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I fell in love with a money pit.

068ball

CB750 Member
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I have a 77k model I bought for 450$. was told the motor was rebuilt but hasn't run in god knows how long. I scoped the motor with a camera and cylinders were clean with nice cross hatching and piston tops had little carbon buildup. scoped the head and looked terrible. like they rebuilt it but never did anything with the valve train. any way, went to start it and gas poured out of everywhere but it ran but only on 2 cylinders. got carbs redone. went to start again ran on different cylinders everytime I started it. let it idle while I tried to figure out why and electrics started smoking and it blew the main fuse. replaced all electrics. just last week she ran on all 4 cylinders!!!! yeah!!! but I know she's way lean. needs different jets. any recommendations for pod filters and 4-1 pipe with short muffler with not much baffles? also once I got it to idle it made what I think is not so good noise. like a metal on metal crunching kinda noise? thinkin cam chain? needs slides maybe? bottom end bearings? the noise went away when I fed it some gas and took it off idle. suggestions?
 
check oil pressure? remove both engine covers and look inside for metal. take off oil filter and inspect for metal, if you find any i would yard out the block and tear it down to little bits and see what is up.
 
I changed the oil. it was really dirty but no cosmic sparkles and I'm assuming there's oil pressure cuz after a few days of letting it sit all the oil in the bladder leaks down to the pan but once started it comes back to the bladder. is that a good enough check or should I find a gauge and check pressure the way the manual says?
 
Oil shouldn't drain out of the tank into the motor, if it does you have a leaking drain back valve in the oil pump. If you start up the motor with all of the oil drained into the motor and non in the tank you have no oil going into the motor until it starts to fill the tank. This is a dry sump motor so all oil is stored in the tank. If it is empty when you go to start it then you need to drain the motor and put it into the tank, otherwise you are running with no oil.

More than likely the noise you are hearing is the primary chains. The 750 chains get slack and have a rattly noise in the bottom end. If it goes away just off idle then it isn't an issue. Rough running and low idle speed will make it sound worse. Carbs out of sinc. make this worse. Also the clutch can make some noise with age...if you pull the clutch lever in and the noise goes away it is more than likely clutch.

Timing chain can make a rattle when loose and there is a manual adjustment.

Main bearings make a duller thump in bottom end and rod bearings make a sharp hit when engine speed is abruptly changed.
 
dirtdigger how would you like to fly out to Plymouth Wisconsin and work on my p.o.s.? I have read a lot of forums in here and it seems like you are the it guy. thanks for the info and advice. where is this drain back valve? how do I go about replacing? I'm trying to get the bike running this year even if it's a little rough then rebuild motor next year and detab frame and beautify it some.
 
Drain back valve is in the oil pump. You can replace it in frame. Remove oil pan and the pump is right there. The shop manual shows where on the pump the drain back valve is. Problem...they are not available from Honda. A guy is making them aftermarket but...he is sold out till further notice. Next best thing, look on ebay maybe? and find another oil pump. I will get try to remember to get the email for this guy so you can get on his list wanting the part.

Sorry cant leave...gotta go move a foot of snow we got last night lol
 
ugh..... I hear ya this winter bs can stop anytime now..... I only get to work on the bike Tuesdays and every once in a great while maybe sneak a Saturday in. it's at my buddy's shop. I had it runnin a bit to try and dial in carbs some last week. I checked the oil can this week and it had not bled down. could something magical have happened and it fixed itself?!...... I'll come over and remove your snow with a spoon if I have to, if u get my cb runnin good.
 
my vision and what was/is my goal for the honda .... get it runnin and lookin rough this year.... slimy crud run, which is only like a month maybe away, not gonna happen..... and ama superbike races at road America is last weekend in May, the cycle parade would be a riot on it, way more fun than my victory would b on a race track.... a lot to do but still maybe possible and I don't wanna rush anything and make it worse. my wife is a money squirrel and it's hard to squeeze parts money out of her but she hasn't shot me down a whole lot yet when I needed to buy somethin for the honda.
 
If it didn't leak down again then there may be some junk floating around down in the pan or in the tank and holding it open. I would pull the pan off and see if there are bits of something in there.
 
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