CB450 Start Up

Hello All,

Just snagged a CB450, 1971 I believe, but early 70's, with those real sick Keihin CV carbs...having difficulty getting her to fire so I'll type out my troubleshooting list follows below:

1. New oil, plugs, battery.

2. Valves. Didn't get to check all the clearances, just the ones on the exhaust side of the engine (rusty screws didn't drill out to get to). However, I'm seeing them move in the front. One of the tappets in the back the tappet with the screw was actually off. What's the deal with that by the way, you just adjust that screw to adjust the cap, there is no locknut like say a 550?

3. Cleaned carbs. However when I'm starting her up I'm getting tons of like just low pressure in general, pressure screws don't really seem to be working (Raising/Lowering pressure) and from the top of the carbs I can like what looks like foam coming out.

I think the compression is good, I get putting, but I should probably get a test in there right? With WOT, what # should I get? Also does anyone have a good way to tune these fucking carburetors from scratch because they're a pain in the ass. IT seems like there's just tons of gunk in the engine? Should I put seafoam in her and just let it sit/any advice on that?

Thanks in advanced

Honda factory Service manual

http://198.57.59.10/manuals/450-500/CB450%20Factory%20Service%20Manual%20%28shrunk%29.pdf

That will answer most of your questions.

Most people point at carbs when they have never messed with them before, 450 CV carbs a by far the easiest to tune compared to later models. They are super simple compared even to my 360 carbs. Sounds like you need a gasket kit for them and another clean. Do not use Keyster JETS or NEEDLES in your rebuilds, just clean the old parts and reuse, even worn out they are more in tolerance usually than keyster is NEW. Only part I use in a rebuild kit is the float valves, replace them. Make sure your floats "float" and are not full of fuel. Syncing is done with a bench sync to start and then by SIGHT and FEEL later. You can add vacuum ports to the intakes if you want too.

ALWAYS SHUT THE FUEL OFF WHEN THE BIKE IS NOT RUNNING OR PARKED. Just trust me, unless you like changing oil often or burning up cams.

Compression needs to be above 160 preferably 170-180 to run well. Anything under that and it will run like a dog, keep in mind that some compression tester will run low on SMALL CC engines.

Buy an impact screw driver if you have one, makes short work of the screws on the engine, well unless they are completely stripped. There should be a lock nut on each Tappet screw, if there is no way to lock it in place it will move, possibly ruining that valve. 450 valves bend really easily BTW.

I would not add seafoam to the engine, just get it running for a good 50 miles, nice and warm, then change the oil, clean the centrifugal oil filter and clean the oil pick up screen. Then run it say another 150 miles then do it again. I use Rotella 15w-40 in mine, its cheap, bike likes it, and its certified for wet clutches as well so no slipping.

Take a step back, take a breather and then work at things one at a time. They are really fun engines and bikes once you get to know them.

Good advice above just one detail i must iron out.

Rotella is not "certified" for wet clutch use. It does however meet or exceed JASO-MA/2 specs, according to Rotellas testing. I use it too.

To the o.p., sounds like you need to slow down a little. Congrats on the bike.

Got it. Thanks.

Ummm...it sounds to me like you need to take the entire engine apart and fix it all properly because it sounds like some tard owned it before and f_cked it up and also left it outside in the rain . . I only got half way thru your description before I started laughing my ass off.

You also need to make more specific and articulate comments describing your problem . . I have no idea what you mean by "making low pressure" . . I also have no idea EXACTLY what you did with the valves and which ones you did it yo but they ALL must be properly adjusted.

Yes a compression test with the throttle wide open will help unless the gauge is a $20.00 pos.

Its simply totally unrealistic to buy a bike that HSS been abused and neglected like it sounds like yours has and think you can simply change the oil and it will run fine for another 50,000 miles but lots of people do think that way.

