low compression, what to do?

keatons

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hello all, I have a 1981 Honda CB750C, and I got a starter and tried to get it going and I figured I'd try a compression test, I have no oil in the cylinders at this point, in order it wend 35psi,35psi,50psi,5psi, and I knew it sounded off and it was, I'm not sure what to do, and the piston looks as I would call burnt in a spot or discolored. i put oil in the one with 5psi and it went to 35, so I'm guessing that means rings? I would like to hop this engine up a bit also, I would like a performance carb, I already partway messed up the original ones, and I don't know if I bore it a bit or just hone it, but from what I see the cylinders look as good as could be, it needs rings and a hone at least. so what should I do, and I also want to put pod filters on, or do I get carbs that come with pods and are jetted for them, sorry for all the rambling on
 
First I would check valve clearances. The number one cause of compression loss on the dohc is tight valve clearances that then burns the valves and seats. Honda spec is too tight and they tighten up and cause compression loss first then they burn the valves if continued to run. I would 1st check clearances and adjust if they are tighter than .005". then recheck compression. I would also verify compression with a different tester unless you have a really good tester. Too many cheap testers give false readings. If you want pods I suggest go to some Keihin CR carbs.

I am not a fan of the dohc engine but if you are looking to hop it up you will need to go to dynoman.net, They are about the only ones that have all the parts to upgrade the dohc. As far as machine work I would contact cyclex, they used to do parts and machine work for the dohc but dont offer parts for them anymore...at least on the website, talk to Ken he may have some stuff laying around yet.
 
so i dont really have 1000 to spend on carbs, what about the 2 murry carbs, I don't have a ton to spend, and I'll go check the values. i tired 3 of the cylinders and not a single one could I fit a .005 feeler gauge in, so what do I do about that, I looked it up to have it at tdc and I checked 3 of them
 
speed costs money how fast you want to go... is the old saying. If you want to hop it up your going backwards by going with the twin carb setup. You need to figure out the mechanical problems before you worry about the carbs anyway. The engine work will take way more than 1000.... I think you are going to be in for a shock in how much it is going to cost to get some more performance out of the motor. Sounds like you need to get a honda manual if you intend to do what you plan on doing. Easy way to check the valves is to turn each cylinder up on tdc.....intake and exhaust lobes will point up....then check clearance. You have to replace shims under the buckets to change the clearances.
 
both of them there do, that cant be good
IMG_6620 (1).jpg
 
Im gonna say it doesnt look like there is any valve clearance but its hard to tell. Some of that wear could be normal if its high mileage but could be tight clearance.
 
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