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Discussion Starter · #1 ·
I've recently acquired a 1974 honda cb450 with 11k original miles.

I don't know how long it has been sitting, but I am wanting to get it to run again.

I figured I should make a thread in project logs since I'm going to be asking so many questions, and I'd rather not have to post tons of new threads for every little question I have, and just keep it all in one place to where I can also show my progress.

Here is the bike:
IMG_0718.jpg

Ill start with my list of questions so far:

1. Compression: So I took the spark plugs out and did a compression test with the kick starter for both sides. I got 85psi for both of them. From what I read, that is extremely low. But I'm not sure if I was doing it right. I would kick the kicker 2 times, compression building, but then after that It was too difficult to kick the kicker down all the way. It would go about halfway before I just couldn't go any more. If it helps, It didn't feel like a hard stop, it was like a cushioned stop. The psi would stop at 85 at that point.

So I guess my question is, is this a good sign? How can I better check the cold compression? Should I get a battery and use the starter to check compression? (question on battery later) Will the engine start with those kinds of psi readings?

2. I found online from the website 4into1.com that I can get the deluxe 450 tune up kit which includes new spark plugs, ignition coils, condenser, right and left ignition points, and 2 carb rebuild kits for $100, plus two more floats for $20 (I checked my floats and they have leaks). My question is, should I purchase this to get working on the bike, or should I do more checks to the engine to make sure that it's runnable, and I'm not just throwing money away into a bike with a **** engine?

3. Battery: So there is no battery that came with it, but there is a battery box. Eventually I want to cafe this, probably over the winter (I'd like to ride it during the fall if I get it running by then), so it's not too far away. My question is, what battery should I get? I like the idea of the lithium batteries, as they are smaller and would work much better in a cafe build, but the smaller ones don't have the power to run the starter, which I might need to actually test the compression or to get it started for the first time. Also, the lithium ones are more expensive, and I also read that they need a new charger designed specifically for lithium batteries, which adds to the cost. I just don't want to dump money into this bike for it to be a dud engine or anything. Any thoughts?
 

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Discussion Starter · #2 ·
Update: I removed the opposite spark plug while testing compression and got both sides as 100psi. Any thoughts on that?
 

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If the compression tester had a long hose it adds volume so the #'s aren't going to be as high. The fsm says 185 but.... 100 is still quite low. Rings could be stuck, maybe dump something in the cylinders and let them soak a week and try again. You're gonna want to change the oil and clean the centrifugal filter anyway. The stock brass in the carbs will be superior to any carb kit so you don't need that unless the gaskets are really good. I wouldn't replace good points either as the older ones might be better than ones you get now. Maybe hook it to a car battery to get it running. I'd suggest a lead acid battery at first and then a new combo reg/rectifier unit to get it charging right will be the best upgrade you can do.
 

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If the compression tester had a long hose it adds volume so the #'s aren't going to be as high. The fsm says 185 but.... 100 is still quite low. Rings could be stuck, maybe dump something in the cylinders and let them soak a week and try again. You're gonna want to change the oil and clean the centrifugal filter anyway
Marvel Mystery Oil. It fairly cheap and will do the trick. Not for the oil change but to dump down the cylinders
 

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Unless you get lucky and the rings aren't stuck to the pistons (and MM oil loosens them enough to make the engine serviceable), you may very well end up tearing the engine down to bring the top end back to good health. As mentioned above, if you don't want to buy a battery for it yet until you know more, I'd use a car battery to properly test compression and then, if it seems as though it has promise, do the usual tune-up adjustments - cam chain, valves, points and timing, give it an oil change (especially since 450s with stock carbs can weep fuel into the bottom end if the petcock is left on all the time, and you should check or change the oil before getting it running for that reason) and assess the overall health of the engine before spending too much money. If the engine needs an overhaul, are you prepared to do that yourself? Also, and not to be critical, but if you're going to ride this when finished and you have difficulty in kicking it over for a compression test right now, it might be advisable to go with a battery capable of running the electric start... a good engine isn't easier to kick over.
 

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Discussion Starter · #6 ·
So I ran the compression test again, not being afraid of really hitting the kicker, and here's what I gathered:

1. On the right cylinder, it would get to 100, but then 1 or 2 kicks after it would jump to 120, then go right back to 100. (didn't test on left)

2. It made some pretty weird noises. I don't know if these are normal as I'm a noob, but I took a video so you can listen for yourself. The sound I hear that occurs most sounds like there's some liquid getting swished around and being sucked on... not too sure though, it's hard to explain. Then there's one kick where it sounds like a ratchet wrench being spun, don't know about that.

Here's the link

Any information would be great.

Tomorrow Ill get some of the marvel mystery oil, seems like walmart has it. So what should I do with that? pour a certain amount down each spark plug hole and let it sit for a while?
 

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Are you holding the throttle open or is it shut? The video I remember of a compression test repeated with closed then open throttle was about a 30 psi difference.

Sounds pretty normal to me but I'm not familiar with how a cb450 should sound, there should be liquid (oil) being moved around though by both the bottom end rolling through it and the oil pump action
 

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Peer down into the spark plug holes with a flashlight while turning it over and you'll be able to see if it's clean and see a it of the valves.
 

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Welcome. I hope you get this bike running. I think everyone already addressed just about everything you asked. I’d add that you want the have both spark plugs removed when you do compression test. With the tool you have your numbers should not be going down. So I’d check that tool and make sure it’s in good order. When I do my compression test I hold the carbs wide open ( in your case the carbs are off so you’re good) and remove both spark plugs. I kick about 4-5 times that should give you your full read, up to seven kicks tops. there should be a point where the psi no longer goes up. But the number should never go back down.

