feel for heat at the headers.
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Administrator
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the spit on the finger test huh!  Some spit on a finger and very quick touch! The spit sizzles but you do not get burned if you do it fast enough!
The ride IS the adventure. The destination is just to get gas!
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LOL, indeed. When the bike is cold, you can just fire it up and check immediately.
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Well, it passes the spit test, got heat from the headers. I have crappy spark plug cables though, i put new plugs on it a couple weeks ago but i guess I'll replace the cables too.
Could a bad fuel/air mixture or carbs. being out of sync cause this type of issue also?
I still haven't been able to get the guy with the compression gauge over, so in the meantime I'm looking for anything else that could be the problem.
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Hi,
It is because you have removed your factory airbox, and installed pod filters. This is the reason your bike is not generating any power in gear. Once you reinstall the factory box, your bike will perform how it should. I know this because I did the same thing you did. The carbs are CV, (constant vacuum), they rely on the airbox to create this situation.
Thanks,
A
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I fully agree with fixnmybike. Without the airbox the vacuum slides don't hold steady, they bounce up and down and therefore your metering needles can not control the fuel-air mixture. This is the best I can figure out for the need of the air-box.
If you're familiar with the SU carburetors, you'll know that the slides have an oil damper build in to stop the fluttering.
Karl
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That makes sense, i figured it had something to do with changing that out, but did not know about the vacuum slides. I can put the stock box back on... all though i don't want to. I know swapping that box out has been done successfully though, how have others got around this same problem?
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Also, i am not opposed to re-jetting, if this will compensate for the vacuum change....
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Hello once again,
Many have tried the same procedure you are wanting to attempt. Most have spent upwards of $300.00 or more tuning, and rejetting, attempting to make the bike work on individual filters. The bottom line is time, and money will be spent. You will get close to achieving the performance level the stock airbox puts out, but it will not match it. Dissapointment will set in, and ultimately the box will be re-installed. I have spent countless hours researching mods from frustrated people who attempted to make the pods work to no avail.
But, best of luck to ya!
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