Since the tappet screws are rusty it has obviously had moisture in the engine which is a VERY bad thing and means that other things like the can chain has rust also and maybe even the cylinders.
.

barnett468 said:

Ummm...it sounds to me like you need to take the entire engine apart and fix it all properly because it sounds like some tard owned it before and f_cked it up and also left it outside in the rain . . I only got half way thru your description before I started laughing my ass off.


You also need to make more specific and articulate comments describing your problem . . I have no idea what you mean by "making low pressure" . . I also have no idea EXACTLY what you did with the valves and which ones you did it yo but they ALL must be properly adjusted.

Yes a compression test with the throttle wide open will help unless the gauge is a $20.00 pos.

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LOL

DohcBikes said:

LOL

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Lol, I'm laughing so fn hard now after seeing your post that i cant even hit the right keys on my stupid fn Verizon tablet that I am currently forced to use because my fn time warner internet AND TV have gone out for the 10th fn time in the last 4 fn months god damn it.

OK, if you just want to fire it up to see if the pig will even lite, one option is to do the following.

0. Turn the gas off and drain the gas from the carbs.

1. Clean the crap out of the spark plugs or get new ones.

2. With the bike in the shade, lay both spark p!ugs on the head with the plug wires connected then turn it over . . if the the spark is pale blue you hit the lotto . . if it is yellow you did not hit the lotto but it should still have enough voltage to fire . . if it is a very faint/weak spark you are screwed.

3. Take photos of the end of the plugs and post them here.

4. Reinstall the p!ugs.

5. Turn ignition on.

6. Open the slides by hand if the air box is out and spray starting fluid in both carbs for one second only . . this will be the shortest burts you can spray in them.

7. Try to start it . . it will either make noise or it won't.
.

barnett468 said:

6. Open the slides by hand if the air box is out and spray starting fluid in both carbs for one second only . . this will be the shortest burts you can spray in them.

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Do not do this. Period. (unless you are in the arctic and it is 40 below) Absolutely the best and easiest way to potentially destroy a perfectly good engine (assuming it is perfectly good). There is absolutely no upside. Getting it to hit on ether will not get it to hit on gasoline if it already will not run on gasoline. It will not indicate very much about what might be wrong. Starting fluid is great for finding intake leaks, but knowledgeable people know better than to take such a dreadful chance of potential and totally needless disaster. In fairness to barnett, "shortest bursts" certainly minimizes the risk - but I expect someone asking this question will likely not quit with the minimum if the engine does not start running- which it won't though it might fire briefly inviting more starting fluid, and I expect that is not part of your recommendation.

Does starting fluid blow up every motor it gets squirted in? Of course not. In fact, I have to say the percentage is quite small, but because the potential damage is so great, and the usefulness under normal temperatures so non existent, it is a bad idea. Catastrophic damage IS possible - I have seen it myself.

Sorry mobius but youre wrong.

This engine has stuck rings, etc. It is easy for people like mike and I to see that.

At times, a shot motor, which is what this is and why i typed LOL and why barnett posted what he did, a shot of ether is enough to make it fire, which can "reverse" some of the effects of a water logged engine, and in turn, allow it to fire on gas.

The motor is already trash.

In addition, please explain how short burst of ether can wreck engines.

jpmobius said:

Do not do this. Period. (unless you are in the arctic and it is 40 below) Absolutely the best and easiest way to potentially destroy a perfectly good engine (assuming it is perfectly good).

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As was mentioned, you are absolutely, positively, wrong in every sense of the word, even of the engine has good compression . . ANY debate to the contrary would simply be laughable and not even worthy of a reply.

jpmobius said:

Getting it to hit on ether will not get it to hit on gasoline if it already will not run on gasoline.

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This is correct and I never said, or implied that it would.

jpmobius said:

It will not indicate very much about what might be wrong.

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Actually, if it does fire, it will in fact indicate a few different things to some extent . . Some of those are that it does have sufficient spark to make it run and that the timing is close enough to make it run and that it likely has enough compression to run on straight gas.

jpmobius said:

Starting fluid is great for finding intake leaks, but knowledgeable people know better than to take such a dreadful chance of potential and totally needless disaster.

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Yes, it's best to have the paramedics and fire department there when you do this just in case it backfires and blows both your balls off before it sends you sailing thru the garage door and across the street into the neighbors Pit Bull cage.

jpmobius said:

In fairness to barnett, "shortest bursts" certainly minimizes the risk - but I expect someone asking this question will likely not quit with the minimum if the engine does not start running

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If someone is told not to stick their finger in the fire because it will get burned and they do it anyway, then they are way too much of a TARD to follow ANY directions and they deserve what they get.

jpmobius said:

which it won't though it might fire briefly inviting more starting fluid, and I expect that is not part of your recommendation.

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Correct, using more starting fluid than I suggested, or trying to keep the engine running by spraying a continual stream of fluid in it is definitely NOT what I am recommending, HOWEVER, I have in FACT run more engines than i can count on straight starting fluid for maybe 15 seconds for various reasons with absolutely no damage to them whatsoever and some of them had around 160 psi of cranking pressure.
.

DohcBikes said:

In addition, please explain how short burst of ether can wreck engines.

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Perhaps his watch is slow and what he thought was one second when he tried it himself was really around 10.

Well if that is the case, point taken. Still think it a bit irresponsible as others with maybe only carb issues might think it a good idea to try the same thing. Probably should have analyzed the op a bit better (not to mention the responses! should have been my first clue!) Have to admit to being quite surprised at barnett's response in the first place - makes sense now. But I will stand on my overly serious post - bad idea on a good engine - at least potentially.

jpmobius said:

Well if that is the case, point taken. Still think it a bit irresponsible as others with maybe only carb issues might think it a good idea to try the same thing. Probably should have analyzed the op a bit better (not to mention the responses! should have been my first clue!) Have to admit to being quite surprised at barnett's response in the first place - makes sense now. But I will stand on my overly serious post - bad idea on a good engine - at least potentially.

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Yup. Never any good reason to introduce starting fluid to a good running engine.

DohcBikes said:

Yup. Never any good reason to introduce starting fluid to a good running engine.

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yup, especially when nitrous works so much better.

Pffft. As if you have a slight clue. ;D

jpmobius said:

Well if that is the case, point taken. Still think it a bit irresponsible as others with maybe only carb issues might think it a good idea to try the same thing.

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Wrong AGAIN . . It would in FACT be irresponsible for "OTHERS" to try this unless it was specifically suggested to them for THEIR particular problem.

Contrary to what the Bible says, I am NOT my brothers keeper, NOR am I responsible for any of the incredibly stupid things others might do.

If one person sees another shooting smack into their veins then does it themselves just because they saw someone else do it, then they deserve what they get . . Besides, this is merely the Lords process of natural selection.

From the Gospel of Barnett, chapter 5 verse 7.

"Blessed are the intelligent for only they shall inherit the earth."
.

DohcBikes said:

Pffft. As if you have a slight clue. ;D

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Well, I just figuered it would cuz I know it sure gets me goin when I huff it from the Redi Whip aerosol dispensers in the dairy section of my local food store.

Let me add some details to this thing. Bike was on the road in 04 and has been barn stored since. Yes, some bolts may be rusty, but water damage is unlikely, tons of neglect is unlikely, it's mint looking, no rust, new tires (5 year lifespan obviously expired, but the tread's essentially perfect, etc.) From what it looks like, someone had tried to get the bike started that had no idea what they were doing. I think this because the timing was way off, the valve tappet was loose etc. What I meant by pressure being low was that on the 450 carbs, there is a pressure screw, which increases, or decreases pressure out of the exhaust. This feels low to me, and doesn't seem to change with adjustment of the screw but I am unsure. Doing a compression test tomorrow before doing anything else, like I said in the 3rd post before the other 15 ones of people spitting nonsense at each other, got it, thanks.