I have 190 psi on both of my cylinders on my 72 CB450 but I have rebuilt my top end.

Your tank is from a 73 CB450 btw, just like mine. And your front forks are not right. Disk should be on the left side. You don’t have a front caliper. You seem to be in the right direction trying to get the bike running before you do cosmetics.




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Discussion Starter · #11 ·
I kick about 4-5 times that should give you your full read, up to seven kicks tops. there should be a point where the psi no longer goes up. But the number should never go back down.

You don’t have a front caliper.
So for me, 4-5 kicks gets me to 100, and it stays there, but 1 or two more kicks after and it'll drop immediately to 80, and another kick gets it back to 100. Just trying to make sense of what's going on with the engine before I start spending money on other stuff.

Also, I just put the wheel on the wrong way. Had to take the wheel off to get it to fit in my car, must have put it back on wrong. And there's a front brake caliper in the box, but no master cylinder
 

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So for me, 4-5 kicks gets me to 100, and it stays there, but 1 or two more kicks after and it'll drop immediately to 80, and another kick gets it back to 100. Just trying to make sense of what's going on with the engine before I start spending money on other stuff.
Sounds like your tester isn't holding pressure.
 

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Discussion Starter · #13 ·
If the compression tester had a long hose it adds volume so the #'s aren't going to be as high. The fsm says 185 but.... 100 is still quite low. Rings could be stuck, maybe dump something in the cylinders and let them soak a week and try again. You're gonna want to change the oil and clean the centrifugal filter anyway. The stock brass in the carbs will be superior to any carb kit so you don't need that unless the gaskets are really good. I wouldn't replace good points either as the older ones might be better than ones you get now. Maybe hook it to a car battery to get it running. I'd suggest a lead acid battery at first and then a new combo reg/rectifier unit to get it charging right will be the best upgrade you can do.
I've picked up some Marvel Mystery Oil as recommended by lots of people on the internet, and I've also got some 15w-40 diesel oil (lots of people say this works well in these bikes).

Should I let the marvel oil sit in the cylinders first, then change the oil later, or should I change the oil first, then add the marvel oil? I wouldn't want to waste $14 on putting new oil in the bike if I just have to empty it again to rebuild the top end. Will the marvel stuff work fine with old oil?
 

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I've picked up some Marvel Mystery Oil as recommended by lots of people on the internet, and I've also got some 15w-40 diesel oil (lots of people say this works well in these bikes).

Should I let the marvel oil sit in the cylinders first, then change the oil later, or should I change the oil first, then add the marvel oil? I wouldn't want to waste $14 on putting new oil in the bike if I just have to empty it again to rebuild the top end. Will the marvel stuff work fine with old oil?
I've never dealt with stuck rings so can just suggest putting a few teaspoons in each cylinder and letting it sit a week. Everyday kicking it over a few times and checking that it's still in there. Wait to add new oil till your ready to try starting it. Suck the mmm out with a straw? Or something. Then if it's runs change oil again soon after that.
 

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Discussion Starter · #15 ·
I just put in the marvel oil, and while hand turning the engine, I noticed that at some points during the turn, there was more resistance during the turn. Note the spark plug holes were open. Would this be a symptom of stuck piston rings or is this just normal?
 

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Ancient dad is right, that is normal.
And as stated by Lefty, your compression tool is not holding up pressure. Borrow someone else’s and try again.


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Discussion Starter · #18 ·
I took the carbs apart and will probably be ordering a carb rebuilt kit from 4into1, as both my floats are filled and a few of the brass pieces are corroded or messed up badly. Question: The kit comes with 150's main jets I think, does anyone else have experience with using pod filters? What size jets have worked for you and with what pods?

Another question about the carbs: How would I go about cleaning the top caps and the needle slides? Here are some pics of what I mean:

IMG_0716.jpg
IMG_0714.jpg
IMG_0712.jpg
IMG_0710.jpg

How would I go about cleaning these, as they do not slide that smoothly. One of the top caps must have had a crack in it, because there was gas buildup at the top that i scraped off. Is this piece still good or do I have to replace it?

How would I go about cleaning the inside of the shafts and everything? I just don't want to mess up the tight tolerance
 

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The pieces look ok to me. Just use carburetor cleaner and a lint free cloth.
Do one piece at a time. Take your time.
Don’t dump money on the carbs until everything else checks out. Compression, ignition, timing, wiring, etc...

I don’t recommend pod filters for cv carbs as they are meant to run with the air box and you will have trouble tuning the carbs. Yes this is debatable and people will argue about it. Yes it technically can run, but not 100 % through out the pull of the throttle. If you’re new to bikes it will drive you nuts.

If you think you can manage, I have a spare set of UNI pod filters that I only used fo a week.

I’m now running mikuni vm32’s

Where are you located? Is this your first bike?



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Discussion Starter · #20 ·
The pieces look ok to me. Just use carburetor cleaner and a lint free cloth.
Do one piece at a time. Take your time.
Don’t dump money on the carbs until everything else checks out. Compression, ignition, timing, wiring, etc...

I don’t recommend pod filters for cv carbs as they are meant to run with the air box and you will have trouble tuning the carbs. Yes this is debatable and people will argue about it. Yes it technically can run, but not 100 % through out the pull of the throttle. If you’re new to bikes it will drive you nuts.

If you think you can manage, I have a spare set of UNI pod filters that I only used fo a week.

I’m now running mikuni vm32’s

Where are you located? Is this your first bike?



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Are foam filters different than pod filters? Do they match more to the stock airbox?

And are you sure that the one top piece will be fine with a crack in it? What should I do, just put epoxy over the top to seal it?
 
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