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Just picked up a CB750K 10th Anniversary Edition for FREE

amaskedman

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My neighbor gave me his CB750K that has been sitting under a tarp. He said it needs a carb rebuilt, but it runs. I charged it, and sure enough it fired up.

What should I do first? The bike is in pretty good shape. Seat is intact, paint is decent, it has a fairing painted to match. I figure I should pull the carbs and rebuilt them, there are videos online. Replaced the plugs, maybe fuel lines, and then the rebuild forks, replace fluids, etc. The brake reservoir needs replaced, the weather got to it.
 

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gday mate,yes clean the tank,drain the carb bowls,replace the plugs,if it runs warm and chuck the oil and the filter,put new decent oil in there ,and see how it goes,if runs rough check the carbs ,dont know what fuel is like in the states,but fuel here is rubbish,leave it to long standing and problems,like dave said dont get carried away,cheers
 
gday mate,yes clean the tank,drain the carb bowls,replace the plugs,if it runs warm and chuck the oil and the filter,put new decent oil in there ,and see how it goes,if runs rough check the carbs ,dont know what fuel is like in the states,but fuel here is rubbish,leave it to long standing and problems,like dave said dont get carried away,cheers
 
forgot ,put fresh brake fluid in the res ,nine times out of ten it will bleed out and be fine,just keep pumping and see,hmmm sent 2 replies
 
I think I found a video on how to drain the carbs. I will drain the tank at the petcock and drain the bowls, put in a fresh gallon of gas, check engine oil, and replace battery (current one isn't holding a charge).
 
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What spark plugs should I get? I drained the gas today, drain the carbs, and charged the battery. Its trying to start, but isn't firing. I think its the plugs.
 
What spark plugs should I get? I drained the gas today, drain the carbs, and charged the battery. Its trying to start, but isn't firing. I think its the plugs.

could be the plugs ,the standard ones n.g.k.bpr5ey,try it mate,if its been a long time since fired up maybe get someone to service and clean the carbs,jets get clogged up easy,could be clean the points,on the right side under the chrome cover,maybe electronic ignition ,some removed the points and installed electronic ,no expert for sure on these things and other folk here would know for sure,good luck mate
 
could be the plugs ,the standard ones n.g.k.bpr5ey,try it mate,if its been a long time since fired up maybe get someone to service and clean the carbs,jets get clogged up easy,could be clean the points,on the right side under the chrome cover,maybe electronic ignition ,some removed the points and installed electronic ,no expert for sure on these things and other folk here would know for sure,good luck mate

This bike never came with points.

Put some gas in it and change oil and see if it fires up. It probably got parked because it started running bad, if they ran it long with no valve clearance check it probably has low compression and possible burned valves. If it runs warm it up a little then check compression, if its not at least 150 you are fitting a loosing battle.
 
What spark plugs should I get? I drained the gas today, drain the carbs, and charged the battery. Its trying to start, but isn't firing. I think its the plugs.

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With just the right length screwdriver you should be able to pull off one of the carb bowls without removing the carbs. A quick peek inside should give you a good estimate of how clean or gummed up they are.
 
Ok, so here is the update. New plugs, drained gas from tank and carbs, new gas. Pulled bottom off of far left carb and it looks brand new. Someone rebuilt carbs recently. Seriously, it looks brand new (black floats, metal is shiny, gasket fresh).

I did noticed the plug wires didnt sit on the plugs very tightly. A couple are very loose. Is there a quick fix for that? I uploaded a video to youtube. I got it running, but its knocking hard, doest run well, and certainly doesnt idle. It took a while to get it fired up.

https://nam05.safelinks.protection....Fr4gGn2HKTO5cSwrZno0tb82A9ZsS07t8=&reserved=0
 
The plug caps don't fit tightly.

Picture this, point the index finger of one hand straight up. Now take the index and middle finger of the other hand and clamp them on the first index finger at a 90 degree angle.

That's how the cap connects to the plug. It's a good spring loaded mechanical and electrical connection but the cap can wobble around.

Anyways, stop right there. Do a compression check.

Everyone here will tell you that's the first thing you do, if you don't have good compression your wasting time with anything/everything else. I ass/u/me'd someone else would post that tidbit so I didn't post it right away. My bad.

I did watch the video, which was a brilliant idea on your part. It's hard to be sure since I'm not hearing it, or feeling it, in person but I believe I hear the cam chain slapping around, which is normal for these engines at low rpm's, and possibly some popping from the exhaust which may indicate burnt or leaking valves. The problem is popping can be caused by too rich or too lean also.

You say "knocking". I'm guessing you mean pre detonation and not rod.
 
I think I got one that will work from Amazon. It will be here on Friday. Lets hope it works. If its under 150 is there any solution? Is it a complete engine tear down at that point?
 
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I think I got one that will work from Amazon. It will be here on Friday. Lets hope it works. If its under 150 is there any solution? Is it a complete engine tear down at that point?

You really want one that screws in and holds the reading until you push the release valve. 150 is a good target but don't forget cold dry cylinders will give a lower result. Start it enough times to at least make the head warm to the touch.

Your looking for variation between cylinders too so be sure to test each cylinder exactly the same way. They should all be very close, one being a lot lower is a sure sign of a leak.

If it fails the compression test, next move is to check the valve clearance.

If you end up with burnt valves you'll just need to rebuild the head, not the entire engine. If you do end up taking anything apart remember the exact location of every bolt, cap, bearing, shim, etc etc as they are all different and must go back into the same location.

Honda is famous for "just machine it smooth and find a bearing/shim that fits, no need to make them all the same".
 
Man, am I jealous. I just got one and it is a horror show compared to yours. If the previous owner didn't burn valves or anything like that you might be in really great shape already.
 
I want to turn it into a café racer. Does that make me a bad person? Turning an anniversary edition bike into a café racer? LOL
 
The dohc bikes really arent worth much so your not really taking anything away from the bike community by building it how you want it. 10th anniversary bike would be kind of neat if you had an original 69 to go with it but its not that big of a deal.
 
not at all mate,dohc fours over here go for good money,got a 78 k7 and turning that into a dirt bike,cant say ever saw an anniversary model here,helps to keep the original bits and dont chop the frame,of course depending on you,with a name like masked man you may be a bad person,lol,take care mate,glen
 
Man, am I jealous. I just got one and it is a horror show compared to yours. If the previous owner didn't burn valves or anything like that you might be in really great shape already.

The guy across the street from me just picked up a 96 Suzuki 750 GSXR that had been sitting in the mud for the last 5 years. He washed off the mud, put in a new battery and a few gallons of gas and it fired right up. :eek:
 